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REDACTED PUBLIC VERSION HPC PCSR3: CHAPTER 9 – AUXILIARY SYSTEMS SUB-CHAPTER 9.4 – HEATING, VENTILATION AND AIR-CONDITIONING SYSTEMS
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TABLE OF CONTENTS
1. GENERAL DESIGN CRITERIA ...... 1 1.1. GENERAL DESIGN OBJECTIVES ...... 1 1.2. GENERAL DESIGN CHARACTERISTICS ...... 5 1.3. GENERAL DESCRIPTION OF EQUIPMENT ...... 9 1.4. FIRE PROTECTION IN THE VENTILATION SYSTEMS ...... 10 2. NUCLEAR AUXILIARY BUILDING VENTILATION SYSTEM (DWN [NABVS]) ...... 11 2.0. SAFETY REQUIREMENTS ...... 11 2.1. ROLE OF THE SYSTEM ...... 18 2.2. DESIGN BASIS ...... 19 2.3. SYSTEM DESCRIPTION AND OPERATION ...... 23 2.4. PRELIMINARY DESIGN SUBSTANTIATION ...... 30 2.5. FUNCTIONAL DIAGRAMS...... 36 3. CONTAINMENT COOLING VENTILATION SYSTEM (EVR [CCVS])36 3.0. SAFETY REQUIREMENTS ...... 36 3.1. ROLE OF THE SYSTEM ...... 40 3.2. DESIGN BASIS ...... 41 3.3. SYSTEM DESCRIPTION AND OPERATION ...... 43 3.4. PRELIMINARY DESIGN SUBSTANTIATION ...... 47 3.5. FUNCTIONAL DIAGRAM ...... 51 4. REACTOR BUILDING INTERNAL FILTRATION SYSTEM (EVF) .... 51 4.0. SAFETY REQUIREMENTS ...... 51 4.1. ROLE OF THE SYSTEM ...... 55 4.2. DESIGN BASIS ...... 56 4.3. SYSTEMAPPROVED DESCRIPTION AND OPERATION ...... 57 4.4. PRELIMINARY DESIGN SUBSTANTIATION ...... 59 4.5. FUNCTIONAL DIAGRAM ...... 63 5. CONTAINMENT SWEEP VENTILATION SYSTEM (EBA [CSVS]) .. 63 5.0. SAFETY REQUIREMENTS ...... 63 5.1. ROLE OF THE SYSTEM ...... 70
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5.2. DESIGN BASIS ...... 72 5.3. SYSTEM DESCRIPTION AND OPERATION ...... 74 5.4. PRELIMINARY DESIGN SUBSTANTIATION ...... 80 5.5. FUNCTIONAL DIAGRAM ...... 89 6. SAFEGUARD BUILDING (CONTROLLED AREA) VENTILATION SYSTEM (DWL [CSBVS]) ...... 89 6.0. SAFETY REQUIREMENTS ...... 90 6.1. ROLE OF THE SYSTEM ...... 99 6.2. DESIGN BASIS ...... 101 6.3. SYSTEM DESCRIPTION AND OPERATION ...... 105 6.4. PRELIMINARY DESIGN SUBSTANTIATION ...... 109 6.5. FUNCTIONAL DIAGRAM ...... 121 7. SAFEGUARD BUILDING (UNCONTROLLED AREA) VENTILATION SYSTEMS ELECTRICAL (DIVISION) (DVL [SBVSE]) ...... 121 7.0. SAFETY REQUIREMENTS ...... 121 7.1. ROLE OF THE SYSTEM ...... 127 7.2. DESIGN BASIS ...... 129 7.3. SYSTEM DESCRIPTION AND OPERATION ...... 132 7.4. PRELIMINARY DESIGN SUBSTANTIATION ...... 140 7.5. FUNCTIONAL DIAGRAM ...... 149 8. MAIN CONTROL ROOM AIR CONDITIONING SYSTEM (DCL [CRACS]) ...... 150 8.0. SAFETY REQUIREMENTS ...... 150 8.1. ROLE OF THE SYSTEM ...... 156 8.2. DESIGN BASIS ...... 157 8.3. SYSTEM DESCRIPTION AND OPERATION ...... 161 8.4. PRELIMINARYAPPROVED DESIGN SUBSTANTIATION ...... 168 8.5. FUNCTIONAL DIAGRAM ...... 179 9. DIESEL BUILDING VENTILATION SYSTEM (DVD) ...... 179 9.0. SAFETY REQUIREMENTS ...... 179 9.1. ROLE OF THE SYSTEM ...... 185 9.2. DESIGN BASIS ...... 186
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9.3. SYSTEM DESCRIPTION AND OPERATION ...... 189 9.4. PRELIMINARY DESIGN SUBSTANTIATION ...... 195 9.5. FUNCTIONAL DIAGRAM ...... 202 10. SAFETY CHILLED WATER SYSTEM (DEL [SCWS]) ...... 202 10.0. SAFETY REQUIREMENTS ...... 203 10.1. ROLE OF THE SYSTEM ...... 210 10.2. DESIGN BASIS ...... 210 10.3. SYSTEM DESCRIPTION AND OPERATION ...... 214 10.4. PRELIMINARY DESIGN SUBSTANTIATION ...... 220 10.5. FUNCTIONAL DIAGRAM ...... 227 11. OPERATIONAL CHILLED WATER SYSTEM (DER [OCWS]) ...... 227 11.0. SAFETY REQUIREMENTS ...... 227 11.1. ROLE OF THE SYSTEM ...... 232 11.2. DESIGN BASIS ...... 233 11.3. SYSTEM DESCRIPTION AND OPERATION ...... 233 11.4. PRELIMINARY DESIGN SUBSTANTIATION ...... 237 11.5. FUNCTIONAL DIAGRAM ...... 241 12. VENTILATION OF THE PUMPING STATION (DVP) ...... 242 12.0. SAFETY REQUIREMENTS ...... 242 12.1. ROLE OF THE SYSTEM ...... 247 12.2. DESIGN BASIS ...... 248 12.3. SYSTEM DESCRIPTION AND OPERATION ...... 249 12.4. PRELIMINARY DESIGN SUBSTANTIATION ...... 255 12.5. FUNCTIONAL DIAGRAM ...... 261 13. VENTILATION OF THE EFFLUENT TREATMENT BUILDING HQA AND HQB (9DWQ [ETBVS]) ...... 262 13.0. SAFETYAPPROVED REQUIREMENTS ...... 262 13.1. ROLE OF THE SYSTEM ...... 267 13.2. DESIGN BASIS ...... 268 13.3. SYSTEM DESCRIPTION AND OPERATION ...... 272 13.4. PRELIMINARY DESIGN SUBSTANTIATION ...... 276 13.5. FUNCTIONAL DIAGRAM ...... 281
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14. FUEL BUILDING VENTILATION SYSTEM (DWK [FBVS]) ...... 281 14.0. SAFETY REQUIREMENTS ...... 281 14.1. ROLE OF THE SYSTEM ...... 289 14.2. DESIGN BASIS ...... 290 14.3. SYSTEM DESCRIPTION AND OPERATION ...... 294 14.4. PRELIMINARY DESIGN SUBSTANTIATION ...... 297 14.5. FUNCTIONAL DIAGRAM ...... 306 15. VENTILATION SYSTEM FOR THE FIRE FIGHTING WATER BUILDING (DVJ) ...... 307 15.0. SAFETY REQUIREMENTS ...... 307 15.1. ROLE OF THE SYSTEM ...... 312 15.2. DESIGN BASIS ...... 312 15.3. SYSTEM DESCRIPTION AND OPERATION ...... 314 15.4. PRELIMINARY DESIGN SUBSTANTIATION ...... 318 15.5. FUNCTIONAL DIAGRAM ...... 323 16. VENTILATION OF THE TURBINE HALL (DVM) ...... 323 16.0. SAFETY REQUIREMENTS ...... 323 16.1. ROLE OF THE SYSTEM ...... 327 16.2. DESIGN BASIS ...... 328 16.3. SYSTEM DESCRIPTION AND OPERATION ...... 329 16.4. PRELIMINARY DESIGN SUBSTANTATION ...... 334 16.5. FUNCTIONAL DIAGRAM ...... 338 17. VENTILATION OF THE CONVENTIONAL ISLAND ELECTRICAL BUILDING (DVF) ...... 338 17.0. SAFETY REQUIREMENTS ...... 339 17.1. ROLE OF THE SYSTEM ...... 343 17.2. DESIGNAPPROVED BASIS ...... 344 17.3. SYSTEM DESCRIPTION AND OPERATION ...... 345 17.4. PRELIMINARY DESIGN SUBSTANTATION ...... 348 17.5. FUNCTIONAL DIAGRAM ...... 353 18. VENTILATION SYSTEM FOR THE VVP AND ARE VALVE ROOMS (DVE) ...... 353
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18.0 SAFETY REQUIREMENTS ...... 353 18.1 ROLE OF THE SYSTEM ...... 358 18.2 DESIGN BASIS ...... 359 18.3 SYSTEM DESCRIPTION AND OPERATION ...... 361 18.4 PRELIMINARY DESIGN SUBSTANTATION ...... 364 18.5 FUNCTIONAL DIAGRAM ...... 368 19. REFERENCES ...... 369
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SUB-CHAPTER 9.4 – HEATING VENTILATION AND AIR CONDITIONING SYSTEMS
1. GENERAL DESIGN CRITERIA
The Heating, Ventilation and Air-Conditioning (HVAC) systems and chilled water systems are described in the subsequent sections of this sub-chapter. General design objectives and a description of the main equipment are provided in this section.
The design criteria specific to the Annulus Ventilation System (EDE [AVS]) are defined in Sub-chapter 6.1, section 2.
As Low As Reasonably Practicable (ALARP) decisions are included in the current section and are presented in the dedicated Chapter 17.
1.1. GENERAL DESIGN OBJECTIVES
HVAC systems are designed according to the Ventilation System Functional Requirements, Sizing and Material Selection document [Ref. 1].
The main objectives of HVAC systems are:
to maintain internal conditions within acceptable limits (air quality, temperature, humidity and contamination) for staff and equipment,
to protect staff and materials against specific risks arising from internal hazards (see Sub-chapter 13.2) and external hazards (see Sub-chapter 13.1), and
to monitor and limit radioactive discharges during normal plant operation and accident conditions (confinement function).
In order to minimise corrosion on the HVAC systems the following equipment is corrosion- resistant:
inlet and outlet louvres,
the first exchanger or heater of the supply trains,
all the isolation, control and non-return dampers, located between the first exchanger and the fresh air inlet of supply trains, and the ductAPPROVEDwork between the first exchanger and the fresh air inlet of the supply trains. The description, nature and objective of the computer code used for the HVAC systems’ thermal calculations is presented in Appendix 3, section 18.
1.1.1. External Conditions
This section deals with the external conditions which are used for the safety-classified HVAC and chilled water systems’ design.
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1.1.1.1. Summer External Conditions
Classified HVAC Systems with Air Conditioning (cooling) Safety Feature
Variable Extreme Heat Profile:
A variable extreme heat profile is used to design the safety-classified HVAC and chilled water systems. This variable extreme heat profile is based on Sub-Chapter 2.1 extreme summer conditions, i.e.:
the 24 hour average extreme high air temperature: { SCI removed },
the 12 hour average extreme high air temperature: { SCI removed } (with { SCI removed }Relative Humidity (RH)), and
the instantaneous extreme high air temperature: { SCI removed } (with { SCI removed } RH).
These extreme summer conditions are used to define a daily sinusoidal temperature variation, from which a bounding “Variable Extreme Heat Profile” is defined in Section 9.4.1 – Figure 1:
When the sinusoidal (daily, 24 hour period) external temperature profile is above { SCI removed }, air conditions of { SCI removed } RH are assumed. The daily duration of this transient condition is { SCI removed }.
When the sinusoidal external temperature profile is below { SCI removed }, air conditions of { SCI removed } RH are assumed. The daily duration of this transient condition is seventeen hours.
These conditions represent a one in 10,000 year event, to include climate change affects until 2099 on an { SCI removed } percentile confidence interval. For more detail and substantiation of these figures see Sub-chapter 2.1.
SECTION 9.4.1 – { SCI REMOVED }
{ This figure contains SCI and has been removed }
Systems that are sized according to this variable extreme heat profile include:
the Diesel Building Ventilation system (DVD),
the Circulating Water Pumping Station Ventilation System (DVP), and
the Ventilation for the Conventional Island Electrical Buildings (DVF). On a case by APPROVEDcase analysis, different external conditions may be used following production of an appropriate safety justification. The Turbine Hall Ventilation System (DVM) is one such case and thus the following commitment is made:
Safety Case Commitment: the DVM system will justify the use of different external conditions than those described in Sub-chapter 9.4 section 1.
Heatwave Approach [Ref. 2]:
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This specific approach has been defined to manage the extreme high air conditions for the design of the Safety Chilled Water System (DEL [SCWS]) units of air-cooled trains 1 and 4, the Safeguard Building (uncontrolled area) Ventilation System Electrical (division) (DVL [SBVSE]), and the Control Room Air Conditioning System (DCL [CRACS]) for the HPC site.
The following external conditions are used for the sizing of these HVAC and chilled water systems:
heatwave transient conditions (five day period): { SCI removed } RH,
constant hot and dry conditions: { SCI removed } RH, and
constant warm and moist conditions: { SCI removed } RH.
Classified HVAC Systems without Air Conditioning (cooling) Safety Feature:
Classified HVAC systems which do not have any Safety Functional Requirements (SFRs) to cool the air in summer or which have only a confinement safety function must use the 12 hour average extreme high conditions ({ SCI removed }) permanently for summer sizing cases.
Systems adopting this approach include:
the Nuclear Auxiliary Building Ventilation system (DWN [NABVS]) (safety-classified for confinement only),
the EDE [AVS] system (no air-cooling safety function),
the Ventilation System for the VVP and ARE Valve Rooms (DVE) air handling unit in the Nuclear Auxiliary Building (HN [NAB]) (not safety-classified for air-conditioning),
the Effluent Treatment Building Ventilation System (9DWQ [ETBVS]) (safety-classified for confinement only),
the Chilled Water System for the Effluent Treatment Buildings (HQA, HQB, HQC) (9DEQ) (as support to the 9DWQ [ETBVS] system), and
the Ventilation System for the HOJ Building (DVJ) (no air-cooling safety function).
Impact of the External Temperature on Heat Gain through Walls in contact with Outside:
For all the HVAC systems (i.e. those that take air directly from outside or not), heat gains through walls in contact with the outside only depend on the buildings characteristics.
For concrete buildings, the 24 hour average extreme high air temperature ({ SCI removed } for the “cold seafront conditions”) is used to calculate heat gains through walls in contact with the outside, in conjunctionAPPROVED with any solar gains. The method for the calculation of thermal exchanges between rooms and the outside is described in the Ventilation System Functional Requirements, Sizing and Material Selection document [Ref. 1].
For structures with walls of low thermal mass, the external air temperature considered for heat gain calculations may need to be increased and must be specifically assessed case-by-case.
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The external temperature has an impact on heat gains through walls when the HVAC system ensures the air-conditioning of a room with at least one wall in contact with outside. Thus, it impacts not only the systems that take air directly from outside listed above, but also the systems located within the buildings that do not take air directly from outside, such as:
the Fuel Building Ventilation System (DWK [FBVS]) (supply of conditioned air from the DWN [NABVS] system),
the Controlled Safeguard Building Ventilation System (DWL [CSBVS]) (supply of conditioned air from the DVL [SBVSE] system, and
the DVE system in the Safeguard Buildings (HL [SB]) (located inside the HL [SB] buildings and ensures local air conditioning with no air supply from outside).
1.1.1.2. Winter External Conditions
The winter external conditions and associated duration to be used for the HVAC and chilled water systems design are (see Sub-chapter 2.1 and Sub-chapter 13.1, section 6.5):
Long duration temperature, { SCI removed }: assumed to exist permanently for design purposes, characterised by a seven day average value. This external condition is associated with a wind velocity of { SCI removed }.
Short duration temperature, { SCI removed }: assumed to exist for seven days for design purposes, characterised by a 24 hour average temperature. This short duration condition is a hazard (Extreme Cold) as defined in Sub-Chapter 13.1, section 6.5.
Instantaneous temperature, { SCI removed }: assumed to exist for six hours for design purposes, characterised by the instantaneous or daily minimum temperature. This instantaneous condition is a hazard (Extreme Cold) as defined in Sub-Chapter 13.1, section 6.5.
The associated percentage RH for all the above winter conditions is 100%.
The short duration and instantaneous temperatures are used to design heating systems for components that need to be protected against freezing during Extreme Cold events.
1.1.2. Internal Conditions
In normal operating conditions (Plant Condition Category (PCC)-1), the ranges of temperature and relative humidity to be maintained within rooms are defined in Section 9.4.1 – Table 1. Thus, HVAC systems are designed to meet these requirements in normal operation.
In fault conditions (from PCC-2 to PCC-4, Design Extension Condition (DEC)-A, Design Basis Initiating Faults (DBIF) and DEC-B) and during Extreme Cold conditions, the minimum and maximum temperatureAPPROVEDs and relative humidity to be maintained within rooms are defined in Section 9.4.1 – Table 2 and Table 3. During these events, HVAC systems are designed to meet at least these requirements. Consistency with requirements inherited from the DBIFs should be checked when the list of DBIFs evolves (see Chapter 15).
During maintenance operations and periodic testing, the temperature ranges listed in Section 9.4.1 – Table 1 may not be achieved. Where this is the case a specific justification will be given. However, temperatures must be at least higher than those specified in Section 9.4.1 – Table 2 and lower than those in Section 9.4.1 – Table 3.
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1.2. GENERAL DESIGN CHARACTERISTICS
1.2.1. Characteristics of Controlled Areas
General Characteristics:
In Controlled Areas, the principles of the NVF/DG001 [Ref. 3] are used for the design of HVAC systems.
The exhaust mass flow rate is higher than the supply mass flow rate in order to maintain a lower pressure in comparison with outside and with Non-controlled Areas, and hence to ensure the confinement of radioactive materials. Thus the direction of air flow is always towards areas of a higher contamination risk.
In principle the supply air is generally distributed to corridors and cascaded to rooms with a higher risk of contamination.
The exhaust air from Controlled Areas is collected, filtered and discharged to the main unit ventilation stack. The principal role of the main unit ventilation stack is to provide adequate dispersion of residual contamination to ensure an acceptable concentration at ground level. The air quality is measured before discharge to the environment. The main unit ventilation stack ensures that discharge minimises the risk of contamination re-entrainment into fresh air inlets.
In Controlled Areas, the minimum air renewal rate depends on the contamination risk of the room. In general:
rooms with iodine risk: four air changes per hour (there are some exceptions where a reduced air renewal rate is used and these are mitigated by having appropriate justification, such as Computational Fluid Dynamics (CFD) analysis, demonstrating that there are no stagnant areas or zones);
rooms with aerosol or non-fixed atmospheric contamination risk: two air changes per hour;
rooms without aerosol or non-fixed atmospheric contamination risk: one air change per hour; and
laboratories: eight air changes per hour.
The air renewal rate is determined by the highest requirement between; heat loads, minimum and maximum temperatures, fresh air requirement (see section 1.1.2.2), unclean processes’ flow rate requirement, flow rate to maintain a depression, or radiological risk flow rate requirement. CharacteristicsAPPROVED of Rooms with Iodine Risk: The exhaust flow rate of the iodine adsorption unit is minimised in order to:
reduce the radwaste consequences of iodine adsorption unit periodic replacement; and
limit the electrical power consumption of heaters upstream of the iodine adsorption unit.
A room is considered as a room with iodine risk if:
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it houses equipment which may contain iodine in gaseous form, and with features that present a risk of leakage (mechanical joints, valves, etc.); or
it has pipework that presents a risk of leakage and contains a fluid with the following two characteristics:
o Radio-activity higher than { SCI removed } of the Radio-activity of the primary coolant in normal operation, and
o temperature in normal operation higher than { SCI removed }
For these “iodine risk rooms”, an additional design measure is applied:
a depression between the iodine room (or groups of rooms) and adjacent rooms is maintained (in accordance with the principles defined in the Ventilation of Radioactive Areas design aid [Ref. 3]).
For the HPC facility, these criteria and design measures are applicable in normal operating conditions (PCC-1) to iodine risk rooms in the Fuel Building (HK [FB]), the HN [NAB] building, the Controlled Areas of the HL [SB] and the Effluent Treatment Building (HQ [ETB]).
In fault conditions it is required to limit the exhaust flow rate to the main unit ventilation stack in order to limit off-site discharge.
The extraction from all rooms located in the Reactor Building (HR [RB]), HK [FB], HN [NAB], HL [SB], and HQ [ETB] buildings is directed to an iodine adsorption unit when the level of contamination is too high to be discharged directly to outside.
1.2.2. Characteristics of Non-controlled Areas
In Non-controlled Areas, ventilation systems can operate in “recirculation mode” to save cooling power in summer or heating power in winter. However, a minimum fresh air rate must be ensured inside the building to maintain acceptable indoor air quality. To define the minimum fresh airflow for personnel, the building occupancy and location of the people are necessary. The supply fresh airflow must also compensate for the exhaust to outside flow rate, which cannot be re-circulated due to unclean processes. The flow rate that cannot be re-circulated is exhausted to the outside without filtration.
The minimum fresh air rate must be calculated in accordance with the following documents, by using the most restrictive criteria:
UK Building Regulations, and
UK Workplace (Health, Safety and Welfare) Regulations. The renewal rateAPPROVED is determined by the highest requirement between heat loads, minimum and maximum temperatures, the fresh air requirement or the unclean processes flow rate requirement.
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1.2.3. Specific Case of Rooms with Risk of Explosive Atmosphere
Rooms presenting a risk of Explosive Atmosphere (ATEX) formation, other than the HR [RB] building, are ventilated with a minimum air change rate of four air changes per hour (see Sub-chapter 13.2, section 6) except for the battery rooms. HVAC equipment located in potentially ATEX areas is designed according to the requirements of the Equipment and Protective Systems Intended for Use in Potentially Explosive Atmospheres Regulation 1996.
The exhaust flow rate in battery rooms is calculated in order to maintain the hydrogen (H2) concentration below the Lower Explosion Limit, whatever the status of the batteries (floating, charging or discharge) as per BS EN 50272-2 [Ref. 4].
The ventilation systems layout must be designed in order to avoid local H2 accumulation leading to the formation of an Explosive Atmosphere. In the case of H2 concentration increasing within battery rooms (e.g. due to loss of HVAC system), an alarm is sent to the Main Control Room (MCR). Additionally, the air transfer from a hazardous to a safe area is prohibited.
The HVAC design for battery rooms is compliant with the following requirements:
UK Workplace (Health, Safety and Welfare) Regulations,
UK Control of Substances Hazardous to Health (COSHH) Regulations,
UK Dangerous Substances and Explosive Atmospheres Regulations (DSEAR),
UK Pressure Equipment Regulations (PER),
BS EN 50272-2 [Ref. 4], and
other input data such as minimum and maximum temperatures, heat loads or fresh air requirement.
1.2.4. Equipment used in HVAC Systems
Equipment requiring seismic qualification and supports, foundations, etc., will be given specific attention. Equipment is installed according to rules facilitating operation and maintenance. a) Air Inlet Pre-filters and Fine Filters:
Air inlet pre-filters are used to filter coarse particles from atmospheric dust and are designed to extend the service life of fine filters. These filters normally have a relatively low efficiency but a higher efficiency filter may be used depending on site specific conditions such as a high level of dust due to an industrial or agricultural environment. The functionAPPROVED of air inlet fine filters is to provide clean air into rooms for equipment and staff. b) Extraction Pre-filters:
The pre-filters used for extraction, upstream of the High Efficiency Particulate Air (HEPA) filters, are designed to extend the service life of HEPA filters by filtering coarse particles from the air flow.
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Extraction pre-filters upstream of the HEPA filters are also useful during maintenance of equipment (some particles could be sent to the exhaust train and pre-filters protect HEPA filters against those particles) and in the case of accident, when the supply HVAC train is lost the exhaust part of the system is exposed to particles that can damage the HEPA filters. c) HEPA filters:
Safety-classified filters have a Decontamination Factor of at least { SCI removed } (safety criterion), corresponding to a filtration efficiency of at least { SCI removed }. However, as a conservative approach the HVAC contract will specify a higher Decontamination Factor than this.
In-situ testing is carried out using the Dispersed Oil Particulate (DOP) test method [Ref. 3] in accordance with prescribed procedures to measure the overall installed decontamination factor and verify that filters are installed correctly and that filter elements are not damaged.
HEPA filters shall be provided with bleed HEPA filters for operator protection which are used during pressure equalisation for HEPA filter replacement. d) Iodine Adsorption Units:
Iodine adsorption units are used in some ventilation systems to adsorb gaseous radioactive iodine in the air flow. When new, they have an efficiency of at least { SCI removed } (decontamination factor of { SCI removed } when using methyl iodide for example). In operation, they have a minimum efficiency of { SCI removed } (decontamination factor of { SCI removed } when using methyl iodide for example) for safety-classified systems (filters required in accident conditions) and { SCI removed } (decontamination factor of { SCI removed }) for other systems (operational iodine adsorption units). e) Iodine Adsorption Units Heaters:
These heaters are located upstream of the iodine adsorption unit to limit the maximum relative humidity to { SCI removed } in the iodine adsorption unit. f) Cooling Coils:
The HVAC systems use cooling coils constructed of finned tubes. If needed, droplet separators and drain funnels are provided to collect and remove condensates. The coils are cooled by chilled water from the DEL [SCWS] system, 9DEQ system or the Operational Chilled Water System (DER [OCWS]), and/or by the Component Cooling Water System (RRI [CCWS]) in the HR [RB] Building. g) Fans:
Fans used in the ventilation systems are supply, recirculation or exhaust fans. The technology of these fans is centrifugal or axial, depending on the system characteristics (flow rate and headAPPROVED loss). They are electrically power supplied. h) Heating Methods:
The ventilation systems use electrical heaters (electrically power supplied) or heating coils (heated by hot water system).
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1.3. GENERAL DESCRIPTION OF EQUIPMENT
The design characteristics of the main mechanical equipment used in HVAC systems are described below (non-exhaustive list): a) Centrifugal Fans:
Centrifugal fans with backward-curved blades are used. Fans have a drive by a direct coupling or a belt. To control the flow rate, a Variable Frequency Drive (VFD) is installed on some fans. Inlet Guide Vanes (IGV) may also be provided to control the air flow rate in certain applications. b) Axial Fans:
Axial fans have a direct drive. c) Coils:
The coils are constructed from continuous tubes with fins. They are formed to ensure a continuous and uninterrupted flow of water in each tube. d) Electrical Heating:
Electrical heaters are composed of reinforced tubular elements in a sheet metal box. e) Filters:
Filters are made from cells with standard dimensions. The filtering medium is disposable. The filtering layer is made from fibreglass, unless otherwise specified. f) Iodine Adsorption Unit:
The iodine adsorption unit is placed in an airtight metal container. It has an adsorption area containing granular activated charcoal. g) Fan-coil Units:
These units provide heating (when they are known as “unit heaters”) or cooling (i.e. Local Cooling Units (LCU)) to the room.
A “unit heater” is composed of a fan and a heater. The casing is made from thick steel. A direct drive axial fan is used. The heating device is either electrical or hot water supplied.
An LCU is equipped with a fan and a cooling coil supplied with chilled water. An inlet filterAPPROVED is installed within Fan-coil Units when supported equipment requires supplied air with a low quantity of dust and particles, such as in Instrumentation and Control (I&C) rooms.
When diversification is required, Fan-coil Units are composed of two coils and two fans diversified to ensure the robustness of the HVAC design. h) Direct Expansion Air-conditioning Units:
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The Direct Expansion Air-conditioning Units can be equipped with a filter, a fan and a cooling coil supplied by a cooling system built into the unit. The cooling system can be air-cooled (separate element) or a water-cooled (built in).
The Direct Expansion Air-conditioning Unit can also house an electrical heater or a heating coil.
All the equipment is housed in a compact metal chassis with double-walled insulated panels. i) Fresh Air Inlets:
Fresh air inlets are fitted with bird-proof grid and louvres. They are designed to prevent the formation of frost and to minimise the admission of saline-laden air which could cause corrosion. They may be fitted with silencers when required.
Where necessary to meet safety requirements, external air inlets of classified buildings are equipped with Explosion Pressure Wave (EPW) dampers to protect components inside of buildings against external explosions and tornados defined in Sub-chapter 13.1.
1.4. FIRE PROTECTION IN THE VENTILATION SYSTEMS
The ventilation systems are required to contribute to the containment and the restriction of the fire, see Sub-Chapter 3.8, section 5, for more details.
1.4.1. Containment of the Fire
The fire containment objective is met through the implementation of the following points:
Ventilation systems within each fire compartment are generally fitted with fire dampers, having at least the same fire rating as the barrier, on ducts crossing any fire barrier at the point of entry and/or exit to the compartment. The compartment can therefore be completely isolated in event of fire by automatically closing these dampers when a fire detection signal occurs (see Sub-chapter 9.5, section 1.2) or by operation of the thermal fuse(s).
In addition to the use of fire dampers, ventilation ducts crossing different fire compartments (including ones attached to another division) can be protected against fire by being constructed from materials providing fire resistance (rating) equal to that of the fire compartment boundaries. In cases where ducts traverse multiple boundaries with different requirements, the rating with the greatest requirement is applied.
Provision for the SFC: fire dampers are considered to be active elements of the protection systems and so single failure must be taken into account when the fire containment function is a nuclear safety requirement. Accordingly, when required, two fire dampers are provided in series. If redundancy is not possible due to layout constraints,APPROVED alternative measures will be taken. 1.4.2. Restriction of the Fire
The ventilation systems must be shut down or isolated from a compartment containing a fire.
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Following a fire in an iodine adsorption unit, an alarm is sent to the MCR and fire dampers upstream and downstream of the iodine trains are automatically closed. The corresponding exhaust line is automatically shut down. In addition, iodine adsorption units are fitted with a fixed internal fire-extinguishing device which is supplied by a water connection between the ventilation systems and the Nuclear Island Protection and Fire- Fighting Water Distribution System (JPI [NIFPS]) or the Nuclear Island Protection and Fire-Fighting Water Distribution System for the HQ [ETB], the Hot Workshop, Hot Warehouse and Facilities for Decontamination (HVD), Hot Laundry (HVL), the KER, SER and TER Tanks (HXA), the Intermediate Level Wastes (HHI), and the Interim Spent Fuel Store (HHK [ISFS]) buildings and the HN [NAB] Tanks Liaison Gallery (HGV) and the Effluent Gallery (HGQ) (9JPI [ETBFPS]).
2. NUCLEAR AUXILIARY BUILDING VENTILATION SYSTEM (DWN [NABVS])
The information reported in this section is, unless otherwise noted, consistent with the reference design, as referenced from Chapter 22.
2.0. SAFETY REQUIREMENTS
The UK EPR Safety Classification principles and the top-down functional approach are presented in Sub-chapter 3.2. These principles help to ensure that the plant is designed, manufactured, constructed, commissioned and operated so that the appropriate level of reliability and integrity is achieved for its Structures, Systems and Components (SSCs).
The HPC functional safety analyses and the application of these safety classification principles to the HPC reference design result in the identification of the safety requirements for all safety systems in accordance with the Safety Functional Requirements Notes (SFRNs) referenced from Sub-chapter 3.2.
This section summarises the results of these safety analyses and specifies the safety requirements that apply to the design of the Nuclear Auxiliary Building Ventilation System (DWN [NABVS]).
The requirements described in the present section are consistent with safety functions to which the DWN [NABVS] system contributes in Plant Condition Category (PCC) and Design Extension Conditions (DEC). Consistency with requirements inherited from the Design Basis Initiating Faults (DBIFs) should be checked when the list of DBIFs evolves (see Chapter 15).
2.0.1. Safety Functions
The three Main Safety Functions (MSFs) necessary to achieve the overall safety objective of protecting peopleAPPROVED and the environment from the harmful effects of ionising radiation are: control of fuel reactivity,
fuel heat removal, and
confinement of radioactive material.
These three MSFs must be achieved during:
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normal operating conditions (PCC-1), including duty functions, control of radioactive release during normal operating conditions, control of main plant parameters, fault initial conditions, Limiting Conditions of Operation (LCO), limitations, monitoring functions, Probabilistic Safety Assessment (PSA) significant functions as part of the preventive line of defence,
fault conditions (PCC-2 to PCC-4, DEC-A and any equivalent Design Basis Initiating Faults (DBIFs)) and DEC-B, and
hazard conditions.
2.0.1.1. Control of Fuel Reactivity
The DWN [NABVS] system does not directly contribute to the MSF of control of fuel reactivity.
2.0.1.2. Fuel Heat Removal
The DWN [NABVS] system does not directly contribute to the MSF of fuel heat removal.
2.0.1.3. Confinement of Radioactive Material
The DWN [NABVS] system must contribute to the achievement of the MSF of confinement of radioactive material as follows:
Environmental protection:
The DWN [NABVS] system carries gaseous fluids containing radioactive material. As such, it must contribute:
o to the confinement of this material with respect to the environment as a whole and the public,
o to the control and reduction of radioactive waste discharge under normal operation, and
o to the prevention of minor radioactive release following a mechanical failure.
Limiting radiological consequences:
o The DWN [NABVS] system must contribute to the static confinement of the Nuclear Auxiliary Building (HN [NAB]) in the event of multiple failure of systems in the HN [NAB] building following an earthquake (PCC-4).
2.0.1.4. Support Contribution to Main Safety Functions The DWN [NABVS]APPROVED system must contribute indirectly to the MSF of confinement of radioactive material as a support system as follows:
The DWN [NABVS] system must contribute to the provision of a pressure reference in order for:
o the Fuel Building Ventilation System (DWK [FBVS]) to confine the controlled area of the Fuel Building (HK [FB]) during normal operation (see section 14),
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o the Safeguard Building Controlled Area Ventilation System (DWL [CSBVS]) to confine the controlled area of the Safeguard Buildings (HL [SB]) during normal operation (see section 6), and
o the Effluent Treatment Building Ventilation System (9DWQ [ETBVS]) to confine the contaminated part of the controlled area of the Radioactive Waste Storage Building (HQA) and the Radioactive Waste Process Building (HQB) during normal operation (see section 13).
The DWN [NABVS] system must contribute to signalling a loss of the DWN [NABVS] extraction in order to initiate the isolation of the Gaseous Waste Processing System (TEG [GWPS]) at the interface with the DWN [NABVS] system (see Sub-chapter 11.3, section 7).
2.0.1.5. Specific Contribution to Hazards Protection
The DWN [NABVS] system must contribute directly to the safety functions that are part of the facility’s hazards protection against the consequences of internal fire (see Sub-chapter 13.2, section 7), earthquake (see Sub-chapter 13.1, section 2) and external explosion (see Sub-chapter 13.1, section 4) as follows:
Internal fire:
o The DWN [NABVS] system must contribute to the containment and prevention of spread of fire.
o The DWN [NABVS] system must contribute to the provision of water to the DWN [NABVS] iodine adsorption units in case of fire inside the iodine adsorption units (see the Nuclear Island Protection and Fire-Fighting Water Distribution System (JPI [NIFPS]) contribution in Sub-chapter 9.5, section 1.3.
Earthquake:
o The DWN [NABVS] system must contribute to the preservation of SC1 Safety Features (SFs) availability following a seismic event.
External explosion:
o The DWN [NABVS] system must contribute to the static confinement of the HN NAB [building] following an external explosion event.
Moreover, the DWN [NABVS] system must be protected against internal and external hazards (see section 2.0.4.2). 2.0.1.6. OtherAPPROVED Safety Functions to be performed in the Preventive Line of Defence The DWN [NABVS] system does not contribute to other safety functions to be performed in the preventive line of defence.
2.0.2. Safety Functional Requirements
2.0.2.1. Control of Fuel Reactivity
Not applicable: the DWN [NABVS] system does not directly contribute to the MSF of control of fuel reactivity.
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2.0.2.2. Fuel Heat Removal
Not applicable: the DWN [NABVS] system does not directly contribute to the MSF of fuel heat removal.
2.0.2.3. Confinement of Radioactive Material
With respect to its contribution to the MSF of confinement of radioactive material, the DWN [NABVS] system must satisfy the following Safety Functional Requirements (SFRs):
Environmental protection:
The DWN [NABVS] system must:
o contain the radioactive material and prevent the risk of leaks,
o limit radioactive discharges to the environment through sufficient filtration of the gaseous effluent conveyed, and
o prevent minor release of radioactivity following a mechanical failure by ensuring that all components which contribute to this requirement are designed to meet the sufficient mechanical requirement in accordance with Sub-chapter 3.2, section 7.
Limiting radiological consequences:
Requirements to ensure the static confinement of HN [NAB] building in case of multiple failure in the HN [NAB] building following an earthquake:
o The DWN [NABVS] system must ensure the isolation of the air openings to meet the static air tightness requirement of the HN [NAB] building in case of multiple failure of systems in the HN [NAB] building following an earthquake (PCC-4);
o The DWN [NABVS] system must ensure the DWN [NABVS] ventilation of the HN [NAB] building is shut down in case of multiple failure of systems in the HN [NAB] building following an earthquake (PCC-4).
The DWN [NABVS] system must ensure compliance with the requirements defined for the radioactive gaseous waste in the waste discharge specifications.
2.0.2.4. Support Contribution to Main Safety Functions
With respect to its indirect contribution to the MSF of confinement of radioactive material, the DWN [NABVS] system must satisfy the following SFRs: The DWNAPPROVED [NABVS] system must provide a pressure reference in order for: o the DWK [FBVS] to confine the controlled area of the HK [FB] during normal operation,
o the DWL [CSBVS] to confine the controlled area of the HL [SB] during normal operation, and
o the 9DWQ [ETBVS] to confine the contaminated part of the controlled area of the HQA and the HQB during normal operation.
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The DWN [NABVS] must send a signal to the TEG [GWPS] system in case of loss of DWN [NABVS] extraction in order for TEG [GWPS] to initiate automatic isolation of TEG [GWPS] system at the interface with the DWN [NABVS] system.
2.0.2.5. Specific Contribution to Hazards Protection
With respect to its specific contribution to the safety functions that are part of the facility hazards protection, the DWN [NABVS] system must satisfy the following SFRs:
Internal fire:
o Requirement for the containment and prevention of spread of fire:
. The DWN [NABVS] system must isolate the ventilation openings of intervention fire compartment in the event of an internal fire so as to maintain fire compartment integrity.
o Requirement for provision of water to the DWN [NABVS] iodine adsorption units in case of fire in the DWN [NABVS] iodine adsorption units:
. The DWN [NABVS] system must ensure the minimum combination (flow rate, pressure) at the interface with the DWN [NABVS] iodine adsorption units in order to control the fire in the DWN [NABVS] iodine adsorption units (see JPI [NIFPS] contribution in Sub-chapter 9.5, section 1.3).
Earthquake:
o The DWN [NABVS] must ensure the stability of DWN [NABVS] components in order not to adversely impact the availability of SC1 SFs following a seismic event.
External explosion:
o The DWN [NABVS] must ensure the isolation of the air openings to meet the static air tightness requirement of the HN [NAB] building following an external explosion event;
o The DWN [NABVS] system must ensure the DWN [NABVS] ventilation of the HN [NABVS] is shutdown following an external explosion event.
2.0.2.6. Other Safety Functions to be performed in the Preventive Line of Defence
Not applicable; the DWN [NABVS] system does not contribute to other safety functions to be performed in the preventative line of defence. 2.0.3. SafetyAPPROVED Features Section 9.4.2 – Table 1 presents the SFs of the DWN [NABVS] system, according to the contributions identified in section 2.0.1 and the SFRNs referenced in Sub-chapter 3.2.
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2.0.4. Classification and Architecture Requirements of Safety Features
2.0.4.1. Requirements arising from Safety Classification
Architecture requirements associated with SFs are essential for designing robust lines of defence consistent with their importance to nuclear safety (see Sub-chapter 3.2). Such requirements strengthen the system design against:
single faults and associated consequences (Single Failure Criterion, SFC) by requiring redundancy;
Loss Of Offsite Power (LOOP) by requiring, among others, a back-up power supply;
Station Black-Out (SBO) by requiring a power supply by the Ultimate Diesel Generators (UDGs);
Common Cause Failures (CCF) by requiring physical separation;
earthquake by defining seismic requirements; and
accident conditions by defining qualification requirements.
Section 9.4.2 – Table 1 presents the requirements arising from safety classification for the DWN [NABVS] system, according to the SFRNs referenced in Sub-chapter 3.2.
2.0.4.2. System Protection against Hazards
2.0.4.2.1. Internal Hazards
The SFs of the DWN [NABVS] system must be protected against internal hazards if those hazards challenge the safety objectives, as defined in Sub-chapter 13.2.
2.0.4.2.2. External Hazards
The SFs of the DWN [NABVS] system must be protected against external hazards if those hazards challenge the safety objectives, as defined in Sub-chapter 13.1.
2.0.4.3. Diversity
The DWN [NABVS] system is not subject to the requirement for diversity.
2.0.5. Requirements defined at the Component Level
2.0.5.1. Generic Safety Requirements 2.0.5.1.1. GenericAPPROVED Mechanical, Electrical and I&C Requirements The mechanical components within the DWN [NABVS] system must comply with the mechanical requirements in accordance with the rules laid out in Sub-chapter 3.2, section 7. The level of requirement is dependent upon whether or not it is a pressure retaining component, the safety class of the component, whether the component acts as an isolating device between interfacing SFs, and on the role of the component as a barrier to the potential release of radioactivity as a result of failure of the component.
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The electrical and Instrumentation and Control (I&C) components in the DWN [NABVS] system must comply with the electrical and I&C requirements associated with their safety class, in accordance with the rules laid out in Sub-chapter 3.2.
2.0.5.1.2. Seismic Requirements
The level of seismic requirements to be applied to DWN [NABVS] system components is related to the Safety Feature Group (SFG) to which the component belongs, and the consequences on other classified components of its failure if it were not seismically qualified. The rules for defining the seismic requirements for a component are defined in Sub-chapter 3.2.
2.0.5.1.3. Qualification for Accident Conditions
The safety-classified parts of the DWN [NABVS] system must be qualified for the operating conditions in which they are required, as specified in Sub-chapter 3.6.
2.0.5.2. Specific Safety Requirements
2.0.5.2.1. High Integrity Components (HIC) Requirements
The DWN [NABVS] system is not subject to any High Integrity Component (HIC) requirements.
2.0.5.2.2. Specific Instrumentation and Control (I&C) Requirements
The DWN [NABVS] system is not subject to any specific I&C requirements; the DWN [NABVS] system does not have any dedicated I&C. The general approach for I&C systems is set out in Chapter 7.
The DWN [NABVS] fire dampers are however operated by the Fire Detection System (JDT [FDS]) dedicated I&C. The specific requirements arising from the JDT system dedicated I&C are described in the JDT [FDS] system chapter (see Sub-chapter 9.5, section 1.2).
2.0.6. Examination, Maintenance, (In-service) Inspection and Testing (EMIT)
2.0.6.1. Start-up Tests
The DWN [NABVS] system must be designed to enable the performance of start-up tests to ensure the adequacy of their design and performance under conditions as representative as possible of the different operating configurations, and in particular their compliance with the SFRs assigned to them in section 2.0.2.
2.0.6.2. In-Service Inspection
The DWN [NABVS] system must be designed to enable surveillance under normal operation of the system characteristics necessary for the fulfilment of their safety-related tasks in order to ensure the performanceAPPROVED of their components, and their availability under normal operation, or in the event of a fault or accident.
2.0.6.3. Periodic Testing
The safety-classified parts of the DWN [NABVS] system must be designed to enable the performance of periodic tests in accordance with the maintenance schedule.
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2.0.6.4. Maintenance
The DWN [NABVS] systems must be designed to enable the implementation of a maintenance schedule (see Sub-chapter 18.2).
2.1. ROLE OF THE SYSTEM
The DWN [NABVS] system performs the functions (or tasks) detailed in the following sections under the different plant operating conditions for which it is required.
2.1.1. Normal Operating Conditions
The DWN [NABVS] system operates continuously. It is designed for the following purposes:
to maintain ambient inside conditions within prescribed limits for correct operation of equipment and/or staff in normal operation (air supply, filtration, heating and cooling),
to ensure during normal operation that contamination is contained at source to avoid its spreading from potentially contaminated areas to potentially less contaminated areas,
to limit the concentration of aerosols and radioactive gases in the atmosphere of the rooms, and
to maintain negative pressure in the HN [NAB] building compared to the outside pressure using an automatic control damper in the air supply trains.
Furthermore, the DWN [NABVS] system is designed for the following:
ensure the conditioning, extraction and filtration of air supplied and extracted by the Fuel Building Ventilation System (DWK [FBVS]) (see section 14),
ensure the operational extraction and filtration of the air extracted by the Controlled-Area Safeguard Building Ventilation System (DWL [CSBVS]) (see section 6),
ensure during plant outages, the conditioning, extraction and filtration of the air from the purging ventilation system of the containment: high-capacity Containment Sweeping Ventilation System (EBA [CSVS]) (see section 5 of this sub-chapter),
ensure during the operation of the plant, the conditioning of the air from the purging ventilation system of the containment: low-capacity EBA [CSVS] system (see section 5 of this sub-chapter), and
limit the radioactivity of the air discharged to the main unit vent stack during normal operation.
2.1.2. FaultAPPROVED and Hazard Conditions
The DWN [NABVS] system contributes to:
the static confinement of the HN [NAB] building in the event of multiple failure of systems in the HN [NAB] building following an earthquake (PCC-4),
the static confinement of the HN [NAB] building following an external explosion event,
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the prevention of the spread of fire into adjacent fire compartments in the event of fire, and
the fire-fighting measures against fire in DWN [NABVS] iodine adsorption units.
2.2. DESIGN BASIS
2.2.1. General Assumptions
The DWN [NABVS] system is designed with the following general assumptions:
Maintain ambient inside conditions compatible with the correct operation of the equipment and/or for staff (temperature, radioactivity and concentration of aerosols):
o The DWN [NABVS] air intake is made up of three filtration and conditioning trains.
o The DWN [NABVS] supply and normal exhaust fans operate at 4 x { SCI removed } during normal operation and 4 x { SCI removed } during plant outage.
Ensure the confinement of radioactive material.
Limit the radioactivity discharged into the environment:
o The DWN [NABVS] High Efficiency Particulate Air (HEPA) filtration is made up of seven trains also called “cells” (see section 2.3.1.1 for a complete description of the role of each cells).
o The DWN [NABVS] iodine adsorption units’ line is made up of four trains. Each iodine adsorption train is capable of filtering the air flow coming from any DWN [NABVS] HEPA filtration cell.
Adjust the pressure in the HN [NABVS] building. Negative pressure must be maintained within the building compared to atmospheric pressure.
2.2.2. Design Assumptions
2.2.2.1. Control of Fuel Reactivity
Not applicable; the DWN [NABVS] system does not directly contribute to the MSF of control of fuel reactivity.
2.2.2.2. Fuel Heat Removal
Not applicable;APPROVED the DWN [NABVS] system does not directly contribute to the MSF of fuel heat removal.
2.2.2.3. Confinement of Radioactive Material
Environmental protection:
o During normal operation, the DWN [NABVS] system must contribute to the confinement of radioactive material by:
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. maintaining a negative pressure in the controlled area of the HN [NAB] building relative to the atmospheric pressure.
o During normal operation, the DWN [NABVS] system must contribute to limiting the radioactivity of the air discharged into the main unit vent stack. The filtration requirements for this criterion are:
. HEPA filters: decontamination factor see section 1.2.4;
. Iodine adsorption units: decontamination factor see section 1.2.4; and
. Iodine adsorption units’ heaters: a maximum exhaust relative humidity, see section 1.2.4.
o The DWN [NABVS] system must ensure that all system components whose mechanical failure could lead to minor release of radioactivity are mechanically classed M3/T3.
Limiting radiological consequences:
o Following an earthquake event, the DWN [NABVS] system must ensure that the isolation of air openings meets the air-tightness requirements (T3) stated in section 1.
2.2.2.4. Support Contribution to Main Safety Functions
Not applicable: there are no quantitative safety-related design assumptions associated with the DWN [NABVS] system.
2.2.2.5. Specific Contribution to Hazards Protection
Internal fire:
o Water provision to the DWN [NABVS] iodine adsorption units in case of fire in the DWN [NABVS] iodine adsorption units:
. The DWN [NABVS] system must guarantee a minimum combination (flow rate, pressure) at the interface with each iodine adsorption units to ensure minimum combination (flow rate, pressure) defined by the supplier at the iodine adsorption units connection (see Sub-chapter 9.5, section 1.3.2.2.5.3).
Earthquake:
o Not applicable: there are no quantitative safety-related design assumptions APPROVEDassociated with the earthquake for the DWN [NABVS] system. External explosion:
o Following an external explosion event (load case defined in Sub-chapter 13.1, section 4), the DWN [NABVS] system must ensure that the isolation of air openings meets the air-tightness requirements (T3) stated in section 1.
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2.2.2.6. Other Safety Functions to be performed in the Preventive Line of Defence
Not applicable: the DWN [NABVS] system does not contribute to other safety functions in the preventative line of defence.
2.2.3. Other Assumptions
2.2.3.1. Air Supply Conditions
Under design basis conditions, the required air supply temperatures in the DWN [NABVS] system are the following:
Summer: { SCI removed }.
Winter: { SCI removed }:
{ SCI removed } with the plant out of operation without internal heat loads.
2.2.3.2. Atmospheric Conditions
See section 1 of this sub-chapter.
2.2.3.3. Environmental Conditions
See section 1 of this sub-chapter.
2.2.3.4. Auxiliary Fluids
During summer the air supply in the DWN [NABVS] system is cooled by cooling coils supplied by the Operational Chilled Water System (DER [OCWS]).
During winter, the air supply in the DWN [NABVS] system is heated by the heating coils supplied by the Electrically-Heated Hot Water System (SEL).
2.2.3.5. Materials
The main distribution and exhaust air ducts are made out of concrete with decontaminable finish.
Other supply and exhaust air ducts are made out of galvanised metal sheet.
Airtight exhaust air ducts are made out of carbon steel welded with finish that can be decontaminated.
The exhaust duct section from the laboratory to the concrete duct is made out of austeniticAPPROVED stainless steel. Components up to the first heater on the supply line are resistant against saline environment.
Pipework connected to the atmospheric buffer tank and the outside are resistant against saline environment.
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2.2.3.6. Air Tightness
All ducts and components, starting at the injection point for the filter testing up to and including the exhaust fans, must fulfil (T3) air tightness requirements (see Sub-chapter 3.2, section 7).
All ducts and components in the iodine adsorption units line have to fulfil the (T3) air tightness requirement.
2.2.3.7. Minimum Air Renewal Rates
In controlled areas, the minimum air renewal rate depends on the radiological risk associated with the room, shown in Section 9.4.2 – Table 2.
SECTION 9.4.2 – TABLE 2 : MINIMAL AIR RENEWAL RATE
Type of room Renewal rate Laboratories { SCI removed } Rooms with iodine risk { SCI removed } Rooms with aerosol or non-fixed atmospheric { SCI removed } contamination risk Rooms without aerosol or non-fixed atmospheric { SCI removed } contamination risk
2.2.3.8. Extraction Characteristics for the Controlled and Contaminated Area
In the controlled area, the exhaust conditions are as follows:
All the air extracted from a controlled area is filtered then directed towards the main unit vent stack where it is monitored before it is discharged into environment;
Air extracted from the controlled areas may be directed through the iodine adsorption units if necessary;
The transfer of air between rooms ventilated by the DWN [NABVS] system is from less contaminated rooms to more contaminated rooms;
The air extraction rate is greater than the air supply rate in order to ensure that the controlled areas remain under negative pressure relative to the atmosphere; and
A differential pressure of at least { SCI removed } is maintained and statically controlled between rooms (or group of rooms) with risk or iodine contamination and adjacent rooms.APPROVED 2.2.4. Assumptions associated with Extreme Situations resulting from Beyond Design Basis Hazards
2.2.4.1. Assumptions associated with Fukushima Provisions
The DWN [NABVS] is not subject to assumptions associated with Fukushima provisions.
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2.2.4.2. Assumptions associated with other non-Fukushima Provisions
The DWN [NABVS] system is not subject to assumptions associated with non-Fukushima provisions.
2.3. SYSTEM DESCRIPTION AND OPERATION
2.3.1. Description
2.3.1.1. General System Description
For an overview of the DWN [NABVS] system, please refer to Section 9.4.2 – Figures 1 to 4 (for more details, see the detailed mechanical diagram of the systems).
The DWN [NABVS] system consists of a supply section made up of three air heating and cooling trains, with four supply fans arranged in a parallel configuration.
The supply section provides conditioned air through an air supply shaft to the HN [NAB] building and to the DWK [FBVS] system and the EBA [CSVS] system via a separate air supply shaft.
During the summer period, the supply air is cooled by cooling coils supplied by the DER [OCWS] system.
During the winter period, the supply air is heated by heating coils supplied by the SEL system.
All areas in the Fuel Building (HK [FB]), the equipment compartment of the Reactor Building (HR [RB]), the controlled area of Safeguard Buildings (HL [SB]) and the HN [NAB] building could potentially contain airborne contamination and are specially grouped together as “cells”.
Including the HR [RB], HL [SB], HK [FB] and the HN [NAB] buildings, there are a total of seven cells:
Cell 1: contains the rooms with the gaseous waste systems such as the TEG [GWPS], the Coolant Treatment System (TEP3 [CTS]), and the Coolant Degasification System (TEP4 [CDS]) in the HN [NAB] building.
Cell 2: contains the rooms with the water treatment systems such as the Nuclear Vent and Drain System RPE [NVDS], the Reactor Boron and Water Make-up System (REA [RBWMS]), the Chemical and Volume Control System (RCV [CVCS]), and the Fuel Pool Cooling (and Purification) System (PTR [FPCS/FPPS] in the HN NAB building.
Cell 3: contains the storage rooms, hot workshop, laboratory rooms, measuring rooms, and HVAC rooms in the HN [NAB], the TEG [GWPS] system, the Condenser Vacuum System (CVI) exhaust and the Handling Tower exhaust of the DWK [FBVS] system from the HKAPPROVED [FB] building. Cell 4/5: the HK [FB] building is divided into two cells. These cells (numbers 4 and 5) represent the separation of the redundant systems in the HK [FB] building. The Fuel Pool belongs to cell 5.
Cell 6: contains the common exhaust from the controlled areas of the HL [SB] buildings.
Cell 7: (normally in standby) is used for sweeping the HR [RB] building in line with EBA3/4 (high capacity circuit) during plant shutdown.
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The exhaust from each cell is first directed through its respective filter units consisting of a coarse filter and a HEPA filter. Downstream of the HEPA filter, the exhaust can be sent either directly to the common exhaust plenum or, in the case of activity detection by the Plant Radiation Monitoring System (KRT [PRMS]), to a common plenum upstream of the iodine adsorption units.
Air collected in the common exhaust plenum is discharged to the main unit vent stack for dispersion of the gaseous waste via two of the four exhaust fans.
Air collected in the common plenum upstream the iodine adsorption units (maximum four cells) passes through the iodine adsorption units and the iodine fans arranged in a parallel configuration, each capable of taking over delivery of the flow rate of a unit if it becomes contaminated. Four units can therefore be treated at the same time. If the EBA [CSVS] high capacity circuit is in operation it is permanently directed to one of the iodine adsorption units. In addition to the seventh cell (EBA [CSVS] high capacity circuit), a maximum of three of the six remaining cells can be directed to the iodine adsorption units. After passing through the iodine adsorption units the air is directed to a common exhaust to be discharged via the main unit vent stack.
The main unit vent stack is installed on the reinforced structure of the HR [RB] building at the connection between the HK [FB] and the HN [NAB] building. Other ventilation systems connected directly to the main unit vent stack are the EBA [CSVS] low capacity circuit, DWL [CSBVS], Annulus Ventilation System (EDE [AVS]), Access Building (controlled area) Ventilation System (DWW [ABVS]), 9DWQ [ETBVS], DWK [FBVS] and the 9DWV system.
Electric convectors are installed in some of the rooms housing equipment or pipework containing boron to avoid boron crystallisation in the borated water systems pipework.
Additional heaters are also required to maintain the room air conditions in winter during normal operating mode or with the plant out of operation. In rooms allocated as work areas, electrical heaters are provided in the supply ducts to maintain the room conditions.
Local air conditioning units supplied with DER [OCWS] cold water are installed in certain rooms to ensure conditions that are acceptable for staff and equipment.
Sampling glove boxes are filtered by HEPA filters and specific iodine adsorption units that are part of the Nuclear Sampling System (REN [NSS]). Specific REN [NSS] exhaust fans are connected to the DWN [NABVS] exhaust ducts.
For fire protection, air ducts running through fire resistant walls are equipped with fire dampers. In the case of a fire in the HN [NAB] building, the staircases are kept free from smoke using mechanically operated air overpressure ensured by the Smoke Control System (DFL). For more details, see Sub-chapter 9.5, section 1.4.
A pressure reference system, which comprises of a buffer tank and pipework, provides the atmospheric pressure reference to the DWK [FBVS], DWL [CSBVS], 9DWQ [ETBVS], DFL/9DFL, 9DWV,APPROVED DWW [ABVS] and EDE [AVS]. The buffer tank is made up of two chambers and is connected to outside to take the atmospheric pressure reference on the roof of the HN [NAB] building. It decouples the pressure reference from any outside atmospheric impacts (such as sudden occurring wind peaks).
2.3.1.2. Description of Main Equipment
A diagram of all general ventilation systems of the controlled area of the HN [NAB], HK [FB], HL [SB] and HR [RB] (except the annulus) buildings is provided in Section 9.4.2 – Figure 1.
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The DWN [NABVS] system comprises the following main equipment items (see the functional diagram provided in section 2.5):
The DWN [NABVS] comprises an air supply line, an extraction line with permanent filtering by HEPA filter, an iodine adsorption units line, an air supply duct network, an extraction duct network, a main unit vent stack and a pressure reference system.
The continuous air supply line includes the following:
an external air inlet on the wall of the HN [NAB] building with a weather louvre and a bird mesh;
a concrete air intake plenum;
three trains of { SCI removed } capacity, mounted in parallel, each equipped with the following:
o motorised building isolation dampers equipped with spring closing mechanism,
o a pre-heating coil supplied by the hot water system (SEL),
o the pre-heating coil is located downstream of the air intake dampers and is provided to maintain outgoing air temperature above { SCI removed } where incoming air temperature is { SCI removed },
o a 2-stage filtering system (coarse filter, fine filter),
o a cooling coil supplied with chilled water (DER [OCWS]),
o the cooling coil is located upstream of the air supply fans and is used to provide an air supply temperature of { SCI removed } where the incoming dry bulb temperature is { SCI removed }
o cooling coil condensation tray connected to the RPE [NVDS] system,
o a heating coil supplied by the hot water system (SEL),
o the heating coil is located upstream of the air supply fans and is used to provide an air temperature of { SCI removed } where incoming air temperature is { SCI removed },
o a sound attenuator, and
o a manual isolation damper. a concreteAPPROVED plenum (connected to: three supply trains and four supply fans); four direct driven centrifugal fans with variable frequency drives installed in parallel (4 x { SCI removed } during normal operation and 4 x { SCI removed } during an outage);
a sound attenuator; and
an automatic control damper in the supply air for keeping sub-atmospheric pressure in the HN [NAB] building.
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The continuous extraction line equipped with HEPA filters includes the following components:
seven steel ductwork lines in parallel, each including a coarse filter and a HEPA filter which can be safely changed, an automatic control damper to keep a constant flow rate, and inlet and outlet isolation dampers,
a concrete plenum (connected to: HEPA filter Cells 1-7 and four exhaust fans),
four direct driven centrifugal fans with variable frequency drive installed in parallel (4 x { SCI removed } during normal operation and 4 x { SCI removed } during an outage),
motorised building isolation dampers equipped with spring closing mechanism,
a shared concrete duct to the main unit vent stack, and
a sound attenuator (downstream of the HEPA filters) in a common concrete duct, subject to detailed noise studies.
The iodine adsorption units line includes the following elements:
a concrete plenum (connected to: HEPA filter Cells 1-7 and four iodine adsorption units),
four trains mounted in parallel, each equipped with the following:
o an inlet motorised isolation damper,
o an electrical heater located upstream of the iodine adsorption unit in order to limit the relative humidity of the air (see section 2.2.2.3), with a temperature threshold sensor to avoid any burn-out event,
o a fire damper upstream of the iodine adsorption unit,
o an iodine adsorption unit installed downstream of the heaters in order to adsorb the radioactive iodine (or other hazardous gas) contained in the air flow,
o a fire damper downstream of the iodine adsorption unit, and
o an outlet motorised isolation damper.
a concrete plenum (connected to: four iodine “booster” fans and four exhaust fans), and
four direct driven centrifugal “booster” fans mounted in parallel each providing the air flow capacity of an iodine adsorption unit. The pressure APPROVEDreference system includes: a buffer tank with two chambers to decouple the pressure reference measurement from any outside atmospheric impacts (as sudden occurring wind peaks), and
the associated pipework.
2.3.1.3. Description of Main Layout
No specific layout provisions are necessary for the DWN [NABVS] system.
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2.3.1.4. Description of System I&C
Not applicable; the DWN [NABVS] system does not have any dedicated I&C.
The DWN [NABVS] fire dampers are however operated by the JDT [FDS] system dedicated I&C. The specific requirements arising from the JDT system dedicated I&C are described in the JDT [FDS] system chapter (see Sub-chapter 9.5, section 1.2).
The control of all functions and sub-functions of the DWN [NABVS] system are ensured by the Process Automation System (PAS). Only the position indications for the building isolation dampers at air intake and at main unit vent stack extraction are included in the Safety Automation System (SAS) (as these dampers are seismically classified as SC1).
2.3.2. Operation
2.3.2.1. System Normal Operation
The DWN [NABVS] system is used when the plant is in operation as well as during outage.
Plant Operation
The DWN [NABVS] system operates continuously. No air is recirculated because of the potential for the presence of airborne contamination in certain areas. A negative pressure is maintained automatically inside the HN [NAB] and HK [RB] buildings with respect to the outside.
The air supply rate is constant and distributed:
to the HN [NAB] building, and
to the HK [FB]) building.
When the air supply of the small-capacity system EBA [CSVS] of the HR [RB] building is open, the air supply rate increases.
The extraction serves:
the HN [NAB] building,
the HK [FB] building, and
the entire controlled area of the four HL [SB] buildings.
Two DWN [NABVS] supply fans and two DWN [NABVS] extraction fans operate during plant operation. The DWN [NABVS] fans flow rate is adjusted by variable speed drives with defined set points. A failure of a variable speed drive would lead to switch to the next available fan and variable speedAPPROVED drive. Plant Outages
During outages of the plant, the DWN [NABVS] supply and extraction systems provide the ventilation described above, simultaneously with a purging air supply in the HR [RB] building (provided by the high-capacity EBA [CSVS] and the low-capacity EBA [CSVS]), and extraction provided by high-capacity EBA [CSVS] in the HR [RB] building.
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When the equipment hatch is open, DWK [FBVS] dampers located on the supply/extraction system in the room in front of the equipment hatch are closed and supply/extraction is performed by the EBA [CSVS] system (see section 5).
When the two doors of the emergency airlock are open, the DWK [FBVS] damper located at the level of the air extraction from the emergency airlock is closed and extraction is performed by the EBA [CSVS] system.
Three DWN [NABVS] supply fans and three DWN [NABVS] extraction fans operate during plant outages. The DWN [NABVS] fans flow rate is adjusted by variable speed drives with defined set points. A failure of a variable speed drive would lead to switch to the next available fan and variable speed drive.
Presence of Iodine in the Rooms in the Nuclear Auxiliary Building, the Fuel Building or the Safeguard Building in Normal Operation.
In this situation, the air in the affected cells is processed by iodine adsorption units. A maximum of four cells can be switched automatically to iodine adsorption units but only three if the high- capacity EBA [CSVS] system is in use.
2.3.2.2. Steady State Operating Conditions
Use of the RIS [SIS] in the Safeguard Building in the Event of a Loss Of Coolant Accident (LOCA)
In this case, Safety Injection System (RIS [SIS]) leaks may lead to an iodine activity level that is incompatible with discharge through the iodine adsorption units in the DWN [NABVS] system. Discharge is thus performed using the DWL [CSBVS] system filters.
The DVL [SBVSE] normal air supply (see section 7 of this sub-chapter) and extraction (DWN [NABVS]) to/from the mechanical HL [SB] buildings controlled areas are automatically shut off.
2.3.2.3. System Transient Operation
Transient Start-up of Iodine Adsorption Units Line
In the event of iodine being released in the rooms of the HN [NAB] building, the HK [FB] building or the controlled areas of the HL [SB] buildings, and if the affected cell is not identified, extraction from the six cells is directed automatically to iodine adsorption units. This is achieved by start-up of two iodine extraction fans at full capacity and shutdown of one of the two operating extraction and air-supply fans.
In this configuration, extraction from all rooms is processed with iodine adsorption units. The air supply and extraction is operated at half capacity.
Multiple Failure in the Nuclear Auxiliary Building (HN [NAB]) and Effluent Treatment Building (HQ [ETB]) dueAPPROVED to an Earthquake
In the event of an earthquake, static confinement of the HN [NAB] building is achieved by closing the isolation dampers in the air supply lines and in the extraction lines so as to contain the radioactivity resulting from failure of the tanks containing radioactive substances in the HN [NAB] building or the formation of breaks in their connection lines.
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To ensure shutdown of the DWN general ventilation, the fans are tripped by a manual trip of the control voltage of their switchboards (via feeders located on switchboards in the HL [SB] buildings). This action will cause supply, exhaust and iodine fans to be tripped.
Fire in Iodine Adsorption Units
When a fire is detected, the operator is advised, the fire dampers located upstream and downstream of the iodine adsorption units (which are fire-resistant and designed to prevent smoke from spreading) are closed and the fan is automatically shut down. Furthermore, the iodine adsorption units of the DWN [NABVS] system are sprayed with water powered by the JPI [NIFPS] system.
Fire inside HN [NAB] Building
Automatic closure of the fire dampers protecting the fire zones is initiated on the activation of a signal from the JDT [FDS] system or passively through activation of a thermal fuse inside a fire damper. The DWN [NABVS] system continues to operate as normal but is limited to the area not affected by the fire.
Loss Of Offsite Power (LOOP)
The electrical convectors inside the boron rooms that ensure minimum room conditions during LOOP in winter and the fire dampers are supplied by the Emergency Diesel Generators (EDGs). However, the majority of DWN [NABVS] system components are not backed up by the EDGs in the event of a LOOP.
The isolation dampers close to their fail-safe position, thus ensuring the static containment of the HN [NAB] building.
The fire dampers are powered by the JDT [FDS] system cabinets, which are powered by emergency power supply and local { SCI removed } batteries (see Sub-chapter 9.5, section 1.2). The fire dampers are also equipped with thermal fuses, thus ensuring closure of the fire dampers in case of fire.
Station Black Out (SBO)
The DWN [NABVS] system is not backed up by the UDGs.
The isolation dampers close to their fail-safe closed position, thus ensuring the static containment of the HN [NAB] building.
The fire dampers are powered by the JDT [FDS] system cabinets, which are powered by emergency power supply and local { SCI removed } batteries (see Sub-chapter 9.5, section 1.2). The fire dampers are also equipped with thermal fuse, thus ensuring closure of the fire dampers in case of fire.
2.3.2.4. OtherAPPROVED Operating Conditions
2.3.2.4.1. Full or Partial System Failure
{ This section contains SCI-only text and has been removed }
2.3.2.4.2. Failures of Server Systems
{ This section contains SCI-only text and has been removed }
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2.3.2.4.3. Failures of Served systems
{ This section contains SCI-only text and has been removed }
2.4. PRELIMINARY DESIGN SUBSTANTIATION
2.4.1. Compliance with Safety Functional Requirements
2.4.1.1. Control of Fuel Reactivity
Not applicable: the DWN [NABVS] system does not directly contribute to the MSF of control of fuel reactivity.
2.4.1.2. Fuel Heat Removal
Not applicable: the DWN [NABVS]system does not directly contribute to the MSF of fuel heat removal.
2.4.1.3. Confinement of Radioactive Material
The DWN [NABVS] system ensures the containment of the radioactive material in normal operating conditions by:
using control dampers in order to control the negative pressure in the HN [NAB] building,
routing air transfers from the potentially less contaminated rooms to the potentially more contaminated rooms,
routing the exhaust air through the HEPA filters to the main unit vent stack, and
routing the exhaust air via iodine adsorption units to the main unit vent stack in case of iodine (or other hazardous gas) presence.
All DWN [NABVS] components whose mechanical failure could lead to minor release of radioactivity are mechanically classed M3/T3.
The studies of radiological consequences in Sub-chapter 15.4 involving the confinement function of the DWN [NABVS] system in the HN [NAB] building consider overall assumptions (fans operating and dampers open) compared with the assumptions related to static sealing of the HN [NAB] building defined in Sub-chapter 6.1, section 1.
2.4.1.4. Support Contribution to Main Safety Functions
The DWN [NABVS] sends a signal to the TEG [GWPS] system in the case of loss of DWN [NABVS] extraction in order to initiate isolation of the TEG [GWPS] system at the interface with the DWN [NABVS]APPROVED system. The DWN [NABVS] provides an atmospheric pressure reference to DWK [FBVS], DWL [CSBVS] and 9DWQ [ETBVS] system via its pressure reference pipework and its buffer tank.
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2.4.1.5. Specific Contribution to Hazards Protection
The hazard studies of PCSR Sub-chapter 13.1 involving functions of the DWN [NABVS] system use values for the following parameters that are in keeping with the design assumptions stated in section 2.2.2:
Internal fire:
o Containment and prevention of spread of fire:
. The contribution to the containment and prevention of spread of fire in the HN [NAB] building is ensured by closure of the fire dampers, by active (automation by the JDT [FDS] system) or ultimately passive (fusible device) means.
o Provision of water to the DWN [NABVS] iodine adsorption units in case of fire in the DWN [NABVS] iodine adsorption units:
. The water demand in terms of flow rate for the iodine adsorption units protection is covered by the Fire Fighting Water Supply System (JAC) pumps (see Sub-chapter 9.5, section 1.3.4.1.5.4).
Earthquake:
o The preservation of the MSF in the event of an earthquake is ensured by having SC2 classified components in order to preserve SC1 SFs following a seismic event.
External explosion:
o The HN [NAB] static containment is achieved following an external explosion event by closure of the DWN [NABVS] building containment dampers.
For each hazard study concerned, these studies show that the design of these functions is such that they meet the acceptance criteria.
These elements ensure that the SFRs stated in section 2.0.2 are met.
2.4.1.6. Other Safety Functions to be performed in the Preventive Line of Defence
Not applicable: the DWN [NABVS] system does not contribute to other safety functions to be performed in the preventive line of defence.
2.4.2. Compliance with Design Requirements The DWN [NABVS]APPROVED system complies with the requirements stated in sections 2.0.4 and 2.0.5, particularly with respect to those detailed in the following sections.
2.4.2.1. Requirements arising from Safety Classification
2.4.2.1.1. Safety Classification
The compliance of the design and manufacture of DWN [NABVS] system materials and equipment performing a safety-related function with requirements from the classification rules (see Sub-chapter 3.2, section 7) is presented in sections 2.4.2.4.1.
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2.4.2.1.2. Single Failure Criterion and Redundancy
Although not subject to the application of the SFC, the main supply line, the HEPA filter line, the iodine adsorption units line and the main exhaust of the DWN [NABVS] system have redundancy of availability, achieved through multiplication of significant active components such as fans and filter lines. In addition to that the main supply as well as the main exhaust fans are supplied by two different electrical trains and cross connected.
The DWN [NABVS] system is not subject to passive single failure.
2.4.2.1.3. Robustness against Loss of Power
The design of the DWN [NABVS] system complies with the emergency power supply requirement stated in section 2.0.4.1, in particular in respect of the following:
DWN [NABVS] building isolation dampers are equipped with a spring type closing mechanism to ensure that the HN [NAB] static containment is achieved following a seismic event.
The DWN [NABVS] fire dampers are powered by the JDT [FDS] system cabinets, which are powered by emergency power supply and local { SCI removed } batteries (see Sub-chapter 9.5, section 1.2.4.2.1.3). The fire dampers are also equipped with thermal fuse, thus ensuring closure of the fire dampers in case of fire.
Furthermore, while not subject to an emergency power supply requirement, the function “boron room” of the DWN [NABVS] system (i.e. the heating required to ensure the minimum temperature in the boron rooms) is provided with a backed-up power supply (EDGs) for the purposes of availability, in the form of an emergency electrical power supply connected to the EDGs.
2.4.2.1.4. Physical Separation
Not applicable; the DWN [NABVS] system is not subject to any requirements for physical separation.
2.4.2.2. System Protection against Hazards
2.4.2.2.1. Internal Hazards
The overall demonstration of the robustness of the plant to internal hazards is covered in Sub-chapter 13.2.
2.4.2.2.2. External Hazards
The overall demonstration of the robustness of the plant to external hazards is covered in Sub-chapter 13.1.APPROVED 2.4.2.3. Diversity
Not applicable: the DWN [NABVS] system is not subject to the requirement for diversity.
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2.4.2.4. Requirements defined at the Component Level
2.4.2.4.1. General Mechanical, Electrical and I&C Requirements
The components of the DWN [NABVS] system equipment performing a safety-related function comply with the general mechanical, electrical, and I&C requirements stated in section 2.0.5.1 as detailed in Section 9.4.2 – Table 3.
SECTION 9.4.2 – TABLE 3 : SAFETY CLASSIFICATION AND DESIGN REQUIREMENTS FOR DWN [NABVS] SYSTEM COMPONENTS
Safety classification Design requirements Mechanical requirement for pressure Highest Highest retaining Description safety safety Seismic Electrical I&C components or function class of requirement requirement requirement leaktightness category SFG requirement for HVAC component Air intake isolation C 3 T3 SC1 C3 C3 dampers Isolation dampers downstream of C 3 T3 SC1 C3 C3 the exhaust fans Pressure relief damper for C 3 T3 SC1 C3 C3 exhaust fans HEPA filtration and iodine C 3 T3 NR C3 C3 adsorption units line Exhaust fans C 3 T3 NR C3 C3 Iodine fans C 3 T3 NR C3 C3 Regulation of HN negative C 3 T3 NR C3 C3 pressure Pressure reference C 3 M3 NR NR NR pipework and buffer tank APPROVED Fire dampers at intervention fire C 3 NT NR C3 C3 compartment boundary
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Safety classification Design requirements Mechanical requirement for pressure Highest Highest retaining Description safety safety Seismic Electrical I&C components or function class of requirement requirement requirement leaktightness category SFG requirement for HVAC component Valves and pipes for provision of water to the C 3 M3 NR NR NR iodine adsorption units This table will be updated after the Safety Classification Component List (SCCLs) studies.
2.4.2.4.2. Seismic Requirements
The DWN [NABVS] system complies with the seismic qualification requirements listed in Section 9.4.2 – Table 3.
2.4.2.4.3. HIC Requirements
Not applicable: the DWN [NABVS] system is not subject to any HIC requirements.
2.4.2.4.4. Specific I&C Requirements
Not applicable: the DWN [NABVS] system does not have any dedicated I&C.
The DWN fire dampers are however operated by the JDT [FDS] system dedicated I&C. The specific requirements arising from the JDT [FDS] system dedicated I&C are described in the JDT [FDS] system chapter (see Sub-chapter 9.5, section 1.2).
2.4.3. Examination, Maintenance, In-service Inspection and Testing (EMIT)
2.4.3.1. Start-up Tests
The DWN [NABVS] system is subject to a start-up test programme in accordance with the procedures set out in Chapter 20 “Commissioning” serving to verify the fulfilment of the following safety functional requirements: closingAPPROVED of the building isolation dampers in the supply line and in the exhaust line, HN [NAB] building negative pressure,
efficiency of HEPA filters,
correct operation of the extraction fans,
controllability of the isolation dampers in the iodine adsorption units line and HEPA filter line,
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efficiency of the iodine adsorption units,
correct operation of the iodine adsorption units heaters, and
correct operation of the fire dampers.
2.4.3.2. In-Service Inspection
The following functions of the DWN [NABVS] system are monitored during normal operation by continuous monitoring:
monitoring of air supply temperatures in the main ventilation lines,
monitoring of the exhaust air for any traces of iodine on detection of which the system activates the iodine adsorption units line, and
monitoring of negative pressure in the controlled area of the HN [NAB] building to guarantee a dynamic containment.
The availability of these functions is therefore verified by continuous monitoring process.
2.4.3.3. Periodic Testing
The safety-classified parts of the DWN [NABVS] system are subject to periodic testing in accordance with the maintenance schedule in order to verify that the following SFRs are fulfilled:
closing of the building isolation dampers in the supply and exhaust line,
HN [NAB] building negative pressure,
efficiency of HEPA filters,
correct operation of the extraction fans,
controllability of the isolation dampers in the iodine adsorption units line and HEPA filter line,
efficiency of the iodine adsorption units, and
correct operation of the iodine adsorption units heaters.
2.4.3.4. Maintenance The DWN [NABVS]APPROVED system is subject to a maintenance programme: Generally, scheduled maintenance is carried out preferentially during periods when the EBA [CSVS] system is not in use (and therefore the overall DWN [NABVS] airflow is reduced);
The inspection and maintenance of supply and exhaust air fans can be performed during normal plant operation (4 x { SCI removed } during normal operation). Scheduled maintenance during plant outages is not possible, because only one supply fan and one exhaust fan remain for back-up (4 x { SCI removed } capacity during normal operation).
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2.5. FUNCTIONAL DIAGRAMS
The functional diagrams of the DWN [NABVS] system are shown in Section 9.4.2 – Figures 1 to 4. (for more details, see the detailed mechanical diagrams of the DWN [NABVS] system).
3. CONTAINMENT COOLING VENTILATION SYSTEM (EVR [CCVS])
The information reported in this section is, unless otherwise noted, consistent with the reference design, as referenced from Chapter 22.
3.0. SAFETY REQUIREMENTS
The UK EPR Safety Classification principles and the top-down functional approach are presented in Sub-chapter 3.2. These principles help to ensure that the plant is designed, manufactured, constructed, commissioned and operated so that the appropriate level of reliability and integrity is achieved for its Structures, Systems and Components (SSCs).
The Hinkley Point C (HPC) functional safety analyses and the application of these safety classification principle to the HPC reference design result in the identification of the safety requirements for all safety systems in accordance with the Safety Functional Requirements Notes (SFRNs) referenced from Sub-chapter 3.2.
This section summarises the outcomes of these safety analyses and specifies the safety requirements that apply to the design of the EVR [CCVS] system.
The requirements described in the present section are consistent with safety functions to which the EVR [CCVS] system contributes in Plant Condition Category (PCC) and Design Extension Conditions (DEC). Consistency with requirements inherited from the Design Basis Initiating Faults (DBIFs) should be checked when the list of DBIFs evolves (see Chapter 15).
3.0.1. Safety Functions
The three Main Safety Functions (MSFs) necessary to achieve the overall safety objective of protecting people and the environment from the harmful effects of ionising radiations are:
control of fuel reactivity,
fuel heat removal, and
confinement of radioactive material. These three MSFsAPPROVED must be achieved during: normal operating conditions (PCC-1), including duty functions, control of radioactive release during normal operating conditions, control of main plant parameters, fault initial conditions, Limiting Conditions of Operation (LCOs), limitations, monitoring functions, Probabilistic Safety Assessment (PSA) significant functions as part of the preventive line of defence;
fault conditions (PCC-2 to PCC-4, DEC-A and any equivalent DBIFs) and DEC-B; and
hazard conditions.
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3.0.1.1. Control of Fuel Reactivity
The EVR [CCVS] system does not directly contribute to the MSF of control of fuel reactivity.
3.0.1.2. Fuel Heat Removal
The EVR [CCVS] system does not directly contribute to the MSF of fuel heat removal.
3.0.1.3. Confinement of Radioactive Material
The EVR [CCVS] system must contribute to the achievement of the MSF of confinement of radioactive material as a frontline system as follows:
To contribute to the prevention of minor radioactive release in normal operation.
3.0.1.4. Support Contribution to Main Safety Functions
The EVR [CCVS] system does not indirectly contribute to the three MSFs.
3.0.1.5. Specific Contribution to Hazard Protection
The EVR [CCVS] system must contribute directly to the safety functions that are part of the facility’s hazards protection against the consequences of earthquake (see Sub-chapter 13.1, section 2) as follows:
Preservation of Seismic Requirement levels (SC1) Safety Features (SFs) availability following a seismic event.
Moreover, the EVR [CCVS] system must be protected against external hazards (see section 3.0.4.2).
3.0.1.6. Other Safety Functions to be Performed in the Preventive Line of Defence
The EVR [CCVS] system must contribute directly to the MSFs as a support system as follows:
to ventilate and cool the reactor pit in order to maintain the required temperature; and
to allow manual shutdown of reactor pit fans in the event of Severe Accident (SA).
3.0.2. Safety Functional Requirements
3.0.2.1. Control of Fuel Reactivity
Not applicable: the EVR [CCVS] system does not directly contribute to the MSF of control of fuel reactivity. APPROVED 3.0.2.2. Fuel Heat Removal
Not applicable: the EVR [CCVS] system does not directly contribute to the MSF of fuel heat removal.
3.0.2.3. Confinement of Radioactive Material
With respect to its contribution to the MSF of confinement of radioactive material, the EVR [CCVS] system must satisfy the following Safety Functional Requirements (SFRs):
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The concerned EVR [CCVS] system components must be designed to meet the mechanical requirements to avoid a mechanical failure.
3.0.2.4. Support Contribution to Main Safety Functions
Not applicable: the EVR [CCVS] system does not indirectly contribute to the three MSFs.
3.0.2.5. Specific Contribution to hazard Protection
With respect to its specific contribution to the safety functions that are part of the facility’s hazards protection, the EVR [CCVS] system must satisfy the following SFRs:
Ensuring the stability / integrity of the EVR [CCVS] system components to avoid damage to higher classified components and ensure that it does not adversely impact the availability of SC1 SFs following a seismic event.
3.0.2.6. Other Safety Functions to be Performed in the Preventive Line of Defence
With respect to its indirect contribution to the MSFs, the EVR [CCVS] system must satisfy the following SFRs:
The EVR [CCVS] system must ensure a temperature in the reactor pit below the maximum temperature required for mechanical resistance of vessel supports in Station Black Out (SBO) situations (DEC-A).
The EVR [CCVS] system must allow manual shutdown of reactor pit fans as precaution in DEC-B conditions in order to avoid additional dispersion of radioactive material throughout the equipment compartment.
Safety Case Commitment: The most restrictive event(s) to consider for the reactor pit ventilation requirement is under consolidation. An SBO event is considered as a decoupling value.
3.0.3. Safety Features and Instrumentation and Control (I&C) Actuation Modes
Section 9.4.3 – Table 2 presents the safety features of the EVR [CCVS] system according to the contributions identified in section 3.0.1 and the SFRNs referenced in Sub-chapter 3.2.
3.0.4. Classification and Architecture Requirements of Safety Features
3.0.4.1. Requirements arising from Safety Classification
Architecture requirements associated with SFs are essential for designing robust lines of defence consistent with their importance to nuclear safety (see Sub-chapter 3.2). Such requirements strengthenAPPROVED the system design against: single failure and associated consequences (Single Failure Criterion (SFC)) by requiring redundancy;
Loss Of Offsite Power (LOOP) by requiring a back-up power supply;
Station Black-Out (SBO) by requiring a power supply by the Ultimate Diesel Generators (UDGs);
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Common Cause Failures (CCFs) by requiring physical separation;
earthquake by defining seismic requirements; and
accident conditions by defining qualification requirements.
Section 9.4.3 – Table 2 presents the requirements arising from safety classification for the EVR [CCVS] system, according to the SFRNs referenced in Sub-chapter 3.2.
3.0.4.2. System Protection against Hazards
3.0.4.2.1. Internal Hazards
The EVR [CCVS] system is not required to be protected against internal hazards.
3.0.4.2.2. External Hazards
The safety features of the EVR [CCVS] system must be protected against external hazards if those hazards challenge the safety objectives, as defined in Sub-chapter 13.1.
3.0.4.3. Diversity
The EVR [CCVS] system is not subject to the requirement for diversity.
3.0.5. Requirements Defined at the Component Level
3.0.5.1. Generic Safety Requirements
3.0.5.1.1. General Mechanical, Electrical and I&C Requirements
The mechanical components within the EVR [CCVS] system must comply with the mechanical requirements in accordance with the rules laid out in Sub-chapter 3.2 section 7. The level of requirement is dependent upon whether or not it is a pressure retaining component, the safety class of the component, whether the component acts as an isolating device between interfacing SFs, and on the role of the component as a barrier to the potential release of radioactivity as a result of failure of the component.
The electrical and Instrumentation and Control (I&C) components in the EVR [CCVS] system must comply with the electrical and I&C requirements associated with their safety class, in accordance with the rules laid out in Sub-chapter 3.2.
3.0.5.1.2. Seismic Requirements
The level of seismic requirements to be applied to the EVR [CCVS] system components is related to the Safety Feature Group (SFG) to which the component belongs, and the consequencesAPPROVED on other classified components of its failure if it were not seismically qualified. The rules for defining the seismic requirements for a component are identified in Sub-chapter 3.2.
3.0.5.1.3. Qualification for Accident Conditions
The safety classified components of the EVR [CCVS] system must be qualified for the operating conditions in which they are required, as specified in Sub-chapter 3.6.
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3.0.5.2. Specific Safety Requirements
3.0.5.2.1. High Integrity Component (HIC) Requirements
The EVR [CCVS] system is not subject to any High Integrity Component (HIC) requirements.
3.0.5.2.2. Specific I&C Requirements
The EVR [CCVS] system is not subject to any specific I&C requirements; the EVR [CCVS] system does not have any dedicated I&C. The general approach for I&C systems is set out in Chapter 7.
3.0.6. Examination, Maintenance, (In-Service) Inspection and Testing (EMIT)
3.0.6.1. Start-up Tests
The EVR [CCVS] system must be designed to enable the performance of start-up tests to ensure the adequacy of its design and performance under conditions as representative as possible of the different operating configurations, and in particular its compliance with the SFRs assigned to it in section 3.0.2.
3.0.6.2. In-Service Inspection
The EVR [CCVS] system must be designed to enable surveillance under normal operation of the system characteristics necessary for the fulfilment of its safety-related tasks in order to ensure the performance of its components, and their availability under normal operation, or in the event of a fault or accident.
3.0.6.3. Periodic Testing
The safety classified components of the EVR [CCVS] system must be designed to enable the performance of periodic tests in accordance with the maintenance schedule.
3.0.6.4. Maintenance
The EVR [CCVS] system must be designed to enable the implementation of a maintenance schedule (see Sub-chapter 18.2).
3.1. ROLE OF THE SYSTEM
The EVR [CCVS] system performs the following functions (or tasks) under the different plant operating conditions for which it is required:
3.1.1. Normal Operating Conditions The EVR [CCVS]APPROVED system is divided into two separate sub-assemblies: a ventilation system for the service area (EVR [CCVS] system service area),
a ventilation system for the equipment compartment (EVR [CCVS] system equipment compartment).
3.1.1.1. EVR [CCVS] System Service Area
The functional role of the EVR [CCVS] system service area is as follows:
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to maintain ambient conditions acceptable for staff working in the Reactor Building (HR [RB]) service area; and
to maintain ambient conditions needed to ensure correct operation of instrumentation and equipment.
3.1.1.2. EVR [CCVS] System Equipment Compartment
The functional role of the EVR [CCVS] system equipment compartment is as follows:
to maintain the ambient conditions necessary to ensure correct operation of the equipment;
to ventilate and cool the control rod mechanisms;
to ventilate and cool the reactor pit; and
to prepare acceptable ambient conditions for staff working in the HR [RB] building equipment compartment during cold shutdown.
3.1.2. Fault and Hazard Operating Conditions
Under these conditions, the EVR [CCVS] system has two SFs:
the ventilation of the reactor pit during SBO, and
the shutdown of the reactor pit fans in DEC-B situations.
3.2. DESIGN BASIS
3.2.1. General Assumptions
The HR [RB] building ambient indoor conditions to be maintained during PCC-1 events with the unit in operation or at shutdown, are provided in Section 9.4.1 – Table 1.
3.2.2. Design Assumptions
3.2.2.1. Control of Fuel Reactivity
Not applicable: the EVR [CCVS] system does not directly contribute to the MSF of control of fuel reactivity.
3.2.2.2. Fuel Heat Removal Not applicable:APPROVED the EVR [CCVS] system does not directly contribute to the MSF of fuel heat removal.
3.2.2.3. Confinement of Radioactive Material
Not applicable: there are no quantitative safety related design assumptions associated with the EVR [CCVS] system.
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3.2.2.4. Support Contribution to Main Safety Functions
Not applicable: the EVR [CCVS] system does not indirectly contribute to the three MSFs.
3.2.2.5. Specific Contribution to Hazard Protection
Not applicable: there are no quantitative safety-related design assumptions associated with the EVR [CCVS] system.
3.2.2.6. Other Safety Functions to be Performed in the Preventive Line of Defence
Concerning Reactor Pit Cooling, the following design assumptions can be made :
assumption on reactor pit fans air flow rate: { SCI removed },
temperature increase of air when passing through reactor pit fans: { SCI removed },
mean temperature to be considered in equipment compartment during normal operation: { SCI removed },
downstream air temperature in the plenum: { SCI removed },
heat loads in the HR [RB] building in SBO: to be determined, and
temperatures in the HR [RB] building in SBO conditions: refer to Section 1 - Table 3.
Concerning Shutdown of Reactor Pit Fans, there are no quantitative safety related design assumptions associated with the EVR [CCVS] system.
Safety Case Commitment: The maximum temperature allowed in the reactor pit in the most restrictive event(s) is under consolidation. As a decoupling value, Section 1 – Table 3 is considered.
3.2.3. Other Assumptions
The EVR [CCVS] system is also subject to the following assumptions:
The EVR [CCVS] system design is consistent with RCC-M requirements as described in Sub-chapter 3.8, section 2.
3.2.4. Assumptions Associated with Extreme Situations Resulting from Beyond Design Basis Hazards
3.2.4.1. Assumptions Associated with Fukushima Provisions
The assumptionsAPPROVED associated with the Fukushima provisions of the EVR [CCVS] system are presented in Chapter 23. The main provision is:
"Shutdown of Reactor Pit Fans".
3.2.4.2. Assumptions Associated with non-Fukushima Provisions
The EVR [CCVS] system is not subject to assumptions associated with non-Fukushima provisions.
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3.3. SYSTEM DESCRIPTION AND OPERATION
3.3.1. Description
3.3.1.1. General System Description
The EVR [CCVS] system is divided into two separate sub-assemblies:
a ventilation system for the service area (EVR [CCVS] system service area); and
a ventilation system for the equipment compartment (EVR [CCVS] system equipment compartment).
3.3.1.2. Description of Main Equipment
The EVR [CCVS] system is composed of the main equipment items detailed in the following sections (see the functional diagram provided in section 3.5).
3.3.1.2.1. EVR [CCVS] system – service area
The EVR [CCVS] system service area operates in a closed circuit mode with local air- conditioning units. Each air-conditioning unit is equipped with a cooling coil connected to the Operational Chilled Water System (DER [OCWS]) and a fan that blows cold air into the zones to which staff access is provided for maintenance activities.
The system operates continuously and the air-conditioning capacity needed is provided by several units, serving the following:
operating floor and annular space,
penetration areas : Safety Injection System (RIS [SIS]) valves rooms and Steam Generator Blowdown System (APG [SGBS]) rooms, and
core instrumentation.
Two of the operating floor local air-conditioning units are connected by a duct to the HR [RB] building dome to avoid hot spots.
3.3.1.2.2. EVR [CCVS] system equipment compartment
The EVR [CCVS] system equipment compartment operates in a closed circuit only for the primary circuit component rooms and the adjacent rooms where the auxiliary systems containing radioactivity are located. Atmospheric contamination resulting from leaks from these systems is contained by this ventilation system. It comprises twoAPPROVED trains, each featuring:
two fans (2 x { SCI removed }) known as “main fans”,
two cooling coils (2 x { SCI removed }) supplied by the Component Cooling Water System (RRI [CCWS]),
two cooling coils (2 x { SCI removed }) supplied by the DER [OCWS] system, and
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two fans (2 x { SCI removed }) known as “reactor pit fans”.
This system operates continuously with two main fans and two pit reactor fans (one fan operating per train and the other as back-up).
Each train blows fresh air into a semi-circular concrete header located above the RIS [SIS] system valve room. Different branches are connected to the semi-circular header to provide the air supply in the various zones:
the four primary coolant pumps,
the four steam generators,
the Chemical and Volume Control System (RCV [CVCS]) rooms, and
the Nuclear Vent and Drain System (RPE [NVDS]) rooms,
the Emergency Feed Water System (ASG [EFWS]) rooms,
the reactor pit; the reactor pit is ventilated by two trains each associated with an air supply branch and equipped with two fans (2 x { SCI removed }).
Other air supplies are taken directly from the shaft upstream of the semi-circular header to supply the air to:
the Control Rod Drive Mechanism (CRDM) area,
the pressuriser area, and
the area under the steam generator compartment ceiling.
3.3.1.3. Description of Main Layout
The EVR [CCVS] system is located in the HR [RB] building.
3.3.1.4. Description of System I&C
Not applicable: the EVR [CCVS] system does not have any dedicated I&C.
3.3.2. OPERATION
3.3.2.1. System Normal Operation
3.3.2.1.1. Plant at power
3.3.2.1.1.1. APPROVEDEVR [CCVS] system – Service area
All local air-conditioning units operate continuously to maintain the specified environmental temperatures. In the instrumentation room, a back-up air-conditioning unit is available in the event of failure of the unit in operation.
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3.3.2.1.1.2. EVR [CCVS] system equipment compartment
On each of the two trains, a main fan and a reactor pit fan operate. The total air flow of the EVR [CCVS] system equipment compartment is { SCI removed }.
As the total volume of the equipment compartment is about { SCI removed }, a flowrate of { SCI removed } is equivalent to about { SCI removed }. This global value is given as an indication, as each room has a different flowrate.
The cooling coils are supplied by the RRI [CCWS] system. If the outlet temperature of the air supply fans reaches { SCI removed } the cooling coils supplied by the DER [OCWS] system are operated to cool the air. The condensates are drained by the RPE [NVDS] system.
3.3.2.1.2. Hot Shutdown
During hot shutdown, the EVR [CCVS] system operation is identical to that of plant at power.
3.3.2.1.3. Cold Shutdown
During cold shutdown, the HR [RB] building is ventilated by the Containment Sweep Ventilation System (EBA [CSVS]) (high and low capacity).
Fresh air is brought in by the EBA [CSVS] system in the service area of the HR [RB] building. The air then gets into the equipment compartment through the EVR [CCVS] system dampers in limit of the two zones and is distributed to all rooms by the fans and ducts of the EVR [CCVS] system equipment compartment.
3.3.2.1.4. Fuel Handling
Operation of the EVR [CCVS] system is not required during fuel handling.
3.3.2.1.5. Fault Conditions
The most restrictive event(s) to consider for the reactor pit ventilation requirement is under consolidation following the Safety Case commitment associated. The event linked to the fault conditions are likely able to evolve.
Partial or Total Loss of Cooling Water
When the RRI [SIS] and DER [OCWS] systems cooling coils are no longer available, the fans continue to operate to prevent hot spots and to provide pit cooling.
Loss of Primary Coolant Accident (LOCA) During and afterAPPROVED this type of accident, the EVR [CCVS] system is not required. Fuel handling accident in the Reactor Building
In the event of a fuel handling accident (although this is not a safety requirement) the EVR [CCVS] system can be used to remove heat released.
Loss Of Offsite Power (LOOP)
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In the event of a LOOP, only the fans associated with the reactor pit have power supplies that are backed up by the EDGs. This way reactor pit ventilation can be maintained in order to slow down the temperature rise in the reactor pit concrete.
Station Blackout (SBO)
In the event of a SBO, only the fans associated with the reactor pit have power supplies that are backed up by the UDGs. This way reactor pit ventilation can be maintained in order to slow down the temperature rise in the reactor pit concrete.
Staff access before / after shutdown
Access to the HR [RB] building is allowed when the reactor is in operation, for maintenance operations, between seven days before and three days after shutdown. In the accessible area, defined as part of the service area, the EVR [CCVS] system service area, maintains environmental conditions acceptable for staff. These conditions are given in Section 9.4.1 – Table 1.
Before and during staff access, fresh air is brought in by the EBA [CSVS] system low flow rate system, for purging purposes.
3.3.2.2. System Transient Operation
3.3.2.2.1. Full or Partial System Failure
Loss of Ventilation in the Equipment Compartment
To make sure that the system is fully available, each of the EVR [CCVS] system equipment compartment's two ventilation trains consists of two main fans (2 x { SCI removed } of the overall flow). So, in the event of fan loss, the other fan starts up automatically.
Loss of the Reactor Pit Ventilation
To make sure that the system is fully available, each of the reactor pit's two ventilation trains are equipped with two fans (2 x { SCI removed } of the overall flow). In the event of fan loss, the other fan starts up automatically.
Loss of the Service Area Ventilation
If this failure occurs when the air conditioning units are required to be operating, it causes loss of cooling and ventilation in the HR [RB] building's rooms that must be served. Consequently, the temperature in the service area will increase according to the temperature in its adjacent areas (outside and equipment compartment).
Impact on Served Systems
The CRDM andAPPROVED the ex-core flux instrumentation are located in the equipment compartment of the HR [RB] building and therefore cooled by the EVR [CCVS] system. Yet, the EVR [CCVS] system is not designed to support either the CRDM or the ex-core instrumentation although they are safety classified. These systems should be resistant to the high temperature reached during loss of the EVR [CCVS] system. The CRDM, for example is designed to sustain temperatures up to { SCI removed }.
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In addition, the instrumentation room located in the service area and cooled by the EVR [CCVS] system is equipped with two local cooling units (2 x 100%). In the event of loss of one Local Cooling Unit (LCU), the second is started up.
3.3.2.2.2. Failures of Systems in Interface (server or served)
3.3.2.2.2.1. Server System Failure
{ This section contains SCI only and has been removed }
3.3.2.2.2.2. { SCI Section Title Removed }
{ This section contains SCI-only text and has been removed }
3.4. PRELIMINARY DESIGN SUBSTANTIATION
The level of detail of evidence of compliance with the safety requirements stated in section 3.0 will develop as the HPC project moves from basic design into detailed design since PCSR3 sequence and system sequence are evolving in parallel. Therefore, the level of details presented in this section depends on the information available at the time of issuing the system chapters.
3.4.1. Compliance with Safety Functional Requirements
3.4.1.1. Control of Fuel Reactivity
Not applicable: the EVR [CCVS] system does not directly contribute to the MSF of control of fuel reactivity.
3.4.1.2. Fuel Heat Removal
Not applicable: the EVR [CCVS] system does not directly contribute to the MSF of fuel heat removal.
3.4.1.3. Confinement of Radioactive Material
The EVR [CCVS] system components which contribute to prevent minor radioactive release are designed with a sufficient mechanical requirement.
3.4.1.4. Support Contribution to Main Safety Functions
Not applicable: the EVR [CCVS] system does not indirectly contribute to the three MSFs.
3.4.1.5. Specific Contributions to Hazards Protection For each hazardAPPROVED study concerned, these studies show that the design of these functions is such that they meet the acceptance criteria.
Ensuring the stability or integrity of all components:
Qualification to keep the components stability or integrity.
These elements ensure that the safety functional requirements stated in section 3.0.2 are met.
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3.4.1.6. Other Safety Functions to be Performed in the Preventive Line of Defence
Other safety functions to be performed in the preventive line of defence involving the EVR [CCVS] system use values for the following parameters that are in keeping with the design assumptions stated in section 3.2.2:
The EVR [CCVS] system must ensure a temperature in the reactor pit below the maximum temperature required for mechanical resistance of vessel supports in SBO situations (DEC-A).
The EVR [CCVS] system must allow manual shutdown of reactor pit fans as precaution in DEC-B conditions in order to avoid additional dispersion of radioactive material throughout the equipment compartment.
3.4.2. Compliance with design requirements
The EVR [CCVS] system complies with the requirements stated in sections 3.0.4 and 3.0.5, particularly with respect to those detailed in the following sections.
3.4.2.1. Requirements arising from Safety Classification
3.4.2.1.1. Safety Classification
The compliance of the design and manufacture of the EVR [CCVS] system materials and equipment performing a safety related function with requirements from the classification rules (see Sub-chapter 3.2, section 7) is presented in section 3.4.2.4.1.
3.4.2.1.2. Single Failure Criterion and Redundancy
Not applicable: the EVR [CCVS] system is not subject to any SFC and redundancy requirements.
Furthermore, although the EVR [CCVS] system is not subject to the application of the SFC, the following redundancy is applied for functional reasons:
The reactor pit ventilation system comprises two trains each equipped with two 2 x { SCI removed } fans, making a global redundancy of 4 x { SCI removed }.
One of the fans in each EVR [CCVS] ventilation system train is supplied by a Division 1 electrical train and the other fan in each system is supplied by a Division 2 electrical train.
3.4.2.1.3. Robustness against Loss of Power
The design of the EVR [CCVS] system complies with the emergency power supply requirement stated in sectionAPPROVED 3.0.4.1, in particular in respect of the following: In the event of SBO, reactor pit fans are provided with a back-up power supply using UDGs. They are also backed up by Emergency Diesel Generators (EDGs).
Furthermore, while not subject to an emergency power supply requirement, the main fans of the EVR [CCVS] system are provided with a backed-up power supply for the purposes of availability, in the form of an emergency electrical power supply connected to the EDGs.
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3.4.2.1.4. Physical Separation
Not applicable: the EVR [CCVS] system is not subject to any requirements for physical separation.
3.4.2.2. System Protection against Hazards
3.4.2.2.1. Internal Hazards
Not applicable: the EVR [CCVS] system is not required to be protected against internal hazards.
3.4.2.2.2. External Hazards
The overall demonstration of the robustness of the plant to external hazards is covered in Sub-chapter 13.1.
3.4.2.3. Diversity
Not applicable: the EVR [CCVS] system is not subject to the requirement for diversity.
3.4.2.4. Requirements defined at the component level
3.4.2.4.1. Generic Mechanical, Electrical and I&C Requirements
The components of the EVR system performing a safety-related function must comply with the general mechanical, electrical and I&C with the associated requirements stated in section 3.0.5.1 as detailed in Section 9.4.3 – Table 1.
SECTION 9.4.3 - TABLE 1 : CLASSIFICATION OF MAIN MECHANICAL AND ELECTRICAL COMPONENTS ASSOCIATED TO THEIR SAFETY FEATURES
Safety classification Design requirements Mechanical requirement for Highest Highest pressure retaining Description safety safety Seismic Electrical I&C components or function class of requirement requirement requirement leaktightness category SFG requirement for HVAC component
Reactor pit C 3 NT SC1 C3 C3 fans
Associated C 3 NT SC1 - C3 SP- sensors Associated APPROVED components (N-R C 3 NT SC1 - - dampers, ducts, pipes) Valves, pipes, cooling coils C 3 M3 SC1 - - in interface with RRI
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Safety classification Design requirements Mechanical requirement for Highest Highest pressure retaining Description safety safety Seismic Electrical I&C components or function class of requirement requirement requirement leaktightness category SFG requirement for HVAC component Valves in interface with C 3 M3 SC1 - - RPE pipes for the main coils
All remaining components are seismic class SC2, but do not otherwise perform any safety- related function.
3.4.2.4.2. Seismic Requirements
The EVR [CCVS] system must comply with the seismic qualification requirements listed in Section 9.4.3 – Table 1.
3.4.2.4.3. HIC Requirements
Not applicable: the EVR [CCVS] system is not subject to any HIC requirements.
3.4.2.4.4. Specific I&C Requirements
Not applicable: the EVR [CCVS] system does not have any dedicated I&C.
3.4.3. Examination, Maintenance, (In-Service) Inspection and Testing (EMIT)
3.4.3.1. Start-up Tests
The EVR [CCVS] system is subject to a start-up test programme in accordance with the procedures set out in Chapter 20 serving to verify the fulfilment of the following SFRs:
The EVR [CCVS] system must ensure a temperature in the reactor pit below the maximum temperature required.
The EVR [CCVS] system must allow manual shutdown of reactor pit fans.
3.4.3.2. In-Service Inspection
The following function of the EVR [CCVS] system is used during normal plant operation under conditions representativeAPPROVED of the fault conditions in which it is required:
"Reactor pit cooling".
The availability of this function is therefore verified as part of normal operation.
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3.4.3.3. Periodic Testing
The safety classified components of the EVR [CCVS] system are subject to periodic testing in accordance with the maintenance schedule in order to verify that the following SFRs are fulfilled:
Shutdown of reactor pit fans.
3.4.3.4. Maintenance
The EVR [CCVS] system is subject to a maintenance programme.
Maintenance of the EVR [CCVS] system circuit is carried out during plant shutdown, when it is possible to access the entire HR [RB] building and when ambient conditions in the HR [RB] building are guaranteed by the EBA [CSVS] system..
3.5. FUNCTIONAL DIAGRAM
The functional diagrams of the EVR [CCVS] system are shown in Section 9.4.3 – Figure 1 for the general diagram of the HR [RB] building ventilation; Section 9.4.3 – Figure 2 for Equipment compartment and; Section 9.4.3 – Figure 3 for Service Area (for more details, see the detailed mechanical diagram of the EVR [CCVS] system).
4. REACTOR BUILDING INTERNAL FILTRATION SYSTEM (EVF)
The information reported in this section is, unless otherwise noted, consistent with the reference design, as referenced from Chapter 22.
4.0. SAFETY REQUIREMENTS
The UK EPR Safety Classification principles and the top-down functional approach are presented in Sub-chapter 3.2. These principles help to ensure that the plant is designed, manufactured, constructed, commissioned and operated so that the appropriate level of reliability and integrity is achieved for its Structures, Systems and Components (SSCs).
The Hinkley Point C (HPC) functional safety analyses and the application of these safety classification principles to the HPC reference design, result in the identification of the safety requirements for all safety systems in accordance with the Safety Functional Requirement Notes (SFRNs) referenced from Sub-chapter 3.2.
This section summarises the results of these safety analyses and specifies the safety requirements that apply to the design of the EVF system. The requirementsAPPROVED described in the present section are consistent with safety functions to which the EVF system contributes in Plant Condition Category (PCC) and Design Extension Conditions (DEC). Consistency with requirements inherited from the Design Basis Initiating Faults (DBIFs) should be checked when the list of DBIFs evolves (see Chapter 15).
4.0.1. Safety Functions
The three Main Safety Functions (MSFs) necessary to achieve the overall safety objective of protecting people and the environment from the harmful effects of ionising radiation are:
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control of fuel reactivity,
fuel heat removal, and
confinement of radioactive material.
These three MSFs must be achieved during:
normal operating conditions (PCC-1), including duty functions, control of radioactive release during normal operating conditions, control of main plant parameters, fault initial conditions, Limiting Conditions of Operation (LCOs), limitations, monitoring functions, Probabilistic Safety Assessment (PSA) significant functions as part of the preventive line of defence,
fault conditions (PCC-2 to PCC-4, DEC-A and any equivalent DBIFs) and DEC-B, and
hazard conditions.
4.0.1.1. Control of Fuel Reactivity
The EVF system does not directly contribute to the MSF of control of fuel reactivity.
4.0.1.2. Fuel Heat Removal
The EVF system does not directly contribute to the MSF of fuel heat removal.
4.0.1.3. Confinement of Radioactive Material
The EVF system does not directly contribute to the MSF of confinement of radioactive material.
4.0.1.4. Support Contribution to Main Safety Functions
The EVF system does not indirectly contribute to the three MSFs.
4.0.1.5. Specific Contribution to Hazards Protection
The EVF system must contribute directly to the safety functions that are part of the facility's hazards protection against the consequences of an earthquake (see Sub-chapter 13.1, section 2) or a fire (see Sub-chapter 13.2, section 7) as follows:
Preservation of Seismic Requirement levels (SC1) Safety Features (SFs) availability following a seismic event.
The system fire dampers reduce the risk of fire propagation through the Reactor Building (HR [RB]).APPROVED 4.0.1.6. Other Safety Functions to be performed in the Preventive Line of Defence
The EVF system does not contribute to other safety functions to be performed in the preventive line of defence.
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4.0.2. Safety Functional Requirements
4.0.2.1. Control of Fuel Reactivity
Not applicable: the EVF system does not directly contribute to the MSF of control of fuel reactivity.
4.0.2.2. Fuel Heat Removal
Not applicable: the EVF system does not directly contribute to the MSF of fuel heat removal.
4.0.2.3. Confinement of Radioactive Material
Not applicable: the EVF system does not directly contribute to the MSF of confinement of radioactive material.
4.0.2.4. Support Contribution to Main Safety Functions
Not applicable: the EVF system does not indirectly contribute to the three MSFs.
4.0.2.5. Specific Contribution to Hazards Protection
With respect to its specific contribution to the safety functions that are part of the facility’s hazards protection, the EVF system must satisfy the following Safety Functional Requirements (SFRs):
Protection of SC1 classified components in case of earthquake:
o Ensuring the stability of all components to avoid damage to higher classified components and ensure that it does not adversely impact the availability of SC1 SFs following a seismic event.
Fire compartmentation:
o Reduce the risk of fire from spreading in the HR [RB] building.
4.0.2.6. Other Safety Functions to be performed in the Preventive Line of Defence
Not applicable: the EVF system does not contribute to other safety functions to be performed in the preventive line of defence.
4.0.3. Safety Features and I&C Actuation Modes
Section 9.4.4 – Table 2 presents the SFs of the EVF system according to the contributions identified in sectionAPPROVED 4.0.1 and the SFRNs referenced in Sub-chapter 3.2. 4.0.4. Classification and Architecture Requirements of Safety Features
4.0.4.1. Requirements Arising from Safety Classification
Architecture requirements associated with safety features are essential for designing robust lines of defence consistent with their importance to nuclear safety as described in Sub-chapter 3.2, section 7. Such requirements strengthen the system design against:
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single faults and associated consequences (Single Failure Criterion (SFC)) by requiring redundancy,
Loss Of Off-site Power (LOOP) by requiring, among others, a back-up power supply,
Station Black-Out (SBO) by requiring a power supply by the Ultimate Diesel Generators (UDGs),
Common Cause Failures (CCF) by requiring physical separation,
earthquake by defining seismic requirements, and
accident conditions by defining qualification requirements.
Section 9.4.4 – Table 2 presents the requirements arising from safety classification for the EVF system, according to the SFRNs referenced in Sub-chapter 3.2.
4.0.4.2. System Protection against Hazards
4.0.4.2.1. Internal Hazards
The EVF system is not required to be protected against internal hazards.
4.0.4.2.2. External Hazards
The EVF system is not required to be protected against external hazards.
4.0.4.3. Diversity
The EVF system is not subject to the requirement for diversity.
4.0.5. Requirements Defined at the Component Level
4.0.5.1. Generic Safety Requirements
4.0.5.1.1. General Mechanical, Electrical and Instrumentation & Control (I&C) Requirements
The mechanical components within the EVF system must comply with the mechanical requirements in accordance with the rules laid out in Sub-chapter 3.2, section 7. The level of requirement is dependent upon whether or not it is a pressure retaining component, the safety class of the component, whether the component acts as an isolating device between interfacing SFs, and on the role of the component as a barrier to the potential release of radioactivity as a result of failure of the component. The electricalAPPROVED and Instrumentation and Control (I&C) components in the EVF system must comply with the electrical and I&C requirements associated with their safety class, in accordance with the rules laid out in Sub-chapter 3.2.
4.0.5.1.2. Seismic Requirements
The level of seismic requirements to be applied to the EVF system components is related to the safety feature group to which the component belongs, and the consequences on other classified components of its failure if it were not seismically qualified. The rules for defining the seismic requirements for a component are identified in Sub-chapter 3.2.
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4.0.5.1.3. Qualification for Accident Conditions
The safety classified parts of the EVF system must be qualified for the operating condition in which they are required, as specified in Sub-chapter 3.6.
4.0.5.2. Specific Safety Requirements
4.0.5.2.1. High Integrity Component (HIC) Requirements
The EVF system is not subject to any High Integrity Component (HIC) requirements.
4.0.5.2.2. Specific I&C Requirements
The EVF system does not have any safety classified dedicated I&C.
However, the EVF system fire dampers are operated by the Fire Detection System (JDT [FDS]) dedicated I&C.
The specific requirements arising from the JDT [FDS] system dedicated I&C are described in the JDT [FDS] system chapter (see Sub-chapter 9.5, section 1.2).
The general approach for I&C systems is set out in Chapter 7.
4.0.6. Examination, Maintenance, (In-Service) Inspection and Testing (EMIT)
4.0.6.1. Start-Up Tests
The EVF system must be designed to enable the performance of start-up tests to ensure the adequacy of its design and performance under conditions as representative as possible of the different operating configurations, and in particular its compliance with the SFRs assigned to it in section 4.0.2.
4.0.6.2. In-Service Inspection
Not applicable.
4.0.6.3. Periodic Testing
The safety classified parts of the EVF system must be designed to enable the performance of periodic tests in accordance with the maintenance schedule.
4.0.6.4. Maintenance
The EVF system must be designed to enable the implementation of a maintenance schedule (see Sub-chapterAPPROVED 18.2). 4.1. ROLE OF THE SYSTEM
The EVF system performs the functions (or tasks) under the different plant operating conditions for which it is required detailed in the following sections.
4.1.1. Normal Operating Conditions
The EVF system operates during normal operation of the plant, in order to:
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reduce the concentration of radioactive iodine and aerosols in the HR [RB] building, and
maintain dynamic containment between the service area and the equipment compartment when there is no access to the HR [RB] building.
In the two-room concept, the equipment compartment and service area (that constitute the HR [RB] building), are physically separated during normal plant operation.
4.1.1.1. Cold Shutdown
The internal filtration system is not required at cold shutdown.
4.1.1.2. Fuel Handling
The internal filtration system is not required during fuel handling.
4.1.2. Fault and Hazard Operating Conditions
The EVF system is not required to operate under fault and hazard conditions.
In the event of a fire, the EVF system fire dampers reduce the risk of fire propagation in the HR [RB] building by isolating the system.
4.2. DESIGN BASIS
4.2.1. General Assumptions
There are no general assumptions linked to the safety role of the EVF system.
4.2.2. Design Assumptions
4.2.2.1. Control of Fuel Reactivity
Not applicable: the EVF system does not directly contribute to the MSF of control of fuel reactivity.
4.2.2.2. Fuel Heat Removal
Not applicable: the EVF system does not directly contribute to the MSF of fuel heat removal.
4.2.2.3. Confinement of Radioactive Material
Not applicable: the EVF system does not directly contribute to the MSF of confinement of radioactive material.
4.2.2.4. SupportAPPROVED Contribution to Main Safety Functions
Not applicable: the EVF system does not indirectly contribute to the three MSFs.
4.2.2.5. Specific Contribution to Hazards Protection
Not applicable: there are no quantitative safety-related design assumptions associated with the EVF system.
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4.2.2.6. Other Safety Functions to be performed in the Preventive Line of Defence
Not applicable: the EVF system does not contribute to other safety functions to be performed in the preventive line of defence.
4.2.3. Other Assumptions
The EVF system is also subject to the following assumptions:
The EVF system design is consistent with RCC-M requirements as described in Sub-chapter 3.8, section 5.
The EVF system design is consistent with fire requirements as described in Sub-chapter 3.8, section 2.
The minimum ventilation flow rate is { SCI removed } which is taken from the Containment Cooling Ventilation System (EVR [CCVS]) used for equipment compartment mixing (see section 3 for further details on EVR [CCVS] system).
4.2.4. Assumptions Associated with Extreme Situations Resulting from Beyond Design-Basis Hazards
4.2.4.1. Assumptions Associated with Fukushima Provisions
The EVF system is not subject to assumptions associated with Fukushima provisions.
4.2.4.2. Assumptions Associated with non-Fukushima Provisions
The EVF system is not subject to assumptions associated with non-Fukushima provisions.
4.3. SYSTEM DESCRIPTION AND OPERATION
4.3.1. Description
4.3.1.1. General System Description
The EVF system is located in the HR [RB] building in the service area. Air is extracted from the EVR [CCVS] system and is mainly discharged into the equipment compartment. Part of the air is discharged into the service area to ensure dynamic containment.
4.3.1.2. Description of Main Equipment
The EVF system is comprised of the following main equipment items (see the functional diagram provided in section 4.5):
A 1 x APPROVED100% extract ductwork system, which extracts air from the equipment compartment, consisting of a motorised isolation damper.
Two fire dampers in series at the inlet of the supply line, to help reduce the risk of fire propagation through the HR [RB] building.
1 x 100% filtration train consisting of an electrical heater, a pre-filter, a High Efficiency Particulate Air (HEPA) filter and an iodine adsorption unit. Each component is installed in an airtight metallic housing.
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2 x 100% fan trains, downstream of the filtration train.
A single duct with a motorised damper blowing filtered air into the equipment compartment.
A single duct with a motorised regulating damper blowing filtered air into the service area and with a motorised isolation damper.
Two fire dampers in series at the exit of each exhaust line, to reduce the risk of fire propagation through the HR [RB] building.
4.3.1.3. Description of Main Layout
The EVF system is located in the HR [RB] building in the service area. Air is extracted from the EVR [CCVS] system exhaust plenum and is mainly discharged into the equipment compartment. Part of the air may be discharged into the service area to ensure dynamic containment.
4.3.1.4. Description of System I&C
The JDT [FDS] system dedicated I&C used for the EVF system fire dampers is described in the JDT [FDS] system chapter (see Sub-chapter 9.5, section 1.2).
4.3.2. Operation
4.3.2.1. System Normal Operation
In the two-room concept, the equipment compartment and service area (that constitute the HR [RB] building), are physically separated during normal plant operation.
Plant at Power:
When the plant is at power, the internal filtration system operates continuously and ensures the dynamic containment of the equipment compartment. The air flow is { SCI removed }. The air is extracted from the equipment compartment and filtered by a pre-filter, a HEPA filter and an iodine adsorption unit.
Part of the flow is diverted to the service area so that the equipment compartment is at negative pressure relative to the service area. The air flow to maintain this dynamic containment is controlled by the differential pressure required between the two zones. The damper ({ SCI removed }), located on the duct that allows air to be injected into the service area, controls the DP between the two zones.
The remainder of the flow is used to purge the equipment compartment in recirculation mode. Hot Shutdown:APPROVED During hot shutdown, the EVF system operation is identical to that of plant at power.
Cold Shutdown:
During outages and cold shutdown, the EVF system is not required. In these conditions, the ventilation is provided by the Containment Sweep Ventilation System (EBA [CSVS]) (see section 5).
Fuel Handling:
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The internal filtration system is not required during fuel handling.
Steady State Operating Conditions:
The EVF system is in steady state during normal plant operation and plant hot shutdown. During plant cold shutdown and faults, the EVF system does not operate.
4.3.2.2. System Transient Operation
4.3.2.2.1. Full or Partial System Failure
{ This section contains SCI-only text and has been removed }
4.3.2.2.2. Failure of Systems in Interface (Server or Served)
The systems that have a direct impact on EVF operations are the following:
The JDT [FDS] system loss has no direct impact on the EVF system operation but affects fire management. The JDT [FDS] system failure prevents fire detection and activation of the fire protection. In this case the fire dampers are closed by the thermal fuse.
The JPI [NIFPS] system is used to spray water in the iodine adsorption unit in case of fire. In case of JPI failure, no water spray is ensured in the iodine adsorption unit.
4.4. PRELIMINARY DESIGN SUBSTANTIATION
The level of detail of evidence of compliance with the safety requirements stated in section 0 will develop as the HPC project moves from basic design into detailed design since PCSR3 sequence and system sequence are evolving in parallel. Therefore, the level of details presented in this section depends on the information available at the time of issuing the system chapters.
4.4.1. Compliance with Safety Functional Requirements
4.4.1.1. Control of Fuel Reactivity
Not applicable: the EVF system does not directly contribute to the MSF of control of fuel reactivity.
4.4.1.2. Fuel Heat Removal
Not applicable: the EVF system does not directly contribute to the MSF of fuel heat removal. 4.4.1.3. ConfinementAPPROVED of Radioactive Material Not applicable: the EVF system does not directly contribute to the MSF of confinement of radioactive material.
4.4.1.4. Support Contribution to Main Safety Functions
Not applicable: the EVF system does not indirectly contribute to the three MSFs.
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4.4.1.5. Specific Contributions to Hazards Protection
Fire compartmentation:
Contribution to the containment and prevention of a fire in the HR [RB] building and the Fuel Building (HK [FB]) by the closure of fire dampers:
Fire damper qualification, and
Fire damper closure.
The fire hazard studies of Sub-chapter 13.2, section 7, will demonstrate that the design of the EVF system (fire dampers) contributes to protection against the spread of fire through the HR [RB] building.
Protection of SC1 Classified Components in Case of Earthquake:
Ensuring the stability of all components:
Qualification to keep the components stability.
The earthquake hazard studies of Sub-chapter 13.1, section 2, will demonstrate that the design and installation provisions applied to all concerned components in the HR [RB] building prevent consequences of earthquake by associating a sufficient seismic requirement in accordance with Sub-chapter 3.2, section 7.
For each hazard study concerned, these studies show that the design of these functions is such that they meet the acceptance criteria.
These elements ensure that the safety functional requirements stated in section 4.0.2 are met.
4.4.1.6. Other Safety Functions to be performed in the Preventive Line of Defence
Not applicable: the EVF system does not contribute to other safety functions to be performed in the preventive line of defence.
4.4.2. Compliance with Design Requirements
The EVF system complies with the requirements stated in sections 4.0.4 and 4.0.5, particularly with respect to those detailed in the following sections.
4.4.2.1. Requirements arising from Safety Classification
4.4.2.1.1. Safety Classification The complianceAPPROVED of the design and manufacture of the EVF system materials and equipment performing a safety-related function with requirements from the classification rules (see Sub-chapter 3.2, section 7) is presented in section 4.4.2.4.1.
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4.4.2.1.2. Single Failure Criterion and Redundancy
Active Single Failure
The design of the EVF system meets the requirements of the active SFC stated in section 4.0.4.1, in particular in respect to the fire dampers. These are placed in series, with two dampers at each of the inlet and outlets of the system.
Furthermore, although not subject to the application of the SFC, the air extraction of the EVF system has redundancy of operation, achieved through duplication of the fan train.
Passive Single Failure
The EVF system safety feature that is required to be robust against passive single failure is the safety fire compartmentation feature. Single failure has been applied to fire dampers and redundancy is adequately ensured. Thus, it is considered that passive single failure is covered by the active single failure on fire dampers, already taken into account in the design.
4.4.2.1.3. Robustness against Loss of Power
The design of the EVF system complies with the emergency power supply requirement stated in section 4.0.4.1, in particular in respect of the following.
Loss of Offsite Power (LOOP)
Active components contributing to firefighting are required to be robust against LOOP. This requirement is met:
by an uninterruptible power supply and a passive closure by thermal fuse (fail-safe design) for the fire dampers, and
by an uninterruptible power supply for the motorised valve ensuring water supply by the JPI [NIFPS] system.
Station Black Out (SBO)
Not applicable: the EVF system is not subject to any requirements for robustness against SBO.
4.4.2.1.4. Physical Separation
The two fire dampers in series at the inlet and the outlets of the EVF system are physically separated by virtue of their installation.
4.4.2.2. System Protection against Hazards 4.4.2.2.1. InternalAPPROVED Hazards Not applicable: the EVF system is not required to be protected against internal hazards.
4.4.2.2.2. External Hazards
Not applicable: the EVF system is not required to be protected against external hazards.
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4.4.2.3. Diversity
Not applicable: the EVF system is not subject to the requirement for diversity.
4.4.2.4. Requirements Defined at the Component Level
4.4.2.4.1. General Mechanical, Electrical and I&C Requirements
The components of the EVF system equipment performing a safety-related function comply with the general mechanical, electrical, and I&C requirements stated in section 4.0.5.1 as detailed in Section 9.4.4 – Table 1.
SECTION 9.4.4 – TABLE 1 : CLASSIFICATION OF MAIN MECHANICAL AND ELECTRICAL COMPONENTS ASSOCIATED TO THEIR SAFETY FEATURES
Safety Design requirements classification Mechanical requirement for Highest Highest Description pressure retaining safety safety Seismic Electrical I&C components or function class of requirement requirement requirement leak-tightness category SFG requirement for HVAC component Fire dampers A 1 NT SC1 C3 C3 Sensor involved in C 3 NR SC1 - C3 fire protection Pipe/valve connected to C 3 NR SC1 C3 C3 JPI system
All remaining main components are seismic class SC2, but do not otherwise perform any safety- related function.
4.4.2.4.2. Seismic Requirements
The EVF system complies with the seismic qualification requirements listed in Section 9.4.4 – Table 1.
4.4.2.4.3. HIC Requirements Not applicable:APPROVED the EVF system is not subject to any HIC requirements. 4.4.2.4.4. Specific I&C Requirements
Not applicable: the EVF system does not have any dedicated I&C.
The demonstration of the compliance with the specific I&C requirements stated in section 4.0.5.2.2 is provided in the JDT [FDS] system chapter (see Sub-chapter 9.5, section 1.2).
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4.4.3. Examination, Maintenance, (In-Service) Inspection and Testing (EMIT)
4.4.3.1. Start-Up Tests
The EVF system is subject to a start-up test programme in accordance with the procedures set out in Chapter 20 serving to verify the fulfilment of the following SFRs:
The EVF system fire dampers inhibit fire from spreading in the HR [RB] building.
4.4.3.2. In-Service Inspection
Not applicable: The EVF system is not subject to in-service inspection.
4.4.3.3. Periodic Testing
The safety classified parts of the EVF system are subject to periodic testing in accordance with the maintenance schedule in order to verify that the following SFRs:
The system fire dampers inhibit fire from spreading in the HR [RB] building.
4.4.3.4. Maintenance
The EVF system is subject to a maintenance programme. Maintenance can be performed during plant outages and during the cold shutdown phase, when the EVF system is not required.
4.5. FUNCTIONAL DIAGRAM
The functional diagram of the EVF system is shown in Section 9.4.4 – Figure 1 (for more details, see the detailed mechanical diagram of the EVF system).
5. CONTAINMENT SWEEP VENTILATION SYSTEM (EBA [CSVS])
The information reported in this section is, unless otherwise noted, consistent with the reference design, as referenced from Chapter 22.
5.0. SAFETY REQUIREMENTS
The UK EPR Safety Classification principles and the top-down functional approach are presented in Sub-chapter 3.2. These principles help to ensure that the plant is designed, manufactured, constructed, commissioned and operated so that the appropriate level of reliability and integrity is achieved for its Structures, Systems and Components (SSCs). The Hinkley PointAPPROVED C (HPC) functional safety analyses and the application of these safety classification principles to the HPC reference design result in the identification of the safety requirements for all safety systems in accordance with the Safety Functional Requirement Notes (SFRNs) referenced from Sub-chapter 3.2.
This section summarises the results of these safety analyses and specifies the safety requirements that apply to the design of the EBA [CSVS] system.
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The requirements described in the present section are consistent with safety functions to which the EBA [CSVS] system contributes in Plant Condition Category (PCC) and Design Extension Conditions (DEC). Consistency with requirements inherited from the Design Basis Initiating Faults (DBIFs) should be checked when the list of DBIFs evolves (see Chapter 15).
5.0.1. Safety Functions
The three Main Safety Functions (MSFs) necessary to achieve the overall safety objective of protecting people and the environment from the harmful effects of ionising radiations are:
control of fuel reactivity,
fuel heat removal, and
confinement of radioactive material.
These three main safety functions must be achieved during:
normal operating conditions (PCC-1), including duty functions, control of radioactive release during normal operating conditions, control of main plant parameters, fault initial conditions, Limiting Conditions of Operation (LCOs), limitations, monitoring functions, Probabilistic Safety Assessment (PSA) significant functions as part of the preventive line of defence,
fault conditions (PCC-2 to PCC-4, DEC-A and any equivalent DBIFs) and DEC-B, and
hazard conditions.
5.0.1.1. Control of Fuel Reactivity
The EBA [CSVS] system does not directly contribute to the MSF of control of fuel reactivity.
5.0.1.2. Fuel Heat Removal
The EBA [CSVS] system does not directly contribute to the MSF of fuel heat removal.
5.0.1.3. Confinement of Radioactive Material
The EBA [CSVS] system must contribute to the achievement of the MSF of confinement of radioactive material as a frontline system as follows:
Third containment barrier:
Case 1: The EBA [CSVS] system must ensure the confinement of this radioactive material in PCC-3, PCC-4, DEC-A and DEC-B situations resulting in a release of radioactAPPROVEDive material in the Reactor Building (HR [RB]) during plant operation; o Static confinement of the HR [RB] building by closure of the containment isolation valves.
o Dynamic confinement of the Fuel Building (HK [FB]) by the EBA [CSVS] system low-capacity iodine filtration trains.
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Case 2: The EBA [CSVS] system must ensure the confinement of radioactive material in PCC-3 and PCC-4 situations resulting in a release of radioactive material into the HR [RB] building during State E with the equipment hatch open. In this configuration, the room in front of the equipment hatch is considered as an extension of the HR [RB] building.
Dynamic confinement of the HR [RB] building ensures air transfer from the HK [FB] building to the HR [RB] building via the EBA [CSVS] system iodine filtration trains. It prevents air transfer from the HR [RB] building to the HK [FB] building.
Under accident conditions, the EBA [CSVS] system must act as a third containment barrier at its containment penetration points. The part of EBA [CSVS] system outside the HR [RB] building (EBA [CSVS] system low-capacity ducts between containment penetrations and iodine adsorption units) must act as an extension of the third containment barrier.
Environmental protection:
The EBA [CSVS] system carries gaseous fluids containing radioactive material. As such, it must contribute:
o to the confinement of this material with respect to the environment as a whole and the public; and
o to the control and reduction of radioactive waste discharges under normal operation.
5.0.1.4. Support Contribution to Main Safety Function
The EBA [CSVS] system contributes indirectly to the MSF of confinement of radioactive material as a support system by:
ensuring the EBA [CSVS] system iodine trains robustness to irradiation in the short, mid and long-term and maintain the accessibility of the EBA [CSVS] system iodine train rooms in the long-term for the maintenance of the EBA [CSVS] system components.
5.0.1.5. Specific Contribution to Hazards Protection
The EBA [CSVS] system must contribute directly to the safety functions that are part of the facility's hazards protection against the consequences of fire (see Sub-chapter 13.2, section 7) and earthquake (see Sub-chapter 13.1, section 2) as follows:
Contribution to the containment and prevention of spread of a fire in the HK [FB] or HR [RB] buildings. PreservationAPPROVED of SC1 Safety Features (SFs) availability following a seismic event. Moreover, the EBA [CSVS] system must be protected against internal and external hazards (see section 5.0.4.2).
5.0.1.6. Other Safety Functions to be performed in the Preventive Line of Defence
The EBA [CSVS] system must contribute to other safety functions to be performed in the preventive line of defence as follows:
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prevent the loss of an iodine filtration train; and
avoid the loss of an iodine filtration train because of clogged filters in Severe Accident (SA).
5.0.2. Safety Functional Requirements
5.0.2.1. Control of Fuel Reactivity
Not applicable: the EBA [CSVS] system does not directly contribute to the MSF of control of fuel reactivity.
5.0.2.2. Fuel Heat Removal
Not applicable: the EBA [CSVS] system does not directly contribute to the MSF of fuel heat removal.
5.0.2.3. Confinement of Radioactive Material
With respect to its contribution to the MSF of confinement of radioactive material, the EBA [CSVS] system must satisfy the following Safety Functional Requirements (SFRs):
Third containment barrier:
Under accident conditions, the EBA [CSVS] system must enable the isolation of the containment at its containment penetration points.
Under fault conditions, the parts of the EBA [CSVS] system forming extensions of the third containment barrier must act as a containment barrier for the fluid conveyed.
For each direct contribution (i.e. non-support functions) of the system stated in section 5.0.1.3 the main functional requirement of the EBA [CSVS] system is to limit radiological consequences:
Case 1: If an event leading to release of activity in the HR [RB] building (PCC-3, PCC-4, DEC-A, DEC-B) or if a more general increase in radioactivity occurs:
o Static confinement of the HR [RB] building:
. the entirety of the HR [RB] building must be isolated by closure of the containment isolation valves.
o Dynamic confinement of the HK [FB] building:
. maintenance of the HK [FB] building at a negative pressure to prevent APPROVEDreleases, . collection of any leaks from the containment penetrations,
. air filtration using the iodine trains before release to the environment.
Case 2: In the event of a fuel handling accident in the HR [RB] building, or a Loss Of Coolant Accident (LOCA) from the Safety Injection System operating in Residual Heat Removal Mode (RIS/RRA [SIS/RHRS]) with the equipment hatch open (the room in front of the equipment hatch is considered as an extension of the HR [RB] building):
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o Dynamic confinement of the HR [RB] building:
. Isolation of all air supply ducts (low capacity, high capacity, and equipment hatch) and isolation of the high-capacity exhaust.
Keeping the building at a negative pressure compared to adjacent buildings, preventing air flow out of the HR [RB] building, to avoid the spread of contamination to adjacent buildings.
Environmental protection:
The EBA [CSVS] system must ensure:
o Air confinement with respect to the environment as a whole and the public;
. Contain the radioactive material and prevent the risk of leaks.
o Control and reduction of radioactive waste discharges under normal operation;
. Limit radioactive discharges into the environment through storage, treatment and control of the waste conveyed.
5.0.2.4. Support Contribution to the Main Safety Function
With respect to its indirect contribution to the MSF of confinement of radioactive material, the EBA [CSVS] system must satisfy the following SFRs:
Ensure the EBA [CSVS] system iodine trains robustness to irradiation in the short, mid and long-term and maintain the accessibility of the EBA [CSVS] system iodine train rooms in the long-term for the maintenance of the EBA [CSVS] system components after an SA:
o Lining of the severe accident pre-filter.
5.0.2.5. Specific Contribution to Hazards Protection
With respect to its specific contribution to the safety functions that are part of the facility’s hazards protection, the EBA [CSVS] system must satisfy the following SFRs:
Fire compartmentation:
Contribution to the containment of a fire in the HR [RB] and HK [FB] buildings, by the closure of fire dampers to maintain the fire compartment integrity. ProtectionAPPROVED of SC1 classified components in case of earthquake: Ensuring the stability of all components in the HR [RB] and HK [FB] buildings to avoid damage to higher classified components and ensure that it does not adversely impact the availability of SC1 SFs following a seismic event.
5.0.2.6. Other Safety Functions to be performed in the Preventive Line of Defence
The EBA [CSVS] system contributes to other safety functions to be performed in the preventive line of defence as follows:
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Prevent the loss of an iodine filtration train;
Monitoring of the temperature downstream of the heater and of the iodine adsorption unit (IAU), and monitoring of the pressure differential around the fan.
Avoid the loss of an iodine train because of clogged filters in SA;
Monitoring of the EBA [CSVS] system filters clogging rate (local measurement of pressure drop across the filters)
5.0.3. Safety Features and Instrumentation & Control (I&C) Actuation Modes
Section 9.4.5 – Table 2 presents the SFs of the EBA [CSVS] system according to the contributions identified in section 5.0.1 and the SFRNs referenced in Sub-chapter 3.2.
5.0.4. Classification and Architecture Requirements of Safety Features
5.0.4.1. Requirements arising from Safety Classification
Architecture requirements associated with SFs are essential for designing robust lines of defence consistent with their importance to nuclear safety as described in Sub-chapter 3.2, section 7. Such requirements strengthen the system design against:
single faults and associated consequences (Single Failure Criterion (SFC)) by requiring redundancy;
Loss Of Off-site Power (LOOP) by requiring, among others, a back-up power supply;
Station Black-Out (SBO) by requiring a power supply by the Ultimate Diesel Generators (UDGs);
Common Cause Failures (CCFs) by requiring physical separation;
earthquake by defining seismic requirements;
accident conditions by defining qualification requirements.
Section 9.4.5 – Table 2 presents the requirements arising from the safety classification for the EBA [CSVS] system, according to the SFRNs referenced in Sub-chapter 3.2.
5.0.4.2. System Protection against Hazards
5.0.4.2.1. Internal Hazards
The SFs of the EBA [CSVS] system must be protected against internal hazards if those hazards challenge the APPROVEDsafety objectives, as defined in Sub-chapter 13.2.
5.0.4.2.2. External Hazards
The SFs of the EBA [CSVS] system must be protected against external hazards if those hazards challenge the safety objectives, as defined in Sub-chapter 13.1.
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5.0.4.3. Diversity
The EBA [CSVS] system is not subject to the requirement for diversity.
5.0.5. Requirements defined at the Component Level
5.0.5.1. Generic Safety Requirements
5.0.5.1.1. General Mechanical, Electrical and I&C Requirements
The mechanical components within the EBA [CSVS] system must comply with the mechanical requirements in accordance with the rules laid out in Sub-chapter 3.2 section 7. The level of requirement is dependent upon whether or not it is a pressure retaining component, the safety class of the component, whether the component acts as an isolating device between interfacing SFs, and on the role of the component as a barrier to the potential release of radioactivity as a result of failure of the component.
The electrical and Instrumentation and Control (I&C) components in the EBA [CSVS] system must comply with the electrical and I&C requirements associated with their safety class, in accordance with the rules laid out in Sub-chapter 3.2.
5.0.5.1.2. Seismic Requirements
The level of seismic requirements to be applied to the EBA [CSVS] system components is related to the Safety Feature Group (SFG) to which the component belongs, and the consequences on other classified components of its failure, if it were not seismically qualified. The rules for defining the seismic requirements for a component are identified in Sub-chapter 3.2.
5.0.5.1.3. Qualification for Accident Conditions
The safety classified parts of the EBA [CSVS] system must be qualified for the operating condition in which they are required, as specified in Sub-chapter 3.6.
5.0.5.2. Specific Safety Requirements
5.0.5.2.1. High Integrity Component (HIC) Requirements
The EBA [CSVS] system is not subject to any High Integrity Components (HIC) requirements.
5.0.5.2.2. Specific I&C Requirements
The EBA [CSVS] system does not have any safety classified dedicated I&C. However, the EBA [CSVS] system fire dampers are operated by the Fire Detection System (JDT [FDS]) dedicated I&C. APPROVED The specific requirements arising from the JDT [FDS] system dedicated I&C are described in the JDT [FDS] system chapter (see Sub-chapter 9.5, section 1.2).
The general approach for I&C systems is set out in Chapter 7.
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5.0.6. Examination, Maintenance, (In-Service) Inspection and Testing (EMIT)
5.0.6.1. Start-up Tests
The EBA [CSVS] system must be designed to enable the performance of start-up tests to ensure the adequacy of its design and performance under conditions as representative as possible of the different operating configurations, and in particular, its compliance with the SFRs assigned to it in section 5.0.2.
5.0.6.2. In-service Inspection
The EBA [CSVS] system must be designed to enable surveillance under normal operation of the system characteristics necessary for the fulfilment of their safety-related tasks in order to ensure the performance of their components, and their availability under normal operation, or in the event of a fault or accident.
5.0.6.3. Periodic Testing
The safety classified parts of the EBA [CSVS] system must be designed to enable the performance of periodic tests in accordance with the maintenance schedule.
5.0.6.4. Maintenance
The EBA [CSVS] system must be designed to enable the implementation of a maintenance schedule (see Sub-chapter 18.2).
5.1. ROLE OF THE SYSTEM
The EBA [CSVS] system performs the following functions (or tasks) under the different plant operating conditions for which it is required:
5.1.1. Normal Operating Conditions
5.1.1.1. Low-capacity EBA
During normal plant operations (PCC-1), without the requirement for HR [RB] building access, the EBA [CSVS] system is not required.
Whenever necessary during normal plant operation, the low-capacity EBA [CSVS] system operates in open circuit mini-purging mode to ventilate the service area of the HR [RB] building to enable the following:
reduction in the activity of the atmosphere in the service area due to the presence of noble gases (Krypton 85 and Xenon 133 in particular) and tritium (tritiated steam); oxygenationAPPROVED of the atmosphere in the service area; creation of overpressure in the stairways, thus protecting the stairways from smoke in the event of fire;
ensuring dynamic confinement between the two areas of the HR [RB] building by extraction of the air from the equipment compartment (High Efficiency Particulate Air (HEPA) filter and iodine adsorption unit) before discharge to the main unit vent stack; and
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limiting discharges to the environment via iodine filtration trains.
During an outage, the low-capacity EBA [CSVS] system acts to complement the high-capacity EBA [CSVS] system.
The air supply is provided by the Nuclear Auxiliary Building Ventilation System (DWN [NABVS]) (see section 2 of this sub-chapter).
5.1.1.2. High-capacity EBA [CSVS] System
The high-capacity EBA [CSVS] system is used during outages for the following purposes:
to reduce the concentration of fission or activation products in the HR [RB] building atmosphere (service area and equipment compartment) to allow permanent access in optimum safe conditions as soon as possible at cold shutdown;
to oxygenate the atmosphere of the equipment compartment; and
to keep the ambient temperature acceptable for staff working in the HR [RB] building during cold shutdown periods.
Treatment of the supplied air (air conditioning, blowing, filtration) and part of the extraction (EBA high capacity) is performed by the DWN [NABVS] system (see section 2 of this sub-chapter).
5.1.2. Fault and Hazard Conditions
The safety function of the EBA [CSVS] system is to contribute to the limitation of radioactive releases. A breakdown is as follows:
If an event leading to release of activity in the containment (PCC-3, PCC-4, DEC-A, DEC-B) or if a more general increase in radioactivity occurs:
The containment isolation valves in the low-capacity and high-capacity EBA [CSVS] system must be closed to ensure the HR [RB] building static confinement.
The Fuel Building Ventilation System (DWK [FBVS]) is isolated. The HK [FB] building is confined through the low-capacity EBA [CSVS] system extraction via the DWK [FBVS] system extraction network connected on the EBA [CSVS] system low-capacity iodine trains.
In the event of a fuel handling accident in the HR [RB] building, or a LOCA from the RIS/RRA [SIS/RHRS] with the equipment hatch open:
o the containment isolation valves of the high-capacity EBA [CSVS] system and APPROVEDthose for air supply of the low-capacity EBA [CSVS] system are closed, o the air supply in front of the equipment hatch is isolated, and
o the extraction of the low-capacity EBA [CSVS] system ensures dynamic confinement of the HR [RB] building; the air is filtered through a HEPA filter and iodine adsorption unit before discharge to the main unit vent stack.
Moreover, in the event of an accident leading to radiological release, the low-capacity EBA [CSVS] system collects and filters the containment penetration leaks from the EBA [CSVS] system and Gaseous Waste Processing System (TEG [GWPS]).
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During long term operation in a severe accident, the EBA [CSVS] system ensures the confinement of the HK [FB] building.
5.2. DESIGN BASIS
5.2.1. General Assumptions
Mini-purging (by the low-capacity EBA [CSVS] system) takes place both before and during access into the service area (plant in operation or prior to plant shutdown).
The system is designed to limit radioactive discharges. It comprises a supply train coming from the DWN [NABVS] system and an exhaust iodine train.
The system provides sufficient air changes in the service area of the HR [RB] building during plant operation.
The system ensures the dynamic confinement of the equipment compartment to avoid the contaminated air from flowing from the equipment compartment to the service area.
HK [FB] Building Confinement
Should a release of activity in the containment (PCC-3, PCC-4, DEC-A, DEC-B) or if a more general increase in radioactivity occurs, the EBA [CSVS] system ensures the HK [FB] building is kept at negative pressure.
HR [RB] Building Confinement
In the event of a fuel handling accident in the HR [RB] building, or a LOCA from the RIS/RRA [SIS/RHRS] with equipment hatch open, the EBA [CSVS] system ensures the HR [RB] building is maintained at a negative pressure.
5.2.2. Design Assumptions
5.2.2.1. Control of Fuel Reactivity
Not applicable: the EBA [CSVS] system does not directly contribute to the MSF of control of fuel reactivity.
5.2.2.2. Fuel Heat Removal
Not applicable: the EBA [CSVS] system does not directly contribute to the MSF of fuel heat removal.
5.2.2.3. Confinement of Radioactive Material Third ContainmentAPPROVED Barrier Case 1: If an event leading to release of activity in the HR [RB] building (PCC-3, PCC-4, DEC-A, DEC-B) or if a more general increase in radioactivity occurs:
Static confinement of the HR [RB] building:
o The entirety of the HR [RB] building must be isolated by closure of the containment isolation valves.
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Dynamic confinement of the HK [FB] building:
o Negative pressure differential (ΔP) to be maintained during the HK [FB] building confinement between the HK [FB] building and the adjacent buildings except the annulus.
Case 2: In the event of a fuel handling accident in the HR [RB] building or a LOCA from the RIS/RRA [SIS/RHRS] with the equipment hatch open (the room in front of the equipment hatch is considered as an extension of the HR [RB] building):
Dynamic confinement of the HR [RB] building:
o Negative pressure differential (ΔP) to be maintained during the HR [RB] building confinement between the HR [RB] building and the adjacent buildings except the annulus.
Environmental Protection
Assumptions on air flow rates:
EBA [CSVS] system low-capacity air flow rate to be ensured during normal operation: { SCI removed };
EBA [CSVS] system low-capacity maximum air flow rate: { SCI removed }.
Assumptions regarding temperature (as detailed in section 1) and relative humidity used for heater sizing (chosen at 100% only for heater sizing to be conservative):
HR [RB] building service area maximum temperature and relative humidity used for heater sizing: { SCI removed }; 100%;
HR [RB] building equipment compartment maximum temperature and relative humidity: { SCI removed }; 100%.
5.2.2.4. Support Contribution to Main Safety Function
Not applicable: there are no quantitative safety-related design assumptions associated with the EBA [CSVS] system.
5.2.2.5. Specific Contribution to Hazards Protection
Not applicable: there are no quantitative safety-related design assumptions associated with the EBA [CSVS] system. 5.2.2.6. OtherAPPROVED Safety Functions to be performed in the Preventive Line of Defence Not applicable: there are no quantitative safety-related design assumptions associated with the EBA [CSVS] system.
5.2.3. Other Assumptions
The EBA [CSVS] system is also subject to the following assumptions:
EBA [CSVS] system design is consistent with RCC-M requirements as described in Sub-chapter 3.8, section 2.
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EBA [CSVS] system design is consistent with fire requirements as described in Sub-chapter 3.8, section 5.
5.2.4. Assumptions associated with Extreme Situations resulting from Beyond Design Basis Hazards
5.2.4.1. Assumptions associated with Fukushima Provisions
The assumptions associated with the Fukushima provisions of the EBA [CSVS] system are presented in Chapter 23. The main provisions are:
Containment Isolation 1;
opening of Fuel Building Extraction and start-up of low capacity EBA [CSVS] iodine filtration (dynamic containment of the HK [FB] building);
opening of EBA [CSVS] penetration leakage outlet lines;
long-term operation;
pre-filtration alignment.
5.2.4.2. Assumptions associated with non-Fukushima Provisions
The EBA [CSVS] system is not subject to assumptions associated with non-Fukushima provisions.
5.3. SYSTEM DESCRIPTION AND OPERATION
5.3.1. Description
5.3.1.1. General System Description
Low-Capacity EBA [CSVS] System
This sub-system comprises of:
For the air supply function:
o A duct line coming from the DWN [NABVS] system plenum located in the HK [FB] building supplies air to the HR [RB] building. In the HR [RB] building, the duct is common with the high-capacity EBA [CSVS] sub-system. On each section of the containment penetration there are two isolation valves. The EBA [CSVS] system low capacity air supply is conditioned by the DWN [NABVS] APPROVEDsystem. o A duct network enabling air distribution into the different parts of the service area.
o Outlets connected to the EBA [CSVS] system supply duct in the HK [FB] building enabling recovery of leaks from the containment penetration.
For the air extraction function:
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o Extraction from the HR [RB] building:
. A duct network extracting air from the different parts of the service area including the dome and from the equipment compartment.
. A common low and high-capacity EBA [CSVS] system duct line located in the HR [RB] building.
o A duct line connecting the common low and high-capacity EBA [CSVS] system duct to the HK [FB] building. On each section of the containment penetration there are two isolation valves.
o Extraction from HK [FB] building:
. Two duct lines connecting the low-capacity EBA [CSVS] system extraction to the DWK [FBVS] system extraction cells equipped with isolation dampers.
. A metallic pre-filter, located upstream of the iodine lines, reduces radiological releases in the event of a severe accident. For other situations, this component is bypassed.
o Common part:
. Two EBA [CSVS] system iodine trains (2 x 100%) enclosed by fire dampers comprising: electric heater, pre-filter, HEPA filter, iodine adsorption unit and fans.
. A duct line for discharge to the main unit vent stack.
High-Capacity EBA [CSVS] System
This sub-system comprises of:
For air supply:
o A duct line coming from the DWN [NABVS] system plenum in the HK [FB] building supplies air to the HR [RB] building. This duct is equipped with two containment isolation valves. The EBA [CSVS] system high capacity air supply is conditioned by the DWN [NABVS] system.
o A duct network ensuring the air supply distribution to the stairways, the service floor and annular space. The duct to the service floor is equipped with a motorised damper. o APPROVEDA duct line coming from the DWN [NABVS] system plenum in the HK [FB] building connected to the DWK [FBVS] system to blow air from the setdown area (in the HK [FB] building) to the HR [RB] building when the equipment hatch is open. This duct is equipped with two motorised dampers.
For extraction:
o An extraction duct network ensuring air extraction from the equipment compartment and service area rooms. It is connected to the low and high- capacity EBA [CSVS] system ducts.
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o A duct line connecting the extraction duct common to the low and high-capacity EBA [CSVS] system to the HK [FB] building. This duct is connected to the DWN [NABVS] system filters. This duct is equipped with two containment isolation valves.
Outlets connected to the EBA [CSVS] system supply and extraction ducts in the HK [FB] building enabling recovery of leaks from the containment penetrations.
5.3.1.2. Description of Main Equipment
The EBA [CSVS] system comprises the following main equipment items (see the functional diagram provided in section 5.5):
eight containment isolation valves which enable the HR [RB] building confinement (two per penetration, for the EBA [CSVS] system high and low-capacity supplies and exhausts);
two redundant iodine trains which enable dynamic confinement and filtration of radioactive releases:
o heater limiting the maximum relative humidity to { SCI removed } upstream of the iodine adsorption unit;
o pre-filter for collection of coarse airborne particulate, in order to preserve the HEPA filter,
o HEPA filter enabling collection of fine airborne particles,
o iodine adsorption unit, and
two redundant isolation dampers on the supply duct in front of the equipment hatch enabling isolation of the supply duct in case of a fault during refuelling or a LOCA with equipment hatch open;
four (2 x 2) isolation dampers on the DWK [FBVS] system connection ducts for the HK [FB] building dynamic confinement;
four (2 x 2) isolation valves on the outlets enabling recovery of air leaks coming from the HR [RB] building penetrations in the HK [FB] building;
six (3 x 2) isolation dampers on the high-capacity EBA [CSVS] system supply and exhaust duct and the EBA [CSVS] system low-capacity supply duct enabling isolation of those ducts;APPROVED fire dampers enabling Safety Fire Compartment (SFS) isolation.
5.3.1.3. Description of Main Layout
The EBA [CSVS] system air supply is provided in the HK [FB] building by the DWN [NABVS] system. The air is supplied to the HR [RB] building through the HR [RB] building penetrations from where it is then distributed throughout the HR [RB] building.
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The air is extracted from the HR [RB] building to the HK [FB] building through the HR [RB] building penetrations via the low and high-capacity EBA [CSVS] system.
The high-capacity EBA [CSVS] system is connected to the DWN [NABVS] system exhaust lines via the HK [FB] building.
The low-capacity EBA [CSVS] system is connected to two redundant iodine trains that are located in the HK [FB] building; the two iodine trains are in separate rooms.
On the four containment penetrations, there is one containment isolation valve on each side of the penetration.
5.3.1.4. Description of System I&C
The JDT [FDS] system dedicated I&C used for the EBA [CSVS] system fire dampers is described in the JDT [FDS] system chapter (see Sub-chapter 9.5, section 1.2).
5.3.2. Operation
5.3.2.1. System Normal Operation
Plant Normal Operation
When the plant is in operation, there is no continuous ventilation of the atmosphere in the HR [RB] building service area. All the containment isolation valves are closed.
Dynamic confinement between the service area and the equipment compartment is ensured by the HR [RB] Internal Filtration System (EVF) (see section 4 of this sub-chapter).
If access is required within the HR [RB] building during plant operation, the EBA [CSVS] low- capacity system is started. Initially, the HR [RB] building is in over pressure. In a first time the HR [RB] building is depressurised. When the pressure is low enough, the EBA [CSVS] system mini-purging can be started.
Depressurisation of the HR [RB] Building
When the plant is in operation, there is no continuous pressure control in the HR [RB] building service area.
If necessary, depressurisation of the service area may be achieved using the extraction portion of the mini-purging system (low-capacity EBA [CSVS] system).
Mini-purging of the HR [RB] Building
In preparation for access to the HR [RB] building during plant operation, the low-capacity EBA [CSVS] systemAPPROVED is started two days before the access is required and operation maintained during the access period.
When the low-capacity EBA [CSVS] system supply and exhaust are switched on, fresh air is taken from outside, conditioned by the DWN [NABVS] system and supplied to the HR [RB] building service area.
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The extraction part of the low-capacity EBA [CSVS] system maintains dynamic confinement between the equipment compartment and the service area in an open circuit. The air extracted is discharged to the main unit vent stack after being filtered by an EBA [CSVS] system iodine train.
Steady State Operating Conditions
Prior to plant shutdown, the EBA [CSVS] system is started in a similar manner as for access with the plant at power. The HR [RB] building must be depressurised initially, then the low- capacity EBA [CSVS] system supply and exhaust are started.
The high-capacity EBA [CSVS] system is started when the RIS/RRA [SIS/RHRS] operates and the activity of the primary coolant is less than a defined value.
At the start of the outage period, dynamic confinement is maintained between the service area and the equipment compartment to purify the air in the equipment compartment and to prepare for worker access to the equipment compartment (purge phase). When all the rooms have been swept and the risk of atmospheric contamination is limited, maintenance of confinement of the equipment compartment is no longer necessary.
During cold shutdown, with no atmospheric contamination, the ventilation of the containment is performed by the EBA [CSVS] system operating in open-circuit mode (high-capacity EBA [CSVS] system and low-capacity EBA [CSVS] system).
Air Supply (Equipment Hatch Closed)
Fresh air is blown into the stairways and the service floor via a motorised damper and then into the equipment compartment via two motorised dampers belonging to the Containment Cooling Ventilation System (EVR [CCVS]) (see section 3 of this sub-chapter).
Air Supply (Equipment Hatch Open)
Part of the high-capacity EBA [CSVS] system supply air flow rate is taken from the total flow rate and redirected to the room in front of the equipment hatch via the connection to the DWK [FBVS] system. From this location, the air flows to the service floor through the open equipment hatch.
Extraction
The EBA [CSVS] system extracts the air from the equipment compartment and the service area.
5.3.2.2. System Transient Conditions
High Level of Activity in the HR [RB] Building (Equipment Hatch Open) In the event ofAPPROVED detection of the following: Activity (measured by the Plant Radiation Monitoring System (KRT [PRMS]) in the HR [RB] building atmosphere due to presence of noble gases (krypton-85 and xenon-133 in particular) and tritium (tritiated steam) following a fuel handling accident during cold shutdown of the reactor.
A rupture in the primary system while it is at a temperature lower than { SCI removed } (if the temperature is above { SCI removed }, the equipment hatch is closed and the HR [RB] building static confinement is realised by closure of all containment isolation valves).
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The high-capacity EBA [CSVS] system supply and extraction and the low-capacity EBA [CSVS] air supply systems are automatically shut down. The corresponding containment isolation valves are closed. The air supply to the room in front of the equipment hatch is isolated. The extraction part of the low-capacity EBA [CSVS] system remains in operation to avoid spreading contamination by maintaining negative pressure in the HR [RB] building and thus a flow into the HR [RB] building through the equipment hatch and airlocks. The extracted air is filtered by a HEPA filter and iodine adsorption unit before being discharged to the main unit vent stack.
The purge / ventilation of the containment is operated again when the activity level in the HR [RB] building is at or below the allowable level.
Loss of Coolant Accident (LOCA)
In the event of a LOCA, the Stage 1 containment isolation signal leads to the closure of the containment isolation valves to ensure the HR [RB] building static confinement.
The dampers located in the HK [FB] building, connecting the low-capacity extraction network to the DWK [FBVS] system are opened and the low-capacity EBA [CSVS] system fan is started to ensure the dynamic confinement of the HK [FB] building. The air is extracted through a HEPA filter and an iodine adsorption unit before being discharged into the main unit vent stack.
In the event of a LOCA, the outlet isolation dampers are closed and the outlet valves are opened. The outlets, located in HK [FB] building (see section 5.3.1.1), are used to recover the leaks coming from the HR [RB] building penetrations and to direct them into the EBA [CSVS] system iodine trains are positioned on the EBA [CSVS] system high capacity and low-capacity supply ducts and the EBA [CSVS] system high-capacity extraction duct.
The EBA [CSVS] system low-capacity air flow rate ensures the HK [FB] building dynamic confinement.
High Pressure in the HR [RB] Building or Safety Injection Signal
In the event of high pressure in the HR [RB] building or a safety injection signal, the mini-purge function of the low-capacity EBA [CSVS] system is shut down (if it is operating) and all the containment isolation valves are closed.
Loss Of Offsite Power (LOOP)
In the event of a LOOP, the electrical supply to the DWN [NABVS] system fans is not backed up. Thus, the air supply is not distributed in the HR [RB] building and the high-capacity EBA [CSVS] system does not extract air. The low-capacity EBA [CSVS] system exhaust is backed up by the Emergency Diesel Generators (EDGs) in order to enable dynamic confinement of the HR [RB] or HK [FB] buildings to be preserved.
Station Blackout (SBO)
The iodine trainsAPPROVED of the low-capacity EBA [CSVS] system are emergency-supplied by the UDGs and enable dynamic confinement of the HK [FB] building to be preserved. Thus, the dampers connecting the low-capacity EBA [CSVS] system extraction and the DWK [FBVS] system extraction network are backed-up by the UDGs.
Severe Accident
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The dampers located in the HK [FB] building, connecting the low-capacity extraction network to the DWK [FBVS] system, are opened. A low-capacity EBA [CSVS] system fan is started up. The air is extracted through a HEPA filter and an iodine adsorption unit before being discharged into the main unit vent stack.
Outlet valves are opened to recover leaks coming from the HR [RB] building penetrations and to direct them into the EBA [CSVS] system iodine trains.
In the event of an SA, minimisation of radiological releases and preservation of the HEPA filter are ensured by the metallic pre-filter, upstream of each iodine line.
5.3.2.3. Other Operating Conditions
5.3.2.3.1. Full or Partial System Failure
{ This section contains SCI-only text and has been removed }
5.3.2.3.2. Failure of Interface Systems (Server or Served)
{ This section contains SCI-only text and has been removed }
5.4. PRELIMINARY DESIGN SUBSTANTIATION
The level of detail of evidence of compliance with the safety requirements stated in section 5.0 will develop as the HPC project moves from basic design into detailed design since the PCSR3 sequence and system sequence are evolving in parallel. Therefore, the level of detail presented in this section depends on the information available at the time of issuing the system chapters.
5.4.1. Compliance with Safety Functional Requirements
5.4.1.1. Control of Fuel Reactivity
Not applicable: the EBA [CSVS] system does not directly contribute to the MSF of control of fuel reactivity.
5.4.1.2. Fuel Heat Removal
Not applicable: the EBA [CSVS] system does not directly contribute to the MSF of fuel heat removal.
5.4.1.3. Confinement of Radioactive Material
Third Containment Barrier
Case 1: If an event leading to release of activity in the HR [RB] building (PCC-3, PCC-4, DEC-A, DEC-B) or if aAPPROVED more general increase in radioactivity occurs: Static confinement of the HR [RB] building:
o Closure of the containment isolation valves:
. valve leaktightness requirements (leaktightness consistent with their mechanical classification), and
. valve closure times.
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Dynamic confinement of the HK [FB] building:
o Maintenance of the HK [FB] building at a negative pressure to prevent releases:
. minimum negative pressure to be ensured in the HK [FB] building compared to adjacent buildings (decoupling value to be confirmed), and
. HK [FB] building connection isolation damper opening time.
o Collection of leaks from the containment penetrations:
. outlet valve opening time,
. outlet isolation damper closure time, and
. damper leaktightness requirements as given in section 1.
o Air filtration using the iodine trains before release to the environment:
. HEPA filter and iodine adsorption unit efficiencies given in section 1, and
. ventilation components reinforced leak tightness;
Case 2: In the event of a fuel handling accident in the HR [RB] building, or a LOCA from the RIS/RRA [SIS/RHRS] with equipment hatch open (the room in front of the equipment hatch is considered as an extension of the HR [RB] building):
Dynamic confinement of the HR [RB] building:
o Isolation of all the EBA [CSVS] system air supply ducts and of the high-capacity exhaust:
. valve closure time (for containment isolation valves),
. valve leaktightness requirement (leaktightness consistent with their mechanical classification),
. isolation dampers closure time for dampers located on the supply duct in front of equipment hatch, and
. isolation dampers leaktightness for dampers located on the supply duct in front of the equipment hatch (requirements given in section 1).
o Maintenance of the HR [RB] building at a negative pressure to prevent releases: APPROVED. minimum negative pressure to be ensured in the HR [RB] building compared to adjacent buildings (decoupling value to be confirmed).
o Air filtration using the iodine filtration trains before release to the environment:
. HEPA filter and iodine adsorption unit efficiencies given in section 1, and
. ventilation components reinforced leaktightness.
Environmental protection:
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o Air confinement with respect to the environment as a whole and the public;
o Contain the radioactive material and prevent the risk of leaks:
. HEPA filter and iodine adsorption unit efficiencies given in section 1,
. heater sizing based on the HR [RB] building maximum temperatures and relative humidity given in section 1 (heater used to heat air before the iodine adsorption unit), and
. ventilation components reinforced leaktightness.
o Control and reduction of radioactive waste discharges under normal operation;
o Limit radioactive discharges into the environment through storage, treatment and control of the waste conveyed:
. HEPA filter and iodine adsorption unit efficiencies given in section 1,
. heater sizing based on the HR [RB] building maximum temperatures and relative humidity given in section 1 (heater used to heat air before the iodine adsorption unit), and
. ventilation components reinforced leaktightness.
Under accident conditions, the lines of the EBA [CSVS] system penetrating the HR [RB] building containment are fitted with two containment isolation valves. Those valves close upon receiving a Phase 1 containment isolation signal.
The parts of the EBA [CSVS] system that contribute to the extension of the third containment barrier meet their associated safety functional requirements. They are mechanically classified in order to meet the leaktightness requirement.
5.4.1.4. Support Contribution to Main Safety Functions
The design assumptions of the EBA [CSVS] system stated in section 5.2.2 are consistent with the requirements of the corresponding systems / equipment items which it supports:
Ensure long-term operation of the HEPA filters and maintenance of the filter in the EBA [CSVS] system ventilation rooms in case of SA:
o Lining of the SA pre-filter:
. pre-filter alignment damper opening time to be defined later, APPROVED. bypass damper closure time to be defined later, and . pre-filter efficiency to be defined later.
5.4.1.5. Specific Contributions to Hazards Protection
Fire Compartmentation
Contribution to the containment and prevention of spread of fire in the HR [RB] and HK [FB] buildings by the closure of fire dampers:
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fire damper qualification,
fire damper closure monitored by position status.
The fire hazard studies of Sub-chapter 13.2, section 7, will demonstrate that the design of the EBA [CSVS] system (fire dampers) contributes to the protection against the spread of fire through the HR [RB] and HK [FB] buildings.
Protection of SC1 Classified Components in case of Earthquake
Ensuring the stability of all components:
seismic qualification to keep the components stability.
The earthquake hazard studies of Sub-chapter 13.1, section 2, will demonstrate that the design and installation provisions applied to all concerned components in HR [RB] and HK [FB] buildings prevent consequences of earthquake by associating a sufficient seismic requirement in accordance with Sub-chapter 3.2, section 7.
For each hazard study concerned, these studies show that the design of these functions is such that they meet the acceptance criteria.
These elements ensure that the SFRs stated in section 5.0.2 are met.
5.4.1.6. Other Safety Functions to be performed in the Preventive Line of Defence
Other safety functions to be performed in the preventive line of defence involving the EBA [CSVS] system use values for the following parameters that are in keeping with the design assumptions stated in section 5.2.2:
To prevent the loss of an iodine filtration train:
o Monitoring of the temperature downstream of the heater and of the iodine adsorption unit and monitoring of the pressure differential around the fan:
. sensors qualification.
To avoid the loss of an iodine train because of clogged filters in SA:
o Monitoring of the EBA [CSVS] system filters clogging rate (local measurement of pressure drop across the filters):
. sensors qualification. These elementsAPPROVED ensure that the safety functional requirements stated in section 5.0.2 are met. 5.4.2. Compliance with Design Requirements
The EBA [CSVS] system complies with the requirements stated in sections 5.0.4 and 5.0.5, particularly with respect to those detailed in the following sections.
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5.4.2.1. Requirements arising from Safety Classification
5.4.2.1.1. Safety Classification
The compliance of the design and manufacture of the EBA [CSVS] system materials and components performing a safety-related function with requirements from the classification rules (see Sub-chapter 3.2, section 7) is presented in section 5.4.2.4.1:
5.4.2.1.2. Single Failure Criterion and Redundancy
Active Single Failure
The design of the EBA [CSVS] system meets the requirements of the active SFC stated in section 5.0.4.1, in particular in respect of the following:
Two redundant iodine trains (2 x 100%) are supplied by two separated electrical divisions.
The dampers isolating the air supply in front of the equipment hatch are 2 x 100% on closure and are supplied by two separated electrical divisions.
Two EBA [CSVS] system dampers are installed in parallel on each connection line between the low-capacity EBA [CSVS] system extraction and the DWK [FBVS] system extraction network to be redundant on opening and are supplied by two separated electrical divisions.
The EBA [CSVS] system outlets are Class 2, therefore the outlet valves are powered by two separated electrical trains to provide redundancy.
The two redundant outlet isolation dampers are supplied by two separated electrical divisions.
The two fire dampers at the SFS limits are redundant on closure.
The EBA [CSVS] system containment penetration isolation system consisting of an isolation valve inside the HR [RB] building and an isolation valve located outside in a connecting building, is redundant.
Passive Single Failure
The EBA [CSVS] system is not subject to passive single failure as stated in Sub-chapter 15.3, section 1.
5.4.2.1.3. Robustness against Loss of Power The design ofAPPROVED the EBA [CSVS] system complies with the emergency power supply requirement stated in section 5.0.4.1, in particular in respect to those detailed in the following sections.:
Loss of Offsite Power (LOOP)
The two iodine trains are supplied by emergency switchboards dedicated to the Nuclear Island (NI) as follows: one train on a switchboard of Division 1 and one train on a switchboard of Division 4.
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The dampers isolating the air supply in front of the equipment hatch are supplied by emergency switchboards dedicated to the NI as follows: one damper on a switchboard of Division 1 and one damper on a switchboard of Division 4. The two air supply dampers at the equipment hatch do not need to be supplied from the emergency switchboard of Division 1 as the fail-safe position of these dampers is the closed position.
The connection dampers between the low-capacity EBA [CSVS] system extraction and the DWK [FBVS] system extraction network are supplied by emergency-supplied switchboards. The two dampers on the same connection train are supplied by different divisions (1 and 4).
For the purpose of maintaining these switchboards, electrical cross-connections are provided with a switchboard of Division 2 for the train supplied by Division 1 and with a switchboard of Division 3 for the train supplied by Division 4.
Those components are supplied by electrical switchboards powered by the EDGs.
In addition, active components contributing to fire-fighting are required to be robust against LOOP. This requirement is met by an uninterruptible power supply and a passive closure by thermal fuse (fail-safe design) for the fire dampers.
Station Blackout (SBO)
The two iodine trains and the connection dampers between the low-capacity extraction EBA [CSVS] system and the DWK [FBVS] system extraction network are supplied by the UDGs.
For the containment isolation valves, the requirements are described in Sub-chapter 6.1, section 3.
5.4.2.1.4. Physical Separation
The EBA [CSVS] system is designed in accordance with the physical separation requirement stated in section 5.0.4.1 in particular in respect of the following:
The EBA [CSVS] system low-capacity iodine trains that are Class 2 are geographically separated: they are located in different rooms. Those rooms are located in different SFS
On the duct providing the EBA [CSVS] system supply in front of the equipment hatch, isolation dampers that are Class 1 are located in separate rooms.
The two isolation valves of each containment penetration of the EBA [CSVS] system are physically separated by virtue of their installation, one on the inside of the reactor, the other on the outside, in a connecting building.
5.4.2.2. System Protection against Hazards 5.4.2.2.1. InternalAPPROVED Hazards The overall demonstration of the robustness of the plant to internal hazards is covered in Sub-chapter 13.2.
5.4.2.2.2. External Hazards
The overall demonstration of the robustness of the plant to external hazards is covered in Sub-chapter 13.1.
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5.4.2.3. Diversity
Not applicable: the EBA [CSVS] system is not subject to the requirement for diversity.
5.4.2.4. Requirements defined at the Component Level
5.4.2.4.1. General Mechanical, Electrical and I&C Requirements
The components of the EBA [CSVS] system equipment performing a safety-related function comply with the general mechanical, electrical, and I&C requirements stated in section 5.0.5.1 as given in Section 9.4.5 – Table 1.
SECTION 9.4.5 – TABLE 1 : CLASSIFICATION OF THE MAIN MECHANICAL AND ELECTRICAL COMPONENTS ASSOCIATED TO THEIR SAFETY FEATURES
Safety classification Design requirements Mechanical requirement for Highest Highest pressure retaining Description safety safety Seismic Electrical I&C components or function class of classification requirement requirement leaktightness category SFG requirement for HVAC component Fan B 2 T3 SC1 C2 C2 Heater B 2 T2 SC1 C2 C2 Pre-filter B 2 T2 SC1 - - HEPA filter B 2 T2 SC1 - - Iodine adsorption B 2 T2 SC1 - - unit Containment isolation A 1 M2 SC1 C1 C1 valve Isolation dampers for supply in A 1 T2 SC1 C1 C1 front of the equipment hatch HK connection B 2 T2 SC1 C2 C2 dampers Outlet valves APPROVEDB 2 M2 SC1 C2 C2 Outlet Isolation B 2 T2 SC1 C2 C2 dampers Fire dampers at SFS A 1 T2/T3/NT SC1 C2/C3 C2/C3 boundary This table will be updated after the Safety Classification Component List (SCCL) studies.
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All remaining main components are seismic class SC2, but do not otherwise perform any safety- related function.
5.4.2.4.2. Seismic Requirements
The EBA [CSVS] system complies with the seismic qualification requirements listed in Section 9.4.5 – Table 1.
5.4.2.4.3. HIC Requirements
Not applicable: the EBA [CSVS] system is not subject to any HIC requirements.
5.4.2.4.4. Specific I&C Requirements
Not applicable: the EBA [CSVS] system does not have any dedicated I&C.
The demonstration of the compliance with the specific I&C requirements stated in section 5.0.5.2.2 is provided in the JDT [FDS] system chapter (see Sub-chapter 9.5, section 1.2).
5.4.3. Examination, Maintenance, (In-service) Inspection and Testing (EMIT)
5.4.3.1. Start-Up Tests
The EBA [CSVS] system is subjected to a start-up test programme in accordance with the procedures set out in Chapter 20 serving to verify the fulfilment of the following SFRs:
Confinement of radioactive material:
HR [RB] building static confinement:
o closing time of the EBA [CSVS] system containment isolation valves, and
o airtightness of the EBA [CSVS] system containment isolation valves.
Dynamic confinement of both HR [RB] and HK [FB] buildings:
o correct operation of the extraction fans,
o correct operation of the heaters,
o efficiency of the HEPA filters,
o efficiency of the iodine adsorption units, and o APPROVEDleaktightness of the duct that are a third barrier extension. Dynamic confinement of the HR [RB] building and the room in front of the equipment hatch, considered as an extension of the HR [RB] building:
o closing time of the outlet isolation dampers on the EBA [CSVS] system high- capacity supply and exhaust and the EBA [CSVS] system low-capacity supply, and
o HR [RB] building negative pressure.
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Dynamic confinement of the HK [FB] building:
o HK [FB] building negative pressure,
o opening time of the HK [FB] building connection dampers to ensure the HK [FB] building confinement, and
o opening time of the outlet valves.
Specific contribution to Hazards protection:
o correct operation of the fire dampers.
Other Safety Functions to be performed in the Preventive Line of Defence:
o availability of iodine trains temperature and pressure differential sensors, and
o availability of filter pressure sensors.
5.4.3.2. In-Service Inspection
The following functions of the EBA [CSVS] system are used during normal plant operation under conditions representative of the fault / hazard conditions in which they are required:
Operation of the Iodine Lines
The availability of these functions is therefore verified as part of normal operation.
The following functions of the EBA [CSVS] system are monitored during normal operation by continuous monitoring systems:
The fan differential pressure and air temperature in the iodine lines are monitored when the lines are in operation.
The availability of these functions is therefore verified by the continuous monitoring process.
5.4.3.3. Periodic Tests
The safety classified parts of the EBA [CSVS] system are subject to periodic testing in accordance with the maintenance schedule in order to verify that the following SFRs are fulfilled:
Confinement of radioactive material:
HR [RB] building static confinement: o APPROVEDclosing of the EBA [CSVS] system containment isolation valves. Dynamic confinement of both HR [RB] and HK [RB] buildings:
o correct operation of the extraction fans,
o correct operation of the heaters,
o efficiency of the HEPA filters,
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o efficiency of the iodine adsorption units, and
o leaktightness of the duct that are a third barrier extension.
Dynamic confinement of the HR [RB] building and the room in front of the equipment hatch, considered as an extension of the HR [RB] building:
o closing of the isolation dampers on the EBA [CSVS] system high-capacity supply and exhaust and the EBA [CSVS] system low-capacity supply, and
o HR [RB] building negative pressure.
Dynamic confinement of the HK [FB] building:
o opening of the dampers that provide connection to the DWK [FBVS] system networks to ensure the HK [FB] building confinement, and
o HK [FB] building negative pressure.
Specific Contribution to Hazards Protection:
o correct operation of the fire dampers.
Other Safety Functions to be performed in the Preventive Line of Defence:
o availability of iodine trains sensors.
5.4.3.4. Maintenance
The EBA [CSVS] system is subject to a maintenance programme:
Maintenance of the iodine trains is performed during plant operation when the low- capacity EBA [CSVS] system is not in operation.
Maintenance of the air-supply isolation dampers for the equipment hatch is performed during plant operation when the high-capacity EBA [CSVS] system is not in operation.
Maintenance of the low-capacity EBA [CSVS] system containment isolation valves is performed only when the plant core is completely unloaded.
Maintenance of the high-capacity EBA [CSVS] system containment isolation valves may be performed during plant operation.
5.5. FUNCTIONAL DIAGRAM
The functionalAPPROVED diagram of the EBA [CSVS] system is shown in Section 9.4.5 – Figure 1 (for more details, see the detailed mechanical diagrams of the EBA [CSVS] system).
6. SAFEGUARD BUILDING (CONTROLLED AREA) VENTILATION SYSTEM (DWL [CSBVS])
The information reported in this section is, unless otherwise noted, consistent with the reference design as referenced from Chapter 22.
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6.0. SAFETY REQUIREMENTS
The UK EPR Safety Classification principles and the top-down functional approach are presented in Sub-chapter 3.2. These principles help to ensure that the plant is designed, manufactured, constructed, commissioned and operated so that the appropriate level of reliability and integrity is achieved for its Structure, Systems and Components (SSCs).
The HPC functional safety analyses and the application of these safety classification principles to the HPC reference design result in the identification of the safety requirements for all safety systems in accordance with the Safety Functional Requirements Notes (SFRNs) referenced from Sub-Chapter 3.2.
This section summarises the results of these safety analyses and specifies the safety requirements that apply to the design of the Safeguard Building (Controlled Area) Ventilation System (DWL [CSBVS]).
The requirements described in the present section are consistent with safety functions to which the DWL [CSBVS] system contributes in Plant Condition Category (PCC) and Design Extension Conditions (DEC). Consistency with requirements inherited from the Design Basis Initiating Faults (DBIFs) should be checked when the list of DBIFs evolves (see Chapter 15).
6.0.1. Safety Functions
The three Main Safety Functions (MSFs) necessary to achieve the overall safety objective of protecting people and the environment from the harmful effects of ionising radiations are:
control of fuel reactivity,
fuel heat removal, and
confinement of radioactive material.
These three MSFs must be achieved during:
normal operating conditions (PCC-1, including duty functions, control of radioactive release during normal operating conditions, control of main plant parameters, fault initial conditions, Limiting Conditions of Operation (LCOs), monitoring functions and Probabilistic Safety Assessment (PSA) significant functions as part of the preventive line of defence,
fault conditions (PCC-2 to PCC-4, DEC-A and any equivalent DBIFs) and DEC-B, and
hazard conditions. 6.0.1.1. ControlAPPROVED of Fuel Reactivity The DWL [CSBVS] system does not directly contribute to the MSF of control of fuel reactivity.
6.0.1.2. Fuel Heat Removal
The DWL [CSBVS] system does not directly contribute to the MSF of fuel heat removal.
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6.0.1.3. Confinement of Radioactive Material
The DWL [CSBVS] system must contribute to the achievement of the MSF of confinement of radioactive material as a frontline system as described in the following sections.
Environmental Protection
The DWL [CSBVS] system carries gaseous effluents containing radioactive material. As such, it must contribute:
to the confinement of this material with respect to the environment as a whole and the public; and
to the control and reduction of radioactive waste discharges to the environment in normal operating conditions as required and during emergency conditions.
Limiting Radiological Consequences
In divisions 1 to 4 of the Safeguard Mechanical Buildings (HLF, HLG, HLH and HLI [SB(M)], hereinafter referred to as HL [SB(M)]):
Confine controlled area in normal operating conditions (PCC-1).
Confine controlled area to collect and filter leaks through containment penetrations following an accident with activity releases in the Reactor Building (HR [RB]) (PCC and DEC situations).
Confine controlled area and Safety Injection System (RIS [SIS]) rooms to anticipate a potential RIS [SIS] leak when it operates in Safety Injection (SI) mode (PCC situations) (see Sub-chapter 6.2).
Ensure long-term availability of dynamic confinement following a Severe Accident (SA) (DEC-B).
In HLF [SB(M)] and HLI [SB(M)] buildings :
Confine controlled area and Containment Heat Removal System (EVU [CHRS]) rooms to anticipate a potential EVU leak when in operation following a SA (DEC-B) (see Sub-chapter 6.1, section 7).
In a given division of the HL [SB(M)] buildings:
Confine controlled area and RIS [SIS] rooms of the division affected by a RIS [SIS] leak while in Residual Heat Removal mode (RIS/RRA [SIS/RHRS]) with the reactor coolant temperatureAPPROVED below { SCI removed } (PCC-4). In HLF [SB(M)] or HLI [SB(M)] buildings:
Limit RIS [SIS] room pressure in the division affected by a RIS/RRA [SIS/RHRS] leak with the reactor coolant temperature above { SCI removed } (PCC-4).
Restore static confinement following a RIS/RRA [SIS/RHRS] leak with the reactor coolant temperature above { SCI removed } (PCC-4).
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In the HR [RB] building:
Confine statically the HR [RB] building extended to the room facing the personnel airlock ({ SCI removed }) following a fuel handling accident in the HR [RB] building or a Loss Of Coolant Accident (LOCA) with the equipment hatch open (PCC-4).
In the Fuel Building (HK [FB]):
Confine dynamically the fuel pool hall following a fuel handling accident in the HK building (PCC-4). The normal ventilation of the fuel pool hall, provided by the Fuel Building Ventilation System (DWK [FBVS]), is isolated in these circumstances (see section 14 of this sub-chapter).
6.0.1.4. Support Contribution to Main Safety Functions
The DWL [CSBVS] system must contribute indirectly to the three MSFs as a support system as follows:
Maintain temperatures compatible with the correct functioning of equipment in the RIS [SIS] pump and heat exchanger rooms in all HL [SB(M)] buildings (see Sub-chapter 6.2).
The DWL [CSBVS] system must contribute indirectly to the MSFs of control of fuel reactivity and fuel heat removal as a support system as follows:
Maintain temperatures compatible with the correct functioning of equipment in the Component Cooling Water System (RRI [CCWS]) and Emergency FeedWater System (ASG [EFWS]) valve rooms in all HL [SB(M)] buildings (see Sub-chapter 9.2, section 2, and Sub-chapter 6.4).
The DWL [CSBVS] system must contribute indirectly to the MSFs of fuel heat removal and confinement of radioactive material as a support system as follows:
Maintain temperatures compatible with the correct functioning of equipment in the EVU [CHRS] main pump rooms in HLF [SB(M)] and HLI [SB(M)] buildings (see Sub-chapter 6.1, section 7).
The DWL [CSVBS] system must contribute indirectly to the MSF of fuel heat removal as a support system as follows:
Maintain temperatures compatible with the correct functioning of equipment in the Fuel Pool Cooling (and Purification) System (PTR [FPCS/FPPS]) third train pump room in HLF [SB(M)] building (see Sub-chapter 9.1, section 3).
The DWL [CSBVS] system must contribute indirectly to the MSF of confinement of radioactive material as a supportAPPROVED system as follows: Ensure the long-term operation and maintenance of the iodine adsorption trains following an SA (DEC-B).
6.0.1.5. Specific Contribution to Hazards Protection
The DWL [CSBVS] system must contribute directly to the safety functions that are part of the facility’s hazards protection against the consequences of internal fire (see Sub-chapter 13.2, section 7), external explosion (see Sub-chapter 13.1, section 4) and earthquake (see Sub-chapter 13.1, section 2) as follows:
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Contribute to the containment and prevention of spread of a fire;
Limit the effects of an external pressure wave inside the HL [SB(M)] buildings in the case of external explosion; and
Preserve seismic requirements (SC1) Safety Features (SFs) availability levels following a seismic event.
Moreover, the DWL [CSBVS] system must be protected against internal and external hazards (see section 6.0.4.2).
6.0.1.6. Other Safety Functions to be performed in the Preventive Line of Defence
The DWL [CSBVS] system must contribute directly to other safety functions to be performed as part of the preventive line of defence as follows:
Monitor availability of local cooling in RIS [SIS] rooms and RRI/ASG [CCWS/EFWS] rooms;
Prevent the loss of an iodine adsorption train because of clogged filters in the case of a SA; and
Limit RIS [SIS] rooms’ pressure in the HLF [SB(M)] and HLI [SB(M)] buildings affected by a RIS/RRA [SIS/RHRS] leak with the reactor coolant temperature above { SCI removed } (PCC-4).
6.0.2. Safety Functional Requirements
6.0.2.1. Control of Fuel Reactivity
Not applicable: the DWL [CSBVS] system does not directly contribute to the MSF of control of fuel reactivity.
6.0.2.2. Fuel Heat Removal
Not applicable: the DWL [CSBVS] system does not directly contribute to the MSF of fuel heat removal.
6.0.2.3. Confinement of Radioactive Material
With respect to its contribution to the MSF of confinement of radioactive material, the DWL [CSBVS] system must satisfy the functional requirements detailed in the following sections.
Environmental Protection The DWL [CSBVS]APPROVED system must: Confine the radioactive material and prevent the risk of leaks; and
Limit radioactive discharges into the environment through abatement, storage, treatment and control of the waste conveyed.
Limiting Radiological Consequences
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In divisions 1 to 4 of the HL [SB(M)] buildings:
Requirement to confine controlled area in normal operating conditions (PCC-1):
o Maintain adequate depression in controlled area with respect to external atmospheric pressure.
Requirements to confine controlled area in order to collect and filter leaks through containment penetrations following an accident with activity releases in the HR [RB] building (PCC and DEC situations):
o Isolate normal ventilation supply and exhaust,
o Maintain a depression in controlled area with respect to external atmospheric pressure, and
o Ensure adequate abatement of radiological materials from extracted air before release to the environment via the main unit vent stack.
Requirements to confine controlled area and RIS [SIS] rooms to anticipate a potential RIS [SIS] leak in the HL [SB(M)] buildings while in SI mode (PCC situations):
o Isolate normal ventilation supply and exhaust,
o Isolate RIS [SIS] room air supply,
o Maintain a depression in controlled area with respect to external atmospheric pressure, and
o Ensure adequate abatement of radiological materials from extracted air before release to the environment via the main unit vent stack.
Requirement to maintain dynamic confinement over the long-term following a SA (DEC-B):
o Enable maintenance or repairs to be carried out on a faulty iodine adsorption train.
In HLF [SB(M)] and HLI [SB(M)] buildings:
Requirements to confine controlled area and EVU [CHRS] rooms to anticipate a potential EVU [CHRS] leak in the HL [SB(M)] buildings when in operation in DEC-B conditions:
o Isolate normal ventilation supply and exhaust, o APPROVEDIsolate EVU room air supply, o Maintain a depression in controlled area with respect to external atmospheric pressure, and
o Ensure adequate abatement of radiological materials from extracted air before release to the environment via the main unit vent stack.
In a given division of the HL [SB(M)] buildings:
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Requirements to confine the controlled area and RIS [SIS] rooms of the division affected by RIS/RRA [SIS/RHRS] leak with a reactor coolant temperature below { SCI removed } (PCC-4):
o Isolate normal ventilation supply and exhaust,
o Isolate RIS [SIS] room air supply,
o Maintain a depression in controlled area with respect to external atmospheric pressure, and
o Ensure adequate abatement of radiological materials from extracted air before release to the environment via the main unit vent stack.
In HLF [SB(M)] or HLI [SB(M)] buildings:
Requirement to protect RIS [SIS] rooms against overpressure in the division affected by a RIS/RRA [SIS/RHRS] leak with the reactor coolant temperature above { SCI removed } (PCC-4):
o Limit the pressure increase in rooms affected by the RIS [SIS] leak.
Requirement to restore static confinement following a RIS/RRA [SIS/RHRS] leak with the reactor coolant temperature above { SCI removed } (PCC-4):
o Restore static confinement within { SCI removed }.
In the HR [RB] building:
Requirement to confine statically the HR [RB] building extended to the room facing the personnel airlock following a fuel handling accident in the HR [RB] building or a LOCA with the equipment hatch opened (PCC-4):
o Isolate air supply of the room facing the personnel airlock.
In the HK [FB] building:
Requirements to confine dynamically the fuel pool hall in the event of a fuel handling accident in the HK [FB] building (PCC-4):
o Ensure start-up of dynamic confinement complies with the completion time derived from radiological studies;
o Maintain a depression in the HK [FB] fuel pool hall with respect to external APPROVEDatmospheric pressure; and o Ensure adequate abatement of radiological materials from extracted air before release to the environment via the main unit vent stack.
6.0.2.4. Support Contribution to Main Safety Functions
With respect to its contribution to the three MSFs, the DWL [CSBVS] system must satisfy the following Safety Functional Requirements (SFRs):
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Requirement to ensure adequate temperature in RIS [SIS] rooms in each HL [SB(M)] buildings:
o Maintain temperatures within specified limits, in all plant conditions, for the correct functioning of the RIS [SIS] pumps and heat exchanger (see Sub-chapter 6.2).
With respect to its contribution to the MSFs of control of fuel reactivity and fuel heat removal, the DWL [CSBVS] system must satisfy the following SFRs:
Requirement to ensure adequate temperature in RRI [CCWS] and ASG [EFWS] rooms in each HL [SB(M)] buildings :
o Maintain temperatures within specified limits, in all plant conditions, for the correct functioning of the RRI [CCWS] and ASG [EFWS] actuators (see Sub-chapter 9.2, section 2, and Sub-chapter 6.4).
With respect to its contribution to the MSFs of fuel heat removal and confinement of radioactive material, the DWL [CSBVS] system must satisfy the following SFRs:
Requirement to ensure adequate temperature in EVU [CHRS] rooms in HLF [SB(M)] and HLI [SB(M)] buildings:
o Maintain temperatures within specified limits, in all plant conditions, for the correct functioning of the EVU [CHRS] main pump (see Sub-chapter 6.1, section 7).
With respect to its contribution to the MSF of fuel heat removal, the DWL [CSBVS] system must satisfy the following SFRs:
Requirement to ensure adequate temperature in PTR [FPCS/FPPS] rooms in HLF [SB(M)] building:
o Maintain temperatures within specified limits, in all plant conditions, for the correct functioning of the third PTR [FPCS/FPPS] train pump (see Sub-chapter 9.1, section 3).
With respect to its contribution to the MSF of confinement of radioactive material, the DWL [CSBVS] system must satisfy the following SFRs:
Requirement to ensure long-term operation of iodine adsorption trains and enable their maintenance following an SA:
o Align the SA pre-filter with the DWL [CSBVS] iodine adsorption trains. 6.0.2.5. SpecificAPPROVED contribution to Hazards Protection With respect to its specific contribution to the safety functions that are part of the facility’s hazards protection, the DWL [CSBVS] system must satisfy the following SFRs:
Internal fire:
o Ensure containment of fire by closure of fire dampers that maintain the fire compartment integrity.
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External explosion:
o Ensure RIS [SIS] burst membrane integrity so as to limit the effects of an explosion pressure wave inside the HL [SB(M)] buildings in the case of an external explosion.
Earthquake:
o Ensure the integrity or stability of DWL [CSBVS] components to avoid damage to higher classified components and ensure that it does not adversely impact the availability of SC1 SFs following a seismic event.
6.0.2.6. Other Safety Functions to be performed in the Preventive Line of Defence
With respect to its contribution to other safety functions to be performed as part of the preventive line of defence, the DWL [CSBVS] system must satisfy the following SFRs:
Requirement to ensure availability of local cooling in RIS [SIS] rooms and RRI/ASG [CCWS/EFWS] rooms:
o Monitor continuously temperatures in RIS [SIS] rooms and RRI/ASG [CCWS/EFWS] rooms so as to be informed of a local cooling failure.
Requirement to prevent the loss of an iodine adsorption train because of clogged filters in SA:
o Monitor the differential pressure across the iodine adsorption train filters.
Requirement to protect RIS [SIS] rooms against overpressure in HLF [SB(M)] and HLI [SB(M)] buildings affected by a RIS/RRA [SIS/RHRS] leak mode with the reactor coolant temperature above { SCI removed } (PCC-4):
o Limit the pressure increase in rooms affected by the RIS [SIS] leak.
6.0.3. Safety Features and Instrumentation and Control (I&C) Actuation Modes
Section 9.4.6 – Table 1 presents the SFs of the DWL [CSBVS] system according to the contributions identified in section 6.0.1 and the SFRNs referenced in Sub-chapter 3.2.
6.0.4. Classification and Architecture Requirements of Safety Features
6.0.4.1. Requirements arising from Safety Classification
Architecture requirements associated with SFs are essential for designing robust lines of defence consistent with their importance to nuclear safety (see Sub-chapter 3.2). Such requirements strengthenAPPROVED the system design against: single faults and associated consequences (Single Failure Criterion (SFC)) by requiring redundancy;
Loss Of Off-site power (LOOP) by requiring, among others, a back-up power supply;
Station Black-Out (SBO) by requiring a power supply by the Ultimate Diesel Generators (UDGs);
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Common Cause Failures (CCF) by requiring physical separation;
earthquake by defining seismic requirements; and
accident conditions by defining qualification requirements.
Section 9.4.6 – Table 1 presents the requirements arising from safety classification for the DWL [CSBVS] system, according to the SFRNs referenced in Sub-chapter 3.2.
6.0.4.2. System Protection against Hazards
6.0.4.2.1. Internal Hazards
The SFs of the DWL [CSBVS] system must be protected against internal hazards if those hazards challenge the safety objectives, as defined in Sub-chapter 13.2.
6.0.4.2.2. External Hazards
The SFs of the DWL [CSBVS] system must be protected against external hazards if those hazards challenge the safety objectives, as defined in Sub-chapter 13.1.
6.0.4.3. Diversity
The DWL system must be subject to the requirement for diversity as defined in general safety principles (Sub-chapter 3.1) and in Sub-chapter 3.7, dealing with diversity.
6.0.5. Requirements defined at the Component Level
6.0.5.1. Generic Safety Requirements
6.0.5.1.1. Generic Mechanical, Electrical and I&C Requirements
The mechanical components within the DWL [CSBVS] system must comply with the mechanical requirements in accordance with the rules laid out in Sub-chapter 3.2, section 7. The level of requirement is dependent upon whether or not it is a pressure retaining component, the safety class of the component, whether the component acts as an isolating device between interfacing SFs, and on the role of the component as a barrier to the potential release of radioactivity as a result of failure of the component.
The electrical and Instrumentation & Control (I&C) components in the DWL [CSBVS] system must comply with the electrical and I&C requirements associated with their safety class, in accordance with the rules laid out in Sub-Chapter 3.2.
6.0.5.1.2. Seismic Requirements The level of seismicAPPROVED requirements to be applied to DWL [CSBVS] system components is related to the Safety Feature Group (SFG) to which the component belongs and the consequences on other classified components of its failure if it were not seismically qualified. The rules for defining the seismic requirements for a component are identified in Sub-chapter 3.2.
6.0.5.1.3. Qualification for Accident Conditions
The safety-classified parts of the DWL [CSBVS] system must be qualified for the operating conditions in which they are required, as specified in Sub-chapter 3.6.
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6.0.5.2. Specific Safety Requirements
6.0.5.2.1. High Integrity Component (HIC) Requirements
The DWL [CSBVS] system is not subject to any High Integrity Component (HIC) requirements.
6.0.5.2.2. Specific I&C Requirements
The DWL [CSBVS] system does not have any dedicated I&C. However, the DWL [CSBVS] system fire dampers are operated by the Fire Detection System (JDT [FDS]) dedicated I&C.
The specific requirements arising from the JDT [FDS] system dedicated I&C are described in Sub-chapter 9.5, section 1.2.
The general approach for I&C systems is set out in Chapter 7.
6.0.6. Examination, Maintenance, (In-service) Inspection and Testing (EMIT)
6.0.6.1. Start-up Tests
The DWL [CSBVS] system must be designed to enable the performance of start-up tests to ensure the adequacy of its design and performance under conditions as representative as possible of the different operating configurations, and in particular its compliance with the SFRs assigned to it in section 6.0.2.
6.0.6.2. In-Service Inspection
The DWL [CSBVS] system must be designed to enable surveillance under normal operation of the system characteristics necessary for the fulfilment of its safety-related tasks in order to ensure the performance of its components, and their availability under normal operation, or in the event of a fault or accident.
6.0.6.3. Periodic Testing
The safety-classified parts of the DWL [CSBVS] system must be designed to enable the performance of periodic tests in accordance with the maintenance schedule.
6.0.6.4. Maintenance
The DWL [CSBVS] system must be designed to enable the implementation of a maintenance schedule (see Sub-chapter 18.2).
6.1. ROLE OF THE SYSTEM
The DWL [CSBVS] system performs the functions (or tasks) detailed in the following sections under the differentAPPROVED plant operating conditions for which it is required. 6.1.1. Normal Operating Conditions
Under normal operation, ventilation of rooms is provided by DWL [CSBVS] ducts connected to the air supply of the Safeguard Building (uncontrolled area) Ventilation Systems Electrical (division) (DVL [SBVSE]), with extraction and filtering connected to the Nuclear Auxiliary Building Ventilation System (DWN [NABVS]).
In normal operating conditions, the DWL [CSBVS] system performs the following tasks:
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Provide adequate airflow to limit aerosol and radioactive gas concentrations in HL [SB(M)] building controlled areas and to avoid air stagnation;
Maintain HL [SB(M)] building controlled areas under depression with respect to external atmospheric pressure;
Maintain contaminated areas under depression with respect to less contaminated areas to prevent contamination dispersion within HL [SB(M)] buildings. In particular, a depression is maintained in rooms identified with iodine risk compared to the other rooms; and
Maintain temperatures within specified limits for correct operation of equipment and/or staff operation.
The DWL [CSBVS] system ventilates the room facing the personnel airlock in interface with the HR [RB] building when the equipment hatch is closed. The exhaust isolation damper is closed preventively when the equipment hatch is open.
The DWL [CSBVS] system provides confinement preventively within the RIS [SIS] rooms when the RIS/RRA [SIS/RHRS] is at a temperature above { SCI removed } in HLF [SB(M)] and HLI [SB(M)] buildings. Supply and exhaust isolation dampers are closed. In this case, the rest of the division is still ventilated normally and ventilation of RIS [SIS] rooms is re-established when the reactor coolant temperature is below { SCI removed }.
6.1.2. Fault and Hazard Operating Conditions
The roles of the DWL [CSBVS] system in fault and hazard operating conditions are the following:
In the HL [SB(M)] buildings:
In the event of an accident: the DWL [CSBVS] system ensures the isolation of the controlled mechanical areas of the HL [SB(M)] buildings when the RIS [SIS] system is used after an accident in the HR [RB] building. It isolates this volume and extracts from it airborne contamination which may have been released, using the dedicated iodine adsorption lines filters and fans of the DWL [CSBVS] system. The DWL [CSBVS] system also isolates the volume potentially contaminated by the EVU [CHRS] when this system is used after an SA. The dynamic confinement of the controlled mechanical area of the HL [SB(M)] buildings is performed by the DWL [CSBVS] extraction trains (filters and fans) as described previously. In the case of an SA, air is diverted through an additional dedicated pre-filter upstream of the DWL [CSBVS] iodine adsorption trains.
In HL [SB(M)] building rooms which have high internal heat loads (such as large pump motors), local cooling units are installed to maintain temperatures compatible with equipment operation. In the RIS [SIS] and ASG/RRI [EFWS/CCWS] rooms, redundant local coolingAPPROVED units are provided, with diverse chilled water supply (back-up line of Safety Chilled Water System (DEL [SCWS]) system, see section 10), electrical supplies and I&C control. They maintain temperature for correct functioning of equipment if the main line of local cooling units is lost. The chilled water supply for the main line of local cooling units is provided by the main line of the DEL [SCWS] system (see section 10).
In the HK [FB] building:
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The filters and the extraction fans of the DWL [CSBVS] system ensure dynamic confinement of the fuel pool hall and extract airborne contamination in the event of a fuel handling accident in the HK [FB] building.
In the HR [RB] building:
Automatic isolation of the air supply in the room facing the personnel airlock is performed by the DWL [CSBVS] system in the event of a fuel handling accident in the HR [RB] building. Extraction of the HR [RB] building air and adsorption of iodine is taken over by the Containment Sweep Ventilation System (EBA [CSVS]), see section 5).
6.2. DESIGN BASIS
6.2.1. General Assumptions
During accident conditions, dynamic confinement is maintained using one of the extraction fans. If the first operating DWL [CSBVS] iodine line fails, the second fan is started in normal-backup mode.
The DWL [CSBVS] system is required to be available during every power plant configuration including shutdown conditions and especially during fuel handling in the HK [FB] building.
The normal method for performing preventive maintenance of local cooling unit fans will be during maintenance of supported systems with the plant in operation or during plant at shutdown if supported systems are not required.
For the specific case of local cooling units in RIS [SIS] and ASG/RRI [EFWS/CCWS] rooms, there is a back-up line of local cooling units that enable preventive maintenance to be performed without losing the local cooling capacity.
The temperature of the air supplied by the DVL [SBVSE] system is normally set at a constant value, currently expected to be { SCI removed }.
External Environment Conditions
The outdoor design temperature conditions are defined in section 1.
Conditions in Rooms
During accident conditions, the DWL [CSBVS] local cooling units are used to maintain the required temperature for operation of the safety systems (RIS [SIS], PTR [FPCS/FPPS], EVU [CHRS], RRI [CCWS], ASG [EFWS]). These local cooling units are also used to fulfil the normal operation temperature requirements.
The DWL [CSBVS] convectors are used for general heating during cold weather conditions to maintain the minimumAPPROVED required temperature in particular in boron rooms. The temperatures to be maintained in these rooms are given in section 1.
Minimum Air Change Rate:
The air change rates for normal operation are given in section 1.
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6.2.2. Design Assumptions
6.2.2.1. Control of Fuel Reactivity
Not applicable: the DWL [CSBVS] system does not directly contribute to the MSF of control of fuel reactivity.
6.2.2.2. Fuel Heat Removal
Not applicable: the DWL [CSBVS] system does not directly contribute to the MSF of fuel heat removal.
6.2.2.3. Confinement of Radioactive Material
Dynamic Confinement
To ensure a depression in the confined areas, the maximum required flow rate from the DWL [CSBVS] extraction fans has been set using maximum assumed building’s leak rates under depression.
Air Filtering
The decontamination factors required for the High Efficiency Particulate Air (HEPA) filters and iodine adsorption units are given in section 1. The decontamination factor for the SA pre-filter is at least 1,000 (solid aerosols).
Taking into account these required efficiencies; the sizing of the filters and iodine adsorption units has been carried out using the following assumptions:
HEPA Filter and Severe Accident Pre-filter:
o source term in DEC-B situations; and
o maximum flow rate per iodine line: { SCI removed }.
Iodine Adsorption Unit:
o source term in DEC-B situations;
o air relative humidity: below { SCI removed }; and
o maximum flow rate per iodine line: { SCI removed }.
The heaters of the iodine adsorption trains have been designed to maintain the relative humidityAPPROVED below { SCI removed } upstream of the iodine adsorption unit assuming: o maximum temperatures in the HL [SB(M)] or HK [FB] building rooms;
o relative humidity upstream: 100%;
o maximum flow rate: { SCI removed }.
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Static Isolation
Quick closing isolation dampers are installed to ensure isolation of normal ventilation, the RIS [SIS] rooms’ air supply, and personnel airlock air supply. Manual isolation dampers are installed to ensure isolation of the EVU [CHRS] rooms’ air supply. The isolation damper leakages shall meet the requirement defined in section 1.
Start-up of HK Dynamic Confinement
Following a fuel handling accident in the HK [FB] building, the DWL [CSBVS] iodine adsorption train is started within { SCI removed } to comply with radiological studies.
Protection against Overpressure
The internal burst pressure of the RIS [SIS] rooms Overpressure Protection (OPP) devices in HLF [SB(M)] and HLI [SB(M)] buildings is set at { SCI removed }.
6.2.2.4. Support Contribution to Main Safety Function
Air-conditioning:
Maximum temperatures in the HL [SB(M)] building controlled areas depend on the qualification temperature of DWL [CSBVS]-served equipment and are given in section 1. In order to make sure that adequate temperature is maintained at all time, the DWL [CSBVS] main and back-up local cooling units have been sized taking into account the following assumptions:
o maximum outdoor temperature for external heat transmissions defined in section 1,
o maximum temperature in adjacent buildings defined in section 1,
o maximum heat loads dissipated by equipment and pipe work in fault conditions or SA conditions,
o permanent state, and
o loss of general ventilation.
6.2.2.5. Specific contribution to Hazards Protection
Fire segregation:
Not applicable: there are no quantitative safety-related design assumptions associated with theAPPROVED DWL [CSBVS] system. External explosion:
The RIS [SIS] burst membranes are designed to withstand an external explosion pressure wave of { SCI removed }.
Earthquake:
Not applicable: there are no quantitative safety-related design assumptions associated with the DWL [CSBVS] system.
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6.2.2.6. Other Safety Functions to be performed in the Preventive Line of Defence
Information of local cooling availability:
Not applicable: there are no quantitative safety-related design assumptions associated with the DWL [CSBVS] system.
Information to avoid the loss of filtration in the case of an SA:
Not applicable: there are no quantitative safety-related design assumptions associated with the DWL [CSBVS] system.
Protection against overpressure:
The internal burst pressure of the RIS [SIS] rooms overpressure protection devices in the HLF [SB(M)] and HLI [SB(M)] buildings is set at { SCI removed }.
6.2.3. Other Assumptions
The DWL [CSBVS] system is also subject to the following assumptions:
The DWL [CSBVS] system design is consistent with RCC-M requirements as described in Sub-chapter 3.8, section 2.
The DWL [CSBVS] system design is consistent with fire requirements as described Sub-chapter 3.8 section 5.
6.2.4. Assumptions associated with Extreme Situations resulting from Beyond Design-Basis Hazards
6.2.4.1. Assumptions associated with Fukushima Provisions
The assumptions associated with the Fukushima provisions of the DWL [CSBVS] system are presented in Chapter 23. The main provisions are:
start-up of dynamic confinement,
isolation of EVU [CHRS] rooms from main ventilation,
isolation of HL [SB(M)] building controlled area ventilation,
local cooling of EVU [CHRS] main pump rooms, local coolingAPPROVED of RIS [SIS] pump and exchanger rooms, local cooling of RRI/ASG [CCWS/EFWS] valve rooms,
long-term operation of the DWL [CSBVS] system, and
pre-filtration alignment.
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6.2.4.2. Assumptions associated with non-Fukushima provisions
The DWL [CSBVS] system is not subject to assumptions associated with non-Fukushima provisions.
6.3. SYSTEM DESCRIPTION AND OPERATION
6.3.1. Description
6.3.1.1. General System Description
The system comprises four networks, each allocated to the mechanical part of a division of the HL [SB] buildings and an iodine extraction system used in the case of accidents. Each part is described below:
Each network allocated to the mechanical part of a division of the HL [SB(M)] buildings comprises a set of air supply ducts connected to the air supply network of the DVL [SBVSE] system, that includes a control damper, two isolation dampers and a fire damper arranged in a series configuration, and a set of extraction ducts that includes the following:
o Two isolation dampers arranged in a series configuration connected to the extraction trains of the DWN [NABVS] system located in the Nuclear Auxiliary Building (HN [NAB]) in the case of normal ventilation isolation. Additionally, two fire dampers arranged in a series configuration are installed on the exhaust line.
o Two isolation dampers arranged in parallel configuration connected to the iodine extraction trains of the DWL [CSBVS] system, used in the event of an accident, located in the HK [FB] building. Additionally, two fire dampers arranged in a series configuration are installed on the exhaust line.
The iodine filtering trains located in the HK [FB] building comprises 2 x 100% trains connected in parallel, each with a flow rate of { SCI removed }. Each train is installed in a separate room and comprises the following:
o two fire dampers located before the iodine train,
o an inlet manual isolation damper,
o an electrical heater,
o a HEPA filter,
o an iodine adsorption unit, o APPROVEDan outlet manual isolation damper, o a fan,
o a non-return damper, and
o two fire dampers located after the iodine train.
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A metallic SA pre-filter, located upstream of iodine lines, minimises radiological releases in the event of an SA and increase the life of the iodine adsorption train’s filters by filtering solid aerosols from the airflow. The SA pre-filter also reduces the radiological dose rate in the DWL [CSBVS] iodine train rooms to enable access for maintenance. For other situations, this equipment is bypassed.
The DWL [CBSVS] system also provides local cooling units in rooms having high heat loads (RIS [SIS], PTR [FPCS/FPPS], EVU [CHRS], RRI [CCWS], ASG [EFWS] rooms). Each cooling unit starts automatically at the required set point temperature or on start-up of an associated pump.
The fuel pool hall DWK [FBVS] system extraction ducts are connected upstream of the iodine adsorption trains of the DWL [CSBVS] system with two isolation dampers arranged in parallel configuration.
6.3.1.2. Description of Main Equipment
The DWL [CSBVS] system comprises the main equipment items detailed in the following sections (see the functional diagram provided in section 6.5).
SA Pre-Filter
The pre-filter is installed in the exhaust air upstream of the iodine line and is provided for SA situations.
DWL Adsorption Train Air Heaters
The function of the air heaters is to heat the air to limit relative humidity to a maximum of { SCI removed } upstream of iodine adsorption units (see also section 6.4.1.3). They are equipped with output regulators.
DWL Adsorption Train Pre-Filters
The pre-filters used in the exhaust air upstream of the HEPA filters are provided to increase the life of the HEPA filters by filtering coarse particles.
DWL Adsorption Train HEPA Filters
The HEPA filters upstream of iodine adsorption units remove radioactive aerosol contaminants.
DWL Adsorption Train Iodine Adsorption Units
The iodine adsorptions units are used in the Heating, Ventilation and Air Conditioning (HVAC) system to adsorb gaseous iodine from extracted air. DWL AdsorptionAPPROVED Train Exhaust Fan The exhaust fans ensure air collection from HL [SB(M)] buildings or HK [FB] building and the release via the main unit vent stack after filtering and adsorption.
Local Cooling Units
To supplement the cooling provided by the DVL [SBVSE] system or when general ventilation is lost, the HL [SB(M)] building rooms which have high internal heat loads are provided with local cooling units.
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Air Transfer Fans
Three air transfer fans are installed in HL { SCI removed } [SB(M)] and HL { SCI removed } [SB(M)] buildings. In these cases, the cooling requirements of the room are provided by the local cooling unit installed in the adjoining room.
Convectors
These convectors are used for general area heating during cold weather conditions in order to maintain minimum required temperatures in HL [SB(M)] building controlled areas.
6.3.1.3. Description of Main Layout
The main DWL [CSBVS] equipment is located as shown in Section 9.4.6 – Table 2.
SECTION 9.4.6 – TABLE 2 : LOCATION OF MAIN DWL [CSBVS] SYSTEM EQUIPMENT
Component Train 1 Train 2 Train 3 Train 4 Local cooling units RIS [SIS] { SCI { SCI { SCI rooms { SCI removed } removed } removed } removed } (main and back-up lines) Local cooling units ASG/RRI { SCI { SCI { SCI [EFWS/CCWS] rooms { SCI removed } removed } removed } removed } (main and back-up lines) Local cooling units EVU [CHRS] { SCI { SCI { SCI { SCI removed } rooms removed } removed } removed } Local cooling units PTR { SCI { SCI { SCI { SCI removed } [FPCS/FPPS] rooms removed } removed } removed } { SCI { SCI { SCI Iodine adsorption trains { SCI removed } removed } removed } removed }
6.3.1.4. Description of System I&C
The JDT [FDS] system dedicated I&C used for the DWL [CSBVS] system fire dampers is described in the JDT [FDS] system chapter (see Sub-chapter 9.5, section 1.2).
6.3.2. Operation
6.3.2.1. System Normal Operation
The DWL [CSBVS] system is used when the plant is in operation or at shutdown. 6.3.2.1.1. PlantAPPROVED in Operation The four air supply and extraction systems for the four divisions are in operation.
In each division, the DVL [SBVSE] system supplies a continuous flow rate to the DWL [CSBVS] system air supply network and the DWN [NABVS] system extracts the air from each division in the controlled areas.
The DWL [CSBVS] iodine train extraction fans are normally shut down and dampers are closed.
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6.3.2.1.2. Plant at Shutdown
The configuration of the DWL [CSBVS] system is the same as during normal operation.
If maintenance operations, that are to be carried out on equipment or systems, lead to a risk of delayed release of iodine the division extraction system may, as a precautionary measure, be aligned in iodine adsorption mode by appropriate setting of the DWN [NABVS] system extraction dampers.
In both cases, the nominal air supply rate is provided by the DVL [SBVSE] system.
6.3.2.1.3. Other Permanent Operating Conditions of the System
Operation of the RIS [SIS] System during a LOCA
In the case of a LOCA, a leak from the RIS [SIS] system may lead to an iodine activity level that is incompatible with extraction via the iodine adsorption trains of the DWN [NABVS] system. As a preventive measure, the air supply (DVL [SBVSE] system) and extraction (DWN [NABVS] system) to and from the HL [SB(M)] buildings are isolated. Extraction is carried out using the iodine adsorption trains of the DWL [CSBVS] system.
Local cooling unit fans, for the rooms containing RIS [SIS] system components, will start if a RIS [SIS] pump is started. Local cooling unit fans for the rooms containing RRI [CCWS] components continue to operate automatically.
Operation of the RIS/RRA [SIS/RHRS] System
RIS/RRA [SIS/RHRS] leak, T > { SCI removed }:
The RIS/RRA [SIS/RHRS] rooms of divisions 1 and 4 are isolated as a preventive measure.
A depressurisation mechanism (burst pressure opening vents type) opens if the pressure rises to too high a level in the RIS [SIS] rooms.
When the venting has relieved the excess pressure, the outlet has closed and the steam has condensed, confinement of the RIS [SIS] rooms by DWL [CSBVS] system is resumed.
RIS/RRA [SIS/RHRS] leak, T< { SCI removed }:
Normal ventilation is maintained.
In the case of leak detection by RIS [SIS] system, the normal air supply and exhaust, and the RIS [SIS] room air supply are isolated. The DWL [CSBVS] iodine adsorption is then automaticallyAPPROVED started. Operation of the EVU [CHRS] System in the Event of an SA
In the event of an SA, all the EVU [CHRS] rooms are isolated from other rooms by closing the air supply dampers located on each supply ductwork prior to EVU [CHRS] pump start. A local cooling unit will start and stop according to the temperature measurements in the EVU [CHRS] rooms.
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Fuel Handling Accident in the HK [FB] Building
These conditions do not affect the ventilation of the HL [SB(M)] buildings.
In these conditions, one of the iodine extraction trains of the DWL [CSBVS] system is used and provides the extraction flow rate to achieve dynamic confinement in the concerned area.
Fuel Handling Accident in the HR [RB] Building
These conditions do not affect the general ventilation of the HL [SB(M)] buildings. Only the personnel airlock neighbouring room ventilation is modified.
The HR [RB] building confinement is ensured by closing the two redundant air supply isolation dampers facing the personnel airlock. The exhaust isolation damper closure is confirmed if necessary, as it will have been closed to ensure that airflow through the personnel airlock is directed towards the HR [RB] building.
Partial or Total Loss of Ultimate Heat Sink (LUHS)
To protect against the loss of DWL [CSBVS] local cooling units, chiller condensers of the main line of the DEL [SCWS] system (DELm) in divisions 1 and 4 and chiller condensers of the back- up line of the DEL [SCWS] system (DELb) are cooled by air. Therefore, following a LUHS situation, cooling function in the EVU [CHRS], PTR [FPCS/FPPS], RIS [SIS] and ASG/RRI [EFWS/CCWS] rooms of all HL [SB(M)] buildings remains available.
Severe Accident
In the event of an SA, minimisation of radiological releases is ensured by the SA pre-filter, located upstream of iodine adsorption lines.
6.3.2.2. System Transient Operation
6.3.2.2.1. Full or Partial DWL [CSBVS[ System Failure
{ This section contains SCI-only text and has been removed }
6.3.2.2.2. Failure of Systems in Interface (Server or Served)
{ This section contains SCI-only text and has been removed }
6.4. PRELIMINARY DESIGN SUBSTANTIATION
6.4.1. Compliance with Safety Functional Requirements 6.4.1.1. ControlAPPROVED of Fuel Reactivity Not applicable: the DWL [CSBVS] system does not directly contribute to the MSF of fuel reactivity.
6.4.1.2. Fuel Heat Removal
Not applicable: the DWL [CSBVS] system does not directly contribute to the MSF of fuel heat removal.
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6.4.1.3. Confinement of Radioactive Material
Environmental Protection
The leak-tightness of the DWL [CSBVS] ductwork and other HVAC components is reinforced (in compliance with rules regarding mechanical classification given in section 6.0.5.1.1) so as to reduce the risk of mechanical failures and protect the environment against potential radioactive leaks. Moreover, in order to limit potential radioactive discharges into the environment under normal operation, extracted air is filtered by the DWN [NABVS] system before discharge to the main unit vent stack.
Limiting Radiological Consequences
In the HL [SB(M)] buildings:
Dynamic confinement of HL [SB(M)] building controlled areas in normal operating conditions:
o Maintain a depression in HL [SB(M)] controlled areas with respect to external atmospheric pressure:
. A motorised control damper on the DWL [CSBVS] supply line of each division (from the DVL [SBVSE] system) is used to control the supply flow rate and maintain, in combination with the extraction provided by the DWN [NABVS] system, a depression of 100 Pa in the controlled area.
Static confinement of HL [SB(M)] building controlled areas to collect leaks through containment penetrations following an accident with activity releases in the HR [RB] building, to anticipate a potential RIS [SIS] leak while in SI mode or EVU [CHRS] leak when in operation in DEC-B conditions, or following a RIS/RRA [SIS/RHRA] leak (in that case it concerns only the division affected):
o Isolate normal ventilation supply and exhaust:
. Redundant quick closing isolation dampers (on supply and exhaust lines) are closed on receipt of a safety injection signal, stage 1 containment isolation signal or signal actuated by a RIS [SIS] leak (high sump level or high pressure). Isolation is ensured by T2 leaktightness as defined in section 1 (inner leaktightness and leaktightness to the environment).
Dynamic confinement of HL [SB(M)] building controlled areas to collect leaks through containment penetrations following an accident with activity releases in the HR [RB] building, to anticipate a potential RIS [SIS] leak while in SI mode or EVU [CHRS] leak when in operation in DEC-B conditions, or following a RIS/RRA [SIS/RHRA] leak (in that case it APPROVEDconcerns only the division affected): o Maintain a depression in HL [SB(M)] controlled areas with respect to external atmospheric pressure:
. The DWL [CSBVS] extraction fans are sized based on assumptions defined in section 6.2.2 so as to maintain a depression in the confined area compared to the external environment pressure.
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o Ensure adequate abatement of radiological materials from extracted air using DWL [CSBVS] emergency adsorption trains before release to the environment via the main unit vent stack:
. The DWL [CSBVS] air heaters upstream of iodine adsorption units are sized based on assumptions defined in section 6.2.2 to keep air relative humidity below { SCI removed } and ensure iodine adsorption unit efficiency.
. The DWL [CSBVS] filters and iodine adsorption units are sized based on assumptions defined in section 6.2.2 so as to provide required decontamination factors.
Confinement of RIS [SIS] rooms when the RIS [SIS] system operates in SI mode or when a RIS/RRA [SIS/RHRS] leak is detected (in that case only for the division affected):
o Isolate RIS [SIS] room air supply:
. RIS [SIS] room quick closing supply isolation dampers are closed on receipt of a safety injection signal, stage 1 containment isolation signal or signal actuated by a RIS [SIS] leak (high sump level or high pressure). Isolation is ensured by T2 leak-tightness as defined in section 1.
Confinement of EVU [CHRS] rooms (in divisions 1 and 4) when this system is in operation following a severe accident in the HR building:
o Isolate EVU [CHRS] room air supply:
. EVU [CHRS] room supply isolation dampers (in divisions 1 and 4) are closed manually before start-up of the EVU [CHRS] pump. Isolation is ensured by T2 leak-tightness as defined in section 1.
Protection of the RIS [SIS] rooms against overpressure following a RIS/RRA [SIS/RHRS] leak with a reactor coolant temperature above { SCI removed } (only possible in division 1 or 4):
o Limit the pressure in the rooms affected by the RIS [SIS] leak:
. The internal burst pressure of the qualified overpressure protection device (membrane) installed in RIS [SIS] rooms of divisions 1 and 4 is set at { SCI removed }.
Restoration of static confinement following a RIS/RRA [SIS/RHRWS] leak with a reactor coolant temperature above { SCI removed } (only possible in division 1 or 4): o APPROVEDRestore static confinement of the RIS [SIS] rooms: . Steel plates are used to close the outlet within { SCI removed }.
Long-term operation of the DWL [CSBVS] system in SA:
o Enable maintenance or repairs to be carried out on a faulty adsorption train:
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. When maintenance or repairs are needed, filtration is switched from the first to the second iodine adsorption train manually from the main control room. Manual isolation dampers are used to isolate the faulty train so that maintenance can be carried out.
In the HR [RB] building:
Static confinement of the room facing the personnel airlock in the case of a fuel handling accident in the HR [RB] building or a LOCA with the equipment hatch opened:
o Isolate the room facing the personnel airlock:
. Redundant quick closing supply isolation dampers are closed on receipt of a high activity signal in the HR [RB] building. Isolation is ensured by T2 leaktightness defined in section 1.
In the HK [FB] building:
Dynamic confinement of HK [FB] fuel pool hall in the event of a fuel handling accident in the HK [FB] building:
o Ensure start-up of dynamic confinement meets the completion time required by radiological studies:
. Mechanical and I&C equipment are chosen to ensure dynamic confinement of fuel pool hall is started in less than { SCI removed } after a fuel handling accident in the HK [FB] building (case of DWL [CSBVS] iodine adsorption train reloading and restart after LOOP).
o Maintain a depression in the fuel pool area with respect to external atmospheric pressure:
. The DWL [CSBVS] extraction fans are sized based on assumptions defined in section 6.2.2 so as to maintain a depression in the confined area compared to the external environment pressure.
o Ensure adequate abatement of radiological materials from extracted air using DWL [CSBVS] emergency adsorption trains before release to the environment via the main unit vent stack:
. The DWL [CSBVS] air heaters upstream of iodine adsorption units are sized based on assumptions defined in section 6.2.2 to keep air relative humidity below { SCI removed } and maintain required iodine adsorption unit efficiency.
. The DWL [CSBVS] filters and iodine adsorption units are sized based on APPROVEDassumptions defined in section 6.2.2 so as to provide required decontamination factors.
6.4.1.4. Support Contribution to Main Safety Functions
Maintenance of adequate temperatures in the HL [SB(M)] building controlled areas:
o Ensure temperatures remain within specified limits compatible with equipment operation:
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. Design assumptions used for the sizing of local cooling units (which are defined in section 6.2.2) enable temperatures to be maintained within limits required for correct operation of supported equipment in all plant conditions.
. Back-up local cooling units installed in RIS [SIS] rooms and ASG/RRI [EFWS/CCWS] rooms are sized based on the same design assumptions and can therefore maintain required temperatures independently in the case of failure of the main line of local cooling units.
Long-term operation and accessibility of the iodine adsorption unit rooms for maintenance:
o Align the SA pre-filter with the DWL [CSBVS] iodine adsorption trains:
. Motorised dampers are used to align the SA pre-filter with iodine adsorption trains manually from the Main Control Room (MCR) when entering an SA condition.
6.4.1.5. Specific Contribution to Hazards Protection
The hazard studies of Sub-chapters 13.1 and 13.2 involving functions of the DWL [CSBVS] system use values for the following parameters that are in keeping with the design assumptions stated in section 6.2.2:
Internal fire:
o Contribute to the containment and prevention of spread of fire in the HL [SB(M)] buildings by closure of the fire dampers:
. Fire damper qualification, and
. Fire damper closure is ensured by active (automation by the JDT [FDS] system) or ultimately passive means (fusible device inside and outside the duct) and is monitored by position status.
External explosion:
o Ensure the RIS [SIS] burst membrane integrity so as to limit the effects of a pressure wave inside the HL [SB(M)] buildings in the case of external explosion:
. The bursting membranes in the RIS [SIS] rooms of divisions 1 and 4 are designed to withstand an external explosion of { SCI removed } so as to protect equipment in HL [SB(M)] building controlled area against the APPROVEDexplosion pressure wave. Earthquake:
o Ensure stability or integrity of DWL [CSBVS] components to avoid damage to higher classified components following a seismic event:
. Qualification to keep the components integrity or stability.
For each hazard study concerned, these studies show that the design of these functions is such that they meet the acceptance criteria.
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These elements ensure that the SFRs stated in section 6.0.2 are met.
6.4.1.6. Other Safety Function to be performed in the Preventive Line of Defence
Other safety function to be performed in the preventive line of defence involving the DWL [CSBVS] system use values for the following parameters that are in keeping with the design assumptions stated in section 6.2.2.
Information of local cooling availability:
o Monitor temperatures in RIS [SIS] rooms and RRI/ASG [CCWS/EFWS] rooms:
. Temperature sensors installed in the RIS [SIS] rooms and RRI/ASG [CCWS/EFWS] rooms monitor temperatures and alarm operators in the case of local cooling failure.
Information to prevent the loss of an iodine adsorption train because of clogged filters in SA:
o Monitor the differential pressure across iodine adsorption train filters:
. Differential pressure measurements are used to alarm operators in the MCR when filters are clogged following an SA.
Protection of the RIS [SIS] rooms against overpressure following a RIS/RRA [SIS/RHRS] leak with a reactor coolant temperature above { SCI removed } (only possible in division 1 and 4):
o Limit the pressure in the rooms affected by the RIS [SIS] leak:
. The internal burst pressure of the qualified overpressure protection device (membrane) installed in RIS rooms of divisions 1 and 4 is set at { SCI removed }.
These elements ensure that the SFRs stated in section 6.0.2 are met.
6.4.2. Compliance with Design Requirements
The DWL [CSBVS] system complies with the requirements stated in sections 6.0.4 and 6.0.5, particularly with respect to those detailed in the following sections.
6.4.2.1. Requirements arising from Safety Classification
6.4.2.1.1. Safety Classification The complianceAPPROVED of the design and manufacture of the DWL [CSBVS] system materials and equipment performing a safety-related function with requirements from the classification rules (see Sub-chapter 3.2, section 7) is presented in section 6.4.2.4.1.
6.4.2.1.2. Single Failure Criterion and Redundancy
Active Single Failure:
The design of the DWL [CSBVS] system meets the requirements of the active SFC stated in section 6.0.4.1.
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The DWL [CSBVS] emergency extraction (class 2) meets the SFC being comprised of 2 x 100% trains that are supplied by different electrical divisions. They are started automatically on receipt of a containment isolation signal or manually from the MCR.
The class 1 and class 2 dampers are provided with redundancy and powered by different electrical divisions.
The class 3 dampers are not provided with redundancy.
Only the class 1 RIS [SIS] room supply isolation dampers are not redundant. However, as the general ventilation is automatically isolated using the same I&C signals as for isolation of RIS [SIS] rooms, it can be treated as a functional redundancy.
Passive Single Failure:
The DWL [CSBVS] system SFs are required to be robust against passive single failure. Single failure has been applied to active components and redundancy is adequately ensured. Application of the passive single failure to this system is discussed in Sub-chapter 15.3, section 1.
Regarding class 1 bursting membranes, passive SFC is not met by physical redundancy but by their design; in particular by membranes being simple, robust and reliable components, and by taking conservative assumptions in associated studies.
6.4.2.1.3. Robustness against loss of power
For normal power supplies, each DWL [CSBVS] train of division 1, 2, 3, 4 is supplied respectively by electrical division 1, 2, 3, 4.
The design of the DWL [CSBVS] system complies with the emergency power supply requirement stated in section 6.0.4.1.
LOOP
The power for the class 1 and class 2 dampers is backed-up by the main diesel generators. The class 3 dampers are not provided with backed-up power supplies.
In the event of LOOP, the fans and others actuators of the DWL [CSBVS] iodine adsorption trains, local cooling unit fans of RRI/ASG [CCWS/EFWS], RIS [SIS], PTR [FPCS/FPPS] and EVU [CHRS] rooms (including back-up lines of local cooling units for RRI/ASG [CCWS/EFWS] and RIS [SIS] rooms) as well as air transfer fans are provided with backed-up power supplies.
Air exhaust isolation dampers to the personnel airlock and EVU [CHRS] supply damper are not power backed-up but have a closed safety position. The RIS [SIS] exhaust dampers have an opened safety position.
All fire dampersAPPROVED are powered by uninterruptible power supplies. The fire dampers also include passive thermal fuses that will close the dampers in event of a fire.
SBO
In the event of SBO, the DWL [CSBVS] iodine adsorption trains components (electric air heaters, exhaust fans and pre-filter motorised isolation dampers) and the HL [SB(M)] and HK [FB] buildings emergency exhaust dampers are provided with backed-up power supplies.
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In divisions 1 and 4 of the HL [SB(M)] buildings, the fans of the main line of the local cooling units in the RIS [SIS], RRI/ASG [CCWS/EFWS], PTR [FPCS/FPPS] and EVU [CHRS] rooms as well as air transfer fans are powered by the UDGs.
Normal ventilation redundant isolation dampers and RIS [SIS] rooms supply isolation dampers have a closed safety position on loss of power which ensures the RIS [SIS] rooms and HL [SB(M)] buildings confinement.
Air supply redundant isolation dampers to the personnel airlock have a closed safety position which ensures HR [RB] building confinement.
6.4.2.1.4. Physical Separation
The DWL [CSBVS] system is designed in accordance with the physical separation requirement stated in section 6.0.4.1, in particular in respect of the following:
Iodine adsorption trains are geographically separated as they are located in different rooms.
Redundant isolation dampers are installed so as to be physically separated.
6.4.2.2. System Protection against Hazards
6.4.2.2.1. Internal Hazards
The overall demonstration of the robustness of the plant to internal hazards is covered in Sub-Chapter 13.2.
6.4.2.2.2. External Hazards
The overall demonstration of the robustness of the plant to external hazards is covered in Sub-Chapter 13.1.
6.4.2.3. Diversity
The design of the DWL [CSBVS] system complies with the diversity requirement stated in section 6.0.4.3 (more details are provided in Sub-chapter 3.7 dealing with diversity).
Local cooling unit in PTR [FPCS/FPPS] rooms in HLF [SB(M)] building support the PTR [FPCS/FPPS] third train, which is a diverse line of the main PTR [FPCS/FPPS] trains.
Local cooling units in RIS [SIS] rooms support the RIS [SIS] system, which is a diverse line of protection in some accidental scenarios.
Similarly, local cooling units in RRI [CCWS] rooms support the RRI [CCWS] system, which takes part in some diverseAPPROVED lines of protection as a support system. At a system level, the key diversity feature for the DWL [CSBVS] system is to provide back-up local cooling in RIS [SIS] rooms and ASG/RRI [EFWS/CCWS] rooms of all HL [SB(M)] buildings. Redundant back-up local cooling units have diverse power supplies, I&C control and chilled water supply (provided by the back-up line of the DEL [SCWS] system (DELb)).
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6.4.2.4. Requirements defined at the Component Level
6.4.2.4.1. General Mechanical, Electrical and I&C Requirements
The components of the DWL [CSBVS] system equipment performing a safety-related function comply with the general mechanical, electrical, I&C requirements stated in section 6.0.5.1 as detailed in Section 9.4.6 – Table 3.
SECTION 9.4.6 – TABLE 3 : CLASSIFICATION OF MAIN MECHANICAL AND ELECTRICAL COMPONENTS ASSOCIATED TO THEIR SAFETY FEATURES
Safety Design requirements
classification
Description
Seismic
Electrical
Mechanical
requirement requirement
classof SFG
leak tightness leak
Highestsafety Highestsafety
components or
requirementfor requirementfor
I&C requirement I&C
functioncategory
HVAC HVAC component pressure retaining Normal ventilation supply and exhaust A 1 T2 SC1 C1 C1 isolation dampers Control damper on DVL A 1 T2/NT SC1 C3 C3 supply line Supply isolation A 1 T2 SC1 C1 C1 dampers to RIS rooms Supply isolation dampers to EVU rooms C 3 T2 SC1 C3 C3 (division 1 and 4) Supply isolation damper A 1 T2 SC1 C1 C1 to personnel airlock Exhaust isolation B 2 T2 SC1 C2 C2 dampers to RIS rooms Fire dampers A 1 T2/T3/NT SC1 C2/C3 C2/C3 Bursting membranes A 1 M2 SC1 - - Steel plates C 3 M2 SC1 - - HL buildings emergency exhaust isolation B 2 T2 SC1 C2 C2 dampersAPPROVED HK building emergency exhaust isolation A 1 T2 SC1 C2 C2 dampers Severe accident pre- B 2 T2 SC1 - - filter HEPA and iodine B 2 T2 SC1 - - adsorption units
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Safety Design requirements
classification
Description
Seismic
Electrical
Mechanical
requirement requirement
classof SFG
leak tightness leak
Highestsafety Highestsafety
components or
requirementfor requirementfor
I&C requirement I&C
functioncategory
HVAC HVAC component pressure retaining Iodine line exhaust fans B 2 T3 SC1 C2 C2 Local cooling units in A 2 M3 SC1 C2 C2 PTR rooms (division 1) Local cooling units in RIS rooms (Main and A 1 M3 SC1 C1 C1 back-up) Local cooling units in ASG and RRI rooms A 1 M3 SC1 C1 C1 (Main and back-up) Local cooling units in EVU rooms (division 1 A 1 M3 SC1 C1 C1 and 4) The table will be updated after the Safety Classification Component Lists (SCCLs) studies.
6.4.2.4.2. Seismic Requirements
The DWL [CSBVS] system complies with the seismic qualification requirements listed in Section 9.4.6 – Table 3.
6.4.2.4.3. HIC Requirements
Not applicable: the DWL [CSBVS] system is not subject to any HIC requirements.
6.4.2.4.4. Specific I&C Requirements
The demonstration of the compliance with the specific I&C requirements state in section 6.0.5.2.2 is provided in the JDT [FDS] system Chapter (see Sub-Chapter 9.5, section 1.2).
6.4.3. Examination, Maintenance, (In-service) Inspection and Testing (EMIT) 6.4.3.1. Start-APPROVEDup Tests The DWL [CSBVS] system is subject to a start-up test programme in accordance with the procedures set out in Chapter 20 serving to verify the fulfilment of the SFRs.
The start-up test programme will verify:
HEPA filter efficiencies,
iodine adsorption unit efficiencies,
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correct operation of SA pre-filter,
heat output requirements of air heaters upstream adsorption trains,
heat output requirements of convectors,
closing operability of:
o normal ventilation supply and exhaust isolation dampers,
o supply isolation dampers to the front of the personnel airlock,
o The RIS [SIS] rooms supply isolation dampers, and
o The EVU [CHRS] rooms supply isolation dampers.
opening operability of:
o The RIS [SIS] room exhaust isolation dampers,
o HL [SB] buildings emergency exhaust dampers, and
o HK [FB] building emergency exhaust dampers.
correct operation of fire dampers,
correct operation of steel plates,
depression maintained in HL [SB(M)] buildings in normal operating conditions,
depression maintained in the confined areas by iodine adsorption trains extraction fans,
start-up of local cooling units fans,
start-up and air flow rate of air transfer fans, and
completion time of start-up of dynamic confinement of HK [FB] building fuel pool hall.
As the local cooling safety requirements cannot be verified directly due to the fact that the test conditions are different to the fault conditions under which they are required to be fulfilled, it will be verified in an extrapolated manner by checking the cooling power of local cooling units.
As the SFR associated to the bursting membranes cannot be directly verified on site due to the fact that the test conditions are different to the fault and hazards conditions under which it is required to beAPPROVED fulfilled, it must be verified in an indirect manner as follows: justification of the qualification of the membranes by testing and calculation of the suppliers.
6.4.3.2. In Service Inspection
The temperature in the PTR [FPCS/FPPS], EVU [CHRS], RIS [SIS] and ASG/RRI [EFWS/CCWS] rooms is monitored continuously during normal operation and can trigger an alarm in the main control room.
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6.4.3.3. Periodic Testing
The safety classified parts of the DWL [CSBVS] system are subject to the following periodic testing in accordance with the maintenance schedule in order to verify that its SFRs are fulfilled:
HEPA filter efficiencies,
iodine adsorption unit efficiencies,
correct operation of SA pre-filter,
heat output requirements of air heaters upstream adsorption trains,
heat output requirements of convectors,
closing operability of:
o normal ventilation supply and exhaust isolation dampers,
o supply isolation dampers to personnel airlock,
o RIS [SIS] rooms supply isolation dampers, and
o EVU [CHRS] rooms supply isolation dampers.
opening operability of:
o RIS [SIS] room exhaust isolation dampers,
o HL [SB(M)] buildings emergency exhaust dampers, and
o HK [FB] building emergency exhaust dampers.
correct operation of fire dampers,
correct aspect of bursting membranes,
correct operation of steel plates,
depression maintained in HL [SB(M)] buildings,
start-up of air transfer fans, start-upAPPROVED of iodine adsorption trains extraction fans, and start-up of local cooling units’ fans.
6.4.3.4. Maintenance
The DWL [CSBVS] system is subject to a maintenance programme.
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6.5. FUNCTIONAL DIAGRAM
The functional diagram of the DWL [CSBVS] system is shown in Section 9.4.6 – Figure 1 (for more details, see the detailed mechanical diagrams of the DWL [CSBVS] system).
7. SAFEGUARD BUILDING (UNCONTROLLED AREA) VENTILATION SYSTEMS ELECTRICAL (DIVISION) (DVL [SBVSE])
The information reported in this section is, unless otherwise noted, consistent with the reference design, as referenced from Chapter 22.
It should be noted that a Basis of Safety Case (BoSC) [Ref. 7] was produced for the Safeguard Building (Uncontrolled Area) Ventilation Systems Electrical (Division) system (DVL [SBVSE]) in mid-2016. The BoSC was based on the proposed design and supporting evidence available at that time, which pre-dated the RC1.2 design. This section uses information where appropriate from the BoSC and develops it further to reflect the RC1.2 design.
7.0. SAFETY REQUIREMENTS
The UK EPR Safety Classification principles and the top-down functional approach are presented in Sub-chapter 3.2. These principles help to ensure that the plant is designed, manufactured, constructed, commissioned and operated so that the appropriate level of reliability and integrity is achieved for its Structures, Systems and Components (SSCs).
The Hinkley Point C (HPC) functional safety analyses and the application of these safety classification principles to the HPC reference design result in the identification of the safety requirements for all safety systems in accordance with the Safety Functional Requirements Notes (SFRNs) referenced from Sub-chapter 3.2.
This section summarises the results of these safety analyses and specifies the safety requirements that apply to the design of the DVL [SBVSE]) system.
The requirements described in the present section are consistent with safety functions to which the DVL [SBVSE] system contributes in Plant Condition Category (PCC) and Design Extension Conditions (DEC). Consistency with requirements inherited from the Design Basis Initiating Faults (DBIFs) should be checked when the list of DBIFs evolves (see Chapter 15).
7.0.1. Safety Functions
The three Main Safety Functions (MSFs) necessary to achieve the overall safety objective of protecting people and the environment from the harmful effects of ionising radiations are:
controlAPPROVED of fuel reactivity,
fuel heat removal, and
confinement of radioactive material.
These three MSFs must be achieved during:
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normal operating conditions (PCC-1), including duty functions, control of radioactive release during normal operating conditions, control of main plant parameters, fault initial conditions, Limiting Conditions of Operation (LCOs), limitations, monitoring functions, Probabilistic Safety Assessment (PSA) significant functions as part of the preventive line of defence,
fault conditions (PCC-2 to PCC-4, DEC-A and any equivalent DBIFs) and DEC-B, and
hazard conditions.
7.0.1.1. Control of Fuel Reactivity
The DVL [SBVSE] system does not directly contribute to the MSF of control of fuel reactivity.
7.0.1.2. Fuel Heat Removal
The DVL [SBVSE] system does not directly contribute to the MSF of fuel heat removal.
7.0.1.3. Confinement of Radioactive Material
The DVL [SBVSE] system does not directly contribute to the MSF of confinement of radioactive material.
7.0.1.4. Support Contribution to Main Safety Function
The DVL [SBVSE] system must indirectly contribute to the three MSF as a support system as follows:
Maintaining the room temperature within specified limits for correct functioning of safety classified equipment in the non-recirculated rooms within the uncontrolled areas of the Safeguard Buildings (HL [SB]).
7.0.1.5. Specific Contribution to Hazards Protection
The DVL [SBVSE] system must contribute directly to the safety functions that are part of the facility's hazards protection against the consequences of fire (see Sub-chapter 13.2, section 7), internal explosion (see Sub-chapter 13.2, section 6), external explosion (see Sub-chapter 13.1, section 4) and earthquake (see Sub-chapter 13.1, section 2) as follows:
Maintaining acceptable temperatures for the operating personnel and safety-related equipment in the Remote Shutdown Station (RSS), in the event of a fire hazard event in the Main Control Room (MCR) leading to the loss of availability of the MCR.
Contributing to the containment and prevention of the spread of smoke / fire in the HL [SB] buildings.APPROVED Preventing internal explosion in the HL [SB] buildings through the air renewal function in the { SCI removed } Direct Current (DC) battery rooms.
Limiting of the consequences of external explosion by External Pressure Wave (EPW) protection dampers located in the DVL [SBVSE] system fresh air intake and exhaust plenums.
Preservation of Seismic Requirement Level 1 (SC1) Safety Feature (SF) availability following a seismic event.
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Moreover, the DVL [SBVSE] system must be protected against internal and external hazards (see section 7.0.4.2.).
7.0.1.6. Other Safety Functions to be performed in the Preventive Line of Defence
The DVL [SBVSE] system must contribute directly to other safety functions to be performed as part of the preventive line of defence as follows:
Maintaining the room temperature within specified limits for correct functioning of safety classified equipment in both the non-recirculated and recirculated rooms within the uncontrolled areas of the HL [SB] buildings.
Monitoring of the central air-conditioning and local cooling of electrical, mechanical and Instrumentation and Control (I&C) rooms to indicate the availability of the central air- conditioning and local cooling to ensure the room temperatures in these rooms remain within specified limits.
Monitoring of the air-conditioning of mechanical rooms and { SCI removed } DC battery rooms to indicate the availability of the air-conditioning to ensure the room temperatures in these rooms remain within specified limits.
Note: as can be seen from sections 7.0.1.4 and 7.0.1.6 and Section 9.4.7 – Table 2, the SFRNs referenced from Sub-chapter 3.2 represent the conditioning role of the DVL [SBVSE] system both as a support role and a frontline role.
The SFs associated with the conditioning role of the DVL [SBVSE] system that are considered as being ‘frontline’ in the SFRNs are mainly performing the Lower Level Safety Function (LLSF): { SCI removed }. However, performing this LLSF clearly represents a support role to the safety systems. Therefore, although the DVL [SBVSE] system conditioning role (excluding hazard mitigation) is reflected in both sections 7.0.1.4 and 7.0.1.6 to maintain consistency with the SFRN and Section 9.4.7 – Table 2, for the remainder of this section the conditioning role of the DVL [SBVSE] system is represented solely as a support contribution to the MSFs in the rest of the section.
7.0.2. Safety Functional Requirements
7.0.2.1. Control of Fuel Reactivity
Not applicable: the DVL [SBVSE] system does not directly contribute to the MSF of control of fuel reactivity.
7.0.2.2. Fuel Heat Removal
Not applicable: the DVL [SBVSE] system does not directly contribute to the MSF of fuel heat removal. APPROVED 7.0.2.3. Confinement of Radioactive Material
Not applicable: the DVL [SBVSE] system does not directly contribute to the MSF of confinement of radioactive material.
7.0.2.4. Support Contribution to Main Safety Function
With respect to its contribution to the three MSFs, the DVL [SBVSE] system must satisfy the following Safety Functional Requirements (SFRs):
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Ventilation and Air-Conditioning of the uncontrolled areas of the HL [SB] buildings:
o Maintain the room temperatures within the permitted temperature range for the correct functioning of safety classified equipment in the uncontrolled areas of the HL [SB] buildings, in PCC, DEC-A and Severe Accident situations, especially during a Loss Of Offsite Power (LOOP) (PCC-2/3/4, DEC-A) or Station Black Out (SBO) (DEC-A).
7.0.2.5. Specific Contribution to Hazards Protection
With respect to its specific contribution to the safety functions that are part of the facility hazards protection, the DVL [SBVSE] system must satisfy the following SFRs:
Fire:
o Maintain the room temperatures in the RSS within the permitted temperature range to ensure human habitability and functionality of equipment required for safety in the event of a fire hazard event in the MCR leading to the loss of availability of the MCR;
o Ensure containment of fire / smoke in the rooms of the uncontrolled areas of the HL [SB] buildings (excluding the Survival Island) by closure of respective fire dampers to maintain fire compartment integrity.
Internal Explosion:
o Ensure a minimum air renewal rate in the { SCI removed } DC battery rooms to facilitate the dilution and exhaust of hydrogen and mitigate the associated risk of explosion.
External Explosion:
o Ensure that the effects of a pressure wave within the HL [SB] buildings due to external explosion are mitigated by EPW dampers, in order to protect the safety- related equipment located in the HL [SB] buildings.
Earthquake:
o Ensure the stability / integrity of the (DVL [SBVSE]) components to avoid damage to higher classified components and ensure that it does not adversely impact the availability of SC1 SFs following a seismic event.
7.0.2.6. Other Safety Functions to be performed in the Preventive Line of Defence
With respect to its contribution to other safety functions to be performed as part of the preventive line of defenceAPPROVED, the DVL [SBVSE] system must satisfy the following SFRs: Monitoring of the air-conditioning of electrical, mechanical and I&C rooms:
o Monitor the temperature of electrical, mechanical and I&C rooms.
7.0.3. Safety Features and I&C Actuation Modes
Section 9.4.7 – Table 2 presents the SFs of the DVL system, according to the contributions identified in section 7.0.1 and the SFRNs referenced in Sub-chapter 3.2.
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7.0.4. Classification and Architecture Requirements of Safety Features
7.0.4.1. Requirements Arising from Safety Classification
Architecture requirements associated with SFs are essential for designing robust lines of defence consistent with their importance to nuclear safety (see Sub-chapter 3.2). Such requirements strengthen the system design against:
single faults and associated consequences (Single Failure Criterion (SFC)) by requiring redundancy;
LOOP by requiring, among others, a backup power supply;
SBO by requiring a power supply by the Ultimate Diesel Generators (UDGs);
Common Cause Failures (CCFs) by requiring physical separation;
earthquake by defining seismic requirements; and
accident conditions by defining qualification requirements.
Section 9.4.7 – Table 2 presents the requirements arising from safety classifications for the DVL [SBVSE] system, according to the SFRNs referenced in Sub-chapter 3.2.
7.0.4.2. System Protection against Hazards
7.0.4.2.1. Internal Hazards
The SFs of the DVL [SBVSE] system must be protected against internal hazards if those hazards challenge the safety objectives, as defined in Sub-chapter 13.2.
7.0.4.2.2. External Hazards
The SFs of the DVL [SBVSE] system must be protected against external hazards if those hazards challenge the safety objectives, as defined in Sub-chapter 13.1.
7.0.4.3. Diversity
The DVL [SBVSE] system must be subject to the requirement for diversity as defined in general safety principles (see Sub-chapter 3.1) and in Sub-chapter 3.7, dealing with diversity.
7.0.5. Requirements Defined at the Component Level
7.0.5.1. Generic Safety Requirements 7.0.5.1.1. GeneralAPPROVED Mechanical, Electrical and I&C Requirements The mechanical components within the DVL [SBVSE] system must comply with the mechanical requirements in accordance with the rules laid out in Sub-chapter 3.2, section 7. The level of requirement is dependent upon whether or not it is a pressure retaining component, the safety class of the component, whether the component acts as an isolating device between interfacing SFs, and on the role of the component as a barrier to the potential release of radioactivity as a result of failure of the component.
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The electrical and I&C components in the DVL [SBVSE] system must comply with the electrical and I&C requirements associated with their safety class, in accordance with the rules laid out in Sub-chapter 3.2.
7.0.5.1.2. Seismic Requirements
The level of seismic requirements to be applied to the DVL [SBVSE] system components is related to the safety feature group to which the component belongs, and the consequences on other classified components of its failure if it were not seismically qualified. The rules for defining the seismic requirements for a component are identified in Sub-chapter 3.2.
7.0.5.1.3. Qualification for Accident Conditions
The safety-classified parts of the DVL [SBVSE] system must be qualified for the operating conditions in which they are required, as specified in Sub-chapter 3.6.
7.0.5.2. Specific Safety Requirements
7.0.5.2.1. High Integrity Component (HIC) Requirements
The DVL [SBVSE] system is not subject to any High Integrity Component (HIC) requirements.
7.0.5.2.2. Specific I&C Requirements
The DVL [SBVSE] system dedicated I&C is subject to safety requirements applicable to Class 1 I&C systems. In addition the following requirements arise from specific I&C requirements:
Control of the cooling by main line fans of Local Cooling Units (LCUs) in I&C rooms (all divisions) and the Component Cooling Water System (RRI [CCWS]) rooms (Divisions 1 and 4 only) is performed by local dedicated I&C components:
o The I&C room LCUs main line fans are normally in operation at all times, therefore these I&C components will also be continuously in service.
o The RRI [CCWS] system room LCUs are generally not operational (depending on heat loads in the RRI [CCWS] system rooms) but are available on standby. Hence, their I&C components will need to be available continuously to ensure that the LCU main line fans are brought into operation automatically when required.
Control of the backup for central air-conditioning of the DVL [SBVSE] system-served rooms and cooling by backup line fans of LCUs in I&C rooms (all divisions) and RRI [CCWS] system rooms (Divisions 1 and 4 only) is performed by a dedicated conventional I&C system, the Non-Computerised Heating, Ventilation and Conditioning (HVAC) I&C SystemAPPROVED (NCHICS): o The NCHICS system must be in operation continuously to ensure that backup systems for the Central Air-Conditioning of the DVL [SBVSE] system-served rooms and LCU cooling of I&C rooms (all divisions) and RRI [CCWS] system rooms (Divisions 1 and 4 only) are brought into operation automatically when required.
The general approach to qualification of dedicated I&C systems in terms of Production Excellence (PE) and Independent Confidence Building Measures (ICBM) is set out in Sub-chapter 7.7.
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Moreover, the DVL [SBVSE] system fire dampers are operated by the Fire Detection System (JDT [FDS]) dedicated I&C. The specific requirements arising from the JDT [FDS] system dedicated I&C are described in the JDT [FDS] system chapter (see Sub-chapter 9.5, section 1.2).
The general approach for I&C systems is set out in Chapter 7.
7.0.6. Examination, Maintenance, (In-Service) Inspection and Testing (EMIT)
7.0.6.1. Start-up Tests
The DVL [SBVSE] system must be designed to enable the performance of start-up tests to ensure the adequacy of its design and performance under conditions as representative as possible of the different operating configurations, and in particular its compliance with the SFRs assigned to it in section 7.0.2.
7.0.6.2. In-Service Inspection
The DVL [SBVSE] system must be designed to enable surveillance under normal operation of the system characteristics necessary for the fulfilment of its safety-related tasks in order to ensure the performance of its components, and their availability under normal operation, or in the event of a fault or accident.
7.0.6.3. Periodic Testing
The safety classified parts of the DVL [SBVSE] system must be designed to enable the performance of periodic tests in accordance with the maintenance schedule.
7.0.6.4. Maintenance
The DVL [SBVSE] system must be designed to enable the implementation of a maintenance schedule (see Sub-chapter 18.2).
7.1. ROLE OF THE SYSTEM
The DVL [SBVSE] system performs the following functions (or tasks) under the different plant operating conditions for which it is required:
The primary safety role of the DVL [SBVSE] system is to maintain a suitable environment, for both plant and personnel, within the uncontrolled areas of the HL [SB] buildings, with the exception of the Survival Island and several valve compartments which are served by independent HVAC systems (Control Room Air-Conditioning System (DCL [CRACS]) and Ventilation System for the Main Steam Supply System (VVP [MSSS]), and Main FeedWater System (ARE [MFWS]) Valve Rooms (DVE) respectively). The DVL [SBVSE]APPROVED system-served rooms contain electrical, I&C and mechanical equipment, which in the main is safety-classified. The distribution of the DVL [SBVSE] system ductwork to these rooms is such that a clear distinction is made between areas whose exhaust air can or cannot be recirculated:
The rooms where return air can be recirculated. These include the I&C rooms, electrical switchgear rooms, access corridors, cable floor and RSS.
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The rooms where exhaust air cannot be recirculated due to the potential for asphyxiation, hydrogen gas build-up (internal explosion risk), contamination concerns or odours. These include the { SCI removed } DC battery rooms, Safety Chilled Water System DEL [SCWS] rooms, Emergency FeedWater System ASG [EFWS] rooms, Containment Heat Removal System (EVU [CHRS]) room, and RRI [CCWS] system rooms.
The DVL [SBVSE] system also provides air to the Safeguard Building (Controlled Area) Ventilation System (DWL [CSBVS]) in normal operation, and participates in hazard mitigation, e.g. external explosion (EPW dampers), internal explosion (H2 extraction) and internal fire (fire dampers and conditioning of the RSS).
7.1.1. Normal Operating Conditions
The DVL [SBVSE] system has the following operational functions during normal plant operation:
Maintaining acceptable ambient (indoor) conditions for equipment and personnel in the uncontrolled areas of the HL [SB] buildings (except for the Survival Island and several valve compartments);
Ensuring air circulation (fresh air supply, minimum air renewal rate and direct exhaust to the outside of polluted air) in the uncontrolled areas of the HL [SB] buildings (except for the Survival Island), to avoid asphyxiation for personnel and explosion in the { SCI removed } DC battery rooms;
Providing supply air to the DWL [CSBVS] system; and
Ensuring fire compartment integrity (fire dampers).
Conditioning of the uncontrolled areas of the HL [SB] buildings is required to be effective at all times under all plant conditions. The DVL [SBVSE] system ensures that the nuclear safety significant plant is maintained within its qualified, environmental limits and provides a stable thermal environment which promotes reliability.
The system also ensures a safe, habitable environment, conducive to satisfactory human performance.
In normal operation, the DVL [SBVSE] system also provides conditioned make-up air to the DWL [CSBVS] system, therefore supporting the maintenance of a suitable environment within the controlled areas of the HL [SB] buildings.
7.1.2. Fault and Hazard Operating Conditions
As a support system, the DVL [SBVSE] system contributes indirectly to all three MSFs because the conditioning system of the uncontrolled areas of the HL [SB] buildings supports actions requiring I&C and / or electrical supply and / or the safety related plant housed in the mechanical rooms. TherefoAPPROVEDre, the DVL [SBVSE] system indirectly supports the three MSFs under all plant conditions.
The DVL [SBVSE] system also contributes (directly and indirectly) to the safety functions that are part of the facility's hazards protection.
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7.2. DESIGN BASIS
7.2.1. General Assumptions
The following general assumptions have been made in respect of the design for the DVL [SBVSE] system:
Designations / descriptions used with respect to the DVL [SBVSE] system main components:
o DVL [SBVSE] system ‘Centralised Ventilation’ main train = ‘DVLm’ (DVLm1 for Division 1, DVLm2 for Division 2, DVLm3 for Division 3 and DVLm4 for Division 4).
o DVL [SBVSE] system ‘Centralised Ventilation’ backup train = ‘DVLb’ (DVLb1 for Division 1, DVLb2 for Division 2, DVLb3 for Division 3 and DVLb4 for Division 4).
o All LCUs in the I&C rooms (all divisions) and RRI [CCWS] system rooms (Divisions 1 and 4 only) each have two diverse fans; a main line fan (referred to as the DVLm LCU fan) and a backup line fan (referred to as the DVLb LCU fan).
Note: the DVL [SBVSE] train and LCU fan changeovers (between main and backup) are decoupled from each other. DVL [SBVSE] train and LCU fan changeovers are also decoupled from DEL [SCWS] train changeover events, i.e. a changeover from DVLm to DVLb (centralised ventilation or LCU fans) does not require a changeover from DELm to DELb. Similarly, a changeover from DELm to DELb does not require a changeover from DVLm to DVLb (centralised ventilation or LCU fans).
The DVL [SBVSE] system is required to maintain a suitable environment within the uncontrolled areas of the HL [SB] buildings with the exception of the Survival Island and several valve compartments which are served by independent HVAC systems; for simplicity and brevity, this is referred to as the “DVL [SBVSE] system-served” area (or “DVL [SBVSE] system-served” rooms) in this section.
The DVLm and DVLb centralised ventilation trains and LCUs are sized to ensure the maximum permitted room temperatures for safety-related equipment are not exceeded taking account of thermal transients arising from:
o The time taken into account in respect of switchover from duty to standby or backup systems (DVL [SBVSE] and DEL [SCWS] systems and also power from start-up of Emergency Diesel Generators (EDGs) / UDGs);
o Loss of the DVL [SBVSE] system but only battery backed (2-hour battery backed and 24-hour battery backed) equipment in operation during Total Loss of AC APPROVEDPower (TLAP) and Extended TLAP; and o Loss of the DVL [SBVSE] system centralised ventilation, for which all equipment in the DVL [SBVSE] system-served rooms is operating without any HVAC available, during the timescale associated with manual actions to restore operation of the DVL [SBVSE] system centralised ventilation (e.g. manual re- opening of fire damper(s) in affected room(s)).
External conditions taken into account in the sizing of the DVL [SBVSE] system are detailed in section 1.
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Only one of the eight DVLm or DVLb trains can be scheduled for maintenance at a time.
The maintenance for the DVL [SBVSE] system equipment must be co-ordinated with the respective DEL [SCWS] equipment and associated electrical power trains and other support systems.
Four DVLm trains are normally in operation (one per division), with all four corresponding DVLb trains available on standby.
All LCUs in the I&C rooms (all divisions) are operational. The LCUs in the Division 1 and 4 RRI [CCWS] system rooms are generally not operational (depending on heat loads in the RRI [CCWS] system rooms) but are available on standby.
The Emergency Exhaust System for the chiller rooms in Divisions 1 and 4, as described in section 7.3.1.2.4, is solely concerned with industrial safety and does not have a nuclear safety role.
Convectors may be required for general heating during cold weather conditions to maintain the minimum required temperature, defined in section 1.
7.2.2. Design Assumptions
7.2.2.1. Control of Fuel Reactivity
Not applicable: the DVL [SBVSE] system does not directly contribute to the MSF of control of fuel reactivity.
7.2.2.2. Fuel Heat Removal
Not applicable: the DVL [SBVSE] system does not directly contribute to the MSF of fuel heat removal.
7.2.2.3. Confinement of Radioactive Material
Not applicable: the DVL [SBVSE] system does not directly contribute to the MSF of confinement of radioactive material.
7.2.2.4. Support Contribution to Main Safety Function
Indirect contribution to the three MSFs:
Ventilation and Air-Conditioning of the uncontrolled areas of the HL [SB] buildings:
o Maintain the room temperatures within the permitted temperature range (defined in section 1) in the DVL [SBVSE] system-served rooms within the uncontrolled APPROVEDareas of the HL [SB] buildings to ensure functionality of equipment required for safety.
7.2.2.5. Specific Contribution to Hazards Protection
The DVL [SBVSE] system contributes to fire, internal explosion, external explosion and earthquake hazards protection:
Internal Explosion:
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o Minimum air renewal rates in the { SCI removed } DC battery rooms must exceed the minimum levels defined in section 1.
External Explosion:
o The DVL [SBVSE] system EPW dampers must satisfy the criteria defined in Sub-chapter 13.1, section 4.
Fire:
o Maintain the room temperatures in the RSS within the permitted temperature range (defined in section 1) to ensure human habitability and functionality of equipment required for safety in the event of a fire hazard event in the MCR leading to the loss of availability of the MCR.
o Contribute to hazard protection to contain and prevent the spread of fire by closure of fire dampers to maintain fire compartments in the event of a fire:
. Not applicable: there are no quantitative safety-related design assumptions associated with fire for the DVL [SBVSE] system.
Earthquake:
o Not applicable: there are no quantitative safety-related design assumptions associated with earthquake for the DVL [SBVSE] system.
7.2.2.6. Other Safety Functions to be performed in the Preventative Line of Defence
Not applicable: there are no quantitative safety-related design assumptions associated with the DVL [SBVSE] system.
7.2.3. Other Assumptions
The DVL [SBVSE] system is also subject to the following assumptions:
The DVL [SBVSE] system design is consistent with RCC-M requirements as described in Sub-chapter 3.8, section 2.
The DVL [SBVSE] system design is consistent with the fire requirements as described in Sub-chapter 3.8, section 5.
7.2.4. Assumptions Associated with Extreme Situations Resulting from Beyond Design-Basis Hazards 7.2.4.1. AssumptionsAPPROVED Associated with Fukushima Provisions The assumptions associated with the Fukushima provisions of the DVL [SBVSE] system are presented in Chapter 23. The main provisions are:
Centralised air-conditioning DVL [SBVSE] system-served rooms containing safety classified equipment; and
Local cooling of I&C rooms (all divisions) and RRI [CCWS] system rooms (Divisions 1 and 4).
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7.2.4.2. Assumptions Associated with non-Fukushima Provisions
The assumptions associated with the other non-Fukushima provisions of the DVL [SBVSE] system are:
Conditioning of safety-classified equipment following TLAP.
7.3. SYSTEM DESCRIPTION AND OPERATION
7.3.1. Description
7.3.1.1. General System Description
The description provided in this section applies equally to both Unit 1 and Unit 2.
The DVL [SBVSE] system comprises:
One centralised ventilation system per division to condition the uncontrolled areas of the HL [SB] buildings (Safeguard Electrical Buildings [HLA–B-C-D [SB(E)] in Divisions 1 to 4; Safeguard Mechanical Buildings [HLF-G-H-I [SB(M)] in Divisions 1 to 4). This comprises:
o One main train AHU per division which can be cooled either by its respective DELm train or DELb train (DELb1 can cool DVLm1 and / or DVLm2 whereas DELb4 can cool DVLm3 and / or DVLm4). The main train includes provisions against CCF as the main line DVL [SBVSE] system trains in Divisions 1 and 4 are diverse from those in Divisions 2 and 3.
o One backup train AHU per division, diverse from the main train, that can be cooled either by its respective DELm train or DELb train (DELb1 can cool DVLb1 and / or DVLb2 whereas DELb4 can cool DVLb3 and / or DVLb4).
Note: the RSS is physically located in Division 3, and is used in the event that the MCR, located in Division 2, becomes unavailable. The RSS can be ventilated by DVLm or DVLb from either of Divisions 2 and 3, but normally Division 2 of the DVL [SBVSE] system is aligned to ventilate the RSS. Connections to supply and exhaust ductworks in Divisions 2 and 3 ensure independent operation of the Division 2 and 3 DVL [SBVSE] systems.
LCUs that are dedicated to the conditioning of specific rooms (I&C rooms in all divisions; RRI [CCWS] system rooms in Divisions 1 and 4 only). Each LCU comprises:
o A main line LCU fan. The main line includes provisions against CCF as the main line DVL [SBVSE] system LCU fans in Divisions 1 and 4 are diverse from those in Divisions 2 and 3. o APPROVEDA backup line LCU fan that is diverse from the main line LCU fan. o Two cooling coils, one fed by DELm and one fed by DELb. The LCU design is such that the cooling can be provided either by the division’s DELm train or by its DELb train. (DELb1 can feed LCUs in Divisions 1 and 2, whereas DELb4 can feed LCUs in Divisions 3 and 4, regardless of which fan is operational).
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Emergency Exhaust System: there is a potential asphyxiation risk associated with the leakage of refrigerant gas into the chiller rooms in each division. The level of risk is dependent upon the mass of refrigerant charge that can leak in the room due to loss of system integrity. The potential risk is higher in rooms housing air cooled chillers (Divisions 1 and 4) than in rooms housing water cooled chillers (Divisions 2 and 3). For Divisions 2 and 3, the DVL [SBVSE] system centralised ventilation system provides sufficient air flow to meet the requirements of industry standards. However, it is necessary to install a dedicated sub-system for the HL [SB] building Divisions 1 and 4 which is triggered by refrigerant gas sensors when a refrigerant leak is detected:
o There are four Emergency Exhaust Systems in total, one for each of the DELm1, DELm4, DELb1 and DELb4 chiller rooms.
o The Emergency Exhaust System is solely concerned with industrial safety and does not have a nuclear safety role.
7.3.1.2. Description of Main Equipment
The DVL [SBVSE] system comprises the following main equipment items (see the functional diagram provided in section 7.5):
7.3.1.2.1. Centralised Ventilation
The DVL [SBVSE] system centralised ventilation is divided into several parts. For each train (DVLm or DVLb), this comprises:
Supply train: this takes the air from the outside and from the recirculation ductwork, conditions it and supplies to the uncontrolled area rooms via the distribution ductwork. Each train comprises:
o dampers,
o filters,
o heaters,
o DELm and DELb cooling coils (in series), and
o a fan.
Normal exhaust train: this is used to extract the air from the rooms for which return air can be recirculated. Each normal exhaust train is linked with its respective supply train through a recirculation line. Each train comprises: o APPROVEDdampers, and o a fan.
Specific exhaust train: this extracts the air from the rooms for which exhaust air cannot be recirculated. This exhaust air is blown outside. Each train comprises:
o dampers, and
o a fan.
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Note: in the case of failure of the DVLm supply and / or normal exhaust fans in a division, there is a general changeover from DVLm to DVLb (supply train, normal exhaust and specific exhaust). However, in the case of failure of the DVLm specific exhaust train within a division and the start-up of the associated DVLb specific exhaust train, a changeover from DVLm to DVLb for the supply train and / or normal exhaust train is not required.
Ductwork and dampers: the DVL [SBVSE] system main and backup trains use shared supply, distribution and exhaust ductwork within a division. This comprises the following components:
o fresh air intake including EPW dampers,
Note: in Divisions 2 and 3, the air inlet / outlet plenums are shared between the DVL [SBVSE] system and Smoke Control System (DFL), and the air inlet plenum is also shared with the DCL [CRACS] system.
o supply ducts (concrete and metal), manual isolation dampers and fire dampers and duct heaters, and
o exhaust: ducts (mainly concrete), silencers, fire dampers and EPW dampers.
Note: in Divisions 1 and 4 the main and backup trains within a single division have common normal exhaust recirculatory ductwork, whereas in Divisions 2 and 3 the main and backup trains within a single division have separate normal exhaust recirculatory ductwork.
7.3.1.2.2. LCUs
LCUs are installed in the I&C rooms (all divisions) and RRI [CCWS] system rooms (Divisions 1 and 4 only). Although the centralised ventilation ensures the minimum air renewal rate required for habitability purposes in these rooms, the operation of the LCUs is required to perform the cooling safety function.
The LCUs comprise the following components:
Two cooling coils: one supplied with chilled water by DELm, the other supplied with chilled water by DELb; and
Two diverse fans and two dampers: each non-return damper is associated with a fan. One fan / damper pair is assigned to DVLm and the other pair is assigned to DVLb.
7.3.1.2.3. Local Heating Means
Convectors may be required for general heating during cold weather conditions to maintain the minimum requiredAPPROVED temperature, defined in section 1. 7.3.1.2.4. Emergency Exhaust System in Chiller Rooms
There are four Emergency Exhaust Systems; one for each of the DELm1, DELm4, DELb1 and DELb4 chiller rooms. Each Emergency Exhaust System comprises:
a supply damper,
a fan, and
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an exhaust damper.
7.3.1.3. Description of Main Layout
Centralised Ventilation
There are four DVL [SBVSE] system main trains and four DVL [SBVSE] system backup trains (one in each division), each comprising supply, normal exhaust and specific exhaust trains.
In Divisions 1 and 4, the layout is as follows (for both main and backup trains):
Supply trains are located at { SCI removed } level;
Normal exhaust trains are located at { SCI removed } level;
Specific exhaust trains are located at { SCI removed } m level.
In Divisions 2 and 3, the layout is as follows (for both main and backup trains):
Supply trains are located at { SCI removed } level;
Normal exhaust trains are located at { SCI removed } level;
Specific exhaust trains are located at { SCI removed } level.
LCUs
LCUs are located in I&C rooms at the { SCI removed } level in each division, three per division in Divisions 1 and 4, and two per division in Divisions 2 and 3.
In Divisions 1 and 4, one LCU has been added in each RRI [CCWS] system room ({ SCI removed }) supplying the three RRI [CCWS] system rooms with duct connections ({ SCI removed }).
Note: the differing layout in Divisions 2 and 3 means that the centralised ventilation alone can provide the cooling safety function in the RRI [CCWS] system rooms in those divisions, so no LCUs are required in Divisions 2 and 3.
Emergency Exhaust System
The Emergency Exhaust System fan location in both Divisions 1 and 4 is as follows:
Main DEL [SCWS] system train chiller rooms (DELm1 and DELm4) at { SCI removed } level; and
BackupAPPROVED DEL [SCWS] system train chiller rooms (DELb1 and DELb4) at { SCI removed } level.
7.3.1.4. Description of System I&C
Local Dedicated I&C Component Control
Control of the cooling by main line fans of LCUs in I&C rooms (all divisions) and RRI [CCWS] system rooms (Divisions 1 and 4 only) is performed by local dedicated I&C components.
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The I&C room LCU main line fans are normally in operation at all times, therefore these I&C components will also be continuously in service.
The RRI [CCWS] system room LCUs are generally not operational (depending on heat loads in the RRI [CCWS] system rooms) but are available on standby. Hence, their I&C components will need to be available continuously to ensure that the LCU main line fans are brought into operation automatically when required.
NCHICS Control
Control of all four DVLb trains and the backup line fans for LCUs in all divisions is provided by a dedicated conventional I&C system, the NCHICS. The NCHICS is diverse from and independent of the Safety Automation System (SAS) and Protection System (RPR [PS]) I&C systems used for control of the DVLm trains and the local dedicated I&C components used for the control of the LCU main line fans.
The NCHICS system monitors the operation of the DVLm system and LCU main line fans. On detection of certain fault conditions (details to be confirmed), the NCHICS system starts the DVLb train and / or individual LCU backup line fans and performs its automatic control when operational.
Note: the operator performs manual actions (from the MCR when possible, after verifying the plant status) to shut down the DVLm train and / or individual LCU main line fans in response to alarm(s) raised during the automatic start of DVLb.
JDT [FDS] System I&C
The JDT [FDS] system dedicated I&C used for the DVL [SBVSE] system fire dampers is described in the JDT [FDS] system chapter (see Sub-chapter 9.5, section 1.2)
7.3.2. OPERATION
The DVL [SBVSE] system in each division operates in all operating modes of the plant as well as during plant outages or during maintenance of one electrical division.
7.3.2.1. System Normal Operation
7.3.2.1.1. DVL in Normal Operation
7.3.2.1.1.1. Centralised Ventilation
In normal operation the centralised ventilation of the DVL [SBVSE] system is configured as follows for each division: The DVLAPPROVED [SBVSE] system main train is in operation. The DVL [SBVSE] system backup train is shut down (it may be started if the main train in that division is unavailable due to its failure or planned maintenance).
The air is distributed in all uncontrolled rooms of the HL [SB] buildings (with the exception of those that are air-conditioned by the DCL [CRACS] system).
The air is extracted from all rooms (of the uncontrolled area).
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The air is extracted from all rooms where there is the potential for asphyxiation, hydrogen gas build up (internal explosion risk), contamination concerns or odour. These include the { SCI removed } DC battery rooms, DEL [SCWS], ASG [EFWS], EVU [CHRS], and RRI [CCWS] systems rooms.
The ventilation functions of the RSS located in Division 3 are provided by the DVL [SBVSE] system located in Division 2, but can alternatively be supplied by the DVL [SBVSE] system located in Division 3 according to the DVL [SBVSE] system train availability.
The temperature of the air supplied by the DVL [SBVSE] system centralised ventilation to the HL [SB] buildings is normally set at a constant value, currently expected to be { SCI removed }.
The centralised ventilation supply air flow, which passes both the cooling coils and the electrical heaters in the AHU, is made up of fresh air from outside of the building, mixed with a variable proportion (nominally around 0-65%) of recirculated air via the normal exhaust.
Control of the supply air temperature can be achieved by one of the three methods listed below depending on the environmental conditions and on the constraints applied:
Chilled water cooling coils (modulation of chilled water flow rate): this mode is used when the external air temperature is too high and cooling power is required. The flow of chilled water, and hence the cooling power delivered to the air, is adjusted to maintain the supply air at the correct temperature.
Electrical heaters (modulation of heater power): this mode is used when the external air temperature is too low and heating power is needed. The heating power delivered to the air by the electrical heaters is adjusted to maintain the supply air at the correct temperature.
Free cooling (modulation of recirculated air fraction): this mode is used when the outside air is cool enough that additional chilled water cooling is not needed. As the outside air temperature reduces, the supply air temperature is maintained by increasing the proportion of warm air recirculated from the normal exhaust and mixed with the outside air in the supply train.
The normal control of DVLm, implemented by the SAS system, uses all three supply air temperature control means. The backup control of DVLm by the RPR [PS] system is not expected to be used often or for long periods, and operates only in full recirculation mode using the cooling coils or heaters to maintain supply air temperature at the setpoint.
7.3.2.1.1.2. LCUs
The DVL [SBVSE] system includes LCUs in the I&C rooms in all divisions and the RRI [CCWS] system rooms in Divisions 1 and 4. All the LCUs have the common features of two diverse fans in parallel andAPPROVED two cooling coils in series (one supplied with chilled water from DELm, the other from DELb). A constant flow rate will be established in a coil when its associated chilled water distribution pump is in service as commanded by the DELm or DELb I&C systems.
The mechanical arrangement of the LCUs means that there is no direct link between the operation of the main and backup fans and that of the main and backup cooling coils. Although the normal configuration will operate the main fan and the main cooling coil together, it is possible for either fan to operate with either coil.
I&C Room LCUs
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The LCUs are required to be in service at all times as they provide the main cooling means for the room. The principle is that warm air is taken from the upper part of the room by the LCU fan and cooled by being drawn past the cooling coils before being routed to the false floor space from where it is returned to the room at floor level to cool the installed systems and components. Increasing / decreasing the air flow past the cooling coils delivers increased / decreased cooling power to the room.
RRI [CCWS] System Room LCUs
For three specific mechanical rooms associated with the RRI [CCWS] and EVU [CHRS] systems in each of Divisions 1 and 4, LCUs are used when required but are not in service at all times. The main line LCU is controlled by local conventional components based on the RRI [CCWS] and EVU [CHRS] systems pump status and on the temperatures in the three associated rooms.
7.3.2.1.2. DVL [SBVSE] System Operation during Maintenance
7.3.2.1.2.1. Centralised Ventilation
The DVL [SBVSE] system functions for a division are normally provided by its DVLm train but, in the event of DVLm failure or planned maintenance, the DVLb train of the same division is capable of providing these functions.
The DVL [SBVSE] system architecture takes into account routine inspection and maintenance requirements so that maintenance can be performed on the DVL [SBVSE] system trains. However, maintenance on two trains simultaneously is not permitted. When maintenance is being performed on one DVL [SBVSE] system train, the train is considered not to be available.
It should be noted that the DVL [SBVSE] system design with two DEL [SCWS] system cooling coils in series (one DELm, one DELb) per supply train means that each DVLm or DVLb train can be cooled interchangeably by either its associated DELb or DELm train. As a result, maintenance of a DELm train does not affect the availability of any operational DVL [SBVSE] system train (i.e. the DVL [SBVSE] system train will be cooled by the DELb train associated with that division whilst DELm maintenance is ongoing). Similarly, during maintenance of a DVLm train, the associated DVLb train will be cooled by the DELm train in that division.
The DVLb controlled by the NCHICS I&C is not expected to be in service often or for long periods, and operates only in full recirculation mode using the cooling coils or heaters to maintain supply air temperature at the setpoint.
7.3.2.1.2.2. LCUs
The DVL [SBVSE] system functions for a division are normally provided by the DVLm fan associated with each LCU. However, in the event of failure or planned maintenance of the DVLm fan within a LCU, the DVLb train of the same division is capable of providing these functions.
LCUs in the I&CAPPROVED rooms are normally in continuous operation, whereas LCUs in the RRI [CCWS] system rooms in Divisions 1 and 4 are not expected to be in operation on a regular basis. Details are yet to be developed but it is not certain whether or not a LCU may remain operational on its DVLb fan while maintenance is carried out on its DVLm fan, see section 7.4.3.4.
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7.3.2.1.3. Partial or Total Loss of the Ultimate Heat Sink (PLUHS or TLUHS)
For the DVL [SBVSE] system, the air flow is cooled by chilled water supplied by the DEL [SCWS] system.
In Divisions 2 and 3, the chilled water trains DELm2 and DELm3 are supplied by water-cooled chillers connected to the RRI [CCWS] system and, in Divisions 1 and 4, trains DELm1, DELm4, DELb1 and DELb4 are supplied by air-cooled chillers.
In the case of PLUHS or TLUHS, the main chillers in Divisions 2 and 3 are lost, however DELm1 and DELm4 remain available to provide cooling for the DVL [SBVSE] system trains and LCUs of Divisions 1 and 4, and DELb1 and DELb4 remain available to provide cooling for the DVL [SBVSE] system trains and LCUs of Divisions 2 and 3.
Hence, the DVL [SBVSE] system will remain operable in all four divisions during a PLUHS or TLUHS event.
7.3.2.1.4. Loss Of Offsite Power (LOOP)
In the event of LOOP, the power supplies to the four DVL [SBVSE] system main trains and the four DVL [SBVSE] system backup trains including both the centralised ventilation and LCUs are backed up by the EDGs.
During a LOOP, the four operational DVL [SBVSE] system trains (normally DVL [SBVSE] system main trains) and LCU main line fans will continue to operate with electrical power supplied by the main EDGs for their respective divisions.
Hence, the DVL [SBVSE] system will remain operable in all four divisions during a LOOP event as in normal operation.
7.3.2.1.5. Station Blackout (SBO)
During SBO, only Divisions 1 and 4 are supplied with power by the UDGs, and for the DVL [SBVSE] system only the main DVL [SBVSE] system trains and the LCU main line fans are supplied with power in these divisions.
The backup line LCU fans in the I&C rooms are also backed up by { SCI removed } DC batteries (in all the divisions). As a consequence, the backup line LCU fans in the I&C rooms are also supplied with power by the UDGs in Divisions 1 and 4.
Hence, the DVL [SBVSE] system will remain operable in Divisions 1 and 4 only during a SBO event. The DVL [SBVSE] system will be unavailable in Divisions 2 and 3.
7.3.2.1.6. Heatwave
To ensure the DEL [SCWS] system chiller plant can be adequately sized to provide efficient cooling to the APPROVEDHVAC systems in both normal and extreme outside conditions, the extreme high external air temperature is managed through the “heatwave approach” (see section 1). This consists of running both DELm and DELb coils at the same time within each DVL [SBVSE] system train and LCU during extreme high external temperature conditions, with DELb trains operating at full load and DELm trains operating at partial load with regulation.
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7.3.2.2. System Transient Operation
7.3.2.2.1. Full or Partial System Failure
{ This section contains SCI-only text and has been removed }
7.3.2.2.2. Failure of Systems in Interface (Server or Served)
7.3.2.2.2.1. Server System Failure
{ This section contains SCI-only text and has been removed }
7.3.2.2.2.2. Served System Failure
{ This section contains SCI-only text and has been removed }
7.4. PRELIMINARY DESIGN SUBSTANTIATION
The level of detail in regards to evidence of compliance with the safety requirements stated in section 7.0 will develop as the HPC project moves from basic design into detailed design since PCSR3 sequence and system sequence are evolving in parallel. Therefore, the level of details provided in this section reflects the level of information available at the time of issuing of the system chapters.
7.4.1. Compliance with Safety Functional Requirements
7.4.1.1. Control of Fuel Reactivity
Not applicable: the DVL [SBVSE] system does not directly contribute to the MSF of control of fuel reactivity.
7.4.1.2. Fuel Heat Removal
Not applicable: the DVL [SBVSE] system does not directly contribute to the MSF of fuel heat removal.
7.4.1.3. Confinement of Radioactive Material
Not applicable: the DVL [SBVSE] system does not directly contribute to the MSF of confinement of radioactive material.
7.4.1.4. Support Contribution to Main Safety Functions
The design assumptions of the DVL [SBVSE] system stated in section 7.2.2 are consistent with the requirementsAPPROVED of the corresponding systems / equipment items which it supports: Ventilation and Air-Conditioning of the uncontrolled areas of the HL [SB] buildings:
o The DVL [SBVSE] system components (including the centralised ventilation system fans and cooling coils, LCU fans and cooling coils, supply train heaters and duct heaters) will be sized to meet the DVL [SBVSE] system-served room t temperature requirements under all summer and winter conditions as defined in section 1.
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7.4.1.5. Specific Contributions to Hazards Protection
The hazard studies of Sub-chapters 13.1 and 13.2 involving functions of the DVL [SBVSE] system use values for the following parameters that are in keeping with the design assumptions stated in section 7.2.2:
Internal Explosion:
o The DVL [SBVSE] system centralised ventilation system fans will be sized to meet the minimum air renewal rate requirements for the { SCI removed } DC battery rooms specified in section 1.
o The { SCI removed } DC battery chargers should be interlocked with the specific exhaust system to ensure that charging is prevented if ventilation of the { SCI removed } DC battery rooms is not operational.
External Explosion:
o The DVL [SBVSE] system EPW dampers must close and protect safety-related equipment within the HL [SB] buildings from the potential effects of a blast wave external to the buildings. The External Explosion studies of Sub-chapter 13.1 will demonstrate that the EPW dampers satisfy the criteria defined in Sub-chapter 13.1, section 4.
Fire:
o Ventilation and air-conditioning of the RSS:
. The DVL [SBVSE] system central ventilation components (including fans, cooling coils, and supply train heaters) will be sized to meet the RSS room temperature requirements as defined in section 1 to ensure human habitability and functionality of equipment required for safety in the event of a fire hazard event in the MCR leading to the loss of availability of the MCR.
o Fire Compartmentation:
. Contribution to the containment and prevention of a fire in the HL [SB] buildings by the closure of fire dampers:
fire damper qualification, and
fire damper closure monitored by position status. Earthquake:APPROVED o Ensure the stability / integrity of DVL [SBVSE] system components to avoid damage to higher classified components:
. DVL [SBVSE] system components will be seismically qualified to confirm that their stability / integrity is ensured following a seismic event.
For each hazard study concerned, these studies show that the design of these functions is such that they meet the acceptance criteria.
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These elements ensure that the safety functional requirements stated in section 7.0.2 are met.
7.4.1.6. Other Safety Functions to be performed in the Preventive Line of Defence
The DVL [SBVSE] system contributes in the preventative line of defence by continuous monitoring for both the DVL [SBVSE] system centralised ventilation trains and LCUs:
Monitoring of the air-conditioning of electrical, mechanical and I&C rooms:
o Monitoring of the temperature of electrical, mechanical and I&C rooms is used to alert operators in the MCR in the event of DVL [SBVSE] system failure.
7.4.2. Compliance with Design Requirements
The DVL [SBVSE] system complies with the requirements stated in sections 7.0.4 and 7.0.5, particularly with respect to those detailed in the following sections.
7.4.2.1. Requirements Arising from Safety Classification
7.4.2.1.1. Safety Classification
The compliance of the design and manufacture of the DVL [SBVSE] system materials and equipment performing a safety-related function with requirements from the classification rules (see Sub-chapter 3.2, section 7) is presented in section 7.4.2.4.1.
7.4.2.1.2. Single Failure Criterion (SFC) and Redundancy
Active Single Failure:
The design of the DVL [SBVSE] system meets the requirements of the active SFC stated in section 7.0.4.1, in particular in respect of the following:
The principal design provision which mitigates against single failures is the general design philosophy of having four independent divisions. One DVL [SBVSE] system division, including separate fresh air intakes and air exhausts, is located in each HL [SB] building. This arrangement ensures separation and independence between the four DVL [SBVSE] system main trains. As such, a single failure of any DVL [SBVSE] system component could at most result in the loss of ventilation in only one division. Three other divisions with independent safety systems would still be available.
Functional redundancy is also provided in the DVL [SBVSE] system design. Each DVL [SBVSE] system main train (DVLm) / LCU main line fan in each HL [SB] building has an associated DVL [SBVSE] system backup train (DVLb) / backup line fan in the same building, which is independent from its main train / main line fan and incorporates diversity of the mechanical design of key components, I&C, heat sink and electrical supplies.APPROVED When maintenance is required or a failure occurs on the main train / LCU main line fan, the associated backup line provides ventilation to the concerned building.
Passive Single Failure:
The design of the DVL [SBVSE] system complies with the requirements of the passive SFC stated in section 7.0.4.1.
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The DVL [SBVSE] system SFs are required to be robust against passive single failure. Single failure has been applied to active components and redundancy is adequately ensured. Application of the passive single failure to this system is discussed in Sub-chapter 15.3, section 1.
7.4.2.1.3. Robustness against Loss of Power
The design of the DVL [SBVSE] system complies with the emergency power supply requirement stated in section 7.0.4.1, in particular in respect of the following:
Ventilation and Air-Conditioning of the uncontrolled areas of the HL [SB] buildings
o The eight DVL [SBVSE] system trains and associated LCU main and backup line fans are electrically independent (see also Sub-chapter 8.6).
o All four divisions of DVLm and DVLb (including LCU main and backup line fans) are backed up by EDGs. During EDG maintenance periods, manual cross- connection of electrical supplies is used to enable the neighbouring division to supply the DVL [SBVSE] system main train and LCU main line fans in the division for which the EDG is unavailable. Hence, in the event of LOOP while one EDG is in maintenance, DVLm in the affected division (including LCU main line fans) can be electrically supplied by its neighbouring division, and the DVL [SBVSE] system will remain operable in all four divisions during a LOOP event.
o In the case of LOOP with failure of an EDG in a division, specific provisions have been taken in the I&C rooms to back up the LCU backup line fans with { SCI removed } DC batteries in order to keep the temperature within the qualification range of I&C cabinets in any division where an EDG failure occurs. Once the { SCI removed } DC batteries are fully discharged, the LCU backup line fans are no longer required to operate as the heat loads in the I&C rooms will be greatly reduced due to loss of power supplies to the { SCI removed } DC battery backed-up I&C equipment.
o Electrical trains 1 and 4 supplying the DVL [SBVSE] system main trains 1 and 4, all Division 1 and 4 LCU main line fans and the Division 1 and 4 I&C room LCU backup line fans are backed up by the two UDGs, which are diverse from the four EDGs, in the case of SBO. The six other DVL [SBVSE] system trains are lost. Hence, the DVL [SBVSE] system will remain operable in Divisions 1 and 4 only during a SBO event. The DVL [SBVSE] system will be unavailable in Divisions 2 and 3.
Fire Dampers:
o The power supplies for the fire dampers are provided via the JDT [FDS] system and are robust against LOOP.
7.4.2.1.4. PhysicalAPPROVED Separation
The DVL [SBVSE] system is designed in accordance with the physical separation requirement stated in section 7.0.4.1, in particular in respect of the following:
The principal physical separation design provision for the DVL [SBVSE] system is based on the general design philosophy of having four independent divisions. One DVL [SBVSE] system division, including separate air intakes and air exhausts, is located in each HL [SB] building.
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For the general air-conditioning, the main and backup lines (supply, normal exhaust and specific exhaust trains) within a division are also, in general, designed to provide segregation between them. The exception to this is the common ductwork within a division (including DVL [SBVSE] system 1 and 4 recirculation ductwork).
Individual LCUs in the I&C rooms (all divisions) and RRI [CCWS] system rooms (Divisions 1 and 4) each contain DVLm and DVLb fans and main and backup cooling coils supplied by their divisions’ DELm and DELb trains respectively. Although a single LCU contains both the main and backup line components, the LCU design includes provisions to segregate the components of different trains, e.g. a metal plate separates the main line and backup line fans within the LCU.
7.4.2.2. System Protection against Hazards
7.4.2.2.1. Internal Hazards
The overall demonstration of the robustness of the plant to internal hazards is covered in Sub-chapter 13.2.
7.4.2.2.2. External Hazards
The overall demonstration of the robustness of the plant to external hazards is covered in Sub-chapter 13.1.
7.4.2.3. Diversity
The design of the DVL [SBVSE] system complies with the diversity requirement stated in section 7.0.4.3, in particular in respect of those detailed in the following sections (more details are provided in Sub-chapter 3.7 dealing with diversity).
Mechanical Diversity:
Diversity requirements are applied for the DVL [SBVSE] system trains and the LCUs. The detailed mechanical diversity is still to be fully defined at this time. However, from a high level perspective:
The DVL [SBVSE] system main and backup lines (LCU fans and general air handing system supply, normal and specific exhaust fans) are diverse; and
Mechanical diversity is provided between the main lines (LCUs and supply, normal and specific exhausts) of Divisions 1 and 4 and Divisions 2 and 3, to reduce the potential for a mechanical CCF affecting all four DVLm trains. Hence, three-way mechanical diversity is provided for both the DVL system trains and the LCUs. Cooling DiversityAPPROVED: There are two levels of diversity:
Each DVL [SBVSE] system supply train (DVLm or DVLb) and each LCU contains two cooling coils in series: one supplied by chilled water from DELm and one supplied by DELb. Consequently, cooling power can be provided by either DELm or DELb; and
DELm and DELb chillers are also diverse in terms of mechanical design, ultimate heat sink (DELm1 and 4 and DELb1 and 4 have air cooled condensers; DELm2 and 3 have water cooled (RRI [CCWS] system) condensers), I&C and electrical support systems.
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Additionally, there is diversity in both the mechanical design, I&C and ultimate heat sink of the DELm chillers between Divisions 1 and 4 and Divisions 2 and 3. Further details are provided in section 10.
Electrical Diversity:
The main components (fans and electrical heaters) of DVLm are supplied by { SCI removed } (LJ*) switchboards, whilst DVLb are supplied by { SCI removed } switchboards. The DVLm dampers and valves will also be supplied by { SCI removed } supplies – the specific switchboards have not yet been finalised but will be diverse from those used by DVLb.
I&C Diversity:
For the DVL [SBVSE] system centralised ventilation, the three I&C systems are based on three different technology platforms (Teleperm XS (TXS) for the RPR [PS] system, SPPA-T2000 for the SAS system, and UNICORN for the NCHICS) that are adequately diverse from each other to prevent systematic CCF of multiple systems. Further information on the individual technology platforms is provided in Sub-chapter 7.7. The RPR [PS] system operates as standby I&C for the SAS I&C system in normal operation for the DVL [SBVSE] system main trains. The NCHICS provides independent control of the backup trains and LCUs.
For the LCUs, the local dedicated I&C for the main line fans is adequately diverse from the NCHICS for the backup line fans to prevent systematic CCF of multiple systems.
7.4.2.4. Requirements Defined at the Component Level
7.4.2.4.1. General Mechanical, Electrical and I&C Requirements
The components of the DVL [SBVSE] system equipment performing a safety-related function comply with the general mechanical, electrical, and I&C requirements stated in section 7.0.5.1 as detailed in Section 9.4.7 – Table 1.
SECTION 9.4.7 - TABLE 1 : CLASSIFICATION OF MAIN MECHANICAL AND ELECTRICAL COMPONENTS ASSOCIATED TO THEIR SAFETY FEATURES
Description Safety classification Design requirements Mechanical requirement for pressure Highest Highest retaining safety safety Seismic Electrical I&C components or function class of requirement requirement requirement leak-tightness category SFG requirement for HVAC component EPW A 1 NT SC1 - - Damper APPROVED Fire Damper A 1 NT SC1 C3 C3 Isolation A 1 NT SC1 C1 C1 Damper Non-Return A 1 NT SC1 C1 C1 Damper
Control A 1 NT SC1 C1 C1
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Description Safety classification Design requirements Mechanical requirement for pressure Highest Highest retaining safety safety Seismic Electrical I&C components or function class of requirement requirement requirement leak-tightness category SFG requirement for HVAC component Damper Supply Train A 1 NT SC1 C1 C1 Heater Duct Heater B 2 NT SC1 C2 C2 Supply Train A 1 NT SC1 C1 C1 Fan Normal Exhaust A 1 NT SC1 C1 C1 Train Fan Specific Exhaust A 1 NT SC1 C1 C1 Train Fan LCU Fan A 1 NT SC1 C1 C1 Supply Train A 1 M3 SC1 C1 C1 Cooling Coil LCU Cooling A 1 M3 SC1 C1 C1 Coil This table will be updated after the Safety Classification Component Lists (SCCLs) studies.
7.4.2.4.2. Seismic Requirements
The DVL [SBVSE] system complies with the seismic qualification requirements listed in Section 9.4.7 – Table 1.
7.4.2.4.3. HIC Requirements
Not applicable: the DVL [SBVSE] system is not subject to any HIC requirements.
7.4.2.4.4. Specific I&C Requirements
NCHICS
Dedicated I&C is provided for the DVL [SBVSE] system backup trains (including DVL [SBVSE] system controlAPPROVED valves which control flow of the DEL [SCWS] system-supplied chilled water to the DVL [SBVSE] system cooling coils) and backup LCU fans in the form of NCHICS which is required to be Class 1 to perform the duty role during the DVL [SBVSE] system main train maintenance, providing operational control of the back-up equipment which is independent of the [RPR] PS and SAS I&C systems.
The NCHICS is effectively a hard wired independent I&C system that uses conventional electrical / analogue / switching electronic circuits without computer / software / data processing. It uses the UNICORN platform, which is discussed further in Sub-chapter 7.7.
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The mechanical, electrical and I&C components in the NCHICS must comply with the electrical and I&C requirements associated with their safety class, in accordance with the rules laid out in Sub-chapter 3.2.
Design and construction must conform to the specific common requirements detailed in the RCC-E (see Sub-chapter 3.8) and relevant standards (e.g. IEC standards).
A Quality Assurance Programme must be applied to the overall life cycle activities of the system.
NCHICS must be qualified for the operating conditions defined in section 1. The NCHICS equipment must meet the seismic requirements defined in Sub-chapter 3.2, section 6.1.
Power for NCHICS is backed up by EDGs.
Test equipment for a Class 1 system would normally be no lower than Class 2. If the maintenance and testing equipment cannot comply with the relevant classification requirements, compensatory measures (such as operational maintenance and testing procedures) will be established to ensure the overall category of the maintenance and testing functions.
Local Dedicated I&C Components
The LCU main line fan sub-systems include dedicated I&C components to perform room temperature measurement and control via regulation of the LCU main line fan speed.
The electrical and I&C components of the LCU must comply with the electrical and I&C requirements associated with their safety class, in accordance with the rules laid out in Sub-chapter 3.2.
Design and construction must conform to the specific common requirements detailed in the RCC-E (see Sub-chapter 3.8) and relevant standards (e.g. IEC standards).
A Quality Assurance Program must be applied to the overall life cycle activities of the system.
The components must be qualified for the operating conditions defined in section 1 and must meet the seismic requirements defined in Sub-chapter 3.2, section 6.1.
Power for the LCU main line fans and I&C equipment is backed up by EDGs.
7.4.3. Examination, Maintenance, (In-Service) Inspection and Testing (EMIT)
7.4.3.1. Start-up Tests
The DVL [SBVSE] system is subject to a start-up test programme in accordance with the procedures set out in Chapter 20 serving to verify the fulfilment of the following SFRs: DemonstrateAPPROVED that the centralised ventilation maintains the room temperatures within specified limits (see section 1) in all operating modes and under the three available modes of temperature control under full heat load conditions;
Demonstrate for the DVLm centralised ventilation trains (supply train, normal exhaust train and specific exhaust train) the automatic fault / failure detection and switch over to the associated DVLb trains;
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Demonstrate for the DVLm specific exhaust trains the automatic fault / failure detection and switch over to the associated DVLb specific exhaust train (supply train, normal exhaust train and specific exhaust train);
Demonstrate that the LCUs maintain the room temperatures within specified limits (see section 1) in the I&C rooms in each division and the RRI [CCWS] system rooms in Divisions 1 and 4 in all operating modes under full heat load conditions;
Demonstrate for each of the LCUs the automatic fault / failure detection and switch over to the associated DVLb train fan;
Demonstrate the automatic fault / failure detection and switch over from Division 2 to Division 3 for centralised ventilation cooling of the RSS;
Demonstrate correct operation of actuated isolation valves and dampers and confirmation of operation by position switches (where appropriate) for the respective modes of operation;
Demonstrate satisfactory operation of control loops for automatic regulation of valves and dampers to maintain specified set point control;
Demonstrate that the minimum air renewal rate in the { SCI removed } DC battery rooms is in line with limits set out in section 1; and
Demonstrate that the EPW dampers meet the performance requirements specified in Sub-chapter 13.1, section 4.
7.4.3.2. In-Service Inspection
The following functions of the DVL [SBVSE] system are monitored during normal operation by continuous monitoring systems:
The room temperature in the mechanical and electrical rooms in the DVL [SBVSE] system-served areas of the HL [SB] buildings which contain safety classified equipment;
The air supply temperature of operational DVLm trains;
The room temperature in the I&C rooms in all divisions and the RRI [CCWS] system rooms in Divisions 1 and 4 which are served by the DVL [SBVSE] system LCUs; and
The air flow rate in the { SCI removed } DC battery rooms for air renewal purposes.
The availability of these functions is therefore verified by the continuous monitoring process. 7.4.3.3. PeriodicAPPROVED testing The safety classified parts of the DVL [SBVSE] system are subject to periodic testing in accordance with the maintenance schedule in order to verify that the following SFRs are fulfilled:
Demonstrate for the DVLm centralised ventilation trains (supply train, normal exhaust train and specific exhaust train) the automatic fault / failure detection and switch over to the associated DVLb trains;
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Demonstrate for the DVLm specific exhaust trains the automatic fault / failure detection and switch over to the associated DVLb specific exhaust train (supply train, normal exhaust train and specific exhaust train);
Demonstrate for each of the LCUs the automatic fault / failure detection and switch over to the associated DVLb train fan;
Demonstrate the automatic fault / failure detection and switch over from Division 2 to Division 3 for centralised ventilation cooling of the RSS;
Demonstrate correct operation of actuated isolation valves dampers and confirmation of operation by position switches (where appropriate) for the respective modes of operation;
Demonstrate satisfactory operation of control loops for automatic regulation of valves and dampers to maintain specified set point control;
Demonstrate that the EPW dampers meet the performance requirements specified in Sub-chapter 13.1, section 4.
7.4.3.4. Maintenance
The DVL [SBVSE] system is subject to a maintenance programme.
Maintenance of centralised ventilation DVLm trains and DVLb trains (each comprising supply, normal exhaust and specific exhaust) may be performed at any time. However, maintenance should only be performed on one DVLm or DVLb train at any time to ensure availability of the remaining trains to perform the safety functions of the system.
LCUs in the I&C rooms are normally in continuous operation. The I&C rooms contain three LCUs per division in Divisions 1 and 4 and two LCUs per division in Divisions 2 and 3. Details are yet to be developed but it is not certain whether or not a LCU may remain operational on its DVLb fan while maintenance is carried out on its LCU DVLm fan. Detailed maintenance arrangements will take into account the requirement to maintain acceptable temperatures in the affected room(s) during maintenance.
Divisions 1 and 4 only contain a single LCU per division in the RRI [CCWS] system rooms. These LCUs are not expected to be in operation on a regular basis as the heat loads in the affected rooms are variable (depending on the RRI [CCWS] system fluid temperature). Detailed maintenance arrangements will take into account the requirement to maintain acceptable temperatures in the affected room(s) during maintenance.
The maintenance of the LCUs is independent of that of the DVL [SBVSE] centralised ventilation system. However, the maintenance both of the DVL [SBVSE] centralised ventilation system and the LCUs must be co-ordinated with the maintenance of their power supplies and with the maintenance ofAPPROVED other support systems, in particular the DEL [SCWS] system. 7.5. FUNCTIONAL DIAGRAM
The functional diagrams of the DVL [SBVSE] system are shown in Section 9.4.7 – Figures 1 and 2 (for more details, see the detailed mechanical diagram of the DVL [SBVSE] system).
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8. MAIN CONTROL ROOM AIR CONDITIONING SYSTEM (DCL [CRACS])
The information reported in this section is, unless otherwise noted, consistent with the reference design, as referenced from Chapter 22.
8.0. SAFETY REQUIREMENTS
The UK EPR Safety Classification principles and the top-down functional approach are presented in Sub-chapter 3.2. These principles help to ensure that the plant is designed, manufactured, constructed, commissioned and operated so that the appropriate level of reliability and integrity is achieved for its Structures, Systems and Components (SSCs).
The Hinkley Point C (HPC) functional safety analyses, and the application of these safety classification principles to the HPC reference design, result in the identification of the safety requirements for all safety systems in accordance with the Safety Functional Requirements Note (SFRNs) referenced from Sub-chapter 3.2.
This section summarises the results of these safety analyses and specifies the safety requirements that apply to the design of the Control Room Air Conditioning System (DCL [CRACS]).
The requirements described in the present section are consistent with safety functions to which the DCL [CRACS] system contributes in Plant Condition Category (PCC) and Design Extension Conditions (DEC). Consistency with requirements inherited from the Design Basis Initiating Faults (DBIFs) should be checked when the list of DBIFs evolves (see Chapter 15).
8.0.1. Safety Functions
The three Main Safety Functions (MSFs) necessary to achieve the overall safety objective of protecting people and the environment from the harmful effects of ionising radiations are:
control of fuel reactivity,
fuel heat removal, and
confinement of radioactive material.
These three MSFs must be achieved during:
normal operating conditions (PCC-1), including duty functions, control of radioactive release during normal operating conditions, control of main plant parameters, fault initial conditions, Limiting Conditions of Operation (LCOs), limitations, monitoring functions, Probabilistic Safety Assessment (PSA) significant functions as part of the preventive line of defenceAPPROVED, fault conditions (PCC-2 to PCC-4, DEC-A) and any equivalent Design Basis Initiating Faults (DBIFs)) and DEC-B, and
hazard conditions.
8.0.1.1. Control of Fuel Reactivity
The DCL [CRACS] system does not directly contribute to the MSF of control of fuel reactivity.
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8.0.1.2. Fuel Heat Removal
The DCL [CRACS] system does not directly contribute to the MSF of fuel heat removal.
8.0.1.3. Confinement of Radioactive Material
The DCL [CRACS] system does not directly contribute to the MSF of confinement of radioactive material.
8.0.1.4. Support Contribution to Main Safety Function
The DCL [CRACS] system does not indirectly contribute to the three MSF (see also the ‘Note’ in section 8.0.1.6).
8.0.1.5. Specific Contribution to Hazards Protection
The DCL [CRACS] system must contribute directly to the safety functions that are part of the facility hazards protection against the consequences of fire (see Sub-chapter 13.2, section 7), earthquake (see Sub-chapter 13.1, section 2), and site contamination (see Sub-chapter 13.1, section 4) as follows:
Contribution to the containment and prevention of spread of fire.
Ensuring preservation of habitable conditions in the Survival Island (see Sub-chapter 6,3, section 2,1 for definition of the survival island) in the event of site radiological contamination resulting from an accident on a neighbouring plant unit.
Preservation of Seismic Requirement levels (SC1) Safety Features (SFs) availability following a seismic event.
Moreover, the DCL [CRACS] system must be protected against internal and external hazards (see section 8.0.4.2).
8.0.1.6. Other Safety Functions to be performed in the Preventive Line of Defence
The DCL [CRACS] system must contribute indirectly to other safety functions to be performed as part of the preventive line of defence as follows:
Preservation of habitable conditions in the Survival Island in the event of external radiological contamination resulting from a release following an accident within the plant unit.
Central Air-Conditioning of Survival Island and (independent) Local Cooling of each Instrumentation and Control (I&C) Computer Room are required in all plant operating conditions, regardless of the external temperature, in order to maintain acceptable temperatureAPPROVED for the operating personnel and I&C system components in rooms that are essential for safety-related control operations.
Static confinement of the Survival Island following Total Loss of AC Power (TLAP) or Extended Total Loss of AC Power (Extended TLAP).
Monitoring of the Central Air-Conditioning of Survival Island and (Independent) Local Cooling of each I&C Computer Room (I&CCR) to ensure the temperature in the Main Control Room (MCR) and each I&CCR remains within specified limits.
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Note: The Heating, Ventilation And Air-Conditioning (HVAC) SFs considered as ‘frontline’ in the SFRNs are mainly performing the Plant Level Safety Function (PLSF) O2: { SCI removed }. However, performing this PLSF clearly represents a support role to the safety systems.
Therefore, although the DCL [CRACS] system ‘PLSF O2’ roles are reflected in section 8.0.1.6 to maintain consistency with the SFRNs and Section 9.4.8 – Table 2, for the remainder of this document the ‘PLSF O2’ roles of the DCL [CRACS] system are represented solely as a support contribution to the ‘main safety functions’.
8.0.2. Safety Functional Requirements
8.0.2.1. Control of Fuel Reactivity
Not applicable: the DCL [CRACS] system does not directly contribute to the MSF of control of fuel reactivity.
8.0.2.2. Fuel Heat Removal
Not applicable: the DCL [CRACS] system does not directly contribute to the MSF of fuel heat removal.
8.0.2.3. Confinement of Radioactive Material
Not applicable: the DCL [CRACS] system does not directly contribute to the MSF of confinement of radioactive material.
8.0.2.4. Support Contribution to Main Safety Function
With respect to its contribution to the three MSFs, the DCL [CRACS] system must satisfy the following Safety Functional Requirements (SFRs):
Ensure preservation of habitable conditions in the Survival Island in the event of radiological contamination from HPC:
o As a preventive measure, in the event of a severe accident within the plant unit, DCL system fresh air intake switchover to iodine lines is carried out manually. The actuated switchover is actioned from the MCR before release reaches the MCR.
o Ensure sufficient filtering of iodine and particulates from the outside air in order to limit the radiological conditions in the Survival Island.
Central Air-Conditioning of Survival Island and (Independent) Local Cooling of each I&CCR are required in all plant operating conditions, whatever the external temperature, in order to maintain acceptable temperature for the operating personnel and I&C system componentsAPPROVED in rooms that are essential for safety-related control operations. o Temperature excursions in the MCR and each I&CCR must not exceed the maximum qualified temperature for safety-related I&C components during transients such as TLAP or Extended TLAP.
Static Confinement of the Survival Island:
o Ensure static confinement of the Survival Island in case of TLAP or Extended TLAP, until power is restored to enable operation of an iodine train. The survival
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island is isolated from outside by manual closing of leak-tight isolation dampers on fresh air intake and exhaust lines. Isolation dampers may be switched from the MCR (actuators battery backed).
8.0.2.5. Specific Contribution to Hazards Protection
With respect to its specific contribution to the safety functions that are part of the facility hazards protection, the DCL [CRACS] system must satisfy the following SFRs:
Fire:
o Ensure the containment of fire in the rooms of the Survival Island by closure of respective fire dampers to maintain fire compartment integrity.
External Radiological Contamination:
o In the event of site radiological contamination due to an accident at a neighbouring plant unit (external hazard), the Central Air-Conditioning of Survival Island system fresh air intake is required to automatically switch over to iodine filtration in order to maintain habitable conditions in the Survival Island.
o Ensure sufficient adsorption of iodine and filtering of particulates from the outside air in order to limit the radiological conditions in the Survival Island.
o Ensure an overpressure of the Survival Island with respect to surroundings.
Earthquake:
o Ensure the stability / integrity of the DCL [CRACS] system components to avoid damage to higher classified components and ensure that it does not adversely impact the availability of SC1 SFs following a seismic event.
8.0.2.6. Other Safety Functions to be performed in the Preventive Line of Defence
With respect to its contribution to other safety functions to be performed as part of the preventive line of defence, the DCL [CRACS] system must satisfy the following SFRs:
Monitoring of the Central Air-Conditioning of Survival Island and (Independent) Local Cooling of each I&CCR:
o Monitoring of the MCR temperature,
o Monitoring of each I&CCR temperature, and
o Monitoring of the operational status of the main DCL [CRACS] system APPROVEDcomponents. 8.0.3. Safety Features and I&C Actuation Modes
Table 2 presents the SFs of the DCL [CRACS] system, according to the contributions identified in section 8.0.1 and the SFRNs referenced in Sub-chapter 3.2.
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8.0.4. Classification and Architecture Requirements of Safety Features
8.0.4.1. Requirements Arising from Safety Classification
Architecture requirements associated with SFs are essential for designing robust lines of defence consistent with their importance to nuclear safety (see Sub-chapter 3.2). Such requirements strengthen the system design against:
single faults and associated consequences (Single Failure Criterion (SFC)) by requiring redundancy,
Loss Of Off-site Power (LOOP) by requiring, among others, a backup power supply,
Station Black-Out (SBO) by requiring a power supply by the Ultimate Diesel Generators (UDGs),
Common Cause Failure (CCF) by requiring physical separation,
earthquake by defining seismic requirements, and
accident conditions by defining qualification requirements.
Section 9.4.8 – Table 2 presents the requirements arising from safety classifications for the DCL [CRACS] system, according to the SFRNs referenced in Sub-chapter 3.2.
8.0.4.2. System Protection against Hazards
8.0.4.2.1. Internal Hazards
The SFs of the DCL [CRACS] system must be protected against internal hazards if those hazards challenge the safety objectives, as defined in Sub-chapter 13.2.
8.0.4.2.2. External Hazards
The SFs of the DCL [CRACS] system must be protected against external hazards if those hazards challenge the safety objectives, as defined in Sub-chapter 13.1.
8.0.4.3. Diversity
The DCL [CRACS] system must be subject to the requirement for diversity as defined in the general safety principles (see Sub-chapter 3.1) and in Sub-chapter 3.7 dealing with diversity.
8.0.5. Requirements Defined at the Component Level 8.0.5.1. GenericAPPROVED Safety Requirements 8.0.5.1.1. General Mechanical, Electrical and I&C Requirements
The mechanical components within the DCL [CRACS] system must comply with the mechanical requirements in accordance with the rules laid out in Sub-chapter 3.2, section 7. The level of requirement is dependent upon: whether or not it is a pressure retaining component, the safety class of the component, whether the component acts as an isolating device between interfacing safety features, and on the role of the component as a barrier to the potential release of radioactivity as a result of failure of the component.
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The electrical and I&C components in the DCL [CRACS] system must comply with the electrical and I&C requirements associated with their safety class, in accordance with the rules laid out in Sub-chapter 3.2.
8.0.5.1.2. Seismic Requirements
The level of seismic requirements to be applied to the DCL [CRACS] system components is related to the Safety Feature Group (SFG) to which the component belongs, and the consequences on other classified components of its failure, if it were not seismically qualified. The rules for defining the seismic requirements for a component are identified in Sub-chapter 3.2.
8.0.5.1.3. Qualification for Accident Conditions
The safety classified parts of the DCL [CRACS] system must be qualified for the operating conditions in which they are required, as specified in Sub-chapter 3.6.
8.0.5.2. Specific Safety Requirements
8.0.5.2.1. High Integrity Component (HIC) Requirements
The DCL [CRACS] system is not subject to any High Integrity HIC requirements.
8.0.5.2.2. Specific I&C Requirements
The DCL [CRACS] system dedicated I&C is subject to safety requirements applicable to ‘Class 2’ I&C systems:
Control of the diverse backup for Central Air-Conditioning of Survival Island and (independently) Local Cooling of each I&CCR is achieved by a dedicated conventional I&C system, the Non-Computerised HVAC Instrument and Control System (NCHICS):
o NCHICS must be in operation continuously to ensure backup systems for the ‘Central Air-Conditioning of Survival Island’ and (independently) backup ‘Local Cooling of each I&CCR’. These are brought into operation automatically should the temperature in the MCR, or the temperature in either of the I&CCRs, rise above the NCHICS activation threshold temperature.
The general approach to qualification of dedicated I&C systems in terms of Production Excellence (PE) and Independent Confidence Building Measures (ICBM) is set out in Sub-chapter 7.7. However, the following specific requirements / exceptions to this general approach are noted here:
There are no specific requirements or exceptions. The DCL [CRACS]APPROVED system fire dampers are operated by the Fire Detection System (JDT [FDS]) dedicated I&C. The specific requirements arising from the JDT [FDS] system dedicated I&C are described in the JDT [FDS] system chapter (see Sub-chapter 9.5, section 1.2).
The general approach for I&C systems is set out in Chapter 7.
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8.0.6. Examination, Maintenance, (In-Service) Inspection and Testing (EMIT)
8.0.6.1. Start-up Tests
The DCL [CRACS] system must be designed to enable the performance of start-up tests to ensure the adequacy of its design and performance under conditions as representative as possible of the different operating configurations, and in particular its compliance with the SFRs assigned to it in section 8.0.2.
8.0.6.2. In-Service Inspection
The DCL [CRACS] system must be designed to enable surveillance under normal operation of the system characteristics necessary for the fulfilment of its safety-related tasks in order to ensure the performance of its components, and their availability under normal operation, or in the event of a fault or accident.
8.0.6.3. Periodic Testing
The safety classified parts of the DCL [CRACS] system must be designed to enable the performance of periodic tests in accordance with the maintenance schedule.
8.0.6.4. Maintenance
The DCL [CRACS] system must be designed to enable the implementation of a maintenance schedule (see Sub-chapter 18.2).
8.1. ROLE OF THE SYSTEM
The DCL [CRACS] system performs the functions (or tasks) detailed in the following sections under the different plant operating conditions for which it is required.
8.1.1. Normal Operating Conditions
The functional role of the DCL [CRACS] system in normal operation and during maintenance operations is as follows:
Provide Central Air-Conditioning of Survival Island for the comfort of operatives and to maintain temperature for correct functioning of safety-classified I&C equipment with two trains in operation.
Provide (independent) local cooling in each of the two I&CCRs for the comfort of operatives and to maintain temperature for correct functioning of safety classified I&C equipment with two Local Cooling Units (LCUs) in operation. 8.1.2. FaultAPPROVED and Hazard Operating Conditions Under the conditions of degraded operation, the role of the DCL [CRACS] system is to:
provide Central Air-Conditioning of Survival Island for the comfort of operatives and to maintain temperature for correct functioning of safety-classified I&C equipment with a minimum of one train in operation (operator comfort may be compromised when operating only one train);
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provide (independent) Local Cooling in each of the two I&CCRs for the comfort of operatives and to maintain temperature for correct functioning of safety classified I&C equipment with a minimum of one LCU in operation;
ensure habitability of the Survival Island during faults and hazards; and
in the event of fire, to prevent the spread of fire into adjacent fire compartments.
8.2. DESIGN BASIS
8.2.1. General Assumptions
The following general assumptions have been made in respect of the design for the DCL [CRACS] system:
Designations / descriptions used with respect to the DCL [CRACS] system main components:
o DCL ‘Central Air-Conditioning of Survival Island’ main line = ‘DCLm’ (DCLm1 for division 1, DCLm2 for division 2, DCLm3 for division 3 and DCLm4 for division 4).
o DCL ‘Central Air-Conditioning of Survival Island’ backup lines = ‘DCLb’ (DCLb1 for division 1 and DCLb4 for division 4).
o LCUs providing ‘Independent Local Cooling of each I&CCR’:
. Main LCUs = ‘LCUm’ (LCUm1 and LCUm2 for the I&CCR in division 2, LCUm3 and LCUm4 for the I&CCR in division 3).
. Backup LCUs = ‘LCUb’ (LCUb1 and LCU2b for the I&CCR in division 2, LCU3b and LCUb4 for the I&CCR in division 3).
o The numbers used in each line / unit designation reflect the division from which support systems such as electrical power and chilled water are provided.
The design for each DCLm, DCLb, LCUm and LCUb is sized to ensure the temperature requirement limits for safety-related equipment are not exceeded taking account of thermal transients arising from:
o The time taken into account in respect of switchover from duty to standby or backup systems (Safety Chilled Water System (DEL [SCWS]) and DCL [CRACS] system and also power from start-up of the Emergency Diesel Generator (EDGs) / UDGs); o APPROVEDLoss of the DCL [CRACS] system but only battery backed ({ SCI removed } battery backed and { SCI removed } battery backed) equipment in operation during TLAP and Extended TLAP.
External conditions taken into account in the sizing of the DCL [CRACS] system components are detailed in section 1.
{ SCI removed }.
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Only one of the four DCLm trains can be scheduled for maintenance at a time; the DCLb trains are considered not to be available during outage of the respective main train for maintenance.
Only one of the two LCUms in each of the I&CCRs can be scheduled for maintenance at a time.
Maintenance of the DCL [CRACS] system equipment must be co-ordinated with that of the support systems such as the DEL [SCWS] system, I&C and electrical power such that only one DCL [CRACS] system train / LCU is impacted.
Two DCLms are in operation normally (only one is required from a safety perspective), single train operation occurs only when three of the four DCLm trains are not available due to a combination of events or failures (maintenance, CCF, SFC etc.).
Two LCUms are in operation normally for each I&CCR (only one is required from safety perspective), single unit operation occurs only when one of the two LCUms are not available due to specific events or failures (maintenance, single failure criteria etc.).
The temperature limits permitted for single train operation / single LCU operation exceed those for normal operation, the period of operation in single train / single LCU operation is assumed to be limited. However, single train / single LCU operating temperatures are within the acceptable long-term qualification requirements for the safety related I&C equipment.
A DCLb train will be started only when the temperature in the MCR rises above the specified safety-related set point for backup train operation.
A LCUb will be started only when the temperature in the respective I&CCR rises above the specified safety-related set point for backup LCU operation.
The maximum cooling load for DCLm occurs during site contamination mode due to the operation of electric heaters upstream of the Iodine Adsorption Units (IAU).
Although not a safety requirement for the DCL [CRACS] system, during a heat wave simultaneous operation of both DELm and DELb trains will be in operation to satisfy the Safeguard Building (uncontrolled area) Ventilation System Electrical (division) (DVL [SBVSE]) requirements; this provides additional robustness in the availability of cooling for the DCL [CRACS] system.
In normal operation fresh air make-up for DCLm may be provided by { SCI removed } from each of the two divisions or 100% from either division.
In event of smoke from an external fire impacting the DCL [CRACS] system fresh air intake the respective air intake is isolated. Should both air intakes be affected then both are isolatedAPPROVED and the DCL [CRACS] operates in full recirculation. 8.2.2. Design Assumptions
8.2.2.1. Control of Fuel Reactivity
Not applicable: the DCL [CRACS] system does not directly contribute to the MSF of control of fuel reactivity.
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8.2.2.2. Fuel Heat Removal
Not applicable: the DCL [CRACS] system does not directly contribute to the MSF of fuel heat removal.
8.2.2.3. Confinement of Radioactive Material
Not applicable: the DCL [CRACS] system does not directly contribute to the MSF of confinement of radioactive material.
8.2.2.4. Support Contribution to Main Safety Function
Indirect contribution to the three MSFs:
Radiological Contamination
o The DCL [CRACS] system contributes to the protection against radiological contamination hazard (resulting from an accident within the plant unit) and habitability of the Survival Island (see also Sub-chapter 6.3) by manual switching of the fresh air intake to the Iodine train thereby filtering radiological particulate (using High Efficiency Particulate Air (HEPA) filters) and IAUs for adsorbing gaseous radioactive iodine:
. the IAUs shall satisfy the criteria defined in section 1;
. the HEPA filters shall satisfy the criteria defined in section 1;
. maintains the Survival Island at positive pressure relative to adjacent rooms; and
. the IAUs are protected by upstream electric heaters to ensure the relative humidity of the air onto the filters does not exceed { SCI removed } in order to ensure the decontamination efficiency is not compromised.
Central Air-Conditioning of Survival Island and (independent) Local Cooling of each I&CCR are required, regardless of the external temperature, in order to maintain acceptable temperature for the operating personnel and I&C system components in rooms that are essential for safety-related control operations:
o The DCL [CRACS] system shall ensure the minimum and maximum room temperatures are not exceeded under the respective operational modes as defined in Section 9.4.1 – Tables 2 and 3. Static ConfinementAPPROVED of the Survival Island: o In case of accident involving TLAP or Extended TLAP the DCL [CRACS] system isolation dampers provide air-tight isolation of the fresh air intake and exhaust ducts, damper leakage shall meet the requirements defined in Section 9.4.1 – Table 4.
8.2.2.5. Specific Contribution to Hazards Protection
The DCL [CRACS] system contributes to extreme weather; fire, earthquake and external radiological contamination hazards protection:
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Fire:
o Not applicable: there are no quantitative safety-related design assumptions associated with fire for the DCL [CRACS] system.
Earthquake:
o Not applicable: there are no quantitative safety-related design assumptions associated with the earthquake for the DCL [CRACS] system.
Site Radiological Contamination:
o The DCL [CRACS] system contributes to the protection against site radiological contamination hazard (resulting from an accident on a neighbouring plant unit) and habitability of the Survival Island (see also Sub-chapter 6.3) by automated switching of the fresh air intake to the Iodine train:
. See the design assumptions associated with Site Radiological Contamination in section 8.2.2.4.
8.2.2.6. Other Safety Functions to be performed in the Preventive Line of Defence
The DCL [CRACS] system contributes to the preventive line of defence:
Monitoring of the Central Air-Conditioning of Survival Island and (Independent) Local Cooling of each I&CCR:
o Not applicable: there are no quantitative safety-related design assumptions associated with the monitoring of the DCL [CRACS] system.
8.2.3. Other Assumptions
The DCL [CRACS] system is also subject to the following assumptions:
The MCR is to be maintained at a positive pressure in the event of external radiological hazard, no specific numerical values have been assigned regarding the over-pressure and there are no requirements for automated control of the pressure.
The pressure between the MCR and the stairs ({ SCI removed }) will be continuously monitored.
The DCL [CRACS] system design is consistent with RCC-M requirements as described in Sub-chapter 3.8, section 2.
The DCL [CRACS] system design is consistent with fire requirements as described in Sub-chapterAPPROVED 3.8, section 5. 8.2.4. Assumptions Associated with Extreme Situations Resulting from Beyond Design-Basis Hazards
8.2.4.1. Assumptions Associated with Fukushima Provisions
The assumptions associated with the Fukushima provisions of the DCL [CRACS] system are presented in Chapter 23. The main provisions are:
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Change-over to iodine filtration;
Central Air-Conditioning of Survival Island by ‘One Train’ and (Independent) Local Cooling of each I&CCR by ‘One LCU’; and
Static Containment of the Survival Island.
8.2.4.2. Assumptions Associated with non-Fukushima Provisions
The assumptions associated with the other non-Fukushima provisions of the DCL [CRACS] system are:
Non-Radiological Site Contamination, and
TLAP.
8.3. SYSTEM DESCRIPTION AND OPERATION
8.3.1. Description
8.3.1.1. General System Description
The description provided in this section applies equally to both Unit 1 and Unit 2.
The DCL [CRACS] system comprises four DCLm recirculatory trains (incorporating additionally two diverse DCLb trains), a single exhaust train, two LCUms (incorporating two diverse LCUbs) for each I&CCR; and four fresh air intake lines from two shared fresh air intake plenums.
Fresh air intake from each of the two plenums can be diverted, in the event of an accident involving site radiological contamination, to one of two dedicated iodine lines (one for each pair of intake lines) comprising IAUs and HEPA filters.
Central Air-Conditioning of Survival Island is provided via four DCLm trains and two diverse DCLb trains to ensure equipment availability for all plant situations. In case of failure of one of the main lines, another standby train starts automatically:
The cooling coils of the four DCLm trains (DCLm1, DCLm2, DCLm3 and DCLm4) are each cooled by separate specific DELm systems of the respective divisions (DELm1, DELm2, DELm3 and DELm4) in normal operation;
All trains have DELm from the respective division (DELm1, DELm2, DELm3 and DELm4) and diverse DELb cooling (coils are configured in series), division 1 and 2 are supplied from DELb1 and division 3 and 4 are supplied from DELb4.
The DCLm or DCLb trains can each be cooled by chilled water from either DELm or DELb. APPROVED
The two I&CCRs are ventilated by DCLm / DCLb trains, however the cooling in each of these rooms is provided independently by two LCUms and two diverse LCUbs:
The arrangement for chilled water cooling for the I&CCR LCUs is similar to that for the DCL [CRACS] system trains:
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o ‘I&CCR 1’ LCU cooling coils are supplied by DELm1 and DELm2 and cooling coils (in series) are supplied by DELb1;
o I&CCR 2 LCU cooling coils are supplied by DELm3 and DELm4 and cooling coils (in series) are supplied by DELb4; and
o the LCUms or LCUbs can be cooled by chilled water from either DELm or DELb.
The DCLm / DCLb lines supply conditioned air to the rooms of the Survival Island, return air from the rooms is recirculated in normal operation with the exception of the kitchen, corridors and sanitary rooms. The air from these rooms is exhaust to atmosphere via a single dedicated exhaust line.
Fresh air make-up is provided from two separate air intake plenums, one in the Safeguard Electrical Building (division 2) (HLB [SB(E)]) and one in the Safeguard Electrical Building (division 3) (HLC [SB(E)]). The fresh air intake plenums are shared with the DVL [SBVSE] system and the Smoke Control System (DFL) in the respective divisions:
The fresh air intake for division 2 can supply fresh air to DCLm1 / DCLb1 and / or DCLm2.
The fresh air intake for division 3 can supply fresh air to DCLm4 / DCLb4 and / or DCLm3.
Each of the two fresh air intake lines can be diverted through a dedicated iodine / HEPA filter line.
Each DCLm train fresh air intake has a main electric heater for normal operation in winter which can be used also to ensure the upstream relative humidity is not more than { SCI removed } when the iodine line is put into operation.
Each DCLb train has a main electric heater and an additional diverse backup electric heater on the fresh air intake.
Each DCL [CRACS] / DVL [SBVSE] / DFL system air inlet and exhaust line includes an Explosion Pressure Wave (EPW) protection device. EPW protection devices automatically close in response to the high pressure explosion wave isolating the ductwork within the building and respective DCL [CRACS] / DVL [SBVSE] / DFL system components from the effects of the external EPW.
The EPW protection devices for the DCL [CRACS] system are identified as DVL [SBVSE] system components (see Section 7).
The Survival Island is maintained at a pressure higher than the atmospheric pressure during accident conditions resulting in external radioactive contamination to ensure its habitability (see also Sub-chapterAPPROVED 6.3) except during static confinement for TLAP or Extended TLAP for which the DCL [CRACS] system is manually isolated pending recovery of electrical power.
8.3.1.2. Description of Main Equipment
Iodine Lines
The pre-filters used for fresh air in the iodine line upstream of the HEPA filters are installed in order to increase the life of the HEPA filters by filtering the coarse particles.
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The HEPA filters upstream of the IAUs remove radioactive aerosol contaminants. The HEPA filters downstream of the IAUs ensure against fine particle carry-over from the IAUs.
The required efficiency value for these safety classified filters is a design assumption given in section 1.
The iodine line booster fans are required to overcome the additional resistance resulting from the filters compared with the normal fresh air intake (when the iodine line is isolated).
Fresh Air Electrical Heaters
Air intake heaters heat outside air during periods of cold weather to ensure the DCL [CRACS] system supply air temperature requirements are met. In addition, air intake heaters on main trains 1 to 4 (DCLm1, DCLm2, DCLm3 and DCLm4) must also be capable of heating fresh air to ensure relative humidity requirements (<{ SCI removed }) are met in order to protect the IAUs in the event of site radiological contamination. Excessive humidity in the fresh air reduces the IAU efficiency.
During operation of an iodine line (site radiological contamination) the respective electric heater is switched on to ensure a { SCI removed } maximum relative humidity onto the IAU.
The two (diverse) backup DCL [CRACS] system heaters (DCLb1 and DCLb4) are equipped with electrical heaters which are controlled automatically.
Air Supply Fans
The Central Air-Conditioning of Survival Island supply fans draw the mixed fresh air and recirculated air through the components of the respective DCLm train supplying air to the Survival Island via a common distribution ductwork. Each of the four DCLm trains contains a supply fan. The two diverse backup DCL [CRACS] system trains (DCLb1 and DCLb4) each have a separate fan.
Supply Air Cooling Coils
The purpose of the main line and backup line supply cooling coils is to cool the mixture of fresh air and recirculated air and maintain set point supply air temperature. Each of the four DCL [CRACS] system trains is equipped with two cooling coils in series.
The cooling coils are supplied by the main DELm chilled water and diverse backup DELb chilled water respectively.
The chilled water flow rate within the supply cooling coils is automatically regulated by independent control valves in order to maintain the control air supply temperature.
Exhaust Fan
A common fanAPPROVED on the exhaust line exhausts air from the kitchen, toilets and corridors to the outside (in normal operation) so that the odours / moisture from these rooms are not recirculated.
LCUs in I&CCRs
Two LCUs are installed in each of the two I&CCRs as support of Class 1 systems the LCUs are Class 1, each LCU comprises:
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one cooling coil supplied by DELm in series with one cooling coil supplied by DELb;
one main fan in parallel with one backup fan;
two non-return dampers (one for each fan outlet).
8.3.1.3. Description of Main Layout
The four DCLm trains and the two DCLb trains are located at the { SCI removed } level of HLB [SB(E)] and HLC [SB(E)]:
DCLm1 and DCLb1 trains are located in { SCI removed } and DCLm2 train is located in { SCI removed } along with the associated common Iodine train.
DCLm4 and DCLb4 trains are located in { SCI removed } and DCLm3 train is located in { SCI removed } along with the associated common iodine train.
LCUms / LCUbs are located within the respective I&CCRs.
8.3.1.4. Description of System I&C
NCHICS Control
Control of both DCLb trains and all four LCUbs is by a dedicated conventional I&C system, the NCHICS system. The NCHICS is diverse from and completely independent of the Safety Automation System (SAS) and the Protection System (RPR [PS]) I&C systems used for control of the DCLm lines and LCUms.
In the case of an increase in the MCR temperature or the temperature of either I&CCR above the specified threshold set point for backup operation, the NCHICS starts one of the DCLb trains or independently one of the LCUbs in the room concerned.
JDT [FDS] System I&C
The JDT [FDS] system dedicated I&C used for the DCL [CRACS] system fire dampers is described in the JDT [FDS] system chapter (see Sub-chapter 9.5, section 1.2)
8.3.2. Operation
The DCL [CRACS] system operates in all power plant operating modes.
8.3.2.1. System Normal Operation
The system is used in normal operating state when the plant is operating and during plant outages. APPROVED 8.3.2.1.1. During Plant Normal Operation
In normal operation the DCL [CRACS] system trains are configured as follows:
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Two DCLm trains are in operation to provide Central Air-Conditioning for the Survival Island. Although operation of any two of the four trains is possible, the normal operating line-up is DCLm1 or DCLm2 in operation with DCLm3 or DCLm4. This line-up is preferred since it allows operation of two DCLm trains on independent outside air intakes. However, no formal restrictions exist on which trains can be used together. The main trains that are not in operation are considered as standby trains. The backup trains DCLb1 and DCLb4 are not operational but available if the temperature in the MCR exceeds the set point for triggering a backup train.
Air from the Survival Island is re-circulated with the exception of the kitchen, sanitary areas and the corridors which are exhausted (in normal operation) to atmosphere via a dedicated single exhaust train.
Fresh air is provided by two, independent, DVL [SBVSE] system concrete shafts which are located in HLB (division 2) and HLC (division 3). Division 2 supplies trains 1 and / or 2 whilst division 3 supplies 3 and / or 4. Fresh air heating is performed by electric heaters which are controlled to satisfy the air temperature requirements measured downstream of the respective heaters. The fresh air mixes with the re-circulated air from the Survival Island and then passes through pre-filters and filters upstream of the cooling coils and fans.
The two iodine filtration lines (one in HLB [SB(E)] and one in HLC [SB(E)]) are isolated and bypassed.
Air cooling is performed by the main cooling coils supplied with DELm chilled water for the respective operation of DCLm trains and temperature control is by regulation of the respective chilled water control valve to maintain the supply air temperature set point (measured in the supply duct downstream of the supply fan).
In normal operation the LCUs for each I&CCR are configured as follows:
Both of the two LCUms re-circulate air within the respective room and cooling is provided from the respective DELm chilled water system, temperature control is by airflow regulation to maintain room set point temperature (measured within the respective I&CCR).
LCUb fans are off but remain available.
8.3.2.1.2. During Maintenance
The system is used continuously during maintenance of a train (unit in operation) or during maintenance of two divisions (unit in outage) or during loss of availability of one or more ventilation elements or functions. During maintenanceAPPROVED the DCL [CRACS] system trains are configured as follows: The operation of the DCL [CRACS] system trains is the same as in ‘normal operation’; two of the four DCLm trains are used although technically only one is required to meet the safety requirements.
The DCL [CRACS] system ‘Central Air-Conditioning of Survival Island’ architecture takes into account routine inspection and maintenance requirements so that maintenance can be performed on the DCLm and DCLb trains. However, maintenance on more than one DCL [CRACS] system train simultaneously is not permitted.
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When maintenance is being performed on one DCL [CRACS] system train, the train is considered not to be available.
DCLbs are integrated with DCLms therefore during some maintenance activities when either DCLm or DCLb train is undergoing maintenance, the associated main / backup train may not be available.
However it may be possible for the DCL [CRACS] system train not undergoing maintenance to be brought into operation manually if required, subject to closure of any access doors / openings that may be open for inspection / cleaning or replacement of cooling coils or filters to prevent bypass of in-line components.
When maintenance is being performed on the exhaust line the system operates in recirculation mode, the air extracted from the kitchen, sanitary areas and corridors is re-circulated. Maintenance of the common exhaust line may be carried out by isolation of the line and isolation of one of the fresh air intake lines.
Planned maintenance can be performed on the iodine trains at any time as they are not normally in operation. Maintenance on both iodine lines simultaneously is not permitted.
During maintenance LCUs for each I&CCR are configured as follows:
In respect of the LCUs one unit remains operational whilst the other is undergoing maintenance, the operational LCUm is backed up by its own diverse LCUb.
LCUbs are integrated with LCUms therefore during some maintenance activities when either LCUm or LCUb is undergoing maintenance, the associated main / backup LCU may not be available.
However it may be possible for the LCU not undergoing maintenance to be brought into operation manually if required, subject to closure of any access doors / openings that may be open for inspection / cleaning or replacement of cooling coils or filters to prevent bypass of in-line components.
8.3.2.1.3. DCL [CRACS] Operation in the Event of Site Radiological Contamination
This state of operation applies when there is a radiological release following an accident on or close to the site. Contamination of the site (radiological contamination) is detected by the Plant Radiation Monitoring System (KRT [PRMS]).
During site radiological contamination the DCL [CRACS] system trains are configured as follows:
On detection of the radiological hazard (by the KRT [PRMS] system) all operational trains areAPPROVED stopped and isolation dampers are closed. Fresh air is directed through the respective iodine lines by opening the respective isolation dampers to divert fresh air from outside through the respective lines.
DCLm1 and DCLm4 are then started.
The main heater upstream of the respective IAU is operated to ensure the relative humidity of the fresh air onto the IAU is less than { SCI removed };
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Air cooling is performed by main cooling coils supplied with DELm chilled water for the respective operating DCLm train and temperature control is by regulation of the respective chilled water control valve to maintain supply air temperature set point (measured in the supply duct downstream of the supply fan).
Note: the default automated mode of operation is described here however alternative configurations are possible in the event that DCLm1 and / or DCLm4 are not available due to maintenance or fault condition. The iodine trains can be configured manually within the MCR for operation of DCLm2 or DCLm3 in place of DCLm1 or DCLm4. When operating an iodine line on DCLm2 or DCLm3, at least two trains shall be in operation in order to satisfy temperature requirements.
Site radiological contamination mode can also be performed by single train operation (e.g.DCLm1 or DCLm4 only) in the event that three trains are not available.
During site radiological contamination LCUs for each I&CCR are configured as follows:
Both of the two LCUms re-circulate air within the respective room and cooling is provided from the respective DELm chilled water system, temperature control is by airflow regulation to maintain room set point temperature (measured within the respective I&CCR).
LCUb fans are off but remain available.
8.3.2.1.4. Partial or Total Loss of the Ultimate Heat Sink (PLUHS or TLUHS)
For the DCL [CRACS] system, the air flow is cooled by the DEL [SCWS] system.
In division 2 and 3, the chilled water DELm2 and DELm3 is supplied by water-cooled chillers connected to the Component Cooling Water System (RRI [CCWS]) and in the two others (division 1 and 4), is supplied by two air-cooled chillers DELm1 and DELm4.
The two diverse backup chillers DELb1 and DELb4 in divisions 1 and 4 are also air cooled.
In the case of PLUHS or LUHS, the main chillers in divisions 2 and 3 are lost however DELb1 and DELb4 remain available to provide cooling for the DCL [CRACS] system trains of division 2 and 3.
8.3.2.1.5. Loss of Offsite Power (LOOP)
The power supplies to the four DCLm trains, the two DCLb trains and all of the LCUs are backed up by the main EDGs. During LOOP and in normal operation, only two of the four trains operate continuously. The safety requirement for the ‘Central Air-Conditioning of the Survival Island’ is that at least one train remains in operation and independently for each I&CCR that one LCU remains in operation. The principles of emergency supply are described in the robustness against loss ofAPPROVED power supply (see section 8.4.2.1.3). 8.3.2.1.6. Station Blackout (SBO)
The power supplies to two of the four DCLm trains and two of the LCUms are backed up by the UDGs. The principles of emergency supply are described in the robustness against loss of power supply (see section 8.4.2.1.3).
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8.3.2.2. System Transient Operation
8.3.2.2.1. Full or Partial System Failure
{ This section contains SCI-only text and has been removed }
8.3.2.2.2. Failure of Systems in Interface (Server or Served)
8.3.2.2.2.1. Server System Failure
{ This section contains SCI-only text and has been removed }
8.3.2.2.2.2. Impact of Served System Failure on DCL [CRACS] System / LCU
{ This section contains SCI-only text and has been removed }
8.4. PRELIMINARY DESIGN SUBSTANTIATION
The level of detail in regards to evidence of compliance with the safety requirements stated in section 8.0 will develop as the HPC project moves from basic design into detailed design since the PCSR3 sequence and system sequence are evolving in parallel. Therefore, the level of detail presented in this section reflects the level of information available at the time of issuing the system chapters.
8.4.1. Compliance with Safety Functional Requirement
8.4.1.1. Control of Fuel Reactivity
Not applicable: the DCL [CRACS] system does not directly contribute to the MSF of control of fuel reactivity.
8.4.1.2. Fuel Heat Removal
Not applicable: the DCL [CRACS] system does not directly contribute to the MSF of fuel heat removal.
8.4.1.3. Confinement of Radioactive Material
Not applicable: the DCL [CRACS] system does not indirectly contribute to the MSF of confinement of radioactive material.
8.4.1.4. Support Contribution to Main Safety Functions
The DCL [CRACS] system contributes indirectly to the three MSFs as: OperativesAPPROVED of the plant located within the Survival Island must be provided with an acceptable environment in which to perform their role in respect of the main safety functions. Changeover to iodine filtration is provided in the event of radiological release resulting from an accident within the plant unit:
o The Safety Requirement for ‘Changeover to Iodine Filtration’ is satisfied if the manually initiated changeover sequence is successful. The iodine train provides adequate filtering of radioactive contaminants from the outside air and the survival island is maintained at a higher pressure than the surrounding rooms:
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. The position status for each isolation damper verifies correct operation of the dampers for the respective Iodine lines;
. The off-coil temperature downstream of the electric heater confirms adequate protection of the IAU efficiency with respect to relative humidity issues for the respective Iodine lines;
. The status of the pressure differential across the fan for each iodine line verifies correct operation of the respective Iodine line booster fans; and
. Installation and routine efficiency testing of HEPA and IAUs ensure efficiency of filters on demand.
The safety-classified I&C equipment in the MCR and each I&CCR must be maintained between specified minimum and maximum temperature limits to ensure correct functioning under all plant operating conditions:
o Central Air-Conditioning of Survival Island is delivered by four DCLm and two DCLb trains, in normal operation two DCLm trains are in operation the remaining two DCLm trains are available standby trains. In the event of one DCLm train failing a standby train is automatically brought into operation.
o Each DCL [CRACS] system train (main and backup) is sized to ensure safe temperatures are maintained in the MCR within specified limits under exceptional conditions with only one train in operation (as stated in Section 9.4.1 – Tables 2 and 3).
o For situations (e.g.: total loss of { SCI removed } Emergency Power Supply Production and Distribution (LJ*) or { SCI removed } AC Uninterrupted Power Supply (UPS) Distribution (LV*) switchboards or TLIC) where all four DCLm trains are no longer available, a DCLb train (on { SCI removed } AC Emergency Power Supply Distribution (LL*) switchboards) is started automatically, a second DCLb train remains available should the first fail to start or fail in service.
o Local Cooling of each I&CCR is delivered by two LCUms and two LCUbs, in normal operation both LCUms in each I&CCR are in operation.
o Each LCU (main and backup) is designed to ensure safe temperatures are maintained in each I&CCR within specified limits under exceptional conditions (as stated in section 1, Tables 2 & 3).
o For situations (e.g.: total loss of LJ* or LV* switchboards or TLIC) where all or both LCUms are no longer available, an LCUb (on LL* switchboards) is started automatically; a second LCUb remains available should the first fail to start or fail in service.
The SurvivalAPPROVED Island must remain habitable during normal operation and during fault and hazard conditions. Survival Island Static Confinement is provided:
o The isolation is performed manually by closing the isolation dampers on fresh air intakes and exhaust lines.
o The isolation dampers are leak-tight and subject to the requirements defined in Section 9.4.1 – Table 4.
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8.4.1.5. Specific Contributions to Hazards Protection
The DCL [CRACS] system contributes to the facilities hazards protection in respect of fire, earthquake and external radiological contamination hazards.
For each hazard study concerned, these studies show that the design of these functions is such that they meet the acceptance criteria:
Fire Containment:
o The DCL [CRACS] system design complies with the fire requirements referenced in Sub-chapter 3.8.5. Contribution to the containment and prevention of spread of fire in the Safeguard Buildings (HL [SB]) by closure of the fire dampers is ensured by active (automation by the JDT [FDS] system) or ultimately passive (fusible device inside and outside the duct) means:
. fire damper qualification, and
. fire damper closure monitored by position status.
Site Radiological Contamination:
o Operatives of the plant located within the Survival Island must be provided with an acceptable environment in which to perform their role in respect of the main safety functions. Changeover to iodine filtration is provided in event of radiological release resulting from an accident within a neighbouring plant unit:
. See the description for support functions to main safety functions in section 8.4.1.4.
Earthquake – ensuring the stability or integrity of all components:
o Seismic qualification of the DCL [CRACS] system equipment and components.
These elements ensure that the SFRs stated in section 8.0.2 are met.
8.4.1.6. Other Safety Functions to be performed in the Preventative Line of Defence
The DCL [CRACS] system contributes in the preventative line of defence by continuous monitoring for both the DCL [CRACS] air conditioning system and local cooling units:
Monitoring of Central Air-Conditioning of Survival Island and Local Cooling of the I&CCRs:
o Monitoring is used to indicate the availability of the SF for one train / one LCU APPROVEDOperation to alert operators in the MCR in the event of its failure. 8.4.2. DCL Section Compliance with Design Requirements
The DCL [CRACS] system complies with the requirements stated in sections 8.0.4 and 8.0.5, particularly with respect to those detailed in the following sections.
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8.4.2.1. Requirements Arising from Safety Classification
8.4.2.1.1. Safety Classification
The compliance of the design and manufacture of the DCL [CRACS] system materials and equipment performing a safety-related function with requirements from the classification rules (see Sub-chapter 3.2, section 7) is presented in section 8.4.2.4.1.
Fire dampers protecting SFS boundaries are duplicated in series to ensure isolation in event of a fire and also in parallel to ensure cooling is maintained in event of accidental damper closure.
8.4.2.1.2. Single Failure Criterion (SFC) and Redundancy.
Active Single Failure:
The design of the DCL [CRACS] system meets the requirements of the active SFC stated in section 8.0.4.1, in particular in respect of the following:
In the event of loss of availability of an active component, the six train architecture (four main trains and two diverse backup trains) ensures that a train is always available to satisfy the safety function.
In the event of loss of availability of an active or passive component, the four local cooling unit architecture (two main units and two diverse backup units) in each of the I&CCRs ensures that a local cooling unit is always available to satisfy the Class 1 safety function.
Although the DCL [CRACS] system is required to meet the SFC, the IAU line operation is only required in the case of a DEC-B situation and / or external hazard. As a result, single failure and maintenance are not taken into account and it is therefore possible to carry out maintenance on the IAU lines. (Only one iodine line is required to satisfy the safety requirement.)
Passive Single Failure:
The DCL [CRACS] system SFs are required to be robust against passive single failure. Single failure has been applied to active components and redundancy is adequately ensured. Application of the passive single failure to this system is discussed in Sub-chapter 15.3, section 1.
8.4.2.1.3. Robustness against Loss of Power
The design of the DCL [CRACS] system complies with the emergency power supply requirement stated in section 8.0.4.1, in particular in respect of the following:
The six DCL [CRACS] system air-conditioning trains are electrically independent (see also sectionAPPROVED 8.4.2.3 regarding diversity): o DCLm1 and DCLm4 are backed up by the EDG and UDG of the respective electrical divisions;
o DCLb1, DCLm2, DCLm3 and DCLb4 are backed up by the EDG only of the respective electrical divisions;
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o the power for the mainline and backup line isolation dampers and for regulating the DCL [CRACS] system chilled water control valves are all { SCI removed } powered from their respective electrical divisions and backed up in a similar manner to the respective main trains, the backup train (DCLb1 and DCLb4) control valves and dampers are powered from a different { SCI removed } switchboard to the main trains;
o this provision ensures the availability of the air-conditioning function in the event of failure of an electrical train or in the event of preventive maintenance; and
o in plant outage, during simultaneous maintenance of two electrical trains, two air- conditioning trains remain available.
The I&CCR local cooling units are electrically independent:
o LCUm1 and LCUm4 are backed up by the EDG and UDG of the respective electrical divisions; and
o LCUb1, LCUm2, LCUm3 and LCUb4 are backed up by the EDG only of the respective electrical divisions.
The two IAU trains are electrically independent:
o The iodine heaters and iodine line fans are { SCI removed } powered from electrical division 1 (line 1) and electrical division 4 (line 4), both are backed up by the EDG and UDG.
o The isolation dampers for the iodine lines and bypass lines are all { SCI removed } powered from the respective electrical divisions, they are backed up by the EDG, UDG and { SCI removed } batteries.
Fire Dampers:
o The power supplies for the fire dampers are provided via the JDT [FDS] system and are robust against LOOP.
8.4.2.1.4. Physical Separation
The DCL [CRACS] system is designed in accordance with the physical separation requirement stated in section 8.0.4.1, in particular in respect of the following:
The DCL trains are physically separated and located within their own room / Nuclear Safety Fire Compartment as follows:
o DCLm1, DCLb1 are located in a dedicated room / Nuclear Safety Fire APPROVEDCompartment; o DCLm2 and associated iodine line are located in a dedicated room / Nuclear Safety Fire Compartment;
o DCLm3 and associated iodine line are located in a dedicated room / Nuclear Safety Fire Compartment; and
o DCLm4, DCLb4 are located in a dedicated room / Nuclear Safety Fire Compartment.
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8.4.2.2. System Protection against Hazards
8.4.2.2.1. Internal Hazards
The overall demonstration of the robustness of the plant to internal hazards is covered in Sub-chapter 13.2.
8.4.2.2.2. External Hazards
The overall demonstration of the robustness of the plant to external hazards is covered in Sub-chapter 13.1.
8.4.2.3. Diversity
The design of the DCL [CRACS] system complies with the diversity requirement stated in section 8.0.4.3, in particular in respect of those detailed in the following sections (more details are provided in Sub-chapter 3.7, dealing with diversity).
Mechanical Diversity:
Diversity requirements are applied for the DCL [CRACS] system trains and the LCUs. The detailed mechanical diversity is still to be fully defined at this time however from a high level perspective:
the main trains DCLm1 and DCLm3 are diverse from DCLm2 and DCLm4;
the backup lines DCLb1 and DCLb4 are diverse from each other;
the electric heaters for DCLm1 and DCLm3 are diverse from those of DCLm2, DCLm4;
the electric heaters of the backup lines DCLb1 and DCLb4 are diverse from each other;
the fans for DCLm1 and DCLm3 are diverse from those of DCLm2 and DCLm4;
the fans of the backup lines DCLb1 and DCLb4 are diverse from each other;
the fans for LCUm1 and LCUm3 are diverse from those of LCUm3 and LCUm4; and
the fans of the LCUbs are diverse from the respective LCUms.
Cooling Diversity (DEL [SCWS]):
There are two levels of diversity:
Each main and backup DCL [CRACS] system supply train and LCU contains two cooling coils inAPPROVED series: one supplied by chilled water from DELm and one supplied by DELb. Consequently, cooling power can be provided by either DELm or DELb; and
DELm and DELb chillers are also diverse in terms of mechanical design, ultimate heat sink (DELm1 and 4 and DELb1 and 4 have air cooled condensers; DELm2 and 3 have water cooled (RRI [CCWS] system) condensers), I&C and electrical support systems.
Additionally, there is diversity in both the mechanical and electrical design and I&C of the DELm chillers between Divisions 1 and 4 and Divisions 2 and 3.
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Electrical Diversity:
The voltage of the backup trains and LCUs are diverse from the voltage of the main trains and LCUs (see section 8.4.2.1.3).
The six DCL [CRACS] system air-conditioning trains are electrically independent and diverse:
o DCLm1 is { SCI removed } powered from electrical division 1;
o DCLb1 is { SCI removed } powered from electrical division 1;
o DCLm2 is { SCI removed } powered from electrical division 2;
o DCLm3 is { SCI removed } powered from electrical division 3;
o DCLm4 is { SCI removed } powered from electrical division 4;
o DCLb4 is { SCI removed } powered from electrical division 4;
o the power for the mainline and backup line isolation dampers and for regulating the DCL [CRACS] system chilled water control valves are all { SCI removed } powered from their respective electrical divisions, the backup train (DCLb1 and DCLb4) control valves and dampers are powered from a different { SCI removed } switchboard to the main trains;
o this provision ensures the availability of the air-conditioning function in the event of failure of an electrical train or in the event of preventive maintenance; and
o in plant outage, during simultaneous maintenance of two electrical trains, two air- conditioning trains remain available.
The I&CCR local cooling units are electrically independent and diverse:
o LCUm1 is { SCI removed } powered from electrical division 1;
o LCUb1 is { SCI removed } powered from electrical division 1;
o LCUm2 is { SCI removed } powered from electrical division 2;
o LCUm3 is { SCI removed } powered from electrical division 3;
o LCUm4 is { SCI removed } powered from electrical division 4; and o APPROVEDLCUb4 is { SCI removed } powered from electrical division 4. I&C Diversity:
The three I&C systems are based on three different technology platforms (Teleperm XS (TXS) for the PS system, SPPA-T2000 for the SAS system and UNICORN for NCHICS) that are adequately diverse from each other to prevent systematic CCF of multiple systems.
The PS system operates as standby I&C for the SAS I&C system in normal operation for the main trains and LCUs. The NCHICS provides completely independent control of the backup trains and LCUs.
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8.4.2.4. Requirements Defined at the Component Level
8.4.2.4.1. General Mechanical, Electrical and I&C Requirements
The components of the DCL [CRACS] system equipment performing a safety-related function comply with the general mechanical, electrical, and I&C requirements stated in section 8.0.5.1 as detailed in Section 9.4.8 – Table 1.
SECTION 9.4.8 - TABLE 1 – CLASSIFICATION OF MAIN MECHANICAL AND ELECTRICAL COMPONENTS ASSOCIATED WITH THE SAFETY FEATURES
Safety classification Design requirements Mechanical requirement for pressure Highest Highest retaining safety safety components Seismic Electrical I&C Description function class of or leak- requirement requirement requirement category SFG tightness requirement for HVAC component Fire Damper A 1 NT SC1 C3 C3 (SFS) Main Fresh Air A 1 T3 SC1 C1 C1 Heater Backup Fresh A 1 T3 SC1 C2 C2 Air Heater Air-Tight Isolation A 1 T3 SC1 C1/C3 C1/C3 Damper Standard Isolation A 1 NT SC1 C1 C1 Damper HEPA Filter C 3 T3 SC1 - - Iodine Adsorption C 3 T3 SC1 - - Unit Iodine Line C 3 NT SC1 C3 C3 Fan Cooling Coil A 1 M3 SC1 - - DCL Fan A 1 NT SC1 C1 C1 LCU Fan APPROVEDA 1 NT SC1 C1 C1 Non-Return A 1 T3 SC1 - - Damper
This table will be updated after the Safety Component Classification List (SCCL) studies.
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8.4.2.4.2. Seismic Requirements
The DCL [CRACS] system complies with the seismic qualification requirements listed in Section 9.4.8 – Table 1.
8.4.2.4.3. HIC Requirements
Not applicable: the DCL [CRACS] system is not subject to any HIC requirements.
8.4.2.4.4. Specific I&C Requirements
Dedicated I&C is provided for DCLb trains (including DCL [CRACS] system control valves) and LCUbs in the form of NCHICS which is required Class 2 to ensure the automated start-up and continued operational control of the backup equipment completely independent of the PS [RPR] and SAS I&C systems.
The NCHICS is effectively a hard wired independent I&C system that uses conventional electrical / analogue / switching electronic circuits or direct acting mechanical means of control without computer / software / digital processing.
The mechanical, electrical and I&C components in the NCHICS must comply with the electrical and I&C requirements associated with their safety class, in accordance with the rules laid out in Sub-chapter 3.2.
Design and construction must conform to the specific common requirements detailed in the RCC-E (see Sub-chapter 3.8) and relevant standards (e.g. IEC standards).
A Quality Assurance Program must be applied to the overall life cycle activities of the system.
NCHICS must be qualified for the operating conditions defined in section 1. The NCHICS equipment must meet the seismic requirements defined in Sub-chapter 3.2, section 6.1.
Power for NCHICS is backed up by the EDG, there is no UDG backup.
Any equipment used to test the NCHICS will be at least Class 2. If the maintenance and testing equipment cannot comply with the relevant classification requirements, compensatory measures (such as operational maintenance and testing procedures) will be established to ensure the overall category of the maintenance and testing functions.
8.4.3. Examination, Maintenance, (In-Service) Inspection and Testing (EMIT)
8.4.3.1. Start-up Tests
The DCL [CRACS] system is subject to a start-up test programme in accordance with the procedures setAPPROVED out in Chapter 20 serving to verify the fulfilment of the following SFRs: Demonstrate that four DCLm trains and two DCLb trains maintain the Survival Island within the specified limits (see Section 9.4.1 – Tables 1, 2 and 3) in all operating modes under full heat load conditions including fault and hazard conditions (where possible / practical).
Demonstrate for the four DCLm trains the automatic fault / failure detection and switch over to the next available standby DCLm train for all conceivable normal operating modes taking account also of units that may not be available for reason of maintenance.
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Demonstrate for the two DCLb trains the automated switch over to the next available backup train.
Demonstrate the automatic detection of radiological site contamination and the automated operation of DCLm trains in conjunction with the respective Iodine lines.
Demonstrate the operation of the heaters upstream of the IAUs in-site contamination mode of operation and take measurements of the upstream and downstream air temperature to verify specified criteria are met to ensure the heater off state will be not more than { SCI removed } Relative air Humidity (RH).
Demonstrate that each of the two LCUms and two diverse LCUbs in each I&CCR can maintain the respective rooms within the specified limits (see section 1 tables 1, 2 & 3) in all operating modes under full heat load conditions including fault and hazard conditions (where possible / practical).
Demonstrate for each of the two LCUms the automatic fault / failure detection and switch over to the next available LCUb on failure of both LCUms to satisfy the temperature requirement.
Demonstrate correct operation of actuated isolation valves and dampers and confirmation of operation by position switches (where appropriate) for the respective modes of operation.
Demonstrate satisfactory operation of control loops for automatic regulation of valves and dampers to maintain specified set point control.
Perform efficiency test on each HEPA filter to verify the filters are installed correctly and provide the required filter efficiency.
Perform efficiency tests on each IAU to verify the unit meets the required decontamination factor / efficiency for iodine removal.
Perform leakage testing on air-tight dampers to demonstrate the closed damper meet the specified leaktightness criteria.
8.4.3.2. In-Service Inspection
The following functions of the DCL [CRACS] system are monitored during normal operation by continuous monitoring systems:
the operational temperature in the MCR;
the air supply temperature of operational DCLm trains;
the operationalAPPROVED temperature in each of the I&CCRs (LCUm availability); The availability of these functions is therefore verified by the continuous monitoring process.
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8.4.3.3. Periodic Testing
The safety classified parts of the DCL [CRACS] system are subject to periodic testing in accordance with the maintenance schedule in order to verify that the following SFRs are fulfilled:
Perform efficiency test on each HEPA filter to verify the filters are installed correctly and provide the required filter efficiency.
Perform efficiency tests on each IAU to verify the unit meets the required decontamination factor / efficiency for iodine removal.
Demonstrate for the four DCLm trains the automatic fault / failure detection and switch over to next available standby DCLm train for all conceivable normal operating modes taking account also of units that may not be available for reason of maintenance.
Demonstrate for the two DCLb trains the automated switch over to the next available backup train.
Demonstrate correct operation of actuated isolation valves dampers and confirmation of operation by position switches (where appropriate) for the respective modes of operation.
Demonstrate satisfactory operation of control loops for automatic regulation of valves and dampers to maintain specified set point control.
Demonstrate the automatic detection of radiological site contamination and the automated operation of DCLm trains in conjunction with the respective iodine lines.
Demonstrate fire damper ‘closure’ both via the JDT [FDS] system and manual triggering to test actuator spring (and also demonstrate ‘opening’ where fire dampers have conflicting safety functions for ‘fire’ and ‘essential cooling’).
Demonstrate the operation of electric heaters and measure their performance.
8.4.3.4. Maintenance
The DCL [CRACS] system is subject to a maintenance programme.
Maintenance of DCLm trains and DCLb trains may be performed at any time however maintenance should only be performed on one train at any time to ensure availability of the remaining trains to perform the safety functions of the system.
All LCUms in the I&CCRs remain in continuous operation, only one LCUm may be taken out of service in each I&CCR.
Where one LCU is taken out of service (for cleaning or replacement of cooling coils for example) the remaining APPROVEDmain LCU provides the full cooling capacity required with availability of the backup in event of a failure.
With regard to the LCU undergoing maintenance, the associated main / backup LCU that is not undergoing maintenance can be brought into operation manually if required subject to closure of any access doors that may be open for inspection / cleaning or replacement of cooling coils.
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Likewise the maintenance of the DCL [CRACS] system must be co-ordinated with the maintenance of the respective DEL [SCWS] / DVL [SBVSE] systems and the respective power supplies (and other support systems). The maintenance of the LCUs is independent of the DVL [SBVSE] system but must be co-ordinated with the DEL [SCWS] system and the respective power supplies (and other support systems).
8.5. FUNCTIONAL DIAGRAM
The functional diagram of the DCL [CRACS] system is shown in Section 9.4.8 – Figure 1 (for more details, see the detailed mechanical diagram of the DCL system).
9. DIESEL BUILDING VENTILATION SYSTEM (DVD)
The information reported in this section is, unless otherwise noted, consistent with the reference design, as referenced from Chapter 22.
9.0. SAFETY REQUIREMENTS
The UK EPR Safety Classification principles and the top-down functional approach are presented in Sub-chapter 3.2. These principles help to ensure that the plant is designed, manufactured, constructed, commissioned and operated so that the appropriate level of reliability and integrity is achieved for its Structures, Systems and Components (SSCs).
The HPC functional safety analyses and the application of these safety classification principles to the HPC reference design result in the identification of the safety requirements for all safety systems in accordance with the Safety Functional Requirements Notes (SFRNs) referenced from Sub-chapter 3.2.
This section summarises the results of these safety analyses and specifies the safety requirements that apply to the design of the Diesel Building Ventilation System (DVD).
The requirements described in the present section are consistent with safety functions to which the DVD system contributes in Plant Condition Category (PCC) and Design Extension Conditions (DEC). Consistency with requirements inherited from the Design Basis Initiating Faults (DBIFs) should be checked when the list of DBIFs evolves (see Chapter 15).
9.0.1. Safety Functions
The three Main Safety Functions (MSFs) necessary to achieve the overall safety objective of protecting people and the environment from the harmful effects of ionising radiation are:
control of fuel reactivity, fuel heatAPPROVED removal, and confinement of radioactive material;
These three MSFs must be achieved during:
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normal operating conditions (PCC-1), including duty functions, control of radioactive release during normal operating conditions, control of main plant parameters, fault initial conditions, Limiting Conditions of Operation (LCO), limitations, monitoring functions, Probabilistic Safety Assessment (PSA) significant functions as part of the preventive line of defence.
fault conditions (PCC-2 to PCC-4, DEC-A) and any equivalent Design Basis Initiating Faults (DBIFs)) and DEC-B, and
hazard conditions.
9.0.1.1. Control of Fuel Reactivity
The DVD system does not directly contribute to the MSF of control of fuel reactivity.
9.0.1.2. Fuel Heat Removal
The DVD system does not directly contribute to the MSF of fuel heat removal.
9.0.1.3. Confinement of Radioactive Material
The DVD system does not directly contribute to the MSF of confinement of radioactive material.
9.0.1.4. Support Contribution to Main Safety Functions
The DVD system must indirectly contribute to the three MSFs as a support system of the Emergency Diesel Generator (EDG) and Ultimate Diesel Generator (UDG) during normal operation, Loss Of Off-site Power (LOOP) and Station Black-Out (SBO) events and during the hazards scenarios described in section 9.0.1.5.
More precisely, as a support system of the EDGs and UDGs, the DVD system must contribute to:
the air-conditioning of the EDG Electrical rooms during normal operation and LOOP,
the heat removal from the EDG halls during LOOP,
the air conditioning of the UDG Electrical rooms during normal operation, LOOP and SBO,
the heat removal from the UDG halls during SBO,
the heating of the EDG halls in winter and extreme low outside temperature, during normal operation, the heatingAPPROVED of the UDG halls in winter and extreme low outside temperature, during normal operation and LOOP,
the air-conditioning of the Severe Accident (SA) batteries and associated switchboards rooms during normal operation, LOOP and SBO, and
the air-conditioning of the rooms housing Class 3 switchboards and transformers during normal operation.
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9.0.1.5. Specific Contribution to Hazards Protection
Preservation of SC1 Safety Features (SFs) availability following a seismic event.
The DVD system must contribute directly to the safety functions that are part of the facility’s hazards protection against the consequences of external explosion, internal explosion and earthquakes (see Sub-chapter 13.1, section 1) as follows:
o protection of classified components following an external explosion,
o prevention of the risk of internal explosion due to hydrogen build-up during normal operation, LOOP and SBO, and
o preservation of the components which ensure the main safety functions within the Diesel Building (HD [DB]) in the event of an earthquake.
The DVD system must contribute indirectly to the safety functions that are part of the facility’s hazards protection against the consequences of external explosion, internal explosion and earthquakes (see Sub-chapter 13.1, section 1) as follows:
o the passive detection of failure of the ventilation in SA battery rooms during normal operation and LOOP.
9.0.1.6. Other Safety Functions to be performed in the Preventive Line of Defence
The DVD system must contribute directly to other safety functions to be performed as part of the preventive line of defence as follows:
prevention of the risk of internal explosion due to hydrogen build-up during normal operation, LOOP and SBO.
The DVD system must contribute indirectly to other safety functions to be performed as part of the preventive line of defence as follows:
the passive detection of failure of the ventilation in SA battery rooms during normal operation and LOOP.
9.0.2. Safety Functional Requirements
9.0.2.1. Control of Fuel Reactivity
Not applicable: the DVD system does not directly contribute to the MSF of control of fuel reactivity. 9.0.2.2. Fuel HeatAPPROVED Removal Not applicable: the DVD system does not directly contribute to the MSF of fuel heat removal.
9.0.2.3. Confinement of Radioactive Material
Not applicable: the DVD system does not directly contribute to the MSF of confinement of radioactive material.
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9.0.2.4. Support Contribution to Main Safety Functions
With respect to its indirect contribution to the MSF of fuel heat removal during normal operation, LOOP and SBO, the DVD system must satisfy the following Safety Functional Requirements (SFRs):
During normal operation and LOOP, the DVD system must ensure appropriate air conditions (temperature) in the EDG Electrical rooms in order to ensure the correct operation of the EDG equipment.
During LOOP, the DVD system must provide enough airflow to exhaust the heat produced by the operational EDGs in order to ensure their correct operation.
During normal operation, LOOP and SBO, the DVD system must ensure good operating air conditions (temperature) in the UDG Electrical rooms in order to ensure the correct operation of the UDG equipment.
During SBO, the DVD system must provide enough airflow to exhaust the heat produced by from the operational UDGs in order to ensure their correct operation.
During normal operation, in winter and during extreme winter conditions, the DVD system must heat the EDG halls in order to ensure their correct operation.
During normal operation and LOOP, in winter and during extreme winter conditions, the DVD system must heat the UDG halls in order to ensure their correct operation.
During normal operation, LOOP and SBO, the DVD system must ensure appropriate air conditions in the SA batteries and associated switchboards rooms in order to ensure the correct operation of the battery equipment.
During normal operation, the DVD system must ensure correct operating air conditions in the rooms housing Class 3 400 V AC Normal Power Supply Distribution (LK*) switchboards and transformers in order to ensure the correct operation of the LK* equipment.
9.0.2.5. Specific Contribution to Hazards Protection
With respect to its specific contribution to the safety functions that are part of the facility’s hazards protection, the DVD system must satisfy the following SFRs:
In case of external explosion, the DVD Explosion Pressure Wave (EPW) dampers must close and the aero-condenser must resist the external explosion wave.
During normal operation, LOOP and SBO, the DVD system must ensure the correct operation of the exhaust (minimum airflow) of the SA battery room in order to prevent the risk of APPROVEDhydrogen build-up and explosion in these rooms. The components of the DVD system that are not already SC1 classified are classified SC2 in order to protect SC1 class components and to preserve SC1 SFs in case of a seismic event.
9.0.2.6. Other Safety Functions to be performed in the Preventive Line of Defence
Not applicable: the DVD system does not contribute to other safety functions to be performed in the preventive line of defence.
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9.0.3. Safety Features and I&C Actuation Modes
Section 9.4.9 – Table 1 presents the SFs of the DVD system [Ref. 8] to [Ref. 12]) according to the contributions identified in section 9.0.1, and the SFRNs referenced in Sub-chapter 3.2.
9.0.4. Classification and Architecture Requirements of Safety Features
9.0.4.1. Requirements arising from Safety Classification
Architecture requirements associated with SFs are essential for designing robust lines of defence consistent with their importance to nuclear safety (see Sub-chapter 3.2). Such requirements strengthen the system design against:
single faults and associated consequences (Single Failure Criterion (SFC)) by requiring redundancy,
LOOP by requiring, among others, a back-up power supply,
SBO by requiring a power supply by the UDGs,
Common Cause Failures (CCF) by requiring physical separation,
earthquake by defining seismic requirements, and
accident conditions by defining qualification requirements.
Section 9.4.9 – Table 1 presents the requirements arising from safety classification for the DVD system, according to the SFRNs referenced in Sub-chapter 3.2.
9.0.4.2. System Protection against Hazards
9.0.4.2.1. Internal Hazards
The SFs of the DVD system must be protected against internal hazards if those hazards challenge the safety objectives, as defined in Sub-chapter 13.2.
9.0.4.2.2. External Hazards
The SFs of the DVD system must be protected against external hazards if those hazards challenge the safety objectives, as defined in Sub-chapter 13.1.
9.0.4.3. Diversity
The DVD system must be subject to the diversity requirement as defined in the general safety principles (seeAPPROVED Sub-chapter 3.1) and in Sub-chapter 3.7, dealing with diversity.
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9.0.5. Requirements defined at the Component Level
9.0.5.1. Generic Safety Requirements
9.0.5.1.1. Generic Mechanical, Electrical and I&C Requirements
The mechanical components within the DVD system must comply with the mechanical requirements in accordance with the rules laid out in Sub-chapter 3.2, section 7. The level of requirement is dependent upon the safety class of the component.
The electrical and Instrumentation & Control (I&C) components in the DVD system must comply with the electrical and I&C requirements associated with their safety class, in accordance with the rules laid out in Sub-chapter 3.2.
9.0.5.1.2. Seismic Requirements
The level of seismic requirements to be applied to the DVD system components is related to the Safety Feature Group (SFG) to which the component belongs, and the consequences on other classified components of its failure if it were not seismically qualified. The rules for defining the seismic requirements for a component are defined in Sub-chapter 3.2.
9.0.5.1.3. Qualification for Accident Conditions
The safety classified parts of the DVD system must be qualified for the operating conditions in which they are required, as specified in Sub-chapter 3.6.
9.0.5.2. Specific Safety Requirements
9.0.5.2.1. High Integrity Component (HIC) Requirements
The DVD system is not subject to any High Integrity Component (HIC) requirements.
9.0.5.2.2. Specific I&C Requirements
The DVD system dedicated I&C is subject to safety requirements applicable to Class 2 I&C systems. In addition the following requirements arise from specific I&C requirements:
The DVD system includes dedicated conventional I&C systems.
The general approach to qualification of dedicated I&C systems in terms of Production Excellence (PE) and Independent Confidence Building Measures (ICBM) is set out in Sub-chapter 7.7.
The general approach for I&C systems is set out in Chapter 7. 9.0.6. Examination,APPROVED Maintenance, (In-service) Inspection and Testing (EMIT) 9.0.6.1. Start-up Tests
The DVD system must be designed to enable the performance of start-up tests to ensure the adequacy of its design and performance under conditions as representative as possible of the different operating configurations, and in particular its compliance with the SFRs assigned to it in section 9.0.2.
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9.0.6.2. In-Service Inspection
The DVD system must be designed to enable surveillance under normal operation of the system characteristics necessary for the fulfilment of its safety-related tasks in order to ensure the performance of its components, and their availability under normal operation, or in the event of a fault or accident.
9.0.6.3. Periodic Testing
The safety classified parts of the DVD system must be designed to enable the performance of periodic tests in accordance with the maintenance schedule.
9.0.6.4. Maintenance
The DVD system must be designed to enable the implementation of a maintenance schedule (see Sub-chapter 18.2).
9.1. ROLE OF THE SYSTEM
The DVD system performs the functions (or tasks) detailed in the following sections under the different plant operating conditions for which it is required.
9.1.1. Normal Operating Conditions
The role of the DVD system is to ventilate the diesel rooms (the emergency diesel rooms and the ultimate diesel rooms). The specific duties are as follows:
to maintain acceptable ambient (inside) conditions for staff and for equipment,
to provide fresh air for staff (compliant with UK Building Regulation),
to ensure appropriate air conditions in the EDG and UDG electrical rooms in order to ensure the correct operation of the equipment,
to ensure the heating of the EDG and UDG halls,
to ensure appropriate air-conditioning of the SA batteries and associated switchboard rooms,
to ensure air-circulation in the SA battery rooms to prevent hydrogen explosion risk,
to ensure appropriate air-conditioning of rooms in the HD [DB] housing Class 3 switchboards and transformers, and to detectAPPROVED the failure of the ventilation in the SA battery rooms. 9.1.2. Fault and Hazard Operating Conditions
The DVD system is required under PCC-2, PCC-3 and PCC-4 operating conditions (short and long LOOP) as defined in Sub-chapters 14.2, 14.3 and 14.4. The specific duties are as follows:
to ensure appropriate air conditions in the EDG and UDG electrical rooms in order to ensure the correct operation of the equipment,
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to remove heat from the EDG halls,
to ensure the heating of the UDG halls,
to ensure appropriate air-conditioning of the SA batteries and associated switchboard rooms,
to ensure air-circulation in the SA battery rooms to prevent hydrogen explosion risk, and
to detect the failure of the ventilation in the SA battery rooms.
The DVD system is required under DEC-A operating conditions (SBO) as defined in Sub-chapter 14.5. The specific duties are as follows:
to ensure appropriate air conditions in UDG electrical rooms in order to ensure the correct operation of the equipment,
to remove heat from the UDG halls,
to ensure appropriate air-conditioning of the SA batteries and associated switchboard rooms,
to ensure air-circulation in the SA battery rooms to prevent hydrogen explosion risk, and
to detect the failure of the ventilation in the SA battery rooms.
The DVD system is required to operate under hazard conditions as defined in Sub-chapter 13.1. The specific duties are as follows:
to protect classified components after an external explosion, and
to protect SC1 components during and following a seismic event.
9.2. DESIGN BASIS
9.2.1. General Assumptions
The DVD system is designed with the following general assumptions:
Two { SCI removed } air supply fans and two { SCI removed } exhaust fans for each EDG and UDG hall ensure the appropriate air flow and the optimum temperature regulation.
Two 100% exhaust fans for the battery rooms ensure redundancy. All the APPROVEDEDG and UDG electrical rooms have an autonomous air-cooling system to ensure robustness against the loss of the main cooling supply.
A local cooling unit ensures the appropriate air flow and the optimum temperature regulation in the electrical rooms housing Class 3 switchboards and transformers.
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9.2.2. Design Assumptions
9.2.2.1. Control of Fuel Reactivity
Not applicable: the DVD system does not directly contribute to the MSF of control of fuel reactivity.
9.2.2.2. Fuel Heat Removal
Not applicable: the DVD system does not directly contribute to the MSF of fuel heat removal.
9.2.2.3. Confinement of Radioactive Material
Not applicable: the DVD system does not directly contribute to the MSF of confinement of radioactive material.
9.2.2.4. Support Contribution to Main Safety Functions
Indirect contribution to the three MSFs:
With respect to its indirect contribution to the three MSFs during normal operation, LOOP and SBO, the DVD system must satisfy the appropriate air conditions as defined in Section 9.4.1 – Tables 1 to 3, and air change rates also defined in section 1.
The assumptions on bounding atmospheric conditions to be taken into account in the design of the DVD system can be found in section 1.
9.2.2.5. Specific Contribution to Hazards Protection
9.2.2.5.1. Risk of Explosive Atmosphere
To prevent the risk of hydrogen build-up and explosion in the battery rooms, ventilation systems are designed in accordance with section 9.1.2.3. Some mechanical components will have to meet ATEX, DSEAR and specific air-tightness requirements.
9.2.2.5.2. Risk of External Explosion
EPW dampers are required to be installed at the inlets and outlets of DVD plenums in order to prevent an EPW from entering the HD [DB] building. The aero-condenser must be qualified to resist an external explosion wave. These components must be able to withstand the load case defined in Sub-chapter 13.1.
9.2.2.5.3. Risk of Seismic Event
The general assumptions used for the DVD system in order to withstand a seismic event can be found in Sub-chapterAPPROVED 13.1. 9.2.2.6. Other Safety Functions to be performed in the Preventive Line of Defence
Not applicable: the DVD system does not contribute to other safety functions to be performed in the preventive line of defence.
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9.2.3. Other Assumptions
9.2.3.1. Supply Air Temperatures for Air Handling Units of Electrical Rooms Ventilation
The temperature set points given in Section 9.4.9 – Table 2 are assumed for the different operating cases.
SECTION 9.4.9 – TABLE 2 : TEMPERATURE SET POINTS FOR OPERATING CASES OF THE DVD SYSTEM
DVD - EDG Buildings DVD - UDG Buildings Supply air Supply air temperature temperature During summer conditions { SCI removed } { SCI removed } During normal winter conditions { SCI removed } { SCI removed } During extreme low outside temperature conditions { SCI removed } { SCI removed }
The different supply air temperatures were assessed considering the specific characteristics of each building.
In normal winter condition, the supply temperature is { SCI removed } for the EDG building and { SCI removed } in the UDG building. In extreme winter conditions, the outside temperature is colder and the system must only comply with the lower fault minimum temperature (see Section 9.4.1 – Table 2), thus the supply temperature can be lower in the EDG building ({ SCI removed }) and in the UDG building ({ SCI removed }).
The outside temperature difference between the two winter conditions is explained in section 9.1.
9.2.3.2. Heat Loads
9.2.3.2.1. External Heat Loads
External heat loads are calculated directly and internally by { SCI removed } (validated software used, see Appendix 3, section 18).
9.2.3.2.2. Internal Heat Loads
Internal Heat Loads from Equipment To assess theAPPROVED heat load for each type of equipment, three types of equipment are considered: equipment emitting a constant heat load (independent of operation),
equipment emitting an off/on steady state heat loads (dependent on their state of operation), and
equipment emitting discontinuous fixed or variable heat loads.
For the sizing of the system, two different assumptions are made, depending of the season:
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In winter, the heat load considered is only from equipment emitting a constant heat load.
In summer, the total maximum heat load from all the equipment is considered.
Internal Heat Load from Electrical Lighting
The heat load from electrical lighting is calculated during summer according to the floor area of the rooms.
{ The remainder of this section contains SCI-only text and has been removed }
9.2.4. Assumptions Associated with Extreme Situations Resulting from Beyond Design Basis Hazards
9.2.4.1. Assumptions Associated with Fukushima Provisions
The assumptions associated with the Fukushima provisions of the DVD system are presented in Chapter 23. The main provisions are [Ref. 9]:
air-conditioning of UDG electrical rooms,
heat removal from UDG halls, and
air-conditioning of SA batteries and associated switchboard rooms.
9.2.4.2. Assumptions Associated with non-Fukushima Provisions
The assumptions associated with the Fukushima provision of the DVD system are presented in Chapter 23. The main provision is:
In normal LOOP and SBO operation, to cool the SA battery room and the SA battery electrical room in order to meet temperature requirement when the batteries are running in Total Loss of AC Power (TLAP) { SCI removed } and { SCI removed }.
9.3. SYSTEM DESCRIPTION AND OPERATION
9.3.1. Description
9.3.1.1. General System Description
The ventilation systems of the HD [DB] buildings ventilate the rooms containing the four EDGs (one per division) and the two UDGs.
Each division has its own separate and independent ventilation system with no connection to the other divisions.APPROVED Each ventilation inlet or outlet of the buildings are protected from missiles by concrete barriers.
For each diesel generator building, the DVD system contains several independent sub-systems.
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Ventilation of the EDG Building
Ventilation and heating of the emergency diesel hall are provided by:
o air intake with motorised isolation dampers with a silencer,
o EPW dampers,
o two { SCI removed } duty air supply fans,
o two { SCI removed } duty extraction fans,
o local fan convectors, and
o an air outlet with a silencer and EPW dampers.
The air-conditioning system for the electrical rooms (emergency diesel buildings) contains the following:
o an air intake with motorised isolation dampers with a silencer,
o EPW dampers,
o filters,
o an electric heater,
o a cooling coil with independent aero-condenser,
o a 100% duty air-supply fan,
o distribution ductwork, and
o the air conditioning system operates in recirculation mode with a fresh air intake.
Ventilation of the fuel tank rooms (emergency diesel buildings) is performed by:
o air transfer from the diesel hall for the main fuel tank room,
o air transfer from the diesel hall for the service fuel tank room,
o a 100% duty extraction fan, and
o an extraction ductwork system with isolation dampers and EPW dampers. VentilationAPPROVED of the rooms housing Class 3 switchboards and transformers (emergency diesel buildings) is performed by:
o a local recirculation cooling unit with a cooling coil and an independent air condenser, and
o part of the air from the air-conditioning system for the electrical rooms of the EDG building is diverted to the rooms housing Class 3 switchboards and transformers.
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Ventilation of the UDG Building
Ventilation and heating of the ultimate diesel hall are provided by:
o air intake with motorised isolation dampers with a silencer,
o EPW dampers,
o two air supply fans with { SCI removed } duty,
o two extraction fans with { SCI removed } duty,
o air heaters, and
o an air outlet with a silencer and EPW dampers.
The air-conditioning system for the electrical rooms (ultimate diesel buildings) contains the following:
o air intake with motor-driven isolation dampers with a silencer,
o EPW dampers,
o filters,
o an electric heater,
o a cooling coil with an independent air cooled condenser,
o a 100% duty air-supply fan,
o distribution ductwork, and
o the air conditioning system operates in recirculation mode with a fresh air intake.
Ventilation of the fuel tank rooms and battery rooms (ultimate diesel buildings) is performed by:
o an air supply from the air-conditioning system of the electrical rooms for the main fuel tank, service fuel tank and battery rooms,
o an in-duct heater unit,
o two 100% duty extraction fans, o APPROVEDan extraction ductwork system with isolation dampers and EPW dampers, and o limit switches to detect the failure of the air extraction.
9.3.1.2. Description of Main Equipment
The DVD system comprises the following main equipment items (see the functional diagram provided in section 9.5).
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9.3.1.2.1. EDG Buildings
External Explosion Hazard Protection for HD [DB] Buildings
The EPW dampers protect the DVD system from external explosion hazard on the inlet lines and the outlet lines.
Heat Removal from EDG Hall
The heat removal from the EDG halls is ensured by two air supply fans and two exhaust fans, two recirculation dampers and eight air inlet dampers.
Heating of the EDG Hall
The heating of the emergency diesel hall is ensured by four electric heaters.
Air-conditioning of the EDG Electrical Rooms
The air-conditioning of the EDG electrical rooms is ensured by the following:
filters,
a cooling coil,
an electrical heater, and
an air supply centrifugal fan.
Air-conditioning of Rooms in HD [DB] Building Housing Class 3 Switchboards and Transformers
This function is ensured by a local cooling unit which comprises a cooling coil associated to a fan.
9.3.1.2.2. UDG Buildings
External Explosion Hazard Protection for HD [DB] Buildings
The EPW dampers protect the DVD system from external explosion hazard on the inlet lines and the outlet lines.
Heat Removal from the UDG Halls
The heat removal from the UDG halls is ensured by two air supply fans and two exhaust fans, one recirculation damper and four air inlet dampers. Heating of theAPPROVED UDG Hall The heating of the ultimate diesel hall is ensured by two electric heaters.
Air-conditioning of the UDG Electrical Rooms and SA Battery and Associated Switchboards Rooms
The air-conditioning of the UDG electrical rooms and SA battery and associated switchboards rooms is ensured by the following:
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filters,
a cooling coil,
an electrical heater, and
an air supply centrifugal fan.
Air-circulation in SA Battery Rooms to prevent Hydrogen Risk
The function is ensured by the exhaust axial fan.
9.3.1.3. Description of Main Layout
On HPC, the four buildings HDA-B-C-D [DB] are ventilated by the DVD system. HDA and HDD both contain two diesel generators (EDG and UDG) whereas HDB and HDC contain only one diesel generator (EDG).
Since each diesel generator and its associated electrical rooms are independently and separately ventilated by the DVD system and have no connection to the other diesel engines, the following terms are used:
“EDG hall” and “UDG hall” refer to the room containing the diesel generator itself.
“EDG building” and “UDG building” refer to the diesel hall and its associated rooms.
Each building is ventilated by its own ventilation train.
For example, had [DB] is composed of an EDG building and an UDG building and for each building:
EDG building is composed of the EDG hall ({ SCI removed }) and associated electrical rooms, fuel tank rooms, etc.
UDG building is composed of the UDG hall ({ SCI removed }) and associated electrical rooms, fuel tank rooms, etc.
The main layout of the DVD system is as follows:
The DVD system provides ventilation for the four EDG buildings and the two UDG buildings.
EPW dampers are installed on each of the air outlets and inlets of the HD [DB] building.
In the diesel generator building, internal flooding is taken into account and the ventilation ducts areAPPROVED installed so as to avoid propagation of flooding from room to room.
9.3.1.4. Description of System I&C
The DVD system includes conventional classified dedicated I&C.
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The DVD system has six classified conventional dedicated independent systems which control the following function:
Air conditioning of the electrical rooms in the EDG (four units) and UDG (two units) building.
These dedicated I&C systems work in an autonomous way and are activated (ON/OFF) by the normal I&C control of the building.
9.3.2. Operation
9.3.2.1. System Normal Operation
In the normal operation of the plant, the diesel generators are switched off. For the electrical rooms, the air is conditioned continuously in recirculation mode with a fresh air supply.
In the EDG buildings:
the air heaters in the diesel generator hall are controlled by thermostats located in the hall;
the ventilation of the fuel tank rooms operates continuously;
the local cooling unit of the rooms housing Class 3 LK* switchboards and transformers operates continuously; and
the power supplies for the ventilation sub-system for the electrical rooms, the air supply and extraction fans in the diesel hall are backed up by the diesel generator in the building. The power supplies for the air heaters and the local cooling unit are not backed up.
In the UDG buildings:
the air heaters in the diesel generator hall are controlled by thermostats located in the hall;
the ventilation of the battery rooms and the fuel tank rooms operates continuously; and
the power supplies for the ventilation sub-system for the electrical rooms, the air supply and extraction fans as well as the air heaters in the diesel hall are backed up by the diesel generator in the building.
9.3.2.2. System Transient Operation
9.3.2.2.1. Partial or Total Loss of the Ultimate Heat Sink (LUHS) – Partial or Total Loss of the RRI-SEC APPROVED[CCWS-ESWS] Cooling Chain (LOCC) For the DVD system, the total or partial Loss of the Ultimate Heat Sink (LUHS) has no impact.
9.3.2.2.2. Loss of Offsite Power (LOOP)
In the event of LOOP, in the EDG building, the air supply isolation dampers, the two { SCI removed } air supply fans and the two { SCI removed } extraction fans in the diesel hall, the air-supply fan and the cooling system in the electrical rooms, are backed up by the corresponding EDG.
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The air conditions to be maintained are the same as those specified in section 9.2.2.4.
In the UDG building, the heater units in the diesel hall, the air supply fan, the cooling system and heaters units in the electrical rooms, the air extraction fans in the fuel tank rooms and the battery rooms and the heater unit in the battery rooms are backed up by the corresponding EDG.
9.3.2.2.3. Station Black-Out (SBO)
During a postulated SBO, only the UDGs are in operation. The power supplies for the air supply isolation dampers, the two { SCI removed } air supply fans and the two { SCI removed } extraction fans in the diesel hall, the extraction fans in the fuel tank rooms and the battery rooms, the air heater in the battery rooms, the cooling system and the air-supply fan in the electrical rooms are backed up by the corresponding UDG.
The air conditions to be maintained are the same as those specified in section 9.2.2.4.
9.3.2.2.4. Full or Partial System Failure
{ This section contains SCI-only text and has been removed }
9.3.2.2.5. Failures of Interfaced Systems (Servers or Served)
{ This section contains SCI-only text and has been removed }
9.4. PRELIMINARY DESIGN SUBSTANTIATION
The level of detail of evidence in regards to compliance with the safety requirements stated in section 9.0 will develop as the HPC project moves from basic design into detailed design since the PCSR3 sequence and system sequence are evolving in parallel. Therefore, the level of detail presented in this section reflects the level of information available at the time of issuing the system chapters.
9.4.1. Compliance with Safety Functional Requirements
9.4.1.1. Control of Fuel Reactivity
Not applicable: the DVD system does not directly contribute to the MSF of control of fuel reactivity.
9.4.1.2. Fuel Heat Removal
Not applicable: the DVD system does not directly contribute to the MSF of fuel heat removal.
9.4.1.3. Confinement of Radioactive Material Not applicable:APPROVED the DVD system does not directly contribute to the MSF of confinement of radioactive material.
9.4.1.4. Support Contribution to Main Safety Functions
The design assumptions of the DVD system, stated in section 9.2.2, are consistent with the requirements of the corresponding systems which it supports:
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During normal operation, LOOP and SBO the DVD system must satisfy that acceptable operating conditions are met in every room in order to ensure the correct operations of equipment and/or good working conditions for operators. The sizing of the system is consistent with the appropriate air and atmospheric conditions stated in section 9.1.
As the SFRs cannot be directly verified due to the fact that the test conditions are different to the extreme conditions under which the SFRs are required to be fulfilled, they must be verified in an extrapolated/indirect manner as follows:
The respect of the minimum and maximum temperature will be verified through the air- flow rate which can be delivered by the fans and the thermal output dissipated by the equipment based on the supplied electrical power.
9.4.1.5. Specific Contribution to Hazards Protection
The hazards studies of Sub-chapters 13.1 and 13.2 involving functions of the DVD system use values for the following parameters that are in keeping with the design assumptions stated in section 9.2.2:
During an external explosion, the DVD EPW dampers close and the aero-condensers are qualified to resist the external explosion wave.
The components of the DVD system that are not already SC1 classified are classified SC2 and therefore do not have unacceptable impacts on SC1 components in the event of an earthquake.
The DVD system ensures the operation of the exhaust of the SA battery room in order to prevent the risk of hydrogen build-up and explosion in these rooms in accordance with EN50272-2 [Ref. 14]. As the SFRs cannot be directly verified due to the fact that the test conditions are different to the fault/hazard conditions under which the SFRs are required to be fulfilled, they must be verified in an extrapolated/indirect manner as follows:
The respect of the maximum level of hydrogen in the SA batteries rooms will be verified through the air-flow rate of the fans and the characteristics of the batteries.
The passive detection of the failure of the extraction of the battery rooms can be checked by the position of the limit switches on the non-return dampers of the exhaust fans.
9.4.1.6. Other Safety Functions to be performed in the Preventive Line of Defence
Not applicable: the DVD system does not contribute to other safety functions to be performed in the preventive line of defence.
9.4.2. Compliance with Design Requirements The DVD systemAPPROVED complies with the requirements stated in sections 9.0.4 and 9.0.5, particularly with respect to those detailed in the following sections.
9.4.2.1. Requirements arising from Safety Classification
9.4.2.1.1. Safety Classification
The compliance of the design and manufacture of the DVD system materials and equipment performing a safety-related function with requirements from the classification rules (see Sub-chapter 3.2, section 7) is presented in section 9.4.2.4.1.
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9.4.2.1.2. Single Failure Criterion and Redundancy
Active Single Failure
The design of the DVD system meets the requirements of the active SFC stated in section 9.0.4.1, in particular in respect of the following:
air-conditioning of the EDG electrical rooms, and
heat removal from the EDG halls.
The four 100% ventilation trains of the DVD system installed (one per building) in the emergency diesel rooms meet the SFC. For each EDG, the rooms have their own ventilation system (DVD system). There is no connection between the ventilation systems of the different divisions of the emergency diesel rooms. Thus a failure in one division cannot affect another division.
For the UDGs and their service systems, the SFC does not apply.
Furthermore, although not subject to the application of the SFC, the air circulation in SA battery rooms of the DVD system has redundancy of availability, achieved through duplication of the 100% extraction fan.
Passive Single Failure
Not applicable: the DVD system is not subject to passive single failure.
9.4.2.1.3. Robustness against Loss of Power
The design of the DVD system complies with the emergency power supply requirements stated in section 9.0.4.1, in particular in respect of the following:
air-conditioning of EDG electrical rooms,
heat removal from EDG halls,
air-circulation in the SA battery rooms to prevent hydrogen risk,
air-conditioning (supply and exhaust) of SA batteries and associated switchboards rooms,
external explosion hazard protection for the HD [DB] building,
heating of the UDG halls, air-conditioningAPPROVED and heating of the SA batteries and associated switchboards, and air-conditioning of the UDG electrical rooms.
Therefore, in the event of LOOP, the following components are backed-up by the EDGs:
air supply fan, the cooling and heating coils of the ventilation of the electrical equipment rooms of the EDG buildings;
dampers, exhaust and supply fans of the EDG hall,
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exhaust fans of the battery rooms in the UDG buildings,
the electric fan assisted air heaters of the UDGs,
the air heating unit for the battery room of the UDG building, and
the air supply fan, the cooling and heating coils of the ventilation of the electrical equipment rooms of the UDG building.
EPW dampers are not backed-up by the EDGs because of their mechanical working system. They are closed or open by the action of springs: when an explosion wave hits them, the damper shuts close on its own without any power required.
The design of the DVD system complies with the ultimate power supply requirements stated in section 9.0.4.1, in particular in respect of the following:
air-conditioning of the UDG Electrical Rooms,
heat removal from the UDG Halls,
air-circulation in the SA battery rooms to prevent hydrogen risk, and
air-conditioning (supply and exhaust) of the SA batteries and associated switchboards rooms.
Therefore, in the event of SBO, the following components are backed-up by the UDGs:
exhaust fans of the battery rooms in the UDG buildings, and
the air heating unit for the battery room.
9.4.2.1.4. Physical Separation
The DVD system is designed in accordance with the physical separation requirement stated in section 9.0.4.1, in particular in respect of the following:
air-conditioning of the EDG electrical rooms, and
heat removal from the EDG halls.
Each of the four 100% ventilation trains is in a different building meeting the physical separation requirement.
Also, while not required, each of the two 100% ventilations trains serving the UDGs is in a different buildingAPPROVED from the EDGs. 9.4.2.2. System Protection against Hazards
9.4.2.2.1. Internal Hazards
The overall demonstration of the robustness of the plant to internal hazards is covered in Sub-chapter 13.2.
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9.4.2.2.2. External Hazards
The overall demonstration of the robustness of the plant to external hazards is covered in Sub-chapter 13.1.
9.4.2.3. Diversity
Diversity is required for the EDGs and UDGs. The diversity requirement studies for the DVD HVAC support system are ongoing and still need to be assessed. If the diversification is required, the definition can be found in the general safety principles (see Sub-chapter 3.1) and in Sub-chapter 3.7, dealing with diversity.
9.4.2.4. Requirements Defined at the Component Level
9.4.2.4.1. General Mechanical, Electrical and I&C Requirements
The components of the DVD system equipment performing a safety-related function comply with the general mechanical, electrical, and I&C requirements stated in section 9.0.5.1 as detailed in Section 9.4.9 – Table 1.
SECTION 9.4.9. – TABLE 1 : CLASSIFICATION OF MAIN MECHANICAL AND ELECTRICAL COMPONENTS ASSOCIATED TO THEIR SAFETY FEATURES
Safety Design requirements classification Mechanical Highest Highest Description requirement safety safety Seismic Electrical I&C for pressure function class of requirement requirement requirement retaining category SFG components
EPW Dampers A 1 NT SC1 - - EDG building
Electrical Dampers inlet A 1 NT SC1 C1 C1 EDG Hall Air supply fans A 1 NT SC1 C1 C1 EDG Hall Heaters of the C 3 NR SC2 C3 C3 EDG hall Air exhaust fans A 1 NT SC1 C1 C1 EDG Hall Cooling Coil EDG Electrical APPROVED B 2 NT SC1 - - rooms Air Supply Fan EDG electrical B 2 NT SC1 C2 C2 rooms EPW Dampers A 2 NT SC1 - - UDG building
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Safety Design requirements classification Mechanical Highest Highest Description requirement safety safety Seismic Electrical I&C for pressure function class of requirement requirement requirement retaining category SFG components Electrical Dampers inlet A 2 NT SC1 C2 C2 UDG Hall Air supply fans A 2 NT SC1 C2 C2 UDG Hall Heaters of the B 3 NR SC1 C3 C3 UDG Hall Air exhaust fans A 2 NT SC1 C2 C2 UDG Hall Cooling Coil UDG battery A 2 NT SC1 - - and Electrical rooms Air supply fans UDG battery and A 2 NT SC1 C2 C2 electrical rooms Air exhaust fans UDG battery A 2 NT SC1 C2 C2 and Electrical rooms Cooling coil in EDG rooms housing Class 3 LK C 3 NR SC2 - - switchboards and transformers Air fan in EDG rooms housing Class 3 LK C 3 NR SC2 C3 C3 switchboards and transformers APPROVED This table will be updated after the Safety Classification Component List (SCCL) studies.
9.4.2.4.2. Seismic Requirements
The DVD system complies with the seismic qualification requirements listed in Section 9.4.9 – Table 1.
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9.4.2.4.3. HIC Requirements
Not applicable: the DVD system is not subject to any HIC requirements.
9.4.2.4.4. Specific I&C Requirements
The DVD system includes conventional dedicated I&C that comply with the I&C and safety requirements listed in the table above, as well as the specific requirements associated to dedicated I&C presented in section 9.0.5.2.2.
9.4.3. Examination, Maintenance, (In-service) Inspection and Testing (EMIT)
9.4.3.1. Start-up Tests
The DVD system is subject to a start-up test programme in accordance with the procedures set out in Chapter 20 serving to verify the fulfilment of the following SFRs:
ensure appropriate air conditions in the EDG and UDG Electrical rooms, in the SA batteries and associated switchboard rooms and in the rooms housing Class 3 LK* switchboards and transformers;
heat the UDG and EDG halls;
exhaust the heat produced by the operational UDGs and EDGs, and
ensure the operation of the exhaust of the SA battery room (hydrogen risks).
These requirements can be fulfilled by:
activation checks on supply and exhaust fans,
nominal flow rate checks on these fans,
activation checks on isolation dampers, and
cooling and/or heating power checks of the air handling units, local cooling units and local heating units.
As the DVD SFRs cannot be verified due to the fact that the test conditions are different to the fault / hazard operating conditions under which the SFRs are required to be fulfilled, they must be verified in an extrapolated/indirect manner as follows:
seismic requirements: see Sub-chapter 13.1, and externalAPPROVED explosion: see Sub-chapter 13.2. 9.4.3.2. In-service Inspection
The following functions of the DVD system are monitored during normal operation by continuous monitoring systems:
Air conditions in the different rooms and halls: temperature measurements.
The availability of these functions is therefore verified by the continuous monitoring process.
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9.4.3.3. Periodic Testing
The safety classified parts of the DVD system are subject to periodic testing in accordance with the maintenance schedule in order to verify that the following SFRs are fulfilled:
ensure appropriate air conditions in the EDG and UDG Electrical rooms, in the SA batteries and associated switchboard rooms and in the rooms housing Class 3 LK* switchboards and transformers;
heat the UDGs and UDG halls,
exhaust the heat produced by the operational UDGs and EDGs, and
ensure the operation of the exhaust of the SA battery room (hydrogen risks).
These requirements can be fulfilled by:
activation checks of the associated heaters and coolers,
activation checks of the associated air fans, and
activation checks on the isolation dampers.
As the DVD SFRs cannot be directly verified due to the fact that the test conditions are different to the fault / hazard operating conditions under which the SFRs are required to be fulfilled, they must be verified in an extrapolated/indirect manner as follows:
seismic requirements: see Sub-chapter 13.1, and
external explosion: see Sub-chapter 13.2.
Some components of the DVD system are always in operation and therefore do not require periodic testing.
9.4.3.4. Maintenance
The DVD system is subject to a maintenance programme.
For the EDG system, only one train is allowed to undergo maintenance in order to keep at least two EDGs available, even if another EDG fails.
For the UDG system, a single train may undergo maintenance, in order to keep at least one UDG available. 9.5. FUNCTIONALAPPROVED DIAGRAM The functional diagrams of the DVD system are shown in section 9.4.9 – Figures 1 to 4 (for more details, see the detailed mechanical diagram of the DVD system).
10. SAFETY CHILLED WATER SYSTEM (DEL [SCWS])
The information reported in this section is, unless otherwise noted, consistent with the reference design, as referenced from Chapter 22.
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It should be noted that a Basis of Safety Case (BoSC) [Ref. 15] was produced for the Safety Chilled Water System (DEL [SCWS]) in mid-2016. The BoSC was based on the proposed design and supporting evidence available at that time, which pre-dated the Reference Configuration 1.2 (RC1.2) design. This section uses information where appropriate from the BoSC and develops it further to reflect the RC1.2 design.
10.0. SAFETY REQUIREMENTS
The UK EPR Safety Classification principles and the top-down functional approach are presented in Sub-chapter 3.2. These principles help to ensure that the plant is designed, manufactured, constructed, commissioned and operated so that the appropriate level of reliability and integrity is achieved for its Structures, Systems and Components (SSCs).
The Hinkley Point C (HPC) functional safety analyses and the application of these safety classification principles to the HPC reference design result in the identification of the safety requirements for all safety systems in accordance with the Safety Functional Requirements Notes (SFRNs) referenced from Sub-chapter 3.2.
This section summarises the results of these safety analyses and specifies the safety requirements that apply to the design of the DEL [SCWS] system.
The requirements described in the present section are consistent with safety functions to which contribute DEL [SCWS] system in Plant Condition Category (PCC) and Design Extension Conditions (DEC). Consistency with requirements inherited from the Design Basis Initiating Faults (DBIFs) should be checked when the list of DBIFs evolves (see Chapter 15).
10.0.1. Safety Functions
The three Main Safety Functions (MSFs) necessary to achieve the overall safety objective of protecting people and the environment from the harmful effects of ionising radiations are:
control of fuel reactivity,
fuel heat removal, and
confinement of radioactive material.
These three MSFs must be achieved during:
normal operating conditions (PCC-1), including duty functions, control of radioactive release during normal operating conditions, control of main plant parameters, fault initial conditions, Limiting Conditions of Operation (LCOs), limitations, monitoring functions, Probabilistic Safety Assessment (PSA) significant functions as part of the preventive line of defence, fault conditionsAPPROVED (PCC-2 to PCC-4, DEC-A and any equivalent DBIFs) and DEC-B, and hazard conditions.
10.0.1.1. Control of Fuel Reactivity
The DEL [SCWS] system does not directly contribute to the MSF of control of fuel reactivity.
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10.0.1.2. Fuel Heat Removal
The DEL [SCWS] system does not directly contribute to the MSF of fuel heat removal.
10.0.1.3. Confinement of Radioactive Material
The DEL [SCWS] system must contribute to the achievement of the MSF of confinement of radioactive material as a frontline system as follows:
To contribute to the prevention of minor radioactive release.
10.0.1.4. Support Contribution to Main Safety Function
The DEL [SCWS] system must indirectly contribute to the three MSFs as a support system as follows:
Chilled water production and distribution for the Safeguard Building (Uncontrolled Area) Ventilation Systems Electrical (division) (DVL [SBVSE]), which provides conditioning to electrical rooms, Instrumentation and Control (I&C) rooms, Remote Shutdown Station (RSS) and mechanical rooms including the Component Cooling Water System (RRI [CCWS]), Containment Heat Removal System (EVU [CHRS]) and DEL [SCWS] equipment rooms.
Chilled water production and distribution for the Control Room Air Conditioning System (DCL [CRACS]).
Chilled water production and distribution for the Safeguard Building (Controlled Area) Ventilation System (DWL [CSBVS]); Safety Injection System (RIS [SIS]) pump and exchanger rooms, which provides cooling to the EVU [CHRS] main pump rooms, RRI [CCWS]/Emergency FeedWater System (ASG [EFWS]) valve rooms and Fuel Pool Cooling (and Purification) System (PTR [FPCS/FPPS]) third train pump room (Division 1 only).
Chilled water production and distribution for the Fuel Building Ventilation System (DWK [FBVS]), which provides cooling to the Chemical and Volume Control System (RCV [CVCS]) pump rooms, the Extra Boration System (RBS [EBS]) pump rooms and the Emergency Lighting Systems for the HK [FB] building (DSK) cabinet rooms.
Note that some individual safety features associated with each of the above Heating, Ventilation and Conditioning (HVAC) systems only contribute indirectly to one or two of the three MSFs. However, for each individual HVAC system, the associated DEL [SCWS] Safety Features (SFs) together contribute indirectly to all three MSFs. Thus, for simplicity and brevity, the DEL [SCWS] production and distribution of chilled water to each of the above HVAC systems is treated in this section as contributing indirectly to all three MSFs. The DEL [SCWS]APPROVED system must contribute indirectly to the MSF of control of fuel reactivity as a support system as follows:
Provision of heat sink to RIS [SIS] Low Head Safety Injection (LHSI) pumps in the event of failure of the RRI [CCWS] system.
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10.0.1.5. Specific Contribution to Hazards Protection
The DEL [SCWS] system must contribute directly to the safety functions that are part of the facility's hazards protection against the consequences of earthquake (see Sub-chapter 13.1, section 2) as follows:
Preservation of Seismic Requirement level 1 (SC1) SF availability following a seismic event.
Moreover, the DEL [SCWS] system must be protected against internal and external hazards (see section 10.0.4.2).
10.0.1.6. Other Safety Functions to be performed in the Preventive Line of Defence
The DEL [SCWS] system must contribute directly to other safety functions to be performed as part of the preventive line of defence as follows:
Monitoring of DEL [SCWS] Chilled Water Production and Distribution for DCL [CRACS], DVL [SBVSE], DWK [FBVS] and DWL [CSBVS] systems and RIS [SIS] LHSI pumps;
Monitoring of the RRI [CCWS] flow rates to DEL [SCWS] in Divisions 2 and 3; and
Contribution to over pressure protection of safety-classified components.
10.0.2. Safety Functional Requirements
10.0.2.1. Control of Fuel Reactivity
Not applicable: the DEL [SCWS] system does not directly contribute to the MSF of control of fuel reactivity.
10.0.2.2. Fuel Heat Removal
Not applicable: the DEL [SCWS] system does not directly contribute to the MSF of fuel heat removal.
10.0.2.3. Confinement of Radioactive Material
With respect to its contribution to the MSF of confinement of radioactive material, the DEL [SCWS] system must satisfy the following Safety Functional Requirements (SFRs):
The concerned DEL [SCWS] components must be designed to meet the mechanical requirements to avoid a mechanical failure. 10.0.2.4. SupportAPPROVED Contribution to Main Safety Function With respect to its contribution to the three MSFs, the DEL [SCWS] system must satisfy the following SFRs:
Produce and distribute chilled water to the DVL [SBVSE] system central ventilation and Local Cooling Units (LCUs) in all plant conditions (DBIF including DEC-A, DEC-B, Fukushima and hazards), to support the DVL [SBVSE] conditioning of the uncontrolled areas of the Safeguard Buildings (HL [SB]) including:
o electrical rooms,
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o I&C rooms,
o RSS, and
o mechanical rooms, including RRI [CCWS], EVU [CHRS] and DEL [SCWS] equipment rooms.
Produce and distribute chilled water to the DCL [CRACS] system central ventilation and LCUs in all plant conditions (DBIF including DEC-A, DEC-B, Fukushima and hazards), to support the conditioning of I&C equipment and provision of habitable conditions for the operators in the Main Control Room (MCR).
Produce and distribute chilled water to the DWL [CSBVS] system LCUs in all plant conditions (DBIF including DEC-A, DEC-B, Fukushima and hazards), to support the conditioning of the following rooms in the controlled areas of the HL [SB] buildings:
o RIS [SIS] pump and exchanger rooms,
o EVU [CHRS] main pump rooms,
o RRI [CCWS]/ASG [EFWS] valve rooms, and
o PTR [FPCS/FPPS] third train pump room (Division 1 only).
Produce and distribute chilled water (Divisions 1 and 4 only) to the DWK [FBVS] system in all plant conditions (DBIF including DEC-A, DEC-B, Fukushima and hazards), to support the conditioning of the following rooms in the Fuel Building (HK [FB]):
o RCV [CVCS] pump rooms,
o RBS [EBS] pump rooms, and
o DSK cabinet rooms.
With respect to its indirect contribution to the MSF of fuel heat removal, the DEL [SCWS] system must satisfy the following SFRs:
Produce and distribute chilled water to the RIS [SIS] system LHSI pump motor cooling (in Divisions 1 and 4 only) in order to ensure correct operation of these pumps in case of Total Loss of Component Cooling (TLOCC) and Station Black-Out (SBO) events.
10.0.2.5. Specific Contribution to Hazards Protection
With respect to its specific contribution to the safety functions that are part of the facility’s hazards protection,APPROVED the DEL [SCWS] system must satisfy the following SFRs: Ensure the stability/integrity of DEL [SCWS] components to avoid damage to higher classified components and ensure that it does not adversely impact the availability of SC1 SFs following a seismic event.
10.0.2.6. Other Safety Functions to be performed in the Preventive Line of Defence
With respect to its contribution to other safety functions to be performed as part of the preventive line of defence, the DEL [SCWS] system must satisfy the following SFRs:
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The DEL [SCWS] system must detect abnormal chiller unit and chilled water parameters during normal operation in order to alert operators of the failure of either the production or distribution of chilled water.
The DEL [SCWS] system must detect abnormal RRI [CCWS] flow rates to DEL [SCWS] in Divisions 2 and 3 in order to alert operators to the failure of the RRI [CCWS] support contribution to DEL [SCWS] trains in Divisions 2 and 3.
Requirement for contribution to over pressure protection of safety classified components:
o Ensure that the pressure in the system is maintained below the design pressure.
10.0.3. Safety Features and I&C Actuation Modes
Section 9.4.10 – Table 2 presents the SFs of the DEL [SCWS] system, according to the contributions identified in section 10.0.1 and the SFRNs referenced in Sub-chapter 3.2.
10.0.4. Classification and Architecture Requirements of Safety Features
10.0.4.1. Requirements Arising from Safety Classification
Architecture requirements associated with SFs are essential for designing robust lines of defence consistent with their importance to nuclear safety (see Sub-chapter 3.2). Such requirements strengthen the system design against:
single faults and associated consequences (Single Failure Criterion, (SFC)) by requiring redundancy,
Loss Of Offsite Power (LOOP) by requiring, among others, a backup power supply,
SBO by requiring a power supply by the Ultimate Diesel Generators (UDGs),
Common Cause Failures (CCF) by requiring physical separation,
earthquake by defining seismic requirements, and
accident conditions by defining qualification requirements.
Section 9.4.10 – Table 2 presents the requirements arising from safety classification for the DEL [SCWS] system, according to the SFRNs referenced in Sub-chapter 3.2.
10.0.4.2. System Protection against Hazards
10.0.4.2.1. Internal Hazards
The SFs of theAPPROVED DEL [SCWS] system must be protected against internal hazards if those hazards challenge the safety objectives, as defined in Sub-chapter 13.2.
10.0.4.2.2. External Hazards
The SFs of the DEL [SCWS] system must be protected against external hazards if those hazards challenge the safety objectives, as defined in Sub-chapter 13.1.
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10.0.4.3. Diversity
The DEL [SCWS] system must be subject to the requirement for diversity as defined in general safety principles (see Sub-chapter 3.1) and in the Sub-chapter 3.7, dealing with diversity.
10.0.5. Requirements Defined at the Component Level
10.0.5.1. Generic Safety Requirements
10.0.5.1.1. General Mechanical, Electrical and I&C Requirements
The mechanical components within the DEL [SCWS] system must comply with the mechanical requirements in accordance with the rules laid out in Sub-chapter 3.2, section 7. The level of requirement is dependent upon whether or not it is a pressure retaining component, the safety class of the component, whether the component acts as an isolating device between interfacing SFs, and on the role of the component as a barrier to the potential release of radioactivity as a result of failure of the component.
The electrical and I&C components in the DEL [SCWS] system must comply with the electrical and I&C requirements associated with their safety class, in accordance with the rules laid out in Sub-chapter 3.2.
10.0.5.1.2. Seismic Requirements
The level of seismic requirements to be applied to the DEL [SCWS] system components is related to the Safety Feature Group (SFG) to which the component belongs, and the consequences on other classified components of its failure, if it were not seismically qualified. The rules for defining the seismic requirements for a component are identified in Sub-chapter 3.2.
10.0.5.1.3. Qualification for Accident Conditions
The safety-classified parts of the DEL [SCWS] system must be qualified for the operating conditions in which they are required, as specified in Sub-chapter 3.6.
10.0.5.2. Specific Safety Requirements
10.0.5.2.1. High Integrity Component (HIC) Requirements
The DEL [SCWS] system is not subject to any High Integrity Components (HIC) requirements.
10.0.5.2.2. Specific I&C Requirements
The DEL [SCWS] system dedicated I&C is subject to safety requirements applicable to Class 1 I&C systems. APPROVEDIn addition the following requirements arise from specific I&C requirements: Control of the DELm1 and DELm4 trains is achieved by a non-computerised two-train Class 1 dedicated system using conventional I&C installed in Divisions 1 and 4 of the HL [SB] buildings.
o The conventional I&C dedicated system is required to be in operation continuously in both Divisions 1 and 4 unless the associated DELm train is declared unavailable for maintenance/repair.
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Control of the DELm2 and DELm3 trains is achieved by a computerised two-train Class 1 dedicated system using TELEPERM XS (TXS) technology which is installed in Divisions 2 and 3 of the HL [SB] buildings.
o The TXS I&C dedicated system is required to be in operation continuously in both Divisions 2 and 3 unless the associated DELm train is declared unavailable for maintenance/repair.
Control of the DELb1 and DELb4 trains is achieved by the Non-Computerised HVAC Instrument and Control System (NCHICS). This is a non-computerised four-train Class 1 dedicated system using UNICORN technology which is installed in Divisions 1 to 4 of the HL buildings. However the DELb functions are implemented by cabinets in Divisions 1 and 4 only.
o NCHICS must be in operation continuously to ensure DEL [SCWS] backup trains are brought into operation automatically in the event of failure of one or more DEL [SCWS] main trains. (DELb1 is required to operate on failure of DELm1 and/or DELm2; DELb4 is required to operate on failure of DELm3 and/or DELm4).
The general approach to qualification of dedicated I&C systems in terms of Production Excellence (PE) and Independent Confidence Building Measures (ICBM) is set out in Sub-chapter 7.7.
The general approach for I&C systems is set out in Chapter 7.
10.0.6. Examination, Maintenance, (In-Service) Inspection and Testing (EMIT)
10.0.6.1. Start-up Tests
The DEL [SCWS] system must be designed to enable the performance of start-up tests to ensure the adequacy of its design and performance under conditions as representative as possible of the different operating configurations, and in particular its compliance with the SFRs assigned to it in section 10.0.2.
10.0.6.2. In-Service Inspection
The DEL [SCWS] system must be designed to enable surveillance under normal operation of the system characteristics necessary for the fulfilment of its safety-related tasks in order to ensure the performance of its components, and their availability under normal operation, or in the event of a fault or accident.
10.0.6.3. Periodic Testing
The safety-classified parts of the DEL [SCWS] system must be designed to enable the performance ofAPPROVED periodic tests in accordance with the maintenance schedule. 10.0.6.4. Maintenance
The DEL [SCWS] system must be designed to enable the implementation of a maintenance schedule (see Sub-chapter 18.2).
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10.1. ROLE OF THE SYSTEM
10.1.1. Normal Operating Conditions
The DEL [SCWS] system contributes to the general operation of the plant by producing and distributing chilled water which provides the heat sink for those HVAC systems located in the HL [SB] and HK [FB] buildings which have safety classified cooling functions.
The DEL [SCWS] system is required to operate continuously under all plant conditions. DEL [SCWS] ensures that its served HVAC systems (DVL [SBVSE], DCL [CRACS], DWL [CSBVS] and DWK [FBVS]) are sufficiently cooled, when required, in order to fulfil their safety classified cooling functions.
10.1.2. Fault and Hazard Operating Conditions
The DEL [SCWS] system is required to operate under degraded operating conditions (DBIF including DEC-A, DEC-B, Fukushima and hazards) by providing the heat sink for the HVAC systems described in section 10.0.2.4.
Moreover, upon failure of RRI [CCWS] which provides the normal heat sink for the RIS [SIS] LHSI pumps of Divisions 1&4, DEL [SCWS] ensures the cooling of these pumps.
10.2. DESIGN BASIS
10.2.1. General Assumptions
The following general assumptions have been made in respect of the design for the DEL [SCWS] system:
Designations/descriptions used with respect to the DEL [SCWS] system main components:
o DEL [SCWS] main train = ‘DELm’ (DELm1 for Division 1, DELm2 for Division 2, DELm3 for Division 3 and DELm4 for Division 4);
o DEL [SCWS] backup train = ‘DELb’ (DELb1 for Division 1 and DELb4 for Division 4).
Four DELm trains are normally in operation (one per division), with both DELb trains available on standby.
Only one of the six DELm or DELb trains can be scheduled for maintenance at a time.
The DEL [SCWS] system is sized for both extreme summer and winter conditions; external conditions taken into account in the sizing of DEL [SCWS] systems are detailed in sectionAPPROVED 1.
During heatwave conditions (see section 1), simultaneous operation of all six DELm and DELb trains is required, and DEL [SCWS] train maintenance is not permitted.
The design for each DELm and DELb train is sized to ensure that for safety-related equipment for which the DEL [SCWS] system provides the heat sink, the permitted ambient (indoor) temperature is not exceeded taking account of thermal transients arising from:
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o the time taken into account in respect of switchover from main or backup systems (DEL [SCWS] trains and also power from start-up of Emergency Diesel Generators (EDGs) / UDGs);
o the grace time taken into account in respect of manual alignment of the DEL [SCWS] backup train(s) following the loss of one or more DEL [SCWS] main trains;
o loss of DEL [SCWS] system (but only { SCI removed } DC battery backed and { SCI removed } DC battery backed equipment in operation) during Total Loss of AC Power (TLAP) and Extended TLAP.
10.2.2. Design Assumptions
10.2.2.1. Control of Fuel Reactivity
Not applicable: the DEL [SCWS] system does not directly contribute to the MSF of control of fuel reactivity.
10.2.2.2. Fuel Heat Removal
Not applicable: the DEL [SCWS] system does not directly contribute to the MSF of fuel heat removal.
10.2.2.3. Confinement of Radioactive Material
Not applicable: there are no quantitative safety-related design assumptions associated with the DEL [SCWS] system.
10.2.2.4. Support Contribution to Main Safety Function
Indirect contribution to the three MSFs:
Produce and distribute chilled water to the DVL [SBVSE], DWL [CSBVS], DCL [CRACS], DWL [CSBVS] and DWK [FBVS] systems in order to support their correct operation in all plant conditions (DBIF including DEC-A, DEC-B, Fukushima and hazards).
Indirect contribution to the MSF of fuel heat removal:
Produce and distribute chilled water to the RIS [SIS] LHSI system pump motors cooling (in Divisions 1 and 4 only) in order to ensure correct operation of these pumps in case of TLOCC and SBO events.
The cooling of the above users is ensured through DEL [SCWS] chillers, pumps and associated pipeworks underAPPROVED following design conditions. System Design Conditions
Under normal outside conditions the DEL [SCWS] system provides chilled water at { SCI removed } to its users. The return temperature from DEL [SCWS] system users must be between { SCI removed } and { SCI removed }.
The outside conditions to be taken into account for the DEL [SCWS] system are defined in section 1; this includes the specific heatwave conditions taken into account as part of the DEL [SCWS] system design.
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Main Data for Division 1 and 4 Main Chillers (DELm1 and DELm4)
Required chiller refrigerating capacity in summer conditions:
o DELm1: ~{ SCI removed }, and
o DELm4: ~{ SCI removed }.
Chiller cooling medium: Air.
Main Data for Division 2 and 3 Main Chillers (DELm2 and DELm3)
Required chiller refrigerating capacity in summer conditions:
o DELm2: ~{ SCI removed }, and
o DELm3: ~{ SCI removed }.
Chiller cooling medium: Demineralised water RRI [CCWS], and
Maximum water temperature (inlet condenser): see Sub-chapter 9.2, section 2.
Main data for Division 1 and 4 Backup Chillers (DELb1 and DELb4)
Required chiller refrigerating capacity in summer conditions:
o DEL [SCWS]b1: ~{ SCI removed }, and
o DEL [SCWS]b4: ~{ SCI removed }.
Chiller cooling medium: Air.
Required Chiller Refrigerating Capacity per Division during Heatwave
Division 1: ~{ SCI removed },
Division 2: ~{ SCI removed },
Division 3: ~{ SCI removed }, and
Division 4: ~{ SCI removed }.
10.2.2.5. Specific Contribution to Hazards Protection
Not applicable: there are no quantitative safety-related design assumptions associated with the DEL [SCWS] system.APPROVED
10.2.2.6. Other Safety Functions to be performed in the Preventative Line of Defence
Requirement for Contribution to Overpressure Protection of Safety Classified Components:
Maintaining the pressure in the system below the following design pressures for each DEL [SCWS] train:
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o DELm1 and DELm4: { SCI removed } abs,
o DELm2 and DELm3: { SCI removed } abs, and
o DELb1 and DELb4: { SCI removed } abs.
Monitoring of the DEL [SCWS] Chilled Water Production and Distribution
Not applicable: there are no quantitative safety-related design assumptions associated with the DEL [SCWS] system.
Monitoring of the RRI [CCWS] Flow Rate to DEL [SCWS] in Divisions 2 and 3
Not applicable: there are no quantitative safety-related design assumptions associated with the DEL [SCWS] system.
10.2.3. Other Assumptions
The DEL [SCWS] system is also subject to the following assumptions:
The DEL [SCWS] system design is consistent with RCC-M requirements as described in Sub-chapter 3.8, section 2.
There is a potential asphyxiation risk associated with the leakage of refrigerant gas into the chiller rooms in each division. This risk is mitigated by the design of the DVL [SBVSE] system which provides conditioning and ventilation of the DEL [SCWS) chiller rooms. Further details are provided in section 7.
10.2.4. Assumptions Associated with Extreme Situations Resulting from Beyond Design-Basis Hazards
10.2.4.1. Assumptions Associated with Fukushima Provisions
The assumptions associated with the Fukushima provisions of the DEL [SCWS] system are presented in Chapter 23. The main provisions are:
chilled water distribution for the DVL [SBVSE] central air-conditioning of recirculated rooms in the HL [SB] buildings (excluding Survival Island);
chilled water distribution for the DVL [SBVSE] local cooling of { SCI removed } I&C rooms;
chilled water distribution for LHSI pumps in Divisions 1 and 4 only; chilled APPROVEDwater distribution for DCL [CRACS]; chilled water distribution for the DVL [SBVSE] central air-conditioning of non-recirculated rooms in HL buildings (excluding RRI [CCWS] and EVU [CHRS] equipment rooms in Divisions 1 and 4);
chilled water distribution for the DVL [SBVSE] local cooling of RRI [CCWS] and EVU [CHRS] equipment rooms in Divisions 1 and 4;
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chilled water distribution for the DWL [CSBVS] local cooling of RIS [SIS] pump and exchanger rooms;
chilled water distribution for the DWL [CSBVS] local air-conditioning of EVU [CHRS] main pump rooms;
chilled water distribution for the DWL [CSBVS] local cooling of RRI [CCWS]/ASG valve rooms; and
chilled water production and circulation.
10.2.4.2. Assumptions Associated with non-Fukushima Provisions
The assumptions associated with the other non-Fukushima provisions of the DEL [SCWS] system are:
TLAP.
10.3. SYSTEM DESCRIPTION AND OPERATION
10.3.1. Description
10.3.1.1. General System Description
The description provided in this section applies equally to both Unit 1 and Unit 2; they are identical.
DEL [SCWS] consists of six independent trains, each able to provide 100% of the cooling needs within a single division (excluding heatwave conditions, see section 10.3.2.1.3). The system comprises four physically segregated main trains (DELm, one per division) and two backup trains (DELb, Divisions 1 and 4 only) which are completely segregated systems from DEL [SCWS] main trains. Cross-connections within the DELb pipework allow DELb1 to provide cooling to Divisions 1 and/or 2, and DELb4 to provide cooling to Divisions 3 and/or 4.
Each train consists of:
a production part made of:
o a chiller unit, either air-cooled (for DELm1, DELm4, DELb1 and DEL]b4 in Divisions 1 and 4) or RRI [CCWS] water-cooled (for DELm2 and DELm3 in Divisions 2 and 3), and
o a three-way valve (only for DELm2 and DELm3 in Divisions 2 and 3). a distributionAPPROVED part made of: o a circulating pump,
o a bypass line equipped with a motorised control valve, in order to regulate the chilled water flow rate through the evaporator,
o distribution pipework, and
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o a surge relief line connected to the distribution circuit comprising an expansion tank to absorb the volume variations in the circuit, and a safety valve to prevent a possible overpressure in the circuit.
The four main trains DELm1, DELm2, DELm3 and DELm4, are normally in service at all times. The two DELb trains are normally on standby and are only required to operate in the event of:
maintenance or failure of a DELm train – in this situation DELb1 is able to provide cooling to Divisions 1 or 2, and DELb4 is able to provide cooling to Divisions 3 or 4, or
heatwave conditions – in this situation, all six DEL [SCWS] trains are run simultaneously to provide additional cooling power.
10.3.1.2. Description of Main Equipment
The DEL [SCWS] system comprises the main equipment items detailed in the following sections (see the functional diagram provided in section 10.5).
10.3.1.2.1. Production Part
Chiller unit: a chiller unit which is responsible for the cooling of the DEL [SCWS] water. It comprises at least one compressor, expansion valve, condenser (heat exchanger on the hot side) and evaporator (heat exchanger on the cold side).
Three-way valves: for DELm 2 and 3 trains which are water cooled by RRI [CCWS], a three-way control valve is installed across the condenser in order to regulate the flow rate of RRI [CCWS] water through it.
10.3.1.2.2. Distribution Part
Circulating pump: each DEL [SCWS] train is equipped with a centrifugal pump upstream of its chiller. It ensures the circulation of chilled water through the chiller and to the DEL [SCWS]-served systems.
Bypass line and valve: a bypass line (containing a strainer to clean up the chilled water / remove particulate (by dilution)) and a control valve are installed in each DEL [SCWS] train in order to regulate the flow of water and maintain a constant flow rate across the evaporator; this is required to ensure successful operation of the DEL [SCWS] chillers. The bypass valve is installed on the chilled water side in parallel to the distribution pipework.
Expansion Tank: each DEL [SCWS] train is equipped with an expansion tank responsible for ensuring water pressure is stable within the DEL [SCWS] circuit.
Safety Valve: each DEL [SCWS] train is equipped with a safety relief valve found betweenAPPROVED the main circuit and expansion tank. The safety relief valve prevents water pressure in DEL [SCWS] from exceeding a maximum value and damaging the pipework and components within the circuit.
10.3.1.3. Description of Main Layout
In Divisions 1 and 4, the layout is as follows for the main lines (DELm1 and DELm4):
chiller main units are located at { SCI removed } level,
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chiller condensers are located at { SCI removed } and { SCI removed } levels,
condenser fans are located at { SCI removed } level,
circulating pumps are located at { SCI removed } level, and
expansion tanks are located at { SCI removed } level.
In Divisions 2 and 3, the layout is as follows for the main lines (DELm2 and DELm3):
chiller main units (including condensers) are located at { SCI removed } level,
circulating pumps are located at { SCI removed } level, and
expansion tanks are located at { SCI removed } level.
In Divisions 1 and 4, the layout is as follows for the backup lines (DELb1 and DELb4):
chiller main units are located at { SCI removed } level,
chiller condensers are located at { SCI removed } level,
condenser fans are located at { SCI removed } level,
circulating pumps are located at { SCI removed } level, and
expansion tanks are located at { SCI removed } level.
10.3.1.4. Description of System I&C
DELm and DELb are Class 1 system implementing functions up to Category A and therefore need to be supported by similarly classified I&C systems.
The I&C architecture requirements for DEL [SCWS] are summarised below:
DELm1 and DELm4: the main lines (production and distribution) in Divisions 1 and 4 are controlled by dedicated Conventional I&C (relay based).
DELm2 and DELm3: the main lines (production and distribution) in Divisions 2 and 3 are controlled by dedicated TXS I&C.
DELb1 and DELb4: the backup lines (production and distribution) in Divisions 1 and 4 are controlled by NCHICS, (UNICORN I&C). The componentAPPROVED level operation of each train is performed automatically by its dedicated I&C system and, in the event of a main train failure, this is detected by the backup train I&C which automatically starts the backup train. Any valve re-alignment that may be required to subsequently optimise the operating configuration is performed locally, as adequate operating grace time is provided by the default alignment.
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10.3.2. OPERATION
10.3.2.1. System Normal Operation
10.3.2.1.1. DELm Train Operation
The four main trains of the DEL [SCWS] system are required to run permanently in normal operation of the plant (PCC-1), regardless of plant state, from 100 % power operation to outage. DEL [SCWS] is { SCI removed } from its own Human Machine Interface (HMI) located close to the chiller main unit. Information on some parameters as well as alarms are sent to the MCR.
Except in the event of maintenance or failure of one DEL [SCWS] main train leading to its shutdown, the DEL [SCWS] main trains shall not be stopped at any time.
The supply of DEL [SCWS] main train chilled water to the DCL [CRACS] and DVL [SBVSE] systems is variable as their cooling needs depend on the outside air conditions.
Each DEL [SCWS] main train is able to supply 100% of the cooling demand of one DCL [CRACS] main train (located in Divisions 2 and 3). In normal operation of the plant, two DCL [CRACS] main trains are used to condition the MCR.
Each DELm train is able to supply 100% of the cooling demand of either:
o One DVL [SBVSE] main train (in its associated division), or
o One DVL [SBVSE] backup train (located it its associated division or the neighbouring division) in the case of maintenance or failure of a DVL [SBVSE] main train.
In addition, the DEL [SCWS] main trains are able to provide chilled water to the following LCUs in their associated divisions:
o DWL [CSBVS] LCUs ensuring the conditioning of the EVU [CHRS] pump rooms, RIS [SIS] pump and exchanger rooms and RRI [CCWS]/ASG [EFWS] valve rooms and the PTR [FPCS/FPPS] third train pump room in the controlled area of the HL [SB] buildings,
o DVL [SBVSE] LCUs ensuring the conditioning in the RRI [CCWS] pump and exchanger rooms (Divisions 1 and 4 only) and I&C rooms (all divisions) in the uncontrolled areas of the HL buildings,
o DCL [CRACS] LCUs ensuring the conditioning in the computer rooms in the Survival Island,
o DWK [FBVS] LCUs (Divisions 1 and 4 only) ensuring the conditioning of the RBS [EBS],APPROVED RCV [CVCS], Reactor Boron and Water Make-up System (REA [RBWMS]) pump rooms and the DSK cabinet rooms in the HK [FB] building, and
o RIS [SIS] LHSI pump motor heat exchanger (Divisions 1 and 4 only).
10.3.2.1.2. DELb Train Operation
The DEL [SCWS] backup train operation is required in the following situations, regardless of the plant state, from 100% power operation to outage:
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In the event of maintenance of a DEL [SCWS] main train, the DEL [SCWS] backup train in its associated division or neighbouring division is required to be operational (i.e. DEL1b during maintenance of DEL1m or DEL2m; DEL4b during maintenance of DEL3m or DEL4m);
In the event of failure of one or more DEL [SCWS] main trains, the associated DEL [SCWS] backup train(s) is (are) required to be operational (i.e. DEL1b following failure of DEL1m or DEL2m; DEL4b following failure of DEL3m or DEL4m);
The DEL [SCWS] backup trains are { SCI removed } from their NCHICS HMI.
Each DELb train is able to supply 100% of the cooling demand of either:
o one DCL [CRACS] main train (located in Divisions 2 and 3), or
o one DCL [CRACS] backup train (located in Divisions 2 and 3), in the case of maintenance or failure of a DCL [CRACS] main train.
Each DELb train is able to supply 100% of the cooling demand of either:
o one DVL [SBVSE] main train (in its associated division), or
o one DVL [SBVSE] backup train (located it its associated division or the neighbouring division) in the case of maintenance or failure of a DVL [SBVSE] main train.
In addition, the DELb trains are able to provide chilled water to the following LCUs in their associated divisions or neighbouring divisions:
DWL [CSBVS] LCUs ensuring the conditioning of the RIS [SIS] pump and exchanger rooms and RRI [CCWS]/ASG [EFWS] valve rooms in the controlled area of the HL [SB] buildings,
DVL [SBVSE] LCUs ensuring the conditioning in the RRI [CCWS] pump rooms (Divisions 1 and 4 only) and I&C rooms (all divisions) in the uncontrolled areas of the HL [SB] buildings, and
DCL [CRACS] LCUs ensuring the conditioning in the computer rooms in the Survival Island.
The DEL [SCWS] backup lines do not supply the DWL [CSBVS] LCUs in the EVU [CHRS] or PTR [FPCS/FPPS] rooms, the DWK [FBVS] LCUs or the RIS [SIS] LHSI pump motor heat exchanger.
10.3.2.1.3. Heatwave Operation The supply ofAPPROVED DELm chilled water to the DCL [CRACS] and DVL [SBVSE] systems is variable because the cooling needs depend on the outside air conditions. Under extreme high external temperature conditions, the cooling needs of these systems are maximised.
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In order to reduce the required size of the air cooled chillers of DELm1, DELm4, DELb1 and DELb4 whilst achieving the necessary cooling power for DVL [SBVSE], a heatwave approach is required (see section 1). Specifically, when operating under extreme high external temperature conditions (see section 1), all four DEL [SCWS] main trains are run simultaneously with the two DEL [SCWS] backup trains (whose flow is each split between two neighbouring divisions). The DEL [SCWS] backup trains will therefore need to be started up manually in advance of a heatwave, as a preventative measure.
This operational mode is facilitated by having two cooling coils, one main (DELm) and one backup (DELb) in series in every DVL [SBVSE] Air Handling Unit (AHU).
Maintenance of one DEL [SCWS] train (main or backup) is not permitted when heatwave conditions are forecasted.
10.3.2.1.4. Partial or Total Loss of the Ultimate Heat Sink (PLUHS or TLUHS)
DELm2 and DELm3 chillers are lost due to the loss of the RRI [CCWS] system cooling.
The four other trains (DELm1, DELm4, DELb1 and DELb4) are unaffected, as their condensers are air-cooled.
In this scenario, DELm1 cools Division 1 users, DELb1 cools Division 2 users; DELb4 cools Division 3 users and DELm4 cools Division 4 users.
Hence, the DEL [SCWS] system will remain operable in all four divisions during a PLUHS or TLUHS event.
10.3.2.1.5. Loss of Offsite Power (LOOP)
Each main train (DELm1, DELm2, DELm3 and DELm4) of the DEL [SCWS] system is supplied by electrical Divisions 1, 2, 3 and 4 respectively. Each electrical independent train supplying the DEL [SCWS] main trains is backed up by EDGs in the case of LOOP.
The backup trains DELb1 and DELb4 of the DEL [SCWS] system are supplied by electrical Divisions 1 and 4 respectively. Each electrical independent train supplying the DEL [SCWS] backup trains is backed up by EDGs in the case of LOOP.
Hence, the DEL [SCWS] system will remain operable in all four divisions during a LOOP event.
10.3.2.1.6. Station Blackout (SBO)
Electrical trains 1 and 4 supplying the DEL [SCWS] main trains 1 and 4 are backed up by the two UDGs in the case of SBO.
The four other trains are lost (DELm2, DELm3, DELb1 and DELb4).
Hence, the DELAPPROVED [SCWS] system will remain operable in Divisions 1 and 4 only during a SBO event. The DEL [SCWS] system will be unavailable in Divisions 2 and 3.
10.3.2.2. System Transient Operation
10.3.2.2.1. Full or Partial System Failure
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10.3.2.2.2. Failure of Systems in Interface (Server or Served)
{ This section contains SCI-only text and has been removed }
10.4. PRELIMINARY DESIGN SUBSTANTIATION
The level of detail in regards to evidence of compliance with the safety requirements stated in section 10.0 will develop as the HPC project moves from basic design into detailed design since PCSR3 sequence and system sequence are evolving in parallel. Therefore, the level of detail presented in this section reflects the level of information available at the time of issuing the system chapters.
10.4.1. Compliance with Safety Functional Requirements
10.4.1.1. Control of Fuel Reactivity
Not applicable: the DEL [SCWS] system does not directly contribute to the MSF of control of fuel reactivity.
10.4.1.2. Fuel Heat Removal
Not applicable: the DEL [SCWS] system does not directly contribute to the MSF of fuel heat removal.
10.4.1.3. Confinement of Radioactive Material
The DEL [SCWS] components which contribute to prevent minor radioactive release are designed with a sufficient mechanical requirement.
10.4.1.4. Support Contribution to Main Safety Functions
The design assumptions of the DEL [SCWS] system stated in section 10.2.2 are consistent with the requirements of the corresponding systems/equipment items which it supports:
Produce and distribute chilled water to the DVL [SBVSE], DWL [CSBVS], DCL [CRACS], DWL [CSBVS] and DWK [FBVS] systems in all plant conditions (DBIF including DEC-A, DEC-B, Fukushima and hazards):
o The DEL [SCWS] system components will be sized to meet the cooling requirements of its served HVAC systems (DVL [SBVSE], DCL [CRACS], DWL [CSBVS] and DWK [FBVS]) under all summer and winter conditions as defined in section 1.
Produce and distribute chilled water to the RIS [SIS] system LHSI pump motors cooling (in DivisionsAPPROVED 1 and 4 only) in the case of TLOCC and SBO events: o The DEL [SCWS] system components will be sized to meet the cooling requirements of the RIS [SIS] system LHSI pump motors in the case of TLOCC and SBO events.
10.4.1.5. Specific Contributions to Hazards Protection
The hazard studies of Sub-chapter 13.1 involving functions of the DEL [SCWS] system use values for the following parameters that are in keeping with the design assumptions stated in section 10.2.2:
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Ensure the stability/integrity of DEL [SCWS] components to avoid damage to higher classified components and ensure that it does not adversely impact the availability of SC1 SFs following a seismic event.
o DEL [SCWS] system components will be seismically qualified to confirm that their stability/integrity is ensured following a seismic event.
For each hazard study concerned, these studies show that the design of these functions is such that they meet the acceptance criteria.
These elements ensure that the SFRs stated in section 10.2.2 are met.
10.4.1.6. Other Safety Functions to be performed in the Preventive Line of Defence
Other safety functions to be performed in the preventive line of defence involving the DEL [SCWS] system use values for the following parameters that are in keeping with the design assumptions stated in section 2.2:
The DEL [SCWS] system must detect abnormal chiller unit and chilled water parameters during normal operation in order to alert operators of the failure of either the production or distribution of chilled water.
o monitoring of the production of chilled water; and
o monitoring of the distribution of adequately chilled water.
The DEL [SCWS] system must detect abnormal RRI [CCWS] flow rates to DEL [SCWS] in Divisions 2 and 3 in order to alert operators to the failure of the RRI [CCWS] support contribution to DEL [SCWS] trains in Divisions 2 and 3.
o monitoring of the RRI [CCWS] flow rates to DEL [SCWS] trains in Divisions 2 and 3.
Requirement for contribution to overpressure protection of safety classified components:
o The design and installation requirements of safety valves ensures that classified parts of the DEL [SCWS] system are protected and ensures that the pressure in the system is maintained below the design pressure.
These elements ensure that the SFRs stated in section 10.2.2 are met.
10.4.2. Compliance with Design Requirements
The DEL [SCWS] system complies with the requirements stated in sections 10.0.4 and 10.0.5, particularly withAPPROVED respect to those detailed in the following sections. 10.4.2.1. Requirements Arising from Safety Classification
10.4.2.1.1. Safety Classification
The compliance of the design and manufacture of DEL [SCWS] system materials and equipment performing a safety-related function with requirements from the classification rules (see Sub-chapter 3.2, section 7) is presented in section 10.4.2.4.1.
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10.4.2.1.2. Single Failure Criterion or Redundancy
Active Single Failure:
The design of the DEL [SCWS] system meets the requirements of the active SFC stated in section 10.0.4.1, in particular in respect of the following:
The principal design provision which mitigates against single failures is the general design philosophy of having four independent Safeguard Divisions. One Class 1 DELm train is located in each HL [SB] building. This arrangement ensures separation and independence between the four DELm trains. As such, a single failure of any DEL [SCWS] component could at most result in the loss of ventilation in only one division. Three other divisions with independent safety systems would still be available.
Further functional redundancy is also provided in the DEL [SCWS] design. Two DELb trains are provided in Divisions 1 and 4. Each DELb train can supply its own division or the neighbouring division (i.e. DELb1 can supply Division 1 or 2, and DELb4 can supply Divisions 3 or 4).
When a failure occurs on a DELm train, the associated backup train provides cooling to the safety-related HVAC systems in the affected building.
Passive Single Failure:
The design of the DEL [SCWS] system complies with the requirements of the passive SFC stated in section 10.0.4.1, in particular in respect of the following:
The DEL [SCWS] system SFs are required to be robust against passive single failure. Single failure has been applied to active components and redundancy is adequately ensured. Application of the passive single failure to this system is discussed in Sub-chapter 15.3, section 1.
10.4.2.1.3. Robustness against Loss of Power
The design of the DEL [SCWS] system complies with the emergency power supply requirement stated in section 10.0.4.1, in particular in respect of the following:
The six DEL [SCWS] trains are electrically independent (see also Sub-chapter 8.6).
All four DELm trains and both DELb trains are backed up by EDGs. During EDG maintenance periods, manual cross-connection of electrical supplies is used to enable the neighbouring division to supply the DEL [SCWS] main line in the division for which the EDG is unavailable. Hence, in the event of LOOP while one EDG is in maintenance, DELm in the affected division can be electrically supplied by its neighbouring division, and the DEL [SCWS] system will remain operable in all four divisions during a LOOP event. APPROVED Electrical trains 1 and 4 supplying the DEL [SCWS] main trains 1 and 4 are backed up by the two UDGs, which are diverse from the four EDGs, in the case of SBO. The four other trains are lost (DELm2, DELm3, DELb1 and DELb4). Hence, the DEL [SCWS] system will remain operable in Divisions 1 and 4 only during a SBO event. The DEL [SCWS] system will be unavailable in Divisions 2 and 3.
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In the event of TLAP/Extended TLAP, DEL [SCWS] will be unavailable in all divisions. However, the design for each DEL [SCWS]m and DELb train is sized to ensure that for safety-related equipment for which the DEL [SCWS] system provides the heat sink, the ambient (indoor) temperature is not exceeded taking account of thermal transients arising from the loss of the DEL [SCWS] system during TLAP and Extended TLAP, see section 10.2.1.
10.4.2.1.4. Physical Separation
The DEL [SCWS] system is designed in accordance with the physical separation requirement stated in section 10.0.4.1, in particular in respect of the following:
The principal single failure design provision for DEL [SCWS] is based on the general design philosophy of having four independent Safeguard Divisions. One Class 1 DELm train including its support systems is located in each HL [SB] building. This arrangement ensures separation and independence between the four DELm trains. As such, a single failure of any DEL [SCWS] component could at most result in the loss of ventilation in only one HL [SB] division. Three other HL [SB] buildings with independent safety systems would still be available.
Functional redundancy is provided through the provision of two additional Class 1 DELb lines in Divisions 1 and 4 which can supply either their own division or the neighbouring division. The chiller rooms for DELb in Divisions 1 and 4 are physically segregated from the DELm chiller rooms in those divisions. The DELb heat sink air inlets and outlets in Divisions 1 and 4 are also on different HL [SB] building levels to the corresponding DELm heat sink air inlets and outlets in Divisions 1 and 4. This reduces the potential for external hazards to affect both DEL [SCWS] trains within either Division 1 or 4.
10.4.2.2. Hazards
10.4.2.2.1. Internal Hazards
The overall demonstration of the robustness of the plant to internal hazards is covered in Sub-chapter 13.2.
10.4.2.2.2. External Hazards
The overall demonstration of the robustness of the plant to external hazards is covered in Sub-chapter 13.1.
10.4.2.3. Diversity
The design of the DEL [SCWS] system complies with the diversity requirement stated in section 10.0.4.3, in particular in respect of the following (more details are provided in Sub-chapter 3.7,APPROVED dealing with diversity): Mechanical Diversity – DELm and DELb (chiller compressors and pumps) are diverse. Additionally, DELm 1 and 4 (chiller compressors and pumps) are diverse from DELm 2 and 3. The level of mechanical diversity is still to be fully defined at this time, but will be consistent with the principles set out in Sub-chapter 3.7.
Heat Sink Diversity – DELm1 and DELm4 trains have air cooled condensers with glycol loop chillers; DELm2 and DELm3 main lines have condensers which are water cooled by RRI [CCWS]; DELb1 and DELm4 are air cooled, with direct expansion chillers, which are diverse from those for all four DEL [SCWS] main lines.
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Electrical Diversity – electrical requirements are specified such that the DELm chillers are supplied by { SCI removed } (LJ switchboards) whilst for DELb they are supplied by { SCI removed } (LH switchboards) and { SCI removed } (LL switchboards). The DELm pumps are supplied by { SCI removed } (LJ switchboards) whilst for DELb they are supplied by { SCI removed } (LH switchboards). The DEL [SCWS] valves are all supported by independent { SCI removed } switchboards – LV for DELm1 and DELm4, LO for DELm2 and DELm3 and LL for DELb1 and DELb4. Hence, independent switchboards are provided between DELm and DELb trains, and also between DELm1/4 and DELm2/3, for chillers, pumps and valves.
I&C Diversity – the three I&C systems (see section 10.4.2.4.4) are based on three different technology platforms (TXS, conventional and UNICORN) that are adequately diverse from each other to prevent systematic common cause failure of multiple systems.
10.4.2.4. Requirements Defined at the Component Level
10.4.2.4.1. General Mechanical, Electrical and I&C Requirements
The components of the DEL [SCWS] system equipment performing a safety-related function comply with the general mechanical, electrical, and I&C requirements stated in section 10.0.5.1 as detailed in Section 9.4.10 – Table 1.
SECTION 9.4.10 – TABLE 1 : CLASSIFICATION OF MAIN MECHANICAL AND ELECTRICAL COMPONENTS ASSOCIATED TO THEIR SAFETY FEATURES
Description Safety classification Design requirements Mechanical requirement for pressure Highest Highest retaining safety safety components Seismic Electrical I&C
function class of or leak- requirement requirement requirement category SFG tightness requirement for HVAC component Chillers A 1 M3 SC1 C1 C1 Pumps A 1 M3 SC1 C1 C1 Bypass Valves A 1 M3 SC1 C1 C1 Three-way A 1 M3 SC1 C1 C1 Valves The data in this table is provisional and will be updated after the Safety Classification Component Lists (SCCLs) studies. 10.4.2.4.2. SeismicAPPROVED Requirements The DEL [SCWS] system complies with the seismic qualification requirements listed in Section 9.4.10 – Table 1.
10.4.2.4.3. HIC Requirements
Not applicable: the DEL [SCWS] system is not subject to any HIC requirements.
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10.4.2.4.4. Specific I&C Requirements
DELm1 and DELm4: The main lines (production and distribution) in Divisions 1 and 4 are controlled by dedicated Conventional I&C (relay based);
DELm2 and DELm3: The main lines (production and distribution) in Divisions 2 and 3 are controlled by dedicated TXS I&C;
DELb1 and DELb4: The backup lines (production and distribution) in Divisions 1 and 4 are controlled by NCHICS (UNICORN I&C). This dedicated I&C is required to be Class 1 to perform the duty role during DEL [SCWS] main train maintenance, providing operational control of the back-up equipment which is completely independent of the DELm I&C.
The mechanical, electrical and I&C components in the dedicated I&C equipment must comply with the electrical and I&C requirements associated with their safety class, in accordance with the rules laid out in Sub-chapter 3.2.
The dedicated I&C equipment must be qualified for the operating conditions defined in section 1 and the seismic requirements defined in Sub-chapter 3.2, section 6.1.
Design and construction of the dedicated I&C equipment must conform to the specific common requirements detailed in the RCC-E (see Sub-chapter 3.8) and relevant standards (e.g. IEC standards).
10.4.3. Examination, Maintenance, (In-Service) Inspection and Testing (EMIT)
10.4.3.1. Start-up Tests
The DEL [SCWS] system is subject to a start-up test programme in accordance with the procedures set out in Chapter 20 serving to verify the fulfilment of the following SFRs:
Demonstrate that DEL [SCWS] four main lines and two backup lines provide adequate cooling to its served systems in all operating mode and hazard conditions through:
o minimum required cooling power,
o minimum required flow rate, and
o correct functional operation of bypass valves and three-way valves.
Demonstrate the automatic start-up of the backup line in case of detection of failure of any one of its associated main lines. 10.4.3.2. InAPPROVED-Service Inspection The following functions of the DEL [SCWS] system are monitored during normal operation by continuous monitoring systems for:
the production of chilled water through minor (pre-alarm) and major alarms in the MCR (representative of e.g. pressure, temperature, leakage, etc.), and
the distribution of adequately chilled water flow rate through:
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o pressure measurement across DEL [SCWS] chiller evaporators with associated alarm (and pre-alarm) in the MCR, and
o low level of pressure within the network with associated alarm (and pre-alarm) in the MCR.
The availability of these functions is therefore verified by the continuous monitoring process.
10.4.3.3. Periodic Testing
The safety-classified parts of the DEL [SCWS] system are subject to periodic testing in accordance with the maintenance schedule in order to verify that the following SFRs are fulfilled:
Demonstrate that DEL [SCWS] four main lines and two backup lines provide adequate cooling to its served systems in all operating mode and hazard conditions through:
o minimum required cooling power,
o minimum required flow rate, and
o correct functional operation of bypass valves and three-way valves.
Demonstrate the automatic start-up of the backup line in case of detection of failure of any one of its associated main lines.
10.4.3.4. Maintenance
The DEL [SCWS] system is subject to a maintenance programme aiming to:
Ensure that DEL [SCWS] four main trains and two backup trains provide adequate cooling to its served systems through:
o minimum required cooling power,
o minimum required flow rate, and
o correct functional operation of bypass valves and three-way valves.
Ensure the automatic start-up of the backup trains in case of failure detection of any one of its associated main trains.
Maintenance of DEL [SCWS] main trains and DEL [SCWS] backup trains may be performed at any time (except during extreme high external temperature conditions, see section 10.3.2.1.3 and section 1). However maintenance should only be performed on one train at any time to ensure availabilityAPPROVED of the remaining trains to perform the safety functions of the system. In the case of maintenance of one DEL [SCWS] main train, the associated DEL [SCWS] backup train is able to take over most of the functions of DEL [SCWS] main train. DELb1 can be used either in Division 1 or 2; DEL [SCWS]b4 in Division 3 or 4. However, DELb trains do not provide cooling to RIS [SIS] system LHSI pump motors or of some LCUs of the DWL [CSBVS] and DWK [FBVS] systems, hence cooling to these systems is not available during maintenance of the associated DELm train.
The maintenance of the DEL [SCWS] system must be co-ordinated with the maintenance of its served systems.
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10.5. FUNCTIONAL DIAGRAM
The functional diagrams of the DEL [SCWS] system are shown in Section 9.4.10 – Figures 1, 2 and 3 (for more details, see the detailed mechanical diagram of the DEL [SCWS] system).
11. OPERATIONAL CHILLED WATER SYSTEM (DER [OCWS])
The information reported in this section is, unless otherwise noted, consistent with the reference design, as referenced from Chapter 22.
11.0. SAFETY REQUIREMENTS
The UK EPR Safety Classification principles and the top-down functional approach are presented in Sub-chapter 3.2. These principles help to ensure that the plant is designed, manufactured, constructed, commissioned and operated so that the appropriate level of reliability and integrity is achieved for its Structures, Systems and Components (SSCs).
The Hinkley Point C (HPC) functional safety analyses and the application of these safety classification principles to the HPC reference design result in the identification of the safety requirements for all safety systems in accordance with the Safety Functional Requirements Notes (SFRNs) referenced from Sub-chapter 3.2.
This section summarises the results of these safety analyses and specifies the safety requirements that apply to the design of the Operational Chilled Water System (DER [OCWS]).
The requirements described in the present section are consistent with safety functions to which contribute DER [OCWS] system in Plant Condition Category (PCC) and Design Extension Conditions (DEC). Consistency with requirements inherited from the Design Basis Initiating Faults (DBIFs) should be checked when the list of DBIFs evolves (see Chapter 15).
11.0.1. Safety Functions
The three Main Safety Functions (MSFs) necessary to achieve the overall safety objective of protecting people and the environment from the harmful effects of ionising radiations are:
control of fuel reactivity,
fuel heat removal, and
confinement of radioactive material.
These three MSFs must be achieved during: normalAPPROVED operating conditions (PCC-1), including duty functions, control of radioactive release during normal operating conditions, control of main plant parameters, fault initial conditions, Limiting Conditions of Operation (LCOs), limitations, monitoring functions, Probabilistic Safety Assessment (PSA) significant functions as part of the preventive line of defence,
fault conditions (PCC-2 to PCC-4, DEC-A and any equivalent DBIFs) and DEC-B, and
hazard conditions.
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11.0.1.1. Control of Fuel Reactivity
The DER [OCWS] system does not directly contribute to the MSF of control of reactivity.
11.0.1.2. Fuel Heat Removal
The DER [OCWS] system does not directly contribute to the MSF of control of fuel heat removal.
11.0.1.3. Confinement of Radioactive Material
The DER [OCWS] system must contribute to the achievement of the MSF of confinement of radioactive material as a frontline system as follows:
Third containment barrier:
Under accident conditions, the DER [OCWS] system must act as a third containment barrier at its containment penetration points.
Environmental protection:
The DER [OCWS] system carries liquid fluids containing radioactive material. As such, it must contribute:
o to the confinement of this material with respect to the environment as a whole and the public, and
o to the control and reduction of radioactive waste discharges under normal operation.
11.0.1.4. Support Contribution to Main Safety Functions
The DER [OCWS] system does not indirectly contribute to the three MSFs.
11.0.1.5. Specific Contribution to Hazard Protection
The DER [OCWS] system must contribute directly to the safety functions that are part of the facility’s hazards protection against the consequences of an earthquake (see Sub-chapter 13.1, section 2) as follows:
Preservation of Seismic Requirement levels (SC1) Safety Features (SFs) availability following a seismic event.
Prevention of minor radioactive release following multiple failures after earthquake.
Moreover, the DER [OCWS] system must be protected against internal and external hazards (see section 11.0.4.2).APPROVED 11.0.1.6. Other Safety Functions to be performed in the Preventive Line of Defence
The DER [OCWS] system must contribute directly to other safety functions to be performed as part of the preventive line of defence as follows:
Contribution to over pressure protection of safety classified components.
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11.0.2. Safety Functional Requirements
11.0.2.1. Control of Fuel Reactivity
Not applicable: the DER [OCWS] system does not directly contribute to the MSF of control of fuel reactivity.
11.0.2.2. Fuel Heat Removal
Not applicable: the DER [OCWS] system does not directly contribute to the MSF of fuel heat removal.
11.0.2.3. Confinement of Radioactive Material
With respect to its contribution to the MSF of confinement of radioactive material, the DER system must satisfy the following Safety Functional Requirements (SFRs):
Third containment barrier:
Under accident conditions, the DER [OCWS] system must enable the isolation of the containment at its containment penetration points.
Environmental protection:
The DER [OCWS] system prevents minor radioactive release or minor fuel degradation within the Nuclear Power Plant (NPP) design basis following a mechanical failure.
11.0.2.4. Support Contribution to Main Safety Functions
Not applicable: the DER [OCWS] system does not indirectly contribute to the three MSFs.
11.0.2.5. Specific Contribution to Hazard Protection
With respect to its specific contribution to the safety functions that are part of the facility’s hazards protection, the DER [OCWS] system must satisfy the following SFRs:
Preservation of SC1 SFs availability following a seismic event:
Ensure the stability/integrity of DER components to avoid damage to higher classified components and ensure that is does no adversely impact the availability of SC1 SFs following a seismic event.
Prevention of minor radioactive release following multiple failures after earthquake:
To prevent the damage in the Nuclear Auxiliary Building (HN [NAB]) following an earthquake,APPROVED sufficient requirements on DER [OCWS] components must be determined. 11.0.2.6. Other Safety Functions to be performed in the Preventive Line of Defence
With respect to its contribution to other safety functions to be performed as part of the preventive line of defence, the DER [OCWS] system must satisfy the following SFRs:
Contribution to overpressure protection of safety classified components:
The DER [OCWS] system must be protected against overpressure.
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11.0.3. Safety Features and Instrumentation and Control (I&C) Actuation Modes
Section 9.4.11 – Table 2 presents the SFs of the DER [OCWS] system according to the contributions identified in section 11.0.1 and the SFRNs referenced in Sub-chapter 3.2.
11.0.4. Classification and Architecture Requirements of Safety Features
11.0.4.1. Requirements arising from Safety Classification
Architecture requirements associated with safety features are essential for designing robust lines of defence consistent with their importance to nuclear safety (Sub-chapter 3.2). Such requirements strengthen the system design against:
single faults and associated consequences (Single Failure Criterion, SFC) by requiring redundancy;
Loss Of Off-site Power (LOOP) by requiring, among others, a back-up power supply;
Station Black-Out (SBO) by requiring a power supply by the Ultimate Diesel Generators (UDGs);
Common Cause Failures (CCF) by requiring physical separation;
earthquake by defining seismic requirements; and
accident conditions by defining qualification requirements.
Section 9.4.11 – Table 2 presents the requirements arising from safety classification for the DER [OCWS] system, according to the SFRNs referenced in Sub-chapter 3.2.
11.0.4.2. System Protection against Hazards
11.0.4.2.1. Internal Hazards
The SFs of the DER [OCWS] system must be protected against internal hazards if those hazards challenge the safety objectives, as defined in Sub-chapter 13.2.
11.0.4.2.2. External Hazards
The SFs of the DER [OCWS] system must be protected against external hazards if those hazards challenge the safety objectives, as defined in Sub-chapter 13.1.
11.0.4.3. Diversity The DER [OCWS]APPROVED system is not subject to the requirement for diversity. 11.0.5. Requirements defined at the Component Level
11.0.5.1. Generic Safety Requirements
11.0.5.1.1. General Mechanical, Electrical and I&C Requirements
The mechanical components within the DER [OCWS] system must comply with the mechanical requirements in accordance with the rules laid out in Sub-chapter 3.2, section 7. The level of
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requirement is dependent upon whether or not it is a pressure retaining component, the safety class of the component, whether the component acts as an isolating device between interfacing safety features, and on the role of the component as a barrier to the potential release of radioactivity as a result of failure of the component.
The electrical and Instrumentation and Control (I&C) components in the DER [OCWS] system must comply with the electrical and I&C requirements associated with their safety class, in accordance with the rules laid out in Sub-chapter 3.2.
11.0.5.1.2. Seismic Requirements
The level of seismic requirements to be applied to DER [OCWS] system components is related to the Safety Feature Group (SFG) to which the component belongs, and the consequences on other classified components of its failure, if it were not seismically qualified. The rules for defining the seismic requirements for a component are identified in Sub-chapter 3.2.
11.0.5.1.3. Qualification for Accident Conditions
The safety classified parts of the DER [OCWS] system must be qualified for the operating conditions in which they are required, as specified in Sub-chapter 3.6.
11.0.5.2. Specific Safety Requirements
11.0.5.2.1. High Integrity Component (HIC) Requirements
The DER system is not subject to any High Integrity Component (HIC) requirements.
11.0.5.2.2. Specific I&C Requirements
The DER [OCWS] system does not have any safety classified dedicated I&C.
The general approach to qualification of dedicated I&C systems in terms of Production Excellence (PE) and Independent Confidence Building Measures (ICBM) is set out in Sub-chapter 7.7.
Besides dedicated I&C, some DER [OCWS] components are controlled by safety classified standard centralised I&C (containment isolation valves).
The general approach for I&C systems is set out in Chapter 7.
11.0.6. Examination, Maintenance, (In-Service) Inspection and Testing (EMIT)
11.0.6.1. Start-Up Tests
The DER [OCWS] system must be designed to enable the performance of start-up tests to ensure the adequacyAPPROVED of its design and performance under conditions as representative as possible of the different operating configurations, and in particular its compliance with the SFRs assigned to it in section 11.0.2.
11.0.6.2. In-Service Inspection
The DER [OCWS] system must be designed to enable surveillance under normal operation of the system characteristics necessary for the fulfilment of its safety-related tasks in order to ensure the performance of its components, and their availability under normal operation, or in the event of a fault or accident.
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11.0.6.3. Periodic Testing
The safety classified parts of the DER [OCWS] system must be designed to enable the performance of periodic tests in accordance with the maintenance schedule.
11.0.6.4. Maintenance
The DER [OCWS] system must be designed to enable the implementation of a maintenance schedule (see Sub-chapter 18.2).
11.1. ROLE OF THE SYSTEM
The DER [OCWS] system performs the functions (or tasks) detailed in the following sections under the different plant operating conditions for which it is required.
11.1.1. Normal Operating Conditions
In normal operation conditions of the plant, the DER [OCWS] system, through its two sub-systems, contributes to the general operation of the plant unit by producing and distributing chilled water and so, providing heat sink for the following systems:
DER [OCWS] sub-system A, namely DERA sub-system, produces chilled water for:
o Containment Cooling Ventilation System (EVR [CCVS]) (four cooling coils in the equipment compartment and 12 cooling coils in the service area),
o Nuclear Auxiliary Building Ventilation System (DWN [NABVS]) (principally six cooling coils),
o Fuel Building Ventilation System (DWK [FBVS]),
o Ventilation System for Main Steam System, Feedwater Flow Control System and Steam Generator Blowdown System bunkers and DER [OCWS] rooms (DVE), and
o Nuclear Vent and Drain System (RPE [NVDS]) for Vacuum Pump in Reactor Building.
DER [OCWS] sub-system B, namely DERB sub-system, produces chilled water for:
o Gaseous Waste Processing System (TEG [GWPS]) (two sealing liquid coolers for the TEG compressors, one pre-dryer, one gas dryer and one gas cooler),
o Coolant Storage and Treatment System (TEP [CSTS]), o APPROVEDNuclear Sampling System (REN [NSS]), and o Steam Generator Secondary Sampling System (RES).
11.1.2. Fault and Hazard Operating Conditions
The DER [OCWS] system is not required to operate under fault and hazard conditions.
However, the containment isolation function is required to operate under PCC-3, PCC-4, DEC-A, DEC-B and hazard conditions.
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11.2. DESIGN BASIS
11.2.1. General Assumptions
The design of the DER [OCWS] system and the installation of the equipment take into account constraints regarding accessibility and periodic tests.
Suitable measures are taken to avoid any risk of freezing and corrosion of the system.
All equipment is made from carbon steel, except for some parts of chiller cooling units which are made of copper.
11.2.2. Design Assumptions
Not applicable: there are no quantitative safety-related design assumptions associated with the DER [OCWS] system.
11.2.3. Other Assumptions
The cooling units provide chilled water to the DER [OCWS] loads:
for DERA sub-system: at a temperature of { SCI removed } with a nominal return temperature of { SCI removed }, and
for DERB sub-system: at a temperature of { SCI removed } with a nominal return temperature of { SCI removed }.
The DER [OCWS] system is controlled centrally from the Main Control Room.
The operating pressure in DERB sub-system is higher than the TEG [GWPS] system.
11.2.4. Assumptions Associated with Extreme Situations resulting from Beyond Design Basis Hazards
11.2.4.1. Assumptions associated with Fukushima Provisions
The assumptions associated with the Fukushima provisions of the DER [OCWS] system are presented in Chapter 23. The main provisions are:
Containment Isolation 1.
11.2.4.2. Assumptions associated with non-Fukushima Provisions
The storage capacity requirement of the severe accident batteries is increased from { SCI removed } to { SCI removed } in order to provide power to the external containment isolation valves.APPROVED
11.3. SYSTEM DESCRIPTION AND OPERATION
11.3.1. Description
11.3.1.1. General System Description
The DER [OCWS] system is identical for both units and has no interconnections between them.
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The DER [OCWS] system, through its two sub-systems, contributes to the general operation of the plant unit by producing and distributing chilled water to its loads.
The system is illustrated in Section 9.4.11 – Figures 1 and 2.
11.3.1.2. Description of Main Equipment
DERA sub-system consists of:
A production loop in series with a distribution loop:
o The production loop with two parallel refrigerating units with their cooling units (2 x { SCI removed }) and their production pumps (2 x { SCI removed }), producing chilled water on the evaporator side of the cooling units.
o The cooling units are cooled by two different Component Cooling Water System (RRI [CCWS]) trains to minimise the risk of unavailability of the heat sink in the production of chilled water. One cooling unit is on the 1b common auxiliaries and the other cooling unit is on the 2b common auxiliaries.
o The distribution loop with two parallel distribution pumps (2 x { SCI removed }), distributing the chilled water to the loads.
o One refrigerating unit (cooling unit and a production pump) and one distribution pump are shutdown depending on the load requirements.
A bypass (or mini-flow) line connecting both suction sides of the production and distribution loops, ensuring an almost constant flow rate in the refrigerating units while the flow rate in the distribution loop is variable (for example, due to flow control by the DVE and DWN [NABVS] systems),
A diaphragm expansion tank with a nitrogen blanket located on the bypass line, enabling the fluid to expand within its expected range of temperature and ensuring a minimum operating pressure in the circuit,
A safety valve whose purpose is to protect the circuit against over pressure,
A return line from the loads,
A filtration device on the return line to keep the circuit free of suspended particles, and
Containment isolation valves.
DERB sub-system consists of: A singleAPPROVED production and distribution loop: o with two parallel refrigerating units with their cooling units (2 x 100%) and pumps (2 x 100%), producing and distributing chilled water to the loads at a constant flow rate,
o the two cooling units are cooled by two different RRI [CCWS] trains in order to ensure a permanent supply of chilled water to the TEG [GWPS] system. One cooling unit is on the common 1b auxiliaries and the other cooling unit is on the common 2b auxiliaries, and
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o one refrigerating unit (cooling unit + pump) is available in standby,
A diaphragm expansion tank with a nitrogen blanket located on the bypass line, enabling the fluid to expand within its expected range of temperature and ensuring a minimum operating pressure in the circuit,
A safety valve whose purpose is to protect the circuit against overpressure,
A return line from the loads,
A filtration device on the return line to keep the circuit free of suspended particles, and
An identical distribution of the electrical switchboards between the refrigerating units and the TEG [GWPS] compressors, enhancing the system availability.
11.3.1.3. Description of Main Layout
The DER [OCWS] cooling units are located in the Nuclear Auxiliary Building. The DER [OCWS] loads are located in the Reactor Building (HR [RB]), HN [NAB] building, Safeguard Auxiliary Buildings (HL [SB]) and Fuel Building (HK [FB]).
11.3.1.4. Description of System I&C
The DER [OCWS] system is controlled by a non-classified dedicated I&C system, but is reliant on other standard centralised I&C systems to perform some classified functions.
Each DER [OCWS] cooling unit performing the chilled water production has an unclassified dedicated independent I&C system, which control the following functions:
the chilled water temperature on evaporator side,
the cooling capacity of the cooling unit, and
the position of the three-way valve on condenser side.
The containment isolation is performed by safety classified standard centralised I&C system, which controls the containment isolation valves (see 11.0.5.2.2).
Standard I&C used for DER [OCWS] system is described in Chapter 7.
11.3.2. Operation
11.3.2.1. System Normal Operation DERA sub-system:APPROVED The cooling capacity supplied depends on the demand made by the ventilation system.
The sub-system primarily fulfils the following functions:
Supplying chilled water to the DWN [NABVS] system.
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Supplying chilled water to the EVR [CCVS] system:
o cooling the EVR [CCVS] system – equipment compartment if the outlet temperature of EVR [CCVS] air supply fans is above { SCI removed },
o cooling the EVR [CCVS] system – service area continuously.
Supply of chilled water to the DWK [FBVS] system.
Supply of chilled water to the ventilation system DVE for Main Steam System (MSS), Feedwater Flow Control System and Steam Generator Blowdown System (APG [SGBS]) bunkers and DER [OCWS] rooms.
Supply of chilled water to the Nuclear Vent and Drain System (RPE [NVDS]) for Vacuum Pump in Reactor Building.
Whether one or two refrigerating units (each comprising a cooling unit and a production pump) and one or two circulation pumps is used depends on the demand made by the ventilation systems. In case the cooling demand is lower than { SCI removed } of the total cooling needs, only one refrigerating unit is in operation.
In the event of failure of a refrigerating unit or circulation pump, the second refrigerating unit or second circulation pump is automatically started as back-up (if not already running). Although this back-up can only provide { SCI removed } of the total cooling needs, it is sufficient when the cooling needs are lower than { SCI removed } of the total cooling needs, also it is not sufficient when the cooling needs are between { SCI removed } and { SCI removed } of the total cooling needs but the resulting heating transient will be significantly slower. This partial redundancy is only for operational reliability and is not a safety requirement.
DERB sub-system:
The sub-system permanently cools the TEG [GWPS], TEP [CSTS], REN [NSS] and RES systems.
One refrigerating unit (comprising a cooling unit and a pump) is continuously operating.
In the event of failure of this refrigerating unit, the second refrigerating unit is automatically started as a back-up.
11.3.2.1.1. Partial or Total Loss of Heat Sink (Loss Of Cooling Chain (LOCC))
Both sub-systems are lost as the cooling chain through the RRI [CCWS] system will be lost.
11.3.2.1.2. Loss Of Off-site Power (LOOP) The DERA subAPPROVED-system is lost during a LOOP. The power supplies to the containment isolation valves (DERA sub-system) are backed-up by the Emergency Diesel Generators (EDGs), and the entire DERB sub-system is backed up by the EDGs.
11.3.2.1.3. Station Black-out (SBO)
Both sub-systems are lost during an SBO.
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However the following components have back-up power supplies:
the containment isolation valves are backed-up by the UDGs,
the outside containment isolation valves are backed-up by { SCI removed } batteries (Severe Accident (SA)), and
the inside containment isolation valve is backed-up by a two hour battery.
11.3.2.2. System Transient Operation
11.3.2.2.1. Full or Partial System Failure
{ This section contains SCI-only text and has been removed }
11.3.2.2.2. Failure of Systems in Interface (Server or Served)
{ This section contains SCI-only text and has been removed }
11.4. PRELIMINARY DESIGN SUBSTANTIATION
The level of detail of evidence of compliance with the safety requirements stated in section 11.0 will develop as the HPC project moves from basic design into detailed design since PCSR3 sequence and system sequence are evolving in parallel. Therefore, the level of details presented in this section depends on the information available at the time of issuing the system chapters.
11.4.1. Compliance with Safety Functional Requirements
11.4.1.1. Control of Fuel Reactivity
Not applicable; the DER [OCWS] system does not directly contribute to the MSF of control of fuel reactivity.
11.4.1.2. Fuel Heat Removal
Not applicable; the DER [OCWS] system does not directly contribute to the MSF of fuel heat removal.
11.4.1.3. Confinement of Radioactive Material
Third containment barrier:
Under accident conditions, and acting as a third containment barrier, the two lines of the DER [OCWS] system penetrating the Reactor Building containment are fitted with two containmentAPPROVED isolation devices. The inlet penetration is fitted with a motorised isolation valve receiving a phase 1 containment isolation signal and a check valve. The outlet penetration is fitted with two motorised isolation valves both receiving a phase 1 containment isolation signal.
Environment protection:
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The DER [OCWS] system combined with the RRI [CCWS] monitoring contributes to the confinement of the radioactive material, by preventing minor radioactive releases or full degradation within the NPP design basis following a mechanical failure located in HN [NAB], HL [SB] and HK [FB] buildings.
11.4.1.4. Support Contribution to Main Safety Functions
Not applicable; the DER [OCWS] system does not indirectly contribute to the three MSFs.
11.4.1.5. Specific Contributions to Hazards Protection
The seismic hazard studies of Sub-chapter 13.1 will demonstrate that the design assumptions of the DER [OCWS] system, contributes to:
Prevention of SC1 features availability following a seismic event:
Ensure stability or integrity of DER components:
o Seismic qualification to keep the components integrity or stability.
Prevention of minor radioactive release following multiple failures after earthquake:
The preservation of the HN [NAB] building with an addition of a passive protection guarantee that the limitation of internal flooding from the Conventional Island (CI) to the Nuclear Island (NI).
11.4.1.6. Other Safety Functions to be performed in the Preventive Line of Defence
Other safety functions to be performed in the preventive line of defence involving the DER [OCWS] system use values for the following parameters that are in keeping with the design assumptions stated in section 11.2.2:
Contribution to over pressure protection of safety classified components:
Proper operation of DER [OCWS] pressure relief valve in HR [RB] building allowing the pressure decrease in case of abnormally high pressure due to the SED system.
Preventing the boiling effect, and balancing the pressure in case of increase of the temperature after total containment isolation of the DER [OCWS] system.
These elements ensure that the safety functional requirements stated in section 11.0.2 are met.
11.4.2. Compliance with Design Requirements
The DER [OCWS] system complies with the requirements stated in sections 11.0.4 and 11.0.5, particularly withAPPROVED respect to those detailed in the following sections. 11.4.2.1. Requirements arising from Safety Classification
11.4.2.1.1. Safety Classification
The compliance of the design and manufacture of DER [OCWS] system materials and equipment performing a safety-related function with requirements from the classification rules (see Sub-chapter 3.2, section 7) is presented in section 11.4.2.4.1.
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11.4.2.1.2. Single Failure Criterion and Redundancy
Active Single Failure
The design of the DER [OCWS] system meets the requirements of the active SFC stated in section 11.0.4.1, in particular with respect to the power supply of the containment isolation valves by means of diversified electrical switchboards.
The DER [OCWS] system containment penetration isolation system consists of an isolation valve inside the HR [RB] building and an isolation valve located outside in a connecting building, which is redundant.
Furthermore, although not subject to the application of the SFC, the refrigerating unit of the DERB sub-system has redundancy of availability, achieved through the duplication of the refrigerating unit (cooling unit and pump).
Passive Single Failure
Not applicable: the design of the DER [OCWS] system is not subject to the passive failure criterion.
11.4.2.1.3. Robustness against Loss of Power
The design of the DER [OCWS] system complies with the emergency power supply requirement stated in section 11.0.4.1, in particular in respect to the power supply backed-up of the containment isolation valves.
Furthermore, while not subject to an emergency power supply requirement, the DERB sub-system is provided with a backed-up power supply for the purposes of plant unit availability, in the form of an emergency electrical power supply to the refrigerating units using the EDGs.
The DERB sub-system is diesel backed to allow the plant unit availability in shutdown state for the TEG and TEP systems if necessary.
11.4.2.1.4. Physical Separation
The two isolation devices of each containment penetration of the DER [OCWS] system are physically separated by virtue of their installation, one on the inside of the HR [RB] building, the other on the outside, in a connecting building.
11.4.2.2. System Protection against Hazards
11.4.2.2.1. Internal Hazards
The overall demonstration of the robustness of the plant to internal hazards in covered in Sub-chapter 13.2.APPROVED 11.4.2.2.2. External Hazards
The overall demonstration of the robustness of the plant to internal hazards in covered in Sub-chapter 13.1.
11.4.2.3. Diversity
Not applicable: the DER [OCWS] system is not subject to the requirement for diversity.
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11.4.2.4. Requirements defined at the Component Level
11.4.2.4.1. General Mechanical, Electrical and I&C Requirements
The components of the DER [OCWS] system equipment performing a safety-related function comply with the general mechanical, electrical, and I&C requirements stated in section 11.0.5.1.1, as detailed below in Section 9.4.11 – Table 1.
SECTION 9.4.11 – TABLE 1 - CLASSIFICATION OF MAIN MECHANICAL AND ELECTRICAL COMPONENTS ASSOCIATED TO THEIR SAFETY FEATURES
Safety classification Design requirements Mechanical requirement for Highest Highest pressure retaining Description safety safety Seismic Electrical I&C components or function class of requirement requirement requirement leak-tightness category SFG requirement for HVAC component Containment penetration A 1 M2 SC1 C1 C1 including isolation valves RRI [CCWS] water side, C 3 M3 NR NR NR cooling unit condensers DER equipment in HK, HL and HR C 3 NR SC2 NR NR buildings DER equipment between HN C 3 NR SC2 NR NR building and HGN High point Other parts of DER in HN NR NR NR NR NR NR building This table will be updated after the Safety Classification Component List (SCCL) studies.
11.4.2.4.2. Seismic Requirements
The DER [OCWS] system complies with the seismic qualification requirements listed in Section 9.4.11 – Table 1. 11.4.2.4.3. HICAPPROVED Requirements Not applicable; the DER [OCWS] system is not subject to any HIC requirements.
11.4.2.4.4. Specific I&C Requirements
The DER [OCWS] system is controlled by a non-classified dedicated I&C system. The non- classified dedicated I&C of DER [OCWS] system is not subject to any specific I&C requirement.
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However, the DER [OCWS] system is reliant on other classified I&C system to perform some classified functions (Containment Isolation including isolation valves). The I&C of the containment isolation is subject to specific requirement.
11.4.3. Examination, Maintenance, In-service Inspection and Testing (EMIT)
11.4.3.1. Start-Up Tests
The DER [OCWS] system is subject to a start-up test programme in accordance with the procedures set out in Chapter 20 “Commissioning” serving to verify the fulfilment of the following SFRs:
closing operability of the containment isolation devices, and
leaktightness of the containment isolation devices.
11.4.3.2. In-Service Inspection
Not applicable: the DER [OCWS] system does not fulfil any safety related tasks during normal operation which requires in-service inspection.
11.4.3.3. Periodic Testing
The safety classified components of the DER [OCWS] system are subject to periodic testing in accordance with the maintenance schedule in order to verify that the following SFRs are fulfilled:
operability (on closing) of the containment isolation devices, and
leaktightness of the containment isolation devices.
11.4.3.4. Maintenance
The DER [OCWS] system is subject to a maintenance programme.
Simultaneous maintenance of the two refrigerating units of either sub-system (DERA or DERB sub-systems) is not authorised. Maintenance is performed on one refrigerating unit at a time, regardless of the state of the plant.
For short-term maintenance such as replacement of an oil valve or replacement of a filter upstream of the pumps, the system is considered to be available.
The electrical switchboards of the containment isolation valves are cross-connected.
Additionally, although not subject to specific requirement, the power supply of the different refrigerating units is provided by different electrical divisions (in order to improve the availability of the plant). APPROVED 11.5. FUNCTIONAL DIAGRAM
The functional diagrams of the DER [OCWS] system are shown in Section 9.4.11 – Figures 1 and 2 (for more details, see the detailed mechanical diagram of the DER [OCWS] system).
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12. VENTILATION OF THE PUMPING STATION (DVP)
The information reported in this section is, unless otherwise noted, consistent with the reference design as referenced from Chapter 22.
12.0. SAFETY REQUIREMENTS
The UK EPR Safety Classification principles and the top-down functional approach are presented in Sub-chapter 3.2. These principles help to ensure that the plant is designed, manufactured, constructed, commissioned and operated so that the appropriate level of reliability and integrity is achieved for its Structures, Systems and Components (SSCs).
The HPC functional safety analyses and the application of these safety classification principles to the HPC reference design result in the identification of the safety requirements for all safety systems in accordance with the Safety Functional Requirements Notes (SFRNs) referenced from Sub-chapter 3.2.
This section summarises the results of these safety analyses and specifies the safety requirements that apply to the design of the Circulating Water Pumping Station Ventilation System (DVP) (Heating, Ventilation and Air Conditioning (HVAC) of the Pumping Station (HP), the Technical Galleries (HG), the Outfall Pond Building (HCA) and the Filtering Debris Recovery Pit (HCB)).
The requirements described in the present section are consistent with safety functions to which the DVP system contributes in Plant Condition Category (PCC) and Design Extension Conditions (DEC). Consistency with requirements inherited from the Design Basis Initiating Faults (DBIFs) should be checked when the list of DBIFs evolves (see Chapter 15).
12.0.1. Safety Functions
The three Main Safety Functions (MSFs) necessary to achieve the overall safety objective of protecting people and the environment from the harmful effects of ionising radiation are:
control of fuel reactivity,
fuel heat removal, and
confinement of radioactive material.
These three MSFs must be achieved during:
normal operating conditions (PCC-1), including duty functions, control of radioactive release during normal operating conditions, control of main plant parameters, fault initial conditions, Limiting Conditions of Operation (LCOs), limitations, monitoring functions, Probabilistic Safety Assessment (PSA) significant functions as part of the preventive line of defence;APPROVED
fault conditions (PCC-2 to PCC-4, DEC-A and any equivalent DBIFs) and DEC-B; and
hazard conditions.
“Other” safety functions cover contribution to hazards protection and the preventive line of defence (Duty Functions, Control of Main Plant Parameters, Initial Conditions, LCOs / Limitations, Monitoring, PSA – Prevention).
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12.0.1.1. Control of Fuel Reactivity
The DVP system does not directly contribute to the MSF of control of fuel reactivity.
12.0.1.2. Fuel Heat Removal
The DVP system does not directly contribute to the MSF of fuel heat removal.
12.0.1.3. Confinement of Radioactive Material
The DVP system does not directly contribute to the MSF of confinement of radioactive material.
12.0.1.4. Support Contribution to Main Safety Functions
The DVP system contributes indirectly to the MSF of fuel heat removal as a support system of:
the Circulating Water Filtration System (CFI [CWFS]),
the Essential Service Water System (SEC [ESWS]), and
the Ultimate Cooling Water System (SRU [UCWS]).
12.0.1.5. Specific Contribution to Hazards Protection
The generic Safety Feature (SF) [{ SCI removed }] dealing with SC2 requirements has the following function:
Preservation of SC1 SFs availability following a seismic event.
The DVP system contributes directly to the safety functions that are part of the facility’s hazard protection against the consequences of under-pressure and overpressure phenomena as follows:
Protection against under-pressure and overpressure phenomena [{ SCI removed }]
12.0.1.6. Other Safety Functions to be performed in the Preventive Line of Defence
The DVP system contributes indirectly to other safety functions to be performed as part of the preventive line of defence as follows:
Monitoring of room air temperature.
12.0.2. Safety Functional Requirements 12.0.2.1. ControlAPPROVED of Fuel Reactivity Not applicable.
12.0.2.2. Fuel Heat Removal
Not applicable.
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12.0.2.3. Confinement of Radioactive Material
Not applicable.
12.0.2.4. Support Contribution to Main Safety Functions
In order to support its indirect contribution to the MSF of fuel heat removal, the DVP system must satisfy the following SFRs:
Ensure an room air temperature lower than maximum room air temperature in all fault conditions in order to ensure an air temperature compatible with safety classified equipment operation, within the HP and HC rooms and associated galleries housing safety classified electrical and electro-mechanical equipment.
Ensure an room air temperature higher than minimum room air temperature in all fault conditions in order to ensure an air temperature compatible with safety classified equipment operation, within the HP and HC rooms and associated galleries housing safety classified equipment with a freeze risk.
12.0.2.5. Specific Contribution to Hazards Protection
In order to support its specific contribution to the safety functions that are part of the facility’s hazards protection, the DVP system must satisfy the following SFRs:
Extreme low temperatures:
The DVP system must maintain room conditions compatible with system operation in event of extreme low temperatures.
Explosion:
The DVP system must contribute to the limitation of a pressure wave inside the HP, the HC building and the associated galleries (Diesel Gallery Trains 1 to 4 (HG-A/B/C/D), Essential Service Water Gallery Trains 1 to 4 (HG-F/G/H/I), and the Diversification Gallery (HGZ)) in order to protect the safety classified equipment within these buildings.
Tornado:
The DVP system must contribute to the limitation of a pressure wave and the non-propagation of missiles inside the HP, the HC building and associated galleries (HG-A/B/C/D/F/G/H/I/Z) in order to protect the safety classified equipment within these buildings.
Wind: The DVPAPPROVED system must contribute to the non-propagation of wind generated missiles inside the HP, the HC building and associated galleries (HG-A/B/C/D/F/G/H/I/Z) in order to protect the safety classified equipment within these buildings.
Fire:
The DVP system must contribute to the prevention of spreading of fire through the ducts, overpressuring of access stairs for staff evacuation and smoke extraction in case of fire event inside the HP, the HC building and associated galleries (HG-A/B/C/D/F/G/H/I/Z) in order to protect the safety classified equipment within these buildings.
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12.0.2.6. Other Safety Functions to be performed in the Preventive Line of Defence
In order to support its contribution to other safety functions to be performed as part of the preventive line of defence, the DVP system must satisfy the following SFRs:
Monitoring of room air temperature:
The DVP system must monitor the air room temperature in order to alert control room staff if the temperature deviates outside the limits for correct function of safety classified equipment.
12.0.3. Safety Features
Sub-chapter 9.4.12 – Table 4 presents the SFs of the DVP system, according to the contributions identified in section 12.0.1 and the SFRNs referenced in Sub-chapter 3.2.
12.0.4. Classification and Architecture Requirements of Safety Features
12.0.4.1. Requirements arising from Safety Classification
Architecture requirements associated with SFs are essential for designing robust lines of defence consistent with their importance to nuclear safety (Sub-chapter 3.2). Such requirements strengthen the system design against:
single faults and associated consequences (Single Failure Criterion (SFC)) by requiring redundancy;
Loss Of Offsite Power (LOOP) by requiring a back-up power supply;
Common Cause Failures (CCF) by requiring, amongst others, physical separation;
earthquake by defining seismic requirements; and
accident conditions by qualification requirements.
Section 9.4.12 – Table 4 presents the requirements arising from safety classification for the DVP system, according to the SFRNs referenced in Sub-chapter 3.2.
12.0.4.2. System Protection against Hazards
12.0.4.2.1. Internal Hazards
The SFs of the DVP system must be protected against internal hazards if those hazards challenge the safety objectives, as defined in Sub-chapter 13.2. 12.0.4.2.2. ExternalAPPROVED Hazards The SFs of the DVP system must be protected against external hazards if those hazards challenge the safety objectives, as defined in Sub-chapter 13.1.
12.0.4.3. Diversity
The DVP system is subject to the requirement for diversity as defined in the general safety principles (see Sub-chapter 3.1) and in Sub-chapter 3.7, dealing with diversity.
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12.0.5. Requirements Defined at the Component Level
12.0.5.1. Generic Safety Requirements
12.0.5.1.1. Generic Mechanical, Electrical and I&C Requirements
The mechanical components of the DVP system must comply with the mechanical requirements in accordance with the rules laid out in Sub-chapter 3.2, section 7. The level of requirement is dependent upon whether or not it is a pressure retaining component, the safety class of the component, whether the component acts as an isolating device between interfacing safety features, and on the role of the component as a barrier to the potential release of radioactivity as a result of failure of the component.
The electrical and Instrumentation & Control (I&C) components in the DVP system must comply with the electrical and I&C requirements associated with their safety class, in accordance with the rules laid out in Sub-chapter 3.2.
The mechanical, electrical and I&C components in the DVP system must comply with the requirements set out in section 1.
12.0.5.1.2. Seismic Requirements
The level of seismic requirements to be applied to DVP system components is related to the Safety Feature Group (SFG) to which the component belongs and the consequences on other classified components of its failure if it were not seismically qualified. The rules for defining the seismic requirements for a component are identified in Sub-chapter 3.2.
12.0.5.1.3. Qualification for Accident Conditions
The safety classified components of the DVP system must be qualified for the operating conditions in which they are required, as specified in Sub-chapter 3.6.
12.0.5.2. Specific Safety Requirements
12.0.5.2.1. High Integrity Component (HIC) Requirements
The DVP system is not subject to any High Integrity Component (HIC) requirements.
12.0.5.2.2. Specific I&C Requirements
The DVP system has safety classified I&C and there will be specific reliability/availability requirements associated with the safety class of I&C architecture. It should further be clarified what is dedicated versus non-dedicated. 12.0.6. Examination,APPROVED Maintenance, In-Service Inspection and Testing (EMIT) 12.0.6.1. Start-Up Tests
The DVP system must be designed to enable the performance of start-up tests to ensure the adequacy of its design and performance under conditions as representative as possible of the different operating configurations, and in particular its compliance with the SFRs assigned to it in section 12.0.2.
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12.0.6.2. In-Service Inspection
The DVP system must be designed to enable surveillance under normal operation of the system characteristics necessary for the fulfilment of its safety-related tasks in order to ensure the performance of its components, and their availability under normal operation, or in the event of a fault or accident.
12.0.6.3. Periodic Testing
The safety classified parts of the DVP system must be designed to enable the performance of periodic tests in accordance with the maintenance schedule.
12.0.6.4. Maintenance
The DVP system must be designed to enable the implementation of a maintenance schedule (see Sub-chapter 18.2).
12.1. ROLE OF THE SYSTEM
The DVP system performs the functions (or tasks) detailed in the following sections, for which it is required.
12.1.1. Normal Plant Operation
The DVP system provides the heating, cooling and air conditioning support system for the rooms housing the classified systems contributing to control of fuel reactivity removal.
The DVP system also contributes to the following non-classified functions:
air renewal required for occasional personnel intervention (comfort and hygiene) and more generally for purification of the rooms; and
cooling and heating of the rooms required to maintain acceptable room conditions (temperature) for good working order of the equipment.
12.1.2. Fault and Hazard Operating Conditions
The DVP system provides the heating and air conditioning support system for the rooms housing the classified systems contributing to heat removal;
It contributes to the limitation of a tornado in order to protect safety classified equipment in the HP. It contributesAPPROVED to mitigating the effects of extreme low temperatures. The DVP system also contributes to following non-classified functions:
In the event of fire, the DVP also ensures:
o isolation of fire in sector or zones to avoid the spread of a fire (SFI or ZFI);
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o creation of overpressure in the access sectors and isolation of smoke transfer to the emergency exits and stairs to facilitate safe means of escape for operators; and
o post-fire smoke control in the electrical rooms.
12.2. DESIGN BASIS
12.2.1. General Assumptions
The DVP system provides air conditioning for the HP, the associated HG-A/B/C/D/F/G/H/I/Z, the HCB and the HCA building ; and maintain room conditions compatible with the correct operation of the equipment, as defined in section 1.
The DVP system is used during normal operating conditions (plant states A to F) as well as during fault conditions and DEC-A and DEC-B.
12.2.2. Design Assumptions
12.2.2.1. Control of Fuel Reactivity
Not applicable: the DVP system does not directly contribute to the MSF of control of fuel reactivity.
12.2.2.2. Fuel Heat Removal
Not applicable: the DVP system does not directly contribute to the MSF of fuel heat removal.
12.2.2.3. Confinement of Radioactive Material
Not applicable: the DVP system does not directly contribute to the MSF of confinement of radioactive material.
12.2.2.4. Support Contribution to Main Safety Functions
In order to support its contribution to the MSF of control of fuel reactivity, the DVP system must satisfy the following SFRs:
Ensure a room air temperature lower than maximum room air temperature in all fault conditions in order to ensure an air temperature compatible with safety class1 and class 2 equipment operation.
Ensure a room air temperature higher than minimum room air temperature in all fault conditions in order to ensure an air temperature compatible with safety class 1 and class 2APPROVED equipment operation. 12.2.2.5. Specific Contribution to Hazards Protection
The DVP system contributes directly to the safety functions that are part of the facility’s hazard protection as follows:
maintaining room air temperature compatible with the correct operation of the safety classified equipment in the event of an “extreme low temperatures”,
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protection against explosion,
protection against tornado,
protection against wind generated missiles, and
protection against fire events.
12.2.2.6. Other Safety Functions to be performed in the Preventive Line of Defence
In order to support its contribution to other safety functions to be performed as part of the preventive line of defence, the DVP system must satisfy the following SFRs:
Ensure a room air temperature lower than maximum room air temperature in all fault conditions in order to ensure an air temperature compatible with safety class 3 equipment operation.
Ensure a room air temperature higher than minimum room air temperature in all fault conditions in order to ensure an air temperature compatible with safety class 3 equipment operation.
Monitor the air room temperature in order to prevent a failure of the DVP equipment.
12.2.3. Other Assumptions
The DVP system includes equipment which is resistant to a marine atmosphere C5M (to prevent corrosion).
12.2.4. Assumptions associated with Extreme Situations resulting from Beyond Design Basis Hazards
12.2.4.1. Assumptions associated with Fukushima Provisions
Studies regarding the DVP system’s Fukushima provisions are ongoing. What follows are general assumptions regarding potential provisions:
Resistance to T7 tornado,
Maintain inside temperature if the instantaneous temperature increases of { SCI removed } in summer, and decrease of { SCI removed } in winter.
12.2.4.2. Assumptions associated with other Non–Fukushima Provisions The DVP systemAPPROVED is not subject to assumptions associated with non-Fukushima provisions. 12.3. SYSTEM DESCRIPTION AND OPERATION
12.3.1. Description
12.3.1.1. General System Description
The DVP system participates in the ventilation of a number of buildings. These include:
Technical Galleries HGx (A, B, C, D, E, F, G, H, I & Z);
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Service Water Pump Building HPx (A-D);
Outfall Pond Building HCA.
For the purposes of describing the system layout the system itself can be divided up into the relevant functions that it provides within the relevant structures. These functions are:
Air Renewal,
Extraction,
Heating,
Monitoring,
Temperature Control, and
Smoke Extraction.
The provision of these functions within the relevant building structure is detailed below.
12.3.1.1.1. Outfall Pond Building (HCA) and Diversification Gallery (HGZ)
Air Renewal
SEC [ESWS] Trains 1-4 and Circulating Water System (CRF [CWS])
For each train of SEC [ESWS] and the CRF [CWS] outfall, air renewal is ensured independently. Each SEC [ESWS] train and the CRF [CWS] outfall is equipped with a dedicated fan which provides the motive force to ensure an adequate air change rate through the associated hall, stairways and lobbies of the train.
Diversification Hall and HGZ
The diversification hall exists independently of the SEC [ESWS] trains. The room is equipped with a dedicated fan which provides the motive force to ensure an adequate air change rate through the diversification hall and its associated stairways and lobbies.
The HGZ gallery is directly connected to the diversification hall within the HCA building. The gallery is supplied with air via a dedicated fan with air being supplied to the dead- end of the HGZ gallery. Air returning naturally will be exhausted via the diversification hall extraction
Cooling
Air conditioningAPPROVED units are present in the 4 trains of SEC [ESWS] and the CRF [CWS] outfall. Heating
Heaters are provided in all parts of the HCA building in order to comply with the relevant temperature requirements. Certain heaters in the SEC [ESWS] trains and the diversification hall are classified and their electrical supplies backed up in case of Loss Of Offsite Power (LOOP).
Monitoring
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Temperature monitoring is provided in the SEC [ESWS] trains, diversification hall and HGZ gallery.
12.3.1.1.2. HOR liaison gallery (HGE)
Air Renewal
Air is drawn into the gallery from the Raw Water Supply and Storage (Basin) (HOR) building. The motive force for this is provided by an extraction fan located in the SEC [ESWS] Weir block. Air is expelled via the SEC [ESWS]weir block to the outside.
12.3.1.1.3. Technical Galleries HGx (A, B, C, D, F, G, H, I)
Air Renewal
For the ventilation of these galleries it is appropriate to consider them as pairs as they are physically connected and therefore their ventilation philosophies are linked.
The pairings are as follows:
A-F,
B-G,
C-H, and
D-I.
The motive force for the ventilation of these galleries is via extraction fans located within the escape shafts associated with the relevant Diesel Gallery (HGx A-D [DB]). Air for each of the pairs of galleries is drawn in via the mechanical pit for the associated SEC [ESWS] train within the HP building. A dedicated exhaust fan and ductwork ensures that air is always expelled to the outside via this route.
These gallery pairs are connected to a number of dead ends leading to the HCA building and Fire Fighting Water Building (HOJ). Air change is ensured within these dead ends via dedicated extraction fans that maintain air circulation.
Cooling
No cooling equipment is required within the galleries.
Heating
Heaters are provided in all escape shafts in order to maintain temperatures within their design requirements. APPROVED 12.3.1.1.4. Service Water Pump Building (HP)
Air Renewal
Air is drawn in via the inlet plenum and distributed within the entrance hall. From this hall air is distributed to the mechanical and electrical pits and onward to the galleries. These areas are detailed separately below:
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Mechanical Pit
Air enters the room through a simple duct and is expelled via extraction fans which are connected to each of the pumps.
Dependant on the operating regime the air is expelled via one of two routes. In warmer periods, air will be expelled to the outside. During cold periods air will be expelled to the entrance hall.
Electrical Pit
Air is drawn in through filters, with the motive force being provided by an extraction fan downstream. These filters avoid introduction of a marine atmosphere into the electrical rooms. Similarly to the mechanical pit, the air exhaust is operating regime dependant. In warmer periods, air will be expelled to the outside. During cold periods air will be expelled to the entrance hall.
Additional Fans
Additional fans are provided to ensure an adequate air change rate in the remaining rooms of the pumping station.
Temperature Control
In order to account for the complex heat transfer characteristics between the rooms of the HP, air conditioning units and heaters are provided. Their operation allows relevant temperature requirements to be respected. They are detailed on the functional diagrams (see section 12.5).
Monitoring
Monitoring is provided within all rooms which are subject to temperature design requirements.
Pressurisation and Smoke Extraction
In the case of fire the DVP system includes a pressurisation system to facilitate the activities of the fire team. This system pressurises the stairwells and secure corridor.
The system also encompasses a dedicated smoke extraction route for the electrical rooms.
12.3.1.2. Description of Main Equipment
The DVP system comprises the following main equipment items (see the functional diagrams provided in section 12.5): Air inletsAPPROVED and outlets: o extraction or blower fans connected to inlet or outlet plenums, and
o ventilation grilles.
Cooling:
o extractor fan connected to hood,
o blower fan, and
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o air conditioning unit.
Heating:
o space heaters or convectors controlled by room thermostats, and
o ventilation and heating system.
Temperature monitoring:
o analogue measurements.
Fire protection:
o fire dampers.
External explosion and tornado:
o anti-blast dampers.
12.3.1.3. Description of Main Layout
The pumping station is broken down into four adjacent independent trains (the Service Water Pump Building trains 1 to 4 (HPA to HPD)). It houses the SEC [ESWS] system, the CFI [CWFS] system, the Intake Coarse Filtration and Trash Removal System (SEF) (trains 1 to 4) and the SRU [UCWS] system (trains 1 and 4) supporting the Nuclear Island (NI) systems: Component Cooling Water System (RRI [CCWS]), Containment Heat Removal System (EVU [CHRS]) and Fuel Pond Cooling (and Purification) System (PTR [FPCS/FPPS]) (third train), and the Conventional Island (CI) systems: the Auxiliary (Raw Water) Cooling System (SEN [ACWS]) and CRF [CWS] system (trains 2 and 3).
The SEC [ESWS] system galleries (HGF to HGI) are broken down into four cable chases, which connect the HP and the HCA building with the NI buildings. The diesel generator galleries (HGA to HGD) connect the HD [DB] buildings with galleries HGF to HGI. These galleries correspond to each pumping station train.
The HCA building contains equipment for releasing the cooling water (from the NI and CI) into the sea. The HCA building is divided into six adjacent independent volumes to be air- conditioned:
Four physically separated volumes (divisions) dedicated to the SEC [ESWS] system (trains 1 to 4) and the SRU [UCWS] system (trains 1 and 4).
One volume dedicated to the CRF [CWS] system and SEN [ACWS] systems (trains 2 and 3),APPROVED One volume dedicated to the diversification gallery for the SEC [ESWS] and SRU [UCWS] systems.
The description of the HCB will be provided at a later stage.
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12.3.1.4. Description of System I&C
The DVP system has safety classified I&C and there will be specific reliability/availability requirements associated with the safety class of I&C architecture. It should further be clarified what is dedicated versus non-dedicated.
12.3.2. Operation
12.3.2.1. System Normal Operation
The DVP system operates independently of the plant state. During normal plant operating conditions, as well as fault conditions (PCC-2 to PCC-4, DEC-A and DEC-B), the operation of the DVP system depends on the room temperature and the status of the actuators in the pumping station and discharge structure:
The air renewal operates continuously.
The air cooling ventilation and the heating (including the CFI [CWFS] ventilation heater) operate automatically; operation is controlled by room temperature sensors.
The SEC [ESWS] shaft ventilation is also controlled by the SEC [ESWS] pump state, and is stopped before start-up of the space heater.
The air conditioning units are in continuous service and operate independently.
The SEC [ESWS] and SEN ventilation, and air renewal of the electrical rooms are aligned seasonally to evacuate the air extracted:
o during “summer” load conditions, towards the outside of the building; and
o during “winter” load conditions, towards the hall (to recycle the extracted heat).
Air Exchange
Air exchange ventilation systems operate on a permanent basis and ensure a minimum air exchange rate of { SCI removed } for all rooms and galleries.
The electrical rooms are maintained at an overpressure of { SCI removed } Pa by the air supply fan.
12.3.2.2. System Transient Operation
High Temperature within the Rooms Housing Safety Classified Equipment
In the event of the maximum room temperature set point (Tmax) in a room housing safety classified equipmentAPPROVED being reached, an alarm is transmitted to the Main Control Room (MCR). Then manual shutdown of non-safety classified equipment should decrease the room temperature in the rooms housing safety classified equipment. Otherwise, the safety classified equipment will be manually switched to an available train.
Low Temperature within the Rooms Housing Safety Classified Equipment
In event of the minimum room temperature set point (Tmin) in a room housing safety classified equipment being reached, an alarm is transmitted to the MCR.
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Then manual shutdown of non-safety classified air renewal ventilation should increase the room temperature in the rooms housing safety classified equipment. Otherwise, the safety classified equipment will be manually switched to an available train.
Extreme Low Temperatures
The heating equipment in operation during "winter" load conditions is designed to cope with extreme low temperatures.
Internal Fire
The closure of fire dampers to isolate each fire safety sector and zone is automatically triggered by a Fire Detection System (JDT [FDS]) signal. The dampers also have fusible links that will passively close them, if required.
External Explosion and Tornado
The passive anti-blast dampers are automatically closed during shock waves. Once the shock wave has passed, the dampers reopen and the ventilation system resumes operation.
Loss Of Off-site Power (LOOP)
The non-safety classified equipment is not backed-up in event of LOOP. This operation condition should decrease the room temperature in the rooms housing safety classified equipment. Otherwise, the safety classified equipment is manually switched to an available train.
The fire dampers in the fire safety sectors and zones (safety functions) are emergency supplied by the Emergency Diesel Generators (EDGs).
Earthquake
In the event of damage to the non-safety classified ventilation duct, the closure of the safety classified non-return dampers avoids deterioration of the room conditions.
12.4. PRELIMINARY DESIGN SUBSTANTIATION
The level of detail of in terms of evidence of compliance with the safety requirements stated in section 0 will develop as the HPC project moves from basic design into detailed design since the PCSR3 sequence and system sequence are evolving in parallel. Therefore, the level of detail presented in this section reflects the level of information available at the time of issuing the system chapters.
12.4.1. Compliance with Safety Functional Requirements 12.4.1.1. ControlAPPROVED of Fuel Reactivity Not applicable: the DVP system does not directly contribute to the MSF of control of fuel reactivity.
12.4.1.2. Fuel Heat Removal
Not applicable: the DVP system does not directly contribute to the MSF of fuel heat removal.
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12.4.1.3. Confinement of Radioactive Material
Not applicable: the DVP system does not directly contribute to the MSF of confinement of radioactive material.
12.4.1.4. Support Contribution to Main Safety Functions
The design assumptions of the DVP system stated in section 12.2.2 are consistent with the requirements of the corresponding systems/equipment items which it supports:
The maximum temperature to be maintained in the HP, HG galleries, the HCA building, which has been used in the sizing of the system, corresponds to the maximum permissible temperature in which the safety classified systems will still be able to operate.
The minimum temperature to be maintained in the HP, the HG galleries, the HCA building, which has been used in the sizing of the system, corresponds to the minimum permissible temperature in which the safety classified systems will still be able to operate.
12.4.1.5. Specific Contributions to Hazards Protection
The hazard studies of Sub-chapters 13.1 and 13.2 involving functions of the DVP system use values for the following parameters that are in keeping with the design assumptions stated in section 12.2.2:
tornado, and
extreme low temperatures.
For each hazard study concerned, these studies show that the design of these functions is such that they meet the acceptance criteria.
Tornado:
The safety classified equipment located within the HP is protected against tornado by providing isolation by closure of the anti-blast damper between the air inlets and outlets.
Extreme low temperatures:
The minimum temperature to be maintained in the HP, HCA, HG Buildings which has been used in the sizing of the system, corresponds to the minimum permissible temperature in which the safety classified systems will still be able to operate:
o All safety classified electrical or mechanical equipment within rooms with a APPROVEDfreeze risk will be compatible with a minimum permissible temperature. These elements ensure that the SFRs stated in section 12.0.2 are met.
12.4.1.6. Other Safety Functions to be performed in the Preventive Line of Defence
Other safety functions to be performed in the preventive line of defence involving the DVP system uses values for the following parameters that are in keeping with the design assumptions stated in section 2.2:
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Monitoring:
The DVP system provides continuous monitoring of the room air temperature and alerts main control room staff if an upper or lower temperature limit has been reached, to ensure that the temperature remains within the range for the correct functioning of the safety classified equipment housed within the HP and outfall structure rooms. Values for temperature alarm set points will be defined as part of the detailed design.
12.4.2. Compliance with Design Requirements
The DVP system complies with the requirements stated in sections 12.0.4 and 12.0.5, particularly with respect to those detailed in the following sections.
12.4.2.1. Requirements arising from Safety Classification
12.4.2.1.1. Safety Classification
The compliance of the design and manufacture of DVP system materials and equipment performing a safety-related function with requirements from the classification rules (see Sub-chapter 3.2, section 7) is presented in section 12.4.2.4.1.
12.4.2.1.2. Single Failure Criterion and Redundancy
The design of the DVP system meets the requirements of the active SFC stated in section 12.0.4.1, in particular in respect of the following:
The physical separation of the ventilation system between four divisions allows the SFC to be met for heating and cooling SEC [ESWS] and CFI [CWFS] safety equipment in the HP building.
12.4.2.1.3. Robustness against LOOP
The design of the DVP system complies with the emergency power supply requirement stated in section 12.0.4.1, in particular in respect of the following:
Loss Of Offsite Power (LOOP)
The cooling HVAC systems with safety classified functions, which are required to maintain temperatures for the availability and protection of safety classified equipment which is backed- up by EDGs, are also backed-up by the EDGs.
12.4.2.1.4. Physical Separation
The DVP system is designed in accordance with the physical separation requirement stated in section 12.0.4.1,APPROVED in particular in respect of the following: The DVP system is divided into four trains which are:
segregated (i.e. geographically / physically independent);
supplied from independent (geographically / physically) electrical boards; and
controlled from independent (geographically / physically) I&C cabinets.
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12.4.2.2. System Protection against Hazards
12.4.2.2.1. Internal Hazards
The overall demonstration of the robustness of the plant to internal hazards is covered in Sub-chapter 13.2.
The design of the DVP system complies with the internal hazard protection requirements stated in Sub-chapter 13.2 in particular in respect of those in Section 9.4.12 – Table 1.
SECTION 9.4.12 – TABLE 1 : INTERNAL HAZARD PROTECTION REQUI9REMENTS FOR THE DVP SYSTEM
Protection General protection Specific protection Internal hazards required in introduced in the design principle of the system Ruptures of piping Failures of tanks, pumps and valves Internal missiles Detailed verification of the system protection against these hazards will Dropped loads be performed as part of the detailed design. Internal explosion Fire Internal flooding
12.4.2.2.2. External Hazards
The overall demonstration of the robustness of the plant to external hazards is covered in Sub-chapter 13.1.
The design of the DVP system complies with the external hazard protection requirements stated in Sub-chapter 13.1 in particular in respect of those in Section 9.4.12 – Table 2.
SECTION 9.4.12 – TABLE 2 : EXTERNAL HAZARD PROTECTION REQUI9REMENTS FOR THE DVP SYSTEM
Protection Specific protection introduced External hazards required in General protection in the design of the system principle Earthquake Aircraft crashAPPROVED External explosion Detailed verification of the system protection against these hazards will External fire be performed as part of the detailed design. External flooding Snow and wind
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Protection Specific protection introduced External hazards required in General protection in the design of the system principle Extreme cold Detailed verification of the system protection against these hazards will Lightning and EMI be performed as part of the detailed design. UHS Hazards
12.4.2.3. Diversity
Not applicable.
12.4.2.4. Requirements defined at the Component Level
12.4.2.4.1. General Mechanical, Electrical and I&C requirements
The components of the DVP system equipment performing a safety-related function comply with the general mechanical, electrical, and I&C requirements stated in section 12.0.5.1 as detailed in Section 9.4.12 – Table 3.
SECTION 9.4.12 – TABLE 3: SAFETY CLASSSIFICATION AND DESIGN REQUIREMENTS OF COMPONENTS OF THE DVP SYSTEM
Safety Description Design requirements classification Mechanical requirement for pressure Highest Highest retaining safety safety Seismic Electrical I&C components or function class of requirement requirement requirement leaktightness category SFG requirement for HVAC component SEC [ESWS] shaft B 2 NT SC1 C2 C2 ventilation CFI [CWFS] B 2 NT SC1 C2 C2 ventilation SEC [ESWS] shaft air B 2 - SC1 C2 C2 conditioning CFI [CWFS] APPROVED air B 2 - SC1 C2 C2 conditioning SEC [ESWS] B 2 - SC1 C2 C2 shaft heaters CFI [CWFS] B 2 - SC1 C2 C2 heaters
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NT = No air-tightness requirement meaning air-tightness at minimum level provided by usual component without gasket.
12.4.2.4.2. Seismic Requirements
The DVP system complies with the seismic qualification requirements listed in Section 9.4.12 – Table 3.
12.4.2.4.3. HIC Requirements
Not applicable.
12.4.2.4.4. Specific I&C Requirements
Not applicable.
12.4.3. Examination, Maintenance, In-Service Inspection and Testing (EMIT)
12.4.3.1. Start-up Tests
The DVP system is subject to a start-up test programme in accordance with the procedures set out in Chapter 20 “Commissioning” serving to verify the fulfilment of the following SFRs:
Ensure a room air temperature higher than minimum room air temperature in all fault conditions in order to ensure an air temperature compatible with safety classified equipment operation:
o Start-up and minimum power of the heating equipment of the HP (and HCA building).
Ensure an room air temperature lower than maximum room air temperature in all fault conditions in order to ensure an air temperature compatible with safety classified equipment operation:
o Start-up and minimum flow rate of the ventilation of the HP; and
o Start-up and minimum power of the air conditioning units of the HP.
The DVP system must monitor the air room temperature in order to prevent a failure of the DVP equipment.
o The DVP room air temperature sensors will be subjected to start-up tests to check their availability. 12.4.3.2. In-APPROVEDService Inspection The following functions of the DVP system are used during normal plant operation under conditions representative of the fault/hazard conditions in which they are required:
safety classified cooling ventilation,
safety classified air conditioning units, and
safety classified heating.
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Tests are carried out during plant operation. They are conducted on each train successively, rather than simultaneously.
Clogging of the filters is regularly checked.
The air conditioning units are serviced in accordance with the manufacturer's guidelines.
The availability of these functions is thus verified as part of normal operation.
12.4.3.3. Periodic Testing
The safety classified parts of the DVP system are subject to periodic testing in accordance with the maintenance schedule in order to verify that the following SFRs are fulfilled:
Ensure an room air temperature higher than minimum room air temperature in all fault conditions in order to ensure an air temperature compatible with safety classified equipment operation:
o start-up of heating equipment.
Ensure an room air temperature lower than maximum room air temperature in all fault conditions in order to ensure an air temperature compatible with safety classified equipment operation:
o start-up of the air conditioning units, and
o start-up and minimum flow rate of the ventilation.
The DVP system must monitor the air room temperature in order to prevent a failure of the DVP equipment.
o the DVP room air temperature sensors will be subjected to periodic tests to check their availability.
12.4.3.4. Maintenance
The DVP system is subject to a maintenance programme to ensure the availability of the main components, and the safety classified components.
Preventive maintenance of the heating equipment and air treatment units is carried out during "summer" load conditions and "winter" load conditions respectively. Maintenance of other ventilation equipment in the system is carried out at the same time as the maintenance of the associated SEC [ESWS] train for the pumping station. 12.5. FUNCTIONALAPPROVED DIAGRAM The functional diagram of the DVP system for pumping station is shown in Section 9.4.12 – Figure 1. This gives a schematic overview of the pumping station.
The functional diagram of the DVP system for the outfall building is shown in Section 9.4.12 – Figure 2 and gives a schematic overview of the outfall building.
The functional diagram of the DVP system for the classified galleries is shown in Section 9.4.12 – Figure 3 and provides a schematic overview of the classified galleries.
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Note: this section does not provide a schematic overview of the HCB because the DVP system is not designed yet in this building.
13. VENTILATION OF THE EFFLUENT TREATMENT BUILDING HQA AND HQB (9DWQ [ETBVS])
The Ventilation System of the controlled area of the Radioactive Waste Buildings (Effluent Treatment Building Ventilation System (DWQ [ETBVS])) is the 9DWQ [ETBVS] system for the Radioactive Waste Storage Building (HQA) and the Radioactive Waste Process Building (HQB) and the 2DWQ [ETBVS] system for the Radioactive Waste Treatment Building (HQC). As the 2DWQ [ETBVS] system design is not sufficiently mature at this stage and the 2DWQ [ETBVS] system architecture to be similar to the 9DWQ [ETBVS] system due to similarities in the building’s operation, this sub-chapter only covers the 9DWQ [ETBVS] system.
The information reported in this section is, unless otherwise noted, consistent with the reference design, as referenced from Chapter 22.
13.0. SAFETY REQUIREMENTS
The UK EPR Safety Classification principles and the top-down functional approach are presented in Sub-chapter 3.2. These principles help to ensure that the plant is designed, manufactured, constructed, commissioned and operated so that the appropriate level of reliability and integrity is achieved for its Structures, Systems and Components (SSCs).
The Hinkley Point C (HPC) functional safety analyses and the application of these safety classification principles to the HPC reference design result in the identification of the safety requirements for all safety systems in accordance with the Safety Functional Requirements Notes (SFRNs) referenced from Sub-chapter 3.2.
This section summarises the results of these safety analyses and specifies the safety requirements that apply to the design of the 9DWQ [ETBVS] system.
The requirements described in the present section are consistent with safety functions to which contribute 9DWQ [ETBVS] system in Plant Condition Category (PCC) and Design Extension Conditions (DEC). Consistency with requirements inherited from the Design Basis Initiating Faults (DBIFs) should be checked when the list of DBIFs evolves (see Chapter 15).
13.0.1. Safety Functions
The three Main Safety Functions (MSFs) necessary to achieve the overall safety objective of protecting people and the environment from the harmful effects of ionising radiation are: controlAPPROVED of fuel reactivity, fuel heat removal, and
confinement of radioactive material.
These three main safety functions must be achieved during:
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normal operating conditions (PCC-1), including duty functions, control of radioactive release during normal operating conditions, control of main plant parameters, fault initial conditions, Limiting Conditions of Operation (LCOs), limitations, monitoring functions, Probabilistic Safety Assessment (PSA) significant functions as part of the preventive line of defence;
fault conditions (PCC-2 to PCC-4, DEC-A and any equivalent DBIFs) and DEC-B; and
hazard conditions.
13.0.1.1. Control of Fuel Reactivity
The 9DWQ [ETBVS] system does not directly contribute to the MSF of control of fuel reactivity.
13.0.1.2. Fuel Heat Removal
The 9DWQ [ETBVS] system does not directly contribute to the MSF of fuel heat removal.
13.0.1.3. Confinement of Radioactive Material
The 9DWQ [ETBVS] system must contribute to the achievement of the MSF of confinement of radioactive material as follows:
Environmental protection:
The 9DWQ [ETBVS] system carries gaseous fluids containing radioactive material. As such, it must contribute to:
o the confinement of this material with respect to the environment as a whole and to the public;
o the control and reduction of radioactive waste discharges under normal operation; and
o the prevention of minor radioactive release following a mechanical failure.
Limiting radiological consequences:
o The 9DWQ [ETBVS] system must contribute to the static containment of the controlled area of the HQA and HQB buildings in the event of multiple failure of systems in the HQA and HQB buildings following an earthquake (PCC-4 and equivalent DBIFs).
13.0.1.4. Support Contribution to Main Safety Functions The 9DWQ [ETBVS]APPROVED system does not indirectly contribute to the three MSFs. 13.0.1.5. Specific Contribution to Hazard Protection
The 9DWQ [ETBVS] system must contribute directly to the safety functions that are part of the facility's hazards protection as follows:
static confinement of the controlled area of the HQA and HQB buildings following an external explosion; and
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preservation of Seismic Requirement levels (SC1) Safety Features (SFs) availability following a seismic event.
13.0.1.6. Other Safety Functions to be performed in the Preventive Line of Defence
The 9DWQ [ETBVS] system does not contribute to other safety functions to be performed in the preventive line of defence.
13.0.2. Safety Functional Requirements
13.0.2.1. Control of Fuel Reactivity
Not applicable: the 9DWQ [ETBVS] system does not directly contribute to the MSF of control of fuel reactivity.
13.0.2.2. Fuel Heat Removal
Not applicable: the 9DWQ [ETBVS] system does not directly contribute to the MSF of fuel heat removal.
13.0.2.3. Confinement of Radioactive Material
With respect to its contribution to the MSF of confinement of radioactive material, the 9DWQ [ETBVS] system must satisfy the following Safety Functional Requirements (SFRs):
Environmental protection:
The 9DWQ [ETBVS] system must:
o contain the radioactive material and prevent the risk of leaks;
o limit radioactive discharges to the environment through sufficient filtration of the gaseous effluent conveyed; and
o prevent minor release of radioactivity following a mechanical failure by ensuring that all components which contribute to this requirement are designed to meet the sufficient mechanical requirement in accordance with Sub-chapter 3.2, section 7.
Limiting radiological consequences:
o The 9DWQ [ETBVS] system must ensure the isolation of the air openings to meet the static air tightness requirements of the HQA and HQB buildings in the event of multiple failure of systems in the HQA and HQB buildings following an APPROVEDearthquake (PCC-4 and equivalent DBIFs). The 9DWQ [ETBVS] system must ensure compliance with the requirements defined for the radioactive gaseous waste in the waste discharge specifications.
13.0.2.4. Support Contribution to Main Safety Functions
Not applicable: the 9DWQ [ETBVS] system does not indirectly contribute to the three MSFs.
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13.0.2.5. Specific Contribution to Hazards Protection
With respect to its specific contribution to the safety functions that are part of the facility hazards protection, the 9DWQ [ETBVS] system must satisfy the following SFRs:
ensure the isolation of the air openings to meet the static air tightness requirements of the HQA and HQB buildings following an external explosion;
protection of system components required in the fulfilment of the MSFs in the HQA and HQB buildings in the event of an earthquake, and
part of the 9DWQ [ETBVS] system has a design requirement of SC2 in order to prevent minor radioactive release following multiple failures after earthquake.
13.0.2.6. Other Safety Functions to be performed in the Preventive Line of Defence
Not applicable: the 9DWQ [ETBVS] system does not contribute to other safety functions to be performed in the preventive line of defence.
13.0.3. Safety Features
Section 9.4.13 – Table 1 presents the SFs of the 9DWQ [ETBVS] system according to the contributions identified in section 13.0.1 and the SFRNs referenced in Sub-chapter 3.2.
13.0.4. Classification and Architecture Requirements of Safety Features
13.0.4.1. Requirements arising from Safety Classification
Architecture requirements associated with SFs are essential for designing robust lines of defence consistent with their importance to nuclear safety (see Sub-chapter 3.2). Such requirements strengthen the system design against:
single faults and associated consequences (Single Failure Criterion (SFC)) by requiring redundancy;
Loss Of Offsite Power (LOOP) by requiring, among others, a back-up power supply;
Station Black Out (SBO) by requiring a power supply by the Ultimate Diesel Generators (UDGs);
Common Cause Failures (CCFs) by requiring physical separation;
earthquake by defining seismic requirements; and accidentAPPROVED conditions by defining qualification requirements. Section 9.4.13 – Table 1 presents the requirements arising from safety classifications for the 9DWQ [ETBVS] system, according to the SFRNs referenced in Sub-chapter 3.2.
13.0.4.2. System Protection against Hazards
13.0.4.2.1. Internal Hazards
The 9DWQ [ETBVS] system is not required to be protected against internal hazards.
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13.0.4.2.2. External Hazards
The Safety Features of the 9DWQ [ETBVS] system must be protected against external hazards if those hazards challenge the safety objectives, as defined in Sub-chapter 13.1.
13.0.4.3. Diversity
The 9DWQ [ETBVS] system is not subject to the requirement for diversity.
13.0.5. Requirements defined at the Component Level
13.0.5.1. Generic Safety Requirements
13.0.5.1.1. Generic Mechanical, Electrical and Instrumentation & Control (I&C) Requirements
The mechanical components within the 9DWQ [ETBVS] system must comply with the mechanical requirements in accordance with the rules laid out in Sub-chapter 3.2, section 7. The level of requirement is dependent upon whether or not it is a pressure retaining component, the safety class of the component, whether the component acts as an isolating device between interfacing safety features, and on the role of the component as a barrier to the potential release of radioactivity as a result of failure of the component.
The electrical and Instrumentation and Control (I&C) components in the 9DWQ [ETBVS] system must comply with the electrical and I&C requirements associated with their safety class, in accordance with the rules laid out in Sub-chapter 3.2.
13.0.5.1.2. Seismic Requirements
The level of seismic requirements to be applied to the 9DWQ [ETBVS] system components is related to the safety feature group to which the component belongs, and the consequences on other classified components of its failure, if it were not seismically qualified. The rules for defining the seismic requirements for a component are identified in Sub-chapter 3.2.
13.0.5.1.3. Qualification for Accident Conditions
The safety classified parts of the 9DWQ [ETBVS] system must be qualified for the operating conditions in which they are required, as specified in Sub-chapter 3.6.
13.0.5.2. Specific Safety Requirements
13.0.5.2.1. High Integrity Component (HIC) Requirements
The 9DWQ [ETBVS] system is not subject to any High Integrity Component (HIC) requirements. 13.0.5.2.2. SpecificAPPROVED I&C Requirements The 9DWQ [ETBVS] system is not subject to any specific I&C requirements; the 9DWQ [ETBVS] system does not have any dedicated I&C. The general approach for I&C systems is set out in Chapter 7.
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13.0.6. Examination, Maintenance, (In-service) Inspection and Testing (EMIT)
13.0.6.1. Start-up Tests
The 9DWQ [ETBVS] system must be designed to enable the performance of start-up tests to ensure the adequacy of its design and performance under conditions as representative as possible of the different operating configurations, and in particular its compliance with the SFRs assigned to it in section 13.0.2.
13.0.6.2. In-service Inspection
The 9DWQ [ETBVS] system must be designed to enable surveillance under normal operation of the system characteristics necessary for the fulfilment of its safety-related tasks in order to ensure the performance of its components, and their availability under normal operation, or in the event of a fault or accident.
13.0.6.3. Periodic Testing
The safety classified components of the 9DWQ [ETBVS] system must be designed to enable the performance of periodic tests in accordance with the maintenance schedule.
13.0.6.4. Maintenance
The 9DWQ [ETBVS] system must be designed to enable the implementation of a maintenance schedule (see Sub-chapter 18.2).
13.1. ROLE OF THE SYSTEM
The 9DWQ [ETBVS] system performs the following functions (or tasks) under the different plant operating conditions for which it is required:
13.1.1. Normal Operating Conditions
The Effluent Treatment Building Ventilation System (9DWQ [ETBVS]) operates continuously. It is designed for the following purposes:
to maintain the ambient (indoor) conditions in the HQA and HQB buildings within prescribed limits for the correct operation of equipment and / or staff in normal operation (air supply, filtration, heating and cooling);
to ensure during normal operation that contamination is contained at source to avoid its spreading from potentially contaminated areas to potentially less contaminated areas;
to ensure, during normal operation, that the exhaust air from the 9DWQ [ETBVS] system for the contaminated part of the controlled area of the HQA and HQB buildings is adequatelyAPPROVED filtered; and to limit the concentration of aerosols and radioactive gases in the atmosphere of the HQA and HQB building rooms.
13.1.2. Fault and Hazard Conditions
The 9DWQ [ETBVS] system contributes to:
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The static containment of the controlled area of the HQA and HQB buildings in the event of multiple failure of systems in the HQA and HQB buildings following an earthquake (PCC-4 and equivalent DBIFs).
The static confinement of the HQA and HQB buildings following an external explosion.
13.2. DESIGN BASIS
13.2.1. General Assumptions
The 9DWQ [ETBVS] system is designed to:
maintain ambient (indoor) conditions necessary for the correct operation of the equipment and / or for staff access (temperature, radioactivity and concentration of aerosols) in the contaminated part of the controlled area of the HQA and HQB buildings by means of a ventilation system composed of two supply and extraction lines (2 x 100% in terms of availability);
ensure the confinement of radioactive material; and
limit the radioactivity discharged from the contaminated part of the controlled area of the HQA and HQB buildings into the environment during normal operation by two filtration lines (2 x 100% in terms of availability) and two iodine adsorption lines (2 x { SCI removed }).
13.2.2. Design Assumptions
13.2.2.1. Control of Fuel Reactivity
Not applicable: the 9DWQ [ETBVS] system does not directly contribute to the MSF of control of fuel reactivity.
13.2.2.2. Fuel Heat Removal
Not applicable: the 9DWQ [ETBVS] system does not directly contribute to the MSF of fuel heat removal.
13.2.2.3. Confinement of Radioactive Material
Environmental Protection:
During normal operation, the 9DWQ [ETBVS] system must contribute to the confinement of radioactive material and prevent risk of leaks by:
o maintaining a negative pressure in the contaminated part of the controlled area APPROVEDof the HQA and HQB buildings relative to the atmospheric pressure, and
o providing a pressure differential of at least { SCI removed } Pa between rooms (or groups of rooms) with risk of iodine contamination and the adjacent rooms by manual adjustment of the balancing dampers during commissioning.
During normal operation, the 9DWQ [ETBVS] system must contribute to limiting the radioactivity of the air discharged into the stack. The filtration safety requirements for this criterion are:
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o High Efficiency Particulate Air (HEPA) filters: decontamination factor as defined in section 1.2.4; and
o iodine traps: decontamination factor greater than { SCI removed } (efficiency { SCI removed }) and relative humidity less than { SCI removed }
The 9DWQ [ETBVS] system must ensure that all system components whose mechanical failure could lead to minor release of radioactivity are mechanically classed M3 / T3.
Limiting Radiological Consequences:
Following an earthquake, the 9DWQ [ETBVS] system must ensure that the isolation of air openings meets the air-tightness requirements stated in Sub-chapter 9.4.1.
The 9DWQ [ETBVS] system iodine line heaters are designed assuming:
o a maximum air inlet temperature of { SCI removed },
o a relative humidity of { SCI removed }, and
o an air temperature of { SCI removed } and RH of { SCI removed } after the iodine heater.
13.2.2.4. Support Contribution to Main Safety Functions
Not applicable: the 9DWQ [ETBVS] system does not indirectly contribute to the three MSFs.
13.2.2.5. Specific Contribution to Hazards Protection
In order to contribute to the static confinement of the HQA and HQB buildings against external explosion, the 9DWQ [ETBVS] system is designed to withstand the load case defined in Sub-chapter 13.1, section 4.
In order to contribute to the preservation of SC1 SFs availability following a seismic event, the 9DWQ [ETBVS] system components are required to be seismically classed SC2.
13.2.2.6. Other Safety Functions to be performed in the Preventive Line of Defence
Not applicable: the 9DWQ [ETBVS] system does not contribute to the other safety functions in the preventive line of defence.
13.2.3. Other Assumptions
13.2.3.1. Air Supply Conditions Under designAPPROVED basis conditions, the required air supply temperatures in the 9DWQ [ETBVS] system are as follows:
Summer: { SCI removed };
Winter: { SCI removed } under long duration temperature for winter (see section 1.1.1.2);
{ SCI removed } under short duration temperature for winter (see section 1) ({ SCI removed } for the Liquid Waste Processing System (9TEU [LWPS]) evaporator rooms).
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13.2.3.2. Atmospheric Conditions
See section 1.1.1.1.
13.2.3.3. Environmental Conditions
See Section 9.4.1 – Table 1.
The following rooms are subject to specific environmental conditions:
the concrete manufacturing room temperature will be maintained above { SCI removed },
the drum storage hall temperature will be maintained above { SCI removed }, and
the 9TEU [LWPS] system evaporator rooms temperature will be maintained above { SCI removed }.
13.2.3.4. Auxiliary Fluids
During summer the air supply in the 9DWQ [ETBVS] system is cooled by cooling coils supplied by the Chilled Water System for the Effluent Treatment Buildings (HQA, HQB) (9DEQ).
During winter the air supply in the 9DWQ [ETBVS] system is heated by the heating coils supplied by the Electrically Heated Hot Water System (9SEL).
13.2.3.5. Materials
The main distribution and exhaust air ducts are made of concrete with decontaminable finish.
Other supply and exhaust air ducts are made of galvanised metal sheet.
Airtight exhaust air ducts are made of carbon steel welded with decontaminable finish.
Components up to the first heater on the supply line are resistant against saline environment.
Pipes connected to the atmospheric buffer tank and the outside are resistant against saline environment.
13.2.3.6. Air Tightness
All ducts and components, starting at the injection point for the filter testing up to and including the exhaust fans, will fulfil the normal (T3) air tightness requirements (see Sub-chapterAPPROVED 3.2, section 7). All ducts and components, in the iodine line have to fulfil the normal (T3) air tightness requirement.
13.2.3.7. Minimum Air Renewal Rates
See section 1.2.
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The following rooms are subjected to specific air renewal rates:
The drum storage room is in a controlled area without any risk of contamination. The air renewal rate in this room is { SCI removed }.
The 9DEQ system room requires a supplementary air flow and a different air removal rate due to the presence of refrigerant (R134a) in the cooling unit.
The purge system is installed and activated for emergency situations and will only be called upon when the refrigerant concentration in the monitored room exceeds the pre-set value.
13.2.3.8. Extraction Characteristics for the Controlled and Contaminated Area
In the controlled and contaminated area, the exhaust conditions are as follows:
all the air extracted by the 9DWQ [ETBVS] system from the contaminated part of the controlled area is filtered, then directed towards the main unit vent stack, where it is monitored before it is discharged into environment;
air extracted from the contaminated part of the controlled area rooms of the HQA and HQB buildings by the 9DWQ [ETBVS] system may be directed through the iodine lines if necessary;
the transfer of the extracted air of the 9DWQ [ETBVS] system is from less contaminated rooms to more contaminated rooms; and
the air extraction rate is greater than the air supply rate in order to ensure that the contaminated part of the controlled area remains under negative pressure relative to the atmosphere.
13.2.3.9. Facilities Specifically ventilated by the 9DWQ [ETBVS] System
The 9DWQ [ETBVS] system provides the ventilation and air conditioning for:
the compacting press hood, the mobile mercury encapsulation unit and the shredder of the Solid Waste Treatment System (TES [SWTS]);
the non-condensable gas of the TEU [LWPS] system; and
the glove boxes of the Effluent Treatment Building Sampling System (9TEN).
13.2.4. Assumptions associated with Extreme Situations Resulting from Beyond Design Basis Hazards
13.2.4.1. AssumptionsAPPROVED associated with Fukushima Provisions
The 9DWQ [ETBVS] system is not subject to assumptions associated with Fukushima provisions.
13.2.4.2. Assumptions associated with other non-Fukushima Provisions
The 9DWQ [ETBVS] system is not subject to assumptions associated with non-Fukushima provisions.
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13.3. SYSTEM DESCRIPTION AND OPERATION
13.3.1. Description
13.3.1.1. General System Description
The 9DWQ [ETBVS] system functional flow diagrams are shown in Section 9.4.13 – Figures 1 to 4.
The 9DWQ [ETBVS] system supplies air to three parts of the HQA and HQB buildings:
the contaminated part of the controlled area,
the uncontrolled area, and
the storage area.
The 9DWQ [ETBVS] system for the contaminated part of the controlled area is made up of an air supply unit, an air extraction unit with permanent filtration via HEPA filters, an iodine adsorption unit, a network of air supply and extraction ducts. The ventilation of the non- controlled and storage area does not provide function of effluent filtration since it serves non- contaminated zones of the building.
The 9DWQ [ETBVS] system for the contaminated part of the controlled area air supply unit is made up of the following elements:
an external air inlet with weather louvre with a bird mesh,
a concrete air intake plenum, and
two parallel conditioning lines (2 x 100%), each fitted with:
o a pre-heating coil supplied by the 9SEL system,
o a two-stage filtering (class coarse filter, fine filter),
o a cooling coil supplied with the 9DEQ system,
o a heating coil supplied by the 9SEL system,
o an automatic supply air flow rate control damper, and
o a centrifugal type air supply fan.
The 9DWQ [ETBVS] system continuous air extraction unit with the HEPA filters comprises the following compAPPROVEDonents:
Two air extraction lines (also referred to as “normal air extraction lines”) in parallel (2 x 100%), each fitted with:
o an automatic extraction air flow rate control damper,
o four pre-filters and four HEPA filters mounted in parallel (4 x { SCI removed }), and
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o a centrifugal type air extract fan.
A concrete duct is common to the two extraction lines up to the Nuclear Auxiliary Building (HN [NAB]).
The 9DWQ [ETBVS] system iodine adsorption unit comprises the following elements:
a plenum, and
two iodine adsorption lines in parallel (2 x { SCI removed }), each fitted with:
o a motorised damper enabling a switch to the iodine adsorption line,
o an automatic isolation damper,
o an electric heater,
o two iodine adsorption units (2 x { SCI removed }) with fire dampers downstream and upstream and fitted with a spray ring powered by the Protection and Distribution of the Nuclear Island Protection and Fire-Fighting Water Distribution System (9JPI [NIFPS]), and
o a booster centrifugal fan.
Local convectors, air heaters or fan heaters may be used locally to supplement heating in the controlled area rooms.
Local cooling units in controlled area rooms may be used to supplement the supply, in order to ensure the cooling duty.
13.3.1.2. Description of Main Equipment
The 9DWQ [ETBVS] system comprises the main equipment items detailed in the following sections (see the functional diagram provided in Section 9.4.13 – Figures 1 to 4).
13.3.1.2.1. Air Supply Lines
Isolation Dampers:
The air supply lines isolation dampers air tightness requirements are specified in section 13.2.3.6.
Pre-heating Coils:
Pre-heating coils are positioned downstream of the air inlet dampers in order to maintain an air temperature aboveAPPROVED { SCI removed } downstream of these coils with an air intake temperature of { SCI removed }.
Cooling Coils:
Cooling coils are positioned upstream of the air supply fans in order to cool the air, if required. Cooling coils ensure an air supply temperature of { SCI removed } in the controlled area.
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Heating Coils:
Heating coils are positioned upstream the air supply fans in order to heat the air, if required. Heating coils ensure an air supply temperature of { SCI removed } during long duration winter conditions and are able to deliver air supply temperature of { SCI removed } during short duration winter conditions in the controlled area.
Air Supply Fans:
The air supply fans air flow rate is adjusted to maintain negative pressure in the building.
13.3.1.2.2. Air Extraction Lines
HEPA Filters:
The efficiency of the HEPA filters of the contaminated part of the controlled area ventilation air extraction lines is specified in section 1.2.4.
Air Extraction Fans:
The air extraction fans air flow rate is adjusted to maintain a constant air flow rate through the HEPA filters.
Iodine Adsorption Lines:
The two iodine adsorption lines are each fitted with:
an electric heater to heat the air to reduce the relative humidity to below { SCI removed } prior to it being admitted to the iodine traps as excessive humidity in the air will reduce the efficiency of the traps;
iodine traps with an efficiency as specified in section 1.2.4; and
the iodine lines booster fans provide the necessary pressure to overcome the additional resistance of the iodine lines.
13.3.1.3. Description of Main Layout
No specific layout provisions are necessary for the 9DWQ [ETBVS] system.
13.3.1.4. Description of the System I&C
Not applicable: the 9DWQ [ETBVS] system does not have any dedicated I&C. The control of all functions and sub-functions of the 9DWQ [ETBVS] system are ensured by the Process Automation System (PAS). Only the position indication for the building isolation dampers at air intake and at APPROVED main unit vent stack extraction are included in the Safety Automation System (SAS) (as these dampers are seismically classified SC1).
13.3.2. Operation
13.3.2.1. System Normal Operation
The 9DWQ [ETBVS] system is normally used when the plant is in operation as well as during outages.
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13.3.2.1.1. Plant in Normal Operation, Iodine Absent
The 9DWQ [ETBVS] system operates as follows:
intake of fresh air from the outside via the air intake louvres;
air conditioning supply via one of the two 100% supply lines (the choice of active lines is made by the operators according to their availability);
distribution and collection of the air in all contaminated parts of the controlled areas covered by the 9DWQ [ETBVS] system;
exhaust air is filtered by the main filtering lines:
o The lines operate in normal configuration in 2 x { SCI removed } for cell extraction and filtration with a shared extraction system on one of the two fans (always operating at 100%) but they are designed in 2 x 100% to provide filtration of the entire flow in the event of unavailability of one of the lines.
o Line 1 is dedicated to filtering of cell 1 (TES [SWTS] system process room).
o Line 2 is dedicated to filtering of cell 2 (TEU [LWPS] system process room).
o Separation into two cells with equivalent flow is carried out so as to allow switchover of either cell to use the iodine adsorption unit.
Discharge to the main unit vent stack via 100% extraction fans.
13.3.2.1.2. Plant in Normal Operation, Iodine Present
The 9DWQ [ETBVS] system operates normally in terms of air conditioning and supply operation; however, the air extraction side operates in line with the control strategy given below:
Switchover from an extraction line to an iodine adsorption line:
o The dampers of the main extraction line are closed and the bypass dampers in the iodine adsorption unit open.
o Two iodine adsorption lines (2 x { SCI removed }) are required to allow adsorption of { SCI removed } of the total exhaust air.
o The “booster” fan is started in order to ensure the air movement along the iodine adsorption line and to route the air to the plenum upstream of the main extraction fans. The pressure rise provided by the booster fan corresponds only to the APPROVEDresistance of the iodine fan ductwork system. Discharge of the air from the contaminated part of the controlled area rooms and the Nuclear Auxiliary Building – Tanks Liaison Gallery (HGV) to the main unit vent stack via a 100% extraction fan.
13.3.2.2. Steady State Operating Conditions
The operation of the 9DWQ [ETBVS] system during steady state is the same as the operation of the 9DWQ [ETBVS] system during power state.
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13.3.2.3. System Transient Operation
13.3.2.3.1. Multiple Failure in the HQA and HQB Buildings due to an Earthquake
In the event of an earthquake, static containment of the HQA and HQB buildings is achieved by closing the isolation dampers in the air supply lines and the non-return dampers in the extraction lines, so as to contain the radioactivity resulting from failure of the tanks containing radioactive substances in the HQA and HQB buildings or, the formation of breaks in their connection lines.
13.3.2.3.2. Fire in the Iodine Traps
An alarm signal is raised in the event of fire in the iodine filter station. The fire dampers upstream and downstream of the affected line are closed along with the shut-down of the booster fan, to ensure the fire and smoke do not propagate outside of the fire enclosure defined by the dampers.
13.3.2.3.3. Fire inside HQA and HQB Buildings
Automatic closure of the fire dampers protecting the fire zones is initiated on the activation of a signal from the Fire Detection System (9JDT [FDS]), or passively through activation of a thermo- fusible link inside or outside a fire damper. The 9DWQ [ETBVS] system continues to operate as normal but is limited to the area not affected by the fire.
13.3.2.3.4. Loss Of Offsite Power (LOOP)
The 9DWQ [ETBVS] system is not backed up by the Emergency Diesel Generator (EDG) in the event of a LOOP. The isolation dampers close to their fail-safe closed position, thus ensuring the static containment of the HQA and HQB buildings.
13.3.2.3.5. Station Black Out (SBO)
The 9DWQ [ETBVS] system is not backed up by the UDG. The isolation dampers close to their fail-safe closed position, thus ensuring the static containment of the HQA and HQB buildings.
13.3.2.4. Other Operating Conditions
13.3.2.4.1. Full or Partial System Failure
{ This section contains SCI-only text and has been removed }
13.3.2.4.2. Failures of Interface Systems (Supply Systems and Loads)
{ This section contains SCI-only text and has been removed } 13.4. PRELIMINARYAPPROVED DESIGN SUBSTANTIATION 13.4.1. Compliance with Safety Functional Requirements
13.4.1.1. Control of Fuel Reactivity
Not applicable: the 9DWQ [ETBVS] system does not directly contribute to the MSF of control of fuel reactivity.
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13.4.1.2. Fuel Heat Removal
Not applicable: the 9DWQ [ETBVS] system does not directly contribute to the MSF of fuel heat removal.
13.4.1.3. Confinement of Radioactive Material
The 9DWQ [ETBVS] system ensures the containment of the radioactive material in normal operating conditions by:
using control dampers in order to control the negative pressure in the HQ- buildings,
routing air transfers from the potentially less contaminated rooms to the potentially more contaminated rooms,
routing the exhaust air through the HEPA filters to the HN [NAB] building stack, and
routing the exhaust air via iodine adsorption units to the stack in case of iodine presence.
The studies of radiological consequences involving the confinement function of the 9DWQ [ETBVS] system in the HQA and HQB buildings consider overall assumptions (fans operating and dampers open) compared with the assumptions related to static sealing of the HQA and HQB buildings defined in Sub-chapter 6.1, section 1.
13.4.1.4. Support Contribution to Main Safety Functions
Not applicable: the 9DWQ [ETBVS] system does not indirectly contribute to the three MSFs.
13.4.1.5. Specific Contributions to Hazards Protection
The hazard studies of Sub-chapter 13.1 involving functions of the 9DWQ [ETBVS] system use values for the following parameters that are in keeping with the design assumptions stated in section 13.2.2:
9DWQ [ETBVS] building containment dampers have to be closed to ensure that the HQA and HQB building static containment is achieved following a seismic event.
Protection of system components required in the fulfilment of the MSFs in the HQA and HQB buildings in the event of an earthquake.
External explosion.
For each hazard study concerned, these studies show that the design of these functions is such that they meet the acceptability criteria. These elementsAPPROVED ensure that the SFRs stated in section 13.0.2 are met. 13.4.1.6. Other Safety Functions to be performed in the Preventive Line of Defence
Not applicable: the 9DWQ [ETBVS] system does not contribute to other safety functions to be performed in the preventive line of defence.
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13.4.2. Compliance with Design Requirements
The 9DWQ [ETBVS] system complies with the requirements stated in sections 13.0.4 and 13.0.5 of this sub-chapter, particularly with respect to those detailed in the following sections.
13.4.2.1. Requirements arising from Safety Classification
13.4.2.1.1. Safety Classification
The compliance of the design and manufacture of the 9DWQ [ETBVS] system materials and equipment performing a safety-related function with requirements from the classification rules (see Sub-chapter 3.2, section 7) is presented below.
13.4.2.1.2. Single Failure Criterion and Redundancy
Although not subject to the application of the SFC, the main supply line, the HEPA filter line, the iodine filter line and the main exhaust of the 9DWQ [ETBVS] system serving the contaminated part of the controlled area have redundancy of availability, achieved through duplication of the isolation, temperature regulation, air supply, filtration and air extraction equipment items.
13.4.2.1.3. Robustness against LOOP
The design of the 9DWQ [ETBVS] system complies with the emergency power supply requirements stated in section 13.0.4.1, in particular in respect of the following:
9DWQ [ETBVS] system building isolation dampers are equipped with a spring type closing mechanism to ensure that the HQA and HQB building static containment is achieved following a seismic event.
13.4.2.1.4. Physical Separation
Not applicable: the 9DWQ [ETBVS] system is not subject to any requirements for physical separation.
13.4.2.2. System Protection against Hazards
13.4.2.2.1. Internal Hazards
Not applicable: the 9DWQ [ETBVS] system is not required to be protected against internal hazards.
13.4.2.2.2. External Hazards
The overall demonstration of the robustness of the plant to external hazards is covered in Sub-chapter 13.1.APPROVED 13.4.2.3. Diversity
Not applicable: The 9DWQ [ETBVS] system is not subject to the requirement for diversity.
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13.4.2.4. Requirements defined at the Component Level
13.4.2.4.1. General Mechanical, Electrical and I&C Requirements
The components of the 9DWQ [ETBVS] system performing a safety-related function comply with the general mechanical, electrical, and I&C requirements stated in section 13.0.5.1 as detailed in Section 9.4.13 – Table 2.
SECTION 9.4.13 – TABLE 2 : SAFETY CLASSIFICATION AND DESIGN REQUIREMENTS FOR COMPONENTS OF THE 9DWQ [ETBVS] SYSTEM
Safety classification Design requirements Mechanical Highest Highest requirement Description safety safety Seismic Electrical I&C for pressure function class of requirement requirement requirement retaining category SFG components Fresh air isolation C 3 T3 SC1 C3 C3 dampers Dampers downstream C 3 T3 SC1 NC NC exhaust fans HEPA filtration and C 3 T3 NC C3 C3 Iodine adsorption Regulation of ETB controlled C 3 T3 NC C3 C3 area negative pressure
13.4.2.4.2. Seismic Requirements
The 9DWQ [ETBVS] system complies with the seismic qualification requirements listed in Section 9.4.13 – Table 2.
13.4.2.4.3. HIC Requirements
Not applicable: the 9DWQ [ETBVS] system is not subject to any HIC requirements.
13.4.2.4.4. Specific I&C Requirements Not applicable:APPROVED the 9DWQ [ETBVS] system does not have any dedicated I&C. 13.4.3. Examination, Maintenance, (In-service) Inspection and Testing (EMIT)
13.4.3.1. Start-up Tests
The 9DWQ [ETBVS] system is subject to a start-up test programme in accordance with the procedures set out in Chapter 20 serving to verify the fulfilment of the following SFRs:
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closing of the building isolation dampers in the supply and exhaust line and locked- closed of the non-return dampers in the exhaust line,
maintaining the contaminated section of the HQA and HQB buildings at negative pressure,
efficiency of HEPA filters,
correct operation of the extraction fans,
controllability of the isolation dampers in the iodine lines and HEPA filter lines,
efficiency of the iodine adsorption units, and
correct operation of the heaters in the iodine lines.
13.4.3.2. In-Service Inspection
The following functions of the 9DWQ [ETBVS] system are monitored during normal operation by continuous monitoring systems:
monitoring of air supply temperatures in the main ventilation lines,
monitoring of the exhaust air for any traces of iodine on detection of which the system activates the iodine lines, and
monitoring of negative pressure in the contaminated area of the HQB building to guarantee a dynamic containment.
The availability of these functions is therefore verified by a continuous monitoring process.
13.4.3.3. Periodic Testing
The safety classified components of the 9DWQ [ETBVS] system are subject to periodic testing in accordance with the maintenance schedule in order to verify that the following SFRs are fulfilled:
closing of the building isolation dampers in the supply and exhaust line and locked- closed of the non-return dampers in the exhaust line,
maintaining the contaminated section of the HQA and HQB buildings at negative pressure,
efficiency of HEPA filters,
correctAPPROVED operation of the extraction fans,
controllability of the isolation dampers in the iodine lines and HEPA filter lines,
efficiency of the iodine adsorption units, and
correct operation of the heaters in the iodine lines.
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13.4.3.4. Maintenance
The 9DWQ [ETBVS] system is subject to a maintenance programme which will be defined at a later date.
13.5. FUNCTIONAL DIAGRAM
The functional diagrams of the 9DWQ [ETBVS] system are shown in Section 9.4.13 – Figures 1 to 4 (for more details, see the detailed mechanical diagram of the 9DWQ [ETBVS] system).
14. FUEL BUILDING VENTILATION SYSTEM (DWK [FBVS])
The information reported in this section is, unless otherwise noted, consistent with the reference design, as referenced from Chapter 22.
14.0. SAFETY REQUIREMENTS
The UK EPR Safety Classification principles and the top-down functional approach are presented in Sub-chapter 3.2. These principles help to ensure that the plant is designed, manufactured, constructed, commissioned and operated so that the appropriate level of reliability and integrity is achieved for its Structures, Systems and Components (SSCs).
The Hinkley Point C (HPC) functional safety analyses and the application of these safety classification principles to the HPC reference design result in the identification of the safety requirements for all safety systems in accordance with the Safety Functional Requirements Notes (SFRNs) referenced from Sub-chapter 3.2.
This section summarises the results of these safety analyses and specifies the safety requirements that apply to the design of the DWK [FBVS] system.
The requirements described in the present section are consistent with safety functions to which the DWK [FBVS] system contributes in Plant Condition Category (PCC) and Design Extension Conditions (DEC). Consistency with requirements inherited from the Design Basis Initiating Faults (DBIFs) should be checked when the list of DBIFs evolves (see Chapter 15).
14.0.1. Safety Functions
The three Main Safety Functions (MSFs) necessary to achieve the overall safety objective of protecting people and the environment from the harmful effects of ionising radiations are:
control of fuel reactivity, fuel heatAPPROVED removal, and confinement of radioactive material.
These three MSFs must be achieved during:
normal operating conditions (PCC-1), including duty functions, control of radioactive release during normal operating conditions, control of main plant parameters, fault initial conditions, Limiting Conditions of Operation (LCOs), limitations, monitoring functions, Probabilistic Safety Assessment (PSA) significant functions as part of the preventive line of defence;
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fault conditions (PCC-2 to PCC-4, DEC-A and any equivalent Design Basis Initiating Faults (DBIFs)) and DEC-B; and
hazard conditions.
14.0.1.1. Control of Fuel Reactivity
The DWK [FBVS] system does not directly contribute to the MSF of control of fuel reactivity.
14.0.1.2. Fuel Heat Removal
The DWK [FBVS] system does not directly contribute to the MSF of fuel heat removal.
14.0.1.3. Confinement of Radioactive Material
The DWK [FBVS] system must contribute to the achievement of the MSF of confinement of radioactive material as a frontline system as detailed in the following sections.
Environmental Protection:
The DWK [FBVS] system carries gaseous fluids containing radioactive material. As such, it must contribute:
to the confinement of this material with respect to the environment as a whole and the public; and
to the control and reduction of radioactive waste discharges under normal operation.
Limiting Radiological Consequences:
The DWK [FBVS] system must ensure:
static confinement of the fuel pool hall in case of a fuel handling accident in the Fuel Building (HK [FB]) (PCC-4 and equivalent DBIF) or loss of two main (without actuation of third) Fuel Pool Cooling (and Purification) System (PTR [FPCS/FPPS]) trains (DEC-A and DEC-B and equivalent DBIF) (see Sub-chapter 9.1, section 3);
isolation of the air supply system of the room facing the emergency airlock (HK2915ZL) in case of a fuel handling accident in the Reactor Building (HR [RB]) (PCC-4 and equivalent DBIF);
isolation of the HK [FB] building normal air supply / extraction system in case of a fault situation leading to a radioactivity discharge in the HR [RB] building (PCC-3, PCC-4, DEC-A and DEC-B and equivalent DBIF); and controlAPPROVED of negative pressure in the HK [FB] building in normal conditions. Long-term Confinement of the HK [FB] Building:
The DWK [FBVS] system must avoid an overpressure in fuel pool area in case of fuel pool boiling in order to maintain the long-term confinement of the HK [FB] building in DEC-A and DEC-B situations and equivalent DBIF.
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14.0.1.4. Support Contribution to Main Safety Functions
The DWK [FBVS] system must indirectly contribute to the MSF of control of fuel reactivity as a support system as follows:
Maintain conditions compatible with the correct operation of equipment in the following rooms:
o The Extra Boration System (RBS [EBS]) pump rooms from PCC-2 to PCC-4, DEC-A and equivalent DBIF (see Sub-chapter 6.5); and
o The RBS [EBS] system boron rooms from PCC-2 to PCC-4 and equivalent DBIF.
The DWK [FBVS] system must indirectly contribute to the MSF of confinement of radioactive material as a support system as follows:
Maintain conditions compatible with the correct operation of equipment in the following rooms:
o The Chemical and Volume Control System (RCV [CVCS]) pump rooms from PCC-2 to PCC-4 and equivalent DBIF (see Sub-chapter 9.3 section 2); and
o The RCV [CVCS] system boron rooms from PCC-2 to PCC-4 and equivalent DBIF.
14.0.1.5. Specific Contribution to Hazards Protection
The DWK [FBVS] system must contribute directly to the safety functions that are part of the facility hazards protection against the consequences of external explosion (see Sub-chapter 13.1, section 4), extreme cold (see Sub-chapter 13.1, section 6.5), fire (see Sub-chapter 13.2, section 7) and earthquake (see Sub-chapter 13.1, section 2) as follows:
limit the effects of an External Pressure Wave (EPW) inside the HK [FB] building in case of external explosion;
maintain conditions for correct operation of equipment / components containing boron in the HK [FB] building in case of extreme cold conditions;
contribution to the containment and prevention of spread of fire in the HK [FB] building; and
preservation of Seismic Requirement Levels (SC1) Safety Features (SFs) availability following a seismic event. 14.0.1.6. OtherAPPROVED Safety Functions to be performed in the Preventive Line of Defence The DWK [FBVS] system must contribute directly to other safety functions to be performed as part of the preventive line of defence as follows:
maintain conditions compatible with the correct operation of equipment in the fuel pool hall from PCC-2 to PCC-4 and equivalent DBIF;
avoid an overpressure in fuel pool area in case of fuel pool boiling in order to maintain the long-term confinement of the HK [FB] building in DEC-A and DEC-B situations and equivalent DBIF;
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monitoring of availability of heating means in the Fuel Pool Area;
monitoring of availability of heating means in the RBS [EBS] system pump rooms;
monitoring of availability of heating means in the RBS [EBS] system boron rooms;
monitoring of availability of local cooling in the RBS [EBS] system pump rooms; and
maintain conditions compatible with the correct operation of the Emergency Lighting Systems (DSK) for the HK [FB] building.
14.0.2. Safety Functional Requirements
14.0.2.1. Control of Fuel Reactivity
Not applicable: the DWK [FBVS] system does not directly contribute to the MSF of control of fuel reactivity.
14.0.2.2. Fuel Heat Removal
Not applicable: the DWK [FBVS] system does not directly contribute to the MSF of fuel heat removal.
14.0.2.3. Confinement of Radioactive Material
With respect to its contribution to the MSF of confinement of radioactive material, the DWK [FBVS] system must satisfy the SFRs detailed in the following sections.
Environmental Protection:
The DWK [FBVS] system must:
contain the radioactive material and prevent the risk of leaks; and
limit radioactive discharges into the environment through storage, treatment and control of the waste conveyed.
Limiting Radiological Consequences:
The DWK [FBVS] system must ensure:
the confinement of the fuel pool hall in case of a fuel handling accident in the HK [FB] building (PCC-4 and equivalent DBIF) or loss of two main PTR [FPCS/FPPS] system trains (without actuation of the third one) (DEC-A and DEC-B and equivalent DBIF);
the isolationAPPROVED of the air supply system of the room facing the emergency airlock in case of a fuel handling accident in the HR [RB] building (PCC-4 and equivalent DBIF);
the isolation of the HK [FB] building normal air supply / extraction system in case of a fault situation leading to a radioactivity discharge in the HR [RB] building (PCC-3, PCC-4, DEC-A and DEC-B and equivalent DBIF); and
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the control of the air supply rate into the HK [FB] building (the air exhaust rate being fixed) in normal operating conditions in order to control the negative pressure in the HK [FB] building and consequently contain radioactive materials.
Long-term Confinement of the HK [FB] Building:
Emergency exhaust is required in case of fuel pool boiling in order to maintain the long- term confinement of the HK [FB] building and to limit the pressure in the fuel pool hall in DEC-A and DEC-B situations and equivalent DBIF.
The DWK [FBVS] system must ensure compliance with the requirements defined for the radioactive gaseous waste in the waste discharge specifications.
14.0.2.4. Support Contribution to Main Safety Functions
With respect to its indirect contribution to the MSF of control of fuel reactivity, the DWK [FBVS] system must satisfy the following SFRs:
The DWK [FBVS] system must maintain the air temperature below the maximum permissible temperature required for correct operation of the RBS [EBS] system pumps during all conditions from PCC-2 to PCC-4 in order to enable the pumps to operate.
The DWK [FBVS] system must maintain the air temperature above the minimum permissible temperature in the RBS [EBS] system pump and boron rooms during all conditions from PCC-2 to PCC-4 in order to avoid boron crystallisation.
With respect to its indirect contribution to the MSF of confinement of radioactive material, the DWK [FBVS] system must satisfy the following SFRs:
The DWK [FBVS] system must maintain the air temperature below the maximum permissible temperature required for correct operation of the RCV [CVCS] system pumps during all conditions from PCC-2 to PCC-4 in order to enable the pumps to operate.
The DWK [FBVS] system must maintain the air temperature above the minimum permissible temperature in the RCV [CVCS] system boron rooms during all conditions from PCC-2 to PCC-4 in order to avoid boron crystallisation.
14.0.2.5. Specific Contribution to Hazards Protection
With respect to its specific contribution to the safety functions that are part of the facility hazards protection, the DWK [FBVS] system must satisfy the SFRs detailed in the following sections.
External Explosion:
Ensure integrity of dampers and ducts directly connected to the external environment so as to limitAPPROVED the effects of EPW inside the HK [FB] building in case of external explosion. Extreme Cold:
Ensure a temperature above a minimum temperature in the HK [FB] building safety boron rooms in case of extreme cold conditions in order to avoid boron crystallisation.
Internal Fire:
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Ensure containment of fire in the HK [FB] building by closure of fire dampers that maintain fire compartment integrity.
Earthquake:
Ensure the integrity or stability of the DWK [FBVS] system components to avoid damage to higher classified components and ensure that it does not adversely impact the availability of SC1 SFs following a seismic event.
14.0.2.6. Other Safety Functions to be performed in the Preventive Line of Defence
With respect to its contribution to other safety functions to be performed as part of the preventive line of defence, the DWK [FBVS] system must satisfy the following SFRs:
The DWK [FBVS] system must maintain the air temperature above the minimum permissible temperature in the fuel pool hall during all conditions from PCC-2 to PCC-4 in order to avoid boron crystallisation;
Emergency exhaust is required in case of fuel pool boiling in order to maintain the long- term confinement of the HK [FB] building and to limit the pressure in the fuel pool hall in DEC-A and DEC-B situations and equivalent DBIF.
The DWK [FBVS] system must provide monitoring of heating in the fuel pool hall in order to indicate the availability of the associated SF and to alert operators in the Main Control Room (MCR) in the event of its failure.
The DWK [FBVS] system must provide monitoring of heating in the RBS [EBS] system pump rooms in order to indicate the availability of the associated SF and to alert operators in the MCR in the event of its failure.
The DWK [FBVS] system must provide monitoring of heating in the RBS [EBS] system boron rooms in order to indicate the availability of the associated SF and to alert operators in the MCR in the event of its failure.
The DWK [FBVS] system must provide monitoring of cooling in the RBS [EBS] system pump rooms in order to indicate the availability of the associated SF and to alert operators in the MCR in the event of its failure.
The DWK [FBVS] system must maintain the air temperature below the maximum permissible temperature in the DSK system cabinets rooms in order to ensure correct operation of the DSK system (PCC-2, PCC-3, PCC-4 and DEC-A and equivalent DBIF).
14.0.3. Safety Features and Instrumentation & Control (I&C) Actuation Modes
Section 9.4.14 – Table 2 presents the SFs of the DWK [FBVS] system, according to the contributions identifiedAPPROVED in section 14.0.1 and the SFRNs referenced in Sub-chapter 3.2.
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14.0.4. Classification and Architecture Requirements of Safety Features
14.0.4.1. Requirements arising from Safety Classification
Architecture requirements associated with SFs are essential for designing robust lines of defence consistent with their importance to nuclear safety (see Sub-chapter 3.2). Such requirements strengthen the system design against:
single faults and associated consequences (Single Failure Criterion (SFC)) by requiring redundancy,
Loss Of Offsite Power (LOOP) by requiring, among others, a back-up power supply,
Station Black Out (SBO) by requiring a power supply by the Ultimate Diesel Generators (UDGs),
Common Cause Failures (CCFs) by requiring physical separation,
earthquake by defining seismic requirements, and
accident conditions by defining qualification requirements.
Section 9.4.14 – Table 2 presents the requirements arising from safety classification for the DWK [FBVS] system, according to the SFRNs referenced in Sub-chapter 3.2.
14.0.4.2. System Protection against Hazards
14.0.4.2.1. Internal Hazards
The SFs of the DWK [FBVS] system must be protected against internal hazards if those hazards challenge the safety objectives, as defined in Sub-chapter 13.2.
14.0.4.2.2. External Hazards
The SFs of the DWK [FBVS] system must be protected against external hazards if those hazards challenge the safety objectives, as defined Sub-chapter 13.1.
14.0.4.3. Diversity
The DWK [FBVS] system may be subject to the requirement for diversity as defined in the general safety principles (see Sub-chapter 3.1) and in Sub-chapter 3.7, dealing with diversity.
14.0.5. Requirements defined at the Component Level 14.0.5.1. GenericAPPROVED Safety Requirements 14.0.5.1.1. Generic Mechanical, Electrical and I&C Requirements
The mechanical components within the DWK [FBVS] system must comply with the mechanical requirements in accordance with the rules laid out in Sub-chapter 3.2, section 7. The level of requirement is dependent upon whether or not it is a pressure retaining component, the safety class of the component, whether the component acts as an isolating device between interfacing SFs, and on the role of the component as a barrier to the potential release of radioactivity as a result of failure of the component.
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The electrical and I&C components in the DWK [FBVS] system must comply with the electrical and I&C requirements associated with their safety class, in accordance with the rules laid out in Sub-chapter 3.2.
14.0.5.1.2. Seismic Requirements
The level of seismic requirements to be applied to the DWK [FBVS] system components is related to the safety feature group to which the component belongs, and the consequences on other classified components of its failure if it were not seismically qualified. The rules for defining the seismic requirements for a component are identified in Sub-chapter 3.2.
14.0.5.1.3. Qualification for Accident Conditions
The safety classified parts of the DWK [FBVS] system must be qualified for the operating conditions in which they are required, as specified in Sub-chapter 3.6.
14.0.5.2. Specific Safety Requirements
14.0.5.2.1. High Integrity Component (HIC) Requirements
The DWK [FBVS] system is not subject to any High Integrity Component (HIC) requirements.
14.0.5.2.2. Specific I&C Requirements
The DWK [FBVS] system does not have any safety classified dedicated I&C. However, the DWK [FBVS] system fire dampers are operated by the Fire Detection System (JDT [FDS]) dedicated I&C.
The specific requirements arising from the JDT [FDS] system dedicated I&C are described in Sub-chapter 9.5, section 1.2. The general approach for I&C systems is set out in Chapter 7.
14.0.6. Examination, Maintenance, (In-Service) Inspection and Testing (EMIT)
14.0.6.1. Start-up Tests
The DWK [FBVS] system must be designed to enable the performance of start-up tests to ensure the adequacy of its design and performance under conditions as representative as possible of the different operating configurations, and in particular its compliance with the SFRs assigned to it in section 14.0.2.
14.0.6.2. In-Service Inspection
The DWK [FBVS] system must be designed to enable surveillance under normal operation of the system characteristics necessary for the fulfilment of its safety-related tasks in order to ensure the performance of its components, and their availability under normal operation, or in the event of a APPROVEDfault or accident. 14.0.6.3. Periodic Testing
The safety-classified parts of the DWK [FBVS] system must be designed to enable the performance of periodic tests in accordance with the maintenance schedule.
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14.0.6.4. Maintenance
The DWK [FBVS] system must be designed to enable the implementation of a maintenance schedule (see Sub-chapter 18.2).
14.1. ROLE OF THE SYSTEM
The DWK [FBVS] system performs the following functions (or tasks) under the different plant operating conditions for which it is required.
14.1.1. Normal Operating Conditions
The DWK [FBVS] system operates continuously and is designed for the following purposes:
to maintain conditions in the HK [FB] building within limits prescribed for correct operation of equipment and / or staff in normal operation;
to ensure during normal operation that contamination is contained at source to avoid its spreading from potentially contaminated areas to potentially less contaminated areas;
to limit the concentration of aerosols and radioactive gases in the atmosphere of the rooms; and
to maintain a negative pressure in the HK [FB] building compared to the external environment pressure using automatic control dampers in the air supply trains.
In addition, the DWK [FBVS] system prevents condensation on the walls of the rooms that are in contact with the external environment and more specifically on the walls of the fuel pool hall.
14.1.2. Fault and Hazard Operating Conditions
The safety roles of the DWK [FBVS] system are as detailed in the sections below.
Confinement of Radioactive Material
To automatically isolate the fuel pool hall air supply and extraction in the event of a fuel handling accident in this hall (PCC-4 and equivalent DBIF). In this case, the fuel pool hall dynamic confinement is ensured by the Safeguard Building (Controlled Area) Ventilation System (DWL [CSBVS]) (see section 6 of this sub-chapter);
To automatically isolate the air supply system of the room facing the emergency airlock in the event of a fuel handling accident in the HR [RB] building (PCC-4 and equivalent DBIF);
To automatically isolate the fuel pool hall air supply and extraction in the event of failure of the APPROVEDtwo main lines of the PTR [FPCS/FPPS] system (DEC-A, DEC-B and equivalent DBIF);
To ensure the static confinement of the HK [FB] building in the event of a Loss Of Coolant Accident (LOCA) (PCC-3, PCC-4, DEC-A, DEC-B and equivalent DBIF) or Total Loss of AC Power (TLAP). The dynamic confinement of the leaks from the HR [RB] building to the HK [FB] building is provided by the low-capacity Containment Sweep Ventilation System (EBA [CSVS]) (see section 5 of this sub-chapter); and
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To open the fuel pool outlet in the event of fuel pool boiling.
Note that for fuel handling accidents in the HR [RB] building, containment is achieved by the low-capacity EBA [CSVS] system.
Support to Main Safety Functions
To maintain required temperature in the RBS [EBS] and RCV [CVCS] systems boron rooms in order to avoid boron crystallisation; and
To maintain required temperature in rooms for correct operation of equipment in RBS [EBS] and RCV [CVCS] pump rooms;
Hazards:
To limit the effects of EPW inside the HK [FB] building;
To maintain conditions in the boron rooms for correct operation of boron equipment / components in case of extreme cold conditions; and
To ensure active and / or passive fire compartmentation in the HK [FB] building.
Other Safety Functions:
To maintain required temperature in the fuel pool hall in order to avoid boron crystallisation;
To open the fuel pool outlet in the event of fuel pool boiling; and
To maintain required temperature in rooms for correct operation of equipment in the DSK system rooms.
14.2. DESIGN BASIS
14.2.1. General Assumptions
The DWK [FBVS] system is designed with the following assumptions:
Isolation dampers are used to ensure the static confinement of the fuel pool hall, HK [FB] building and air supply system of the room facing the emergency airlock during accident conditions.
Local Cooling Units (LCUs) are used to remove the heat loads and to ensure a correct operation for the RBS [EBS] and RCV [CVCS] systems pumps and the DSK system. It should be noted that the instantaneous extreme high air temperature defined in section 1 is not takenAPPROVED account for the DWK [FBVS] LCUs because fresh air is not directly used by DWK [FBVS] system. The DWK [FBVS] system air supply is provided by DWN [NABVS] system.
Convectors are used to maintain minimum required temperature in all boron rooms in order to be consistent with the general design criteria applicable to the Heating, Ventilation And Air-Conditioning (HVAC) systems, as described in section 1.
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The DWK [FBVS] system air supply is provided by the Nuclear Auxiliary Building Ventilation System (DWN [NABVS]) (see section 2) and has the following characteristics:
Summer: { SCI removed };
Winter: { SCI removed } ({ SCI removed } with the plant out of operation without internal heat loads).
The general design criteria regarding the HVAC systems are defined in section 1:
the summer and winter external conditions,
the inside conditions,
the equipment requirements, and
the characteristics for the controlled area.
In case of loss of DWN [NABVS] system, the HK [FB] building long term conditioning requirements are respected, (according to the different fault conditions) with a grace delay of { SCI removed } days or more. Consequently, no additional safety classified HVAC cooling means is necessary for DWK [FBVS] system.
14.2.2. Design Assumptions
14.2.2.1. Control of Fuel Reactivity
Not applicable: the DWK [FBVS] system does not directly contribute to the MSF of control of fuel reactivity.
14.2.2.2. Fuel Heat Removal
Not applicable: the DWK [FBVS] system does not directly contribute to the MSF of control of fuel heat removal.
14.2.2.3. Confinement of Radioactive Material
Environmental Protection:
Not applicable: there are no quantitative safety-related design assumptions associated with the DWK [FBVS] system.
Limiting Radiological Consequences:
In order to isolate the fuel pool hall, the DWK [FBVS] isolation dampers located on the air supply APPROVED/ extraction system of the fuel pool hall must be closed quickly. These isolation damper leakage rates shall meet the requirement defined in section 1.
In order to isolate the air supply system of the room facing the emergency airlock, the DWK [FBVS] system isolation dampers located on the air supply of the emergency airlock must be closed quickly. These isolation damper leakage rates shall meet the requirement defined in section 1.
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In order to isolate the HK [FB] building, the DWK [FBVS] system isolation dampers located on the HK [FB] building normal air supply / extraction system must be closed quickly. These isolation dampers leakage rates shall meet the requirement defined in section 1.
The DWK [FBVS] system must control the air supply rate into the HK [FB] building (the air removal rate being fixed) in normal operating conditions in order to control the negative pressure ({ SCI removed } compared to the external atmospheric pressure) in the HK [FB] building and consequently contain radioactive materials.
Long-term Confinement of the HK [FB] Building:
In the HK [FB] building fuel pool hall, the burst membrane internal opening pressure is set at { SCI removed }.
14.2.2.4. Support Contribution to Main Safety Functions
Cooling of RBS [EBS] and RCV [CVCS] Pumps Rooms:
Maximum temperatures in the HK [FB] building depend on the qualification temperatures of DWK [FBVS] system-served equipment and are given in section 1. In order to make sure that adequate temperature is maintained at all times, the DWK [FBVS] system local cooling units have been sized taking into account the following assumptions:
o maximum external temperature for external heat transmissions defined in section 1,
o maximum temperature in adjacent buildings defined in section 1,
o permanent state,
o maximum heat loads dissipated by equipment and pipework in fault conditions, and
o loss of general ventilation.
Heating of the RBS [EBS] and RCV [CVCS] Systems Boron Rooms:
Minimum temperatures required to prevent from boron crystallisation in the HK [FB] building boron rooms are given in section 1.
14.2.2.5. Specific Contribution to Hazards protection
The DWK [FBVS] system must contribute directly to the safety functions as follows: External Explosion:APPROVED In order to protect safety classified equipment located in the HK [FB] building, the DWK [FBVS] system must ensure that dampers and ducts directly connected to the external environment are protected against external explosions These dampers and ducts must satisfy the criteria defined in Sub-chapter 13.1, section 4.
Extreme Cold Conditions:
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Minimum temperatures required to prevent from boron crystallisation in the HK [FB] building boron rooms are given in section 1.
Fire:
Not applicable: there are no quantitative safety-related design assumptions associated with the DWK [FBVS] system.
Earthquake:
Not applicable: there are no quantitative safety-related design assumptions associated with the DWK [FBVS] system.
14.2.2.6. Other Safety Functions to be performed in the Preventive Line of Defence
Heating in Fuel Pool Area:
Minimum temperature required to prevent boron crystallisation in the fuel pool area is given in section 1.
Long-term Confinement of the HK [FB] Building:
In the HK [FB] building fuel pool hall, the burst membrane internal opening pressure is set at { SCI removed }.
Monitoring of Cooling in RBS [EBS] Pump Rooms:
Not applicable: there are no quantitative safety-related design assumptions associated with the DWK [FBVS] system.
Monitoring of Heating in RBS [EBS] Rooms and Fuel Pool Area:
Not applicable: there are no quantitative safety-related design assumptions associated with the DWK [FBVS] system.
Cooling of the DSK Cabinets Rooms:
Maximum temperatures in the DSK system cabinets rooms depend on the qualification temperatures of the DWK [FBVS] system-served equipment and are given in section 1. In order to make sure that adequate temperature is maintained at all times, the DWK [FBVS] system local cooling units have been sized taking into account the following assumptions:
o maximum external temperature for external heat transmissions defined in APPROVEDsection 1, o maximum temperature in adjacent buildings defined in section 1,
o permanent state,
o maximum heat loads dissipated by equipment and pipework in fault conditions, and
o loss of general ventilation.
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14.2.3. Other Assumptions
The DWK [FBVS] system is also subject to the following assumptions:
The DWK [FBVS] system design is consistent with RCC-M requirements as described in Sub-chapter 3.8, section 2.
The DWK [FBVS] system design is consistent with fire requirements as described in Sub-chapter 3.8, section 5.
14.2.4. Assumptions associated with Extreme Situations resulting from Beyond Design Basis Hazards
14.2.4.1. Assumptions associated with Fukushima Provisions
The assumptions associated with the Fukushima provisions of the DWK [FBVS] system are presented in Chapter 23. The main provisions are described below:
confinement in the HK [FB] building fuel handling hall,
isolation of the HK [FB] building normal air supply / extraction system, and
emergency exhaust of spent fuel pool hall.
14.2.4.2. Assumptions associated with non-Fukushima Provisions
The DWK [FBVS] system is not subject to assumptions associated with non-Fukushima provisions.
14.3. SYSTEM DESCRIPTION AND OPERATION
14.3.1. Description
14.3.1.1. General System Description
The DWK [FBVS] system comprises an air supply duct network and an extraction duct network.
The air supply duct network is connected to the DWN [NABVS] system main air supply duct.
The extraction duct network comprises two separate networks that correspond to Cells 4 and 5. These two networks are connected to the DWN [NABVS] system.
It should be noted that the handling tower extraction duct network is also connected to the DWN [NABVS] systemAPPROVED (via cell 3). Moreover, the DWK [FBVS] system duct network is served by the low-capacity EBA [CSVS] extraction system in order to ensure iodine adsorption during dynamic confinement of the HK [FB] building. An exhaust duct equipped with motorised isolation dampers is located in the fuel pool hall in order to ensure extraction by the DWL [CSBVS] system when iodine is present
Furthermore, an outlet is installed between the fuel pool hall and the main unit vent stack in order to relieve the over-pressure produced by the steam in case of fuel pool boiling.
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Convectors, fan coil heaters and LCUs are installed in the HK [FB] building rooms in order to maintain conditions in this building for correct operation of equipment and / or staff.
14.3.1.2. Description of Main Equipment
The DWK [FBVS] system comprises the following main equipment items (see the functional diagram provided in section 14.5):
Isolation dampers:
o Motorised isolation dampers isolate the air supply and extraction of the fuel pool hall, the HK [FB] building and the room facing the emergency airlock.
Pressure control dampers:
o Motorised control dampers are used on the air supply to regulate the negative pressure in the HK [FB] building compared to the external atmospheric pressure (DWN [NABVS] buffer tank reference pressure (see section 2)).
Convectors:
o Used to ensure minimum temperatures in the boron rooms to avoid boron crystallisation.
Fan coil heaters:
o Used to maintain required temperatures in the large volume rooms (fuel pool hall, handling tower and handling hall).
Local cooling units:
o These units are equipped with cooling coils (used to cool down the air) and fans (they ensure the air flow through the cooling coil). They are used to maintain temperatures in the HK [FB] building rooms (RBS [EBS] system pump rooms, RCV [CVCS] system pump rooms and the DWK [FBVS] system cabinet rooms) which have high internal heat load.
Burst membrane
o This component is used to ensure limitation of overpressure in the fuel pool hall.
14.3.1.3. Description of Main Layout
All components of the DWK [FBVS] system are located in the HK [FB] building. 14.3.1.4. DescriptionAPPROVED of System I&C The JDT [FDS] system dedicated I&C used for the DWK [FBVS] system fire dampers is described in the JDT [FDS] system chapter (see Sub-chapter 9.5, section 1.2).
14.3.2. Operation
14.3.2.1. System Normal Operation
The DWK [FBVS] system is used when the plant is in operation or shutdown.
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Plant Operation
The DWK [FBVS] system operates continuously. No air is recirculated because of the potential for the presence of airborne contamination in certain areas.
In plant operation, the DWK [FBVS] system must:
maintain the conditions in the HK [FB] building within limits prescribed for correct operation of equipment and / or staff in normal operation in association with the DWN [NABVS] system;
maintain a negative pressure in the HK [FB] building compared to the external environment and fixed at { SCI removed };
ensure that contamination is contained at source to avoid its spreading from potentially contaminated areas to potentially less contaminated areas; and
reduce the concentration of aerosols and radioactive gases in the atmosphere.
The air supply rate is constant and distributed to the HK [FB] building.
Plant Outages:
When the equipment hatch and the two airlocks are open, the DWK [FBVS] system dampers located at the level of the air extraction from the emergency airlock are closed and extraction is performed by the EBA [CSVS] system.
Fuel Handling Accident in the HK [FB] Building
In the case of a fuel handling accident in the HK [FB] building, the air supply in the zone to be contained is isolated by closing the airtight dampers. The extraction via the DWK [FBVS] system is isolated and directed to the DWL [CSBVS] system, equipped with High Efficiency Particulate Air (HEPA) filters and iodine adsorption units
Fuel Handling Accident in HR [RB] Building:
The air supply and the extraction used during plant outages (high-capacity EBA [CSVS] system), and the low-capacity EBA [CSVS] system air supply, are isolated. The DWK [FBVS] system air supply and extraction of the room facing the equipment hatch are preventively isolated before the opening of the equipment hatch.
The air supply in the room facing the emergency airlock is automatically isolated. The air extraction is preventively isolated before the opening of the emergency airlock.
Static confinement of the HK [FB] building is ensured by closing the isolation dampers located on the HK [FB]APPROVED building normal air supply / extraction. Dynamic confinement of the rooms facing the equipment hatch and emergency airlock is ensured by the low-capacity EBA [CSVS] system equipped with HEPA filters and iodine adsorption units.
Loss Of Coolant Accident (LOCA):
In the event of a LOCA, static confinement of the HK [FB] building is achieved by closing the isolation dampers located at the air supply and at the extraction of the normal ventilation of the
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HK [FB] building. The static confinement of the HK [FB] building is carried out on a Stage 1 confinement isolation signal.
Moreover, the dynamic confinement of the HK [FB] building ensures collection and filtering before the release of any leak from the HR [RB] building to the HK [FB] building. The dynamic confinement is ensured by the low-capacity EBA [CSVS] system, which is equipped with iodine filtration lines.
Station Blackout (SBO):
In the event of an SBO, static confinement of the HK [FB] building is achieved: the isolation dampers located at the air supply and at the extraction of the normal ventilation of the HK [FB] building have a fail-safe closed position in the event of a loss of power supply.
Severe Accident initiated by a LOCA:
For this Severe Accident (SA) type, the containment isolation Stage 1 signal leads to the same actions as for the LOCA (see Loss Of Coolant Accident above). These actions are performed before entry into SA management.
Loss of the Four Emergency Diesel Generators and the Two Ultimate Diesel Generators (TLAP):
In the event of an TLAP, static confinement of the HK [FB] building is achieved: The isolation dampers located at the air supply and the isolation dampers located at the extraction of the HK [FB] building normal ventilation are closed (fail-safe closed position in the event of a loss of power).
Fuel Pool Boiling in the HK [FB] building:
In case of fuel pool boiling, outlet (burst membrane) is opened if the pressure increases in the fuel pool hall due to steam.
14.3.2.2. System Transient Operation
14.3.2.2.1. Full or partial System Failure
{ This section contains SCI-only text and has been removed }
14.3.2.2.2. Failure of Systems in Interface (server or served)
{ This section contains SCI-only text and has been removed }
14.4. PRELIMINARY DESIGN SUBSTANTIATION The level of detailAPPROVED in terms of evidence of compliance with the safety requirements stated in section 9.4.14 will develop as the HPC project moves from basic design into detailed design since the PCSR3 sequence and system sequence are evolving in parallel. Therefore, the level of detail presented in this section reflects the level of information available at the time of issuing the system chapters.
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14.4.1. Compliance with Safety Functional Requirements
14.4.1.1. Control of Fuel Reactivity
Not applicable: the DWK [FBVS] system does not directly contribute to the MSF of control of fuel reactivity
14.4.1.2. Fuel Heat Removal
Not applicable: the DWK [FBVS] system does not directly contribute to the MSF of control of fuel heat removal.
14.4.1.3. Confinement of Radioactive Material
Environmental Protection:
The leaktightness of the DWK [FBVS] system ductwork and other HVAC system components is reinforced (in compliance with rules regarding mechanical classification given in section 14.0.5.1.1) so as to reduce the risk of mechanical failures and protect the environment against potential radioactive leaks. Moreover, in order to limit potential radioactive discharges into the environment under normal operation, extracted air is filtered by the DWN [NABVS] system before discharge to the main unit ventilation stack.
Limiting Radiological Consequences:
The DWK [FBVS] system ensures:
Isolation of the fuel pool hall:
o Redundant quick closing isolation dampers (on supply and exhaust lines) are closed on receipt of a KRT [PRMS] system signal. Isolation is ensured by T2 leak-tightness as defined in section 1 (inner leaktightness and leaktightness to the environment).
Isolation of the air supply system of the room facing the emergency airlock:
o Redundant quick closing isolation dampers (on supply lines) are closed on receipt of a KRT [PRMS] signal. Isolation is ensured by T2 leak-tightness as defined in section 1 (inner leaktightness and leaktightness to the environment).
Isolation of the HK [FB] building normal air supply / extraction system:
o Redundant quick closing isolation dampers (on supply and exhaust lines) are closed on receipt of a containment isolation phase 1 signal. Isolation is ensured by T3 leak-tightness as defined in section 1 (inner leaktightness and APPROVEDleaktightness to the environment). Control of Negative Pressure in the HK [FB] building:
o Control dampers are used to control the air supply rate into the HK [FB] building in normal operating conditions in order to control the negative pressure ({ SCI removed }) in the HK [FB] building.
Long-term Confinement of the HK [FB] Building:
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Limit the pressure in the fuel pool area in case of fuel pool boiling:
o The burst membrane pressure of the qualified overpressure protection device installed in the fuel pool area is set at { SCI removed }.
14.4.1.4. Support Contribution to Main Safety Functions
The design assumptions of the DWK [FBVS] system stated in section 14.2.2 are consistent with the requirements of the corresponding system / equipment items which it supports:
Maintenance of adequate temperature in the HK [FB] building rooms:
o Ensure temperatures remain within specified limits compatible with equipment operation:
. Design assumptions used for the sizing of local cooling units (which are defined in section 14.2.2) enable rooms temperatures to be maintained within limits required for correct operation of supported equipment in all plant conditions. LCUs are started and turned off automatically based on temperature measurement or when the associated pump is started.
o Ensure minimum temperature in the boron rooms:
. Design assumptions used for the sizing of convectors (which are defined in section 14.2.2) enable temperatures in the boron rooms to avoid boron crystallisation. Convectors are started and turned off automatically based on temperature measurement in the boron rooms.
14.4.1.5. Specific Contribution to Hazards Protection
The hazard studies of Sub-chapters 13.1 and 13.2 involving functions of the DWK [FBVS] system use values for the following parameters that are in keeping with the design assumptions stated in section 14.2.2:
External explosion:
o The dampers and ducts directly connected to the external environment are resistant to EPW.
Extreme cold:
o Ensure minimum temperatures in boron rooms in case of extreme cold conditions:
. Design assumptions used for the sizing of convectors (which are defined APPROVEDin section 14.2.2) enable temperatures in the boron rooms to avoid boron crystallisation. Convectors are started and turned off automatically based on temperature measurement in the boron rooms.
Internal fire:
o Contribute to the containment and prevention of spread of fire in the HK [FB] building by closure of the fire dampers:
. Fire dampers qualification; and
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. Fire damper closure is ensured by active (automation by JDT [FDS] system) or ultimately passive (fusible device inside and outside the duct) means and is monitored by position status.
Earthquake:
o Ensure stability or integrity of the DWK [FBVS] system components to avoid damage to higher classified components following a seismic event:
. Seismic qualification to keep the component integrity or stability.
For each hazard study concerned, these studies show that the design of these functions is such that they meet the acceptability criteria.
These elements ensure that the system functional requirements stated in section 14.0.2 are met.
14.4.1.6. Other Safety Functions to be performed in the Preventive Line of Defence
Other safety functions to be performed in the preventive line of defence involving the DWK [FBVS] system uses values for the following parameters that are in keeping with the design assumptions stated in section 14.2.2:
Maintenance of adequate temperature in the fuel pool area:
o Ensure minimum temperature in the fuel pool area:
. Design assumptions used for the sizing of fan coil heaters (which are defined in section 14.2.2) enable temperatures in the boron rooms to avoid boron crystallisation. Convectors are started and turned off automatically based on temperature measurement in the boron rooms.
Limit the pressure in the fuel pool area in case of fuel pool boiling:
o The burst membrane pressure of the qualified overpressure protection device installed in the fuel pool area is set at { SCI removed }.
Information of local heating availability:
o Monitor temperatures in the RBS [EBS] system boron rooms and fuel pool hall:
. Temperature sensors installed in these rooms monitor temperatures and alarm operators in case of local heating failure. InformationAPPROVED of local cooling availability: o Monitor temperatures in the RBS [EBS] system pump rooms:
. Temperature sensors installed in these rooms monitor temperatures and alarm operators in case of local heating failure.
Maintenance of adequate temperature in the DSK system cabinets rooms:
o Ensure temperatures remain within specified limits compatible with equipment operation:
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. Design assumptions used for the sizing of local cooling units (which are defined in section 14.2.2) enable temperatures to be maintained within limits required for correct operation of supported equipment in all plant conditions. Local cooling units are started and turned off automatically based on temperature measurement or when the associated pump is started.
These elements ensure that the SFRs stated in section 14.0.2 are met.
14.4.2. Compliance with Design Requirements
The DWK [FBVS] system complies with the requirements stated in sections 14.0.4 and 14.0.5, particularly with respect to the aspects detailed in the following sub-sections.
14.4.2.1. Requirements arising from Safety Classification
14.4.2.1.1. Safety Classification
The compliance of the design and manufacture of the DWK [FBVS] system materials and equipment performing a safety-related function with requirements from the classification rules (see Sub-chapter 3.2, section 7) is presented in section 14.4.2.4.1.
14.4.2.1.2. Single Failure Criterion and Redundancy
Active Single Failure:
The design of the DWK [FBVS] system meets the requirements of the active SFC stated in section 14.0.4.1, in particular in respect of the following:
Redundant isolation dampers are located on the supply / extraction of the fuel pool hall and installed in series;
Redundant isolation dampers are located on the normal air supply and extraction in the HK [FB] building and installed in series;
Redundant isolation damper is located on the air supply of the room facing the emergency airlock and installed in series;
Convectors located in the RBS [EBS] system pumps rooms and boron rooms are installed according to the DWK [FBVS] system winter sizing with an additional convector in case of failure of one convector;
Fan coil heaters of the fuel pool hall are doubled; and
Fire dampers located between Safety Fire Compartments (SFS) are doubled and installedAPPROVED in series. Regarding the cooling of the RBS [EBS] system pumps, there is one local cooling unit for each RBS [EBS] system pump room. If the first RBS [EBS] system pump is unavailable, the second pump takes over. It is the same reasoning for the local cooling units.
In addition, each LCU is associated with specific DEL [SCWS] line.
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Passive Single Failure:
The DWK [FBVS] system safety features are required to be robust against passive single failure. Single failure has been applied to active components and redundancy is adequately ensured. Application of the passive single failure to this system is discussed in Sub-chapter 15.3, section 1.
14.4.2.1.3. Robustness against loss of power
The design of the DWK [FBVS] system complies with the emergency power supply requirement stated in section 14.0.4.1, in particular in respect of those detailed in the following sections.
Loss Of Off-site Power (LOOP):
DWK [FBVS] system isolation dampers located on the supply / extraction of the fuel pool hall have a fail-safe position closed in case of LOOP to ensure the fuel pool hall static confinement.
DWK [FBVS] system isolation dampers located on the normal air supply / extraction system of the HK [FB] building have a fail-safe position closed in case of LOOP to ensure the HK [FB] building static confinement.
DWK [FBVS] system isolation dampers located on the air supply of the room facing the emergency airlock have a fail-safe position closed in case of LOOP to ensure static confinement.
DWK [FBVS] system local cooling units in the RBS [EBS] system pump rooms are backed-up by Emergency Diesel Generators (EDGs).
DWK [FBVS] system convectors located in the RBS [EBS] system pump rooms and boron rooms are backed-up by EDGs.
DWK [FBVS] system fan coil heaters in the fuel pool hall are backed-up by EDGs.
DWK [FBVS] system local cooling units in the DSK system cabinets rooms are backed- up by EDGs.
The RCV [CVCS] system LCUs and convectors are not backed up in case of LOOP.
In addition, active components contributing to fire-fighting are required to be robust against LOOP. This requirement is met by an uninterruptible power. Fire dampers can also be closed passively by thermal fuse (fail-safe design).
Station Black Out (SBO): DWK [FBVS]APPROVED system isolation dampers located on the supply / extraction system of the fuel pool hall have a fail-safe position closed in case of SBO to ensure the fuel pool hall static confinement.
DWK [FBVS] system isolation dampers located on the normal air supply / extraction system of the HK [FB] building have a fail-safe position closed in case of SBO to ensure the HK [FB] building static confinement.
DWK [FBVS] system local cooling units in the DSK system cabinets rooms are backed-up by UDGs.
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14.4.2.1.4. Physical Separation
All Class 1 and 2 DWK [FBVS] system components are installed in compliance with the layout rules.
14.4.2.2. System Protection against Hazards
14.4.2.2.1. Internal Hazards
The overall demonstration of the robustness of the plant to internal hazards is covered in Sub-chapter 13.2.
14.4.2.2.2. External Hazards
The overall demonstration of the robustness of the plant to external hazards is covered in Sub-chapter 13.1.
14.4.2.3. Diversity
The diversity requirement stated in section 14.0.4.3 is not applicable to the DWK [FBVS] system and components. In particular in respect of the following:
Heating of RBS [EBS] system pump rooms,
Heating of RBS [EBS] system boron rooms,
Heating of RCV [CVCS] system boron rooms,
Cooling of RBS [EBS] system pump rooms, and
Cooling of RCV [CVCS] system pump rooms.
The DWK [FBVS] components involved in these safety features only support safety features which are identified as a diverse line and are not diverse themselves; (more details are provided in Sub-chapter 3.7 dealing with diversity).
14.4.2.4. Requirements defined at the Component Level
14.4.2.4.1. General Mechanical, Electrical and I&C Requirements
The components of the DWK [FBVS] system equipment performing a safety-related function comply with the general mechanical, electrical, and I&C requirements stated in section 14.0.5.1 as detailed in Section 9.4.14 – Table 1.
SECTION 9.4.14 – TABLE 1 : CLASSIFICATION OF MAIN MECHANICAL AND ELECTRICAL APPROVEDCOMPONENTS ASSOCIATED TO THEIR SAFETY FEATURES
Safety classification Design requirements
Description
Seismic
function
category
Electrical
Mechanical
requirement requirement requirement
class of SFG
Highestsafety Highestsafety I&C requirement I&C
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Safety classification Design requirements
Description
Seismic
function
category
Electrical
Mechanical
requirement requirement requirement
class of SFG
Highestsafety Highestsafety I&C requirement I&C Fuel pool isolation dampers A 1 T2 SC1 C1 C1 Fuel building normal supply/ B 2 T3 SC1 C2 C2 exhaust isolation dampers Supply isolation damper facing A 1 T2 SC1 C1 C1 the emergency airlock Local cooling units in RBS [EBS] A 1 M3 SC1 C1 C1 pump rooms Convectors in RBS [EBS] pump B 2 NT SC1 C2 C2 and boron rooms Convectors in RCV [CVCS] boron B 3 NT SC1 C3 C3 rooms Fan coil heaters units in fuel pool B 2 NT SC1 C2 C2 hall Fire dampers between SFS A 1 M3 SC1 C3 C3 Local cooling units in RCV B 3 NT/M3* SC1 C3 C3 [CVCS] pump rooms Burst membrane A 1 M2 SC1 - - Isolation dampers of the handling tower (connected to the external B 2 T2 SC1 C2 C2 environment) Convectors in safety boron rooms C 3 NT SC2 C3 C3 Control dampers maintaining negative pressure in the HK [FB] C 3 T3 SC2 C3 C3 building Pressure sensors controlling negative pressure in the HK [FB] C 2 M2 SC1 - C3 building Temperature sensors monitoring B 2 - SC1 - C2 heating in fuel pool hall Temperature sensors monitoring heating in RBS [EBS] pump B 2 - SC1 - C2 rooms Temperature sensors monitoring heating in RBSAPPROVED [EBS] boron B 2 - SC1 - C2 rooms Temperature sensors monitoring cooling in RBS [EBS] pump B 2 - SC1 - C2 rooms Local cooling units in DSK C 3 NT/M3* SC1 C3 C3 cabinets rooms * NT for the fan / M3 for the cooling coil (linked with the DEL [SCWS] system)
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This table will be updated after the Safety Classification Component Lists (SCCLs) studies.
14.4.2.4.2. Seismic Requirements
The DWK [FBVS] system complies with the seismic qualification requirements listed in Section 9.4.14 – Table 1.
14.4.2.4.3. HIC Requirements
Not applicable: the DWK [FBVS] system is not subject to any HIC requirements.
14.4.2.4.4. Specific I&C Requirements
The demonstration of the compliance with the specific I&C requirements stated in section 14.0.5.2.2 is provided in the JDT [FDS] system chapter (see Sub-chapter 9.5, section 1.2).
14.4.3. Examination, Maintenance, (In-Service) Inspection and Testing (EMIT)
14.4.3.1. Start-up Tests
The DWK [FBVS] system is subject to a start-up test programme in accordance with the procedures set out in Chapter 20 to verify the fulfilment of the following SFRs:
The start-up test program will verify:
closing operability of:
o isolation dampers of the fuel pool hall;
o isolation dampers of the HK [FB] building normal air supply / extraction system;
o isolation dampers of the air supply of the room facing the emergency airlock;
negative pressure in the HK [FB] building rooms;
electrical power of convectors and fan coil heaters;
correct operation of fire dampers;
start-up of local cooling units fans; and
start-up of fan coil heaters.
As the local air-cooling safety requirements cannot be verified directly due to the fact that the test conditions are different to the fault conditions under which they are required to be fulfilled, they will be verifiedAPPROVED in an extrapolated manner by checking the cooling power of local cooling units.
As the DWK [FBVS] system SFR associated to the burst membrane cannot be directly verified on site due to the fact that the test conditions are different to the fault and hazards conditions under which it is required to be fulfilled; it must be verified in an indirect manner as follow:
Justification of the qualification of the burst membrane by testing and calculations by the supplier.
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14.4.3.2. In-service Inspection
The following functions of the DWK [FBVS] system are monitored during normal operation (and can trigger an alarm in the MCR):
heating in fuel pool area,
heating in RBS [EBS] system pump rooms;
heating of RBS [EBS] system boron rooms; and
cooling of RBS [EBS] system pump rooms.
The availability of these functions is therefore verified by the continuous monitoring process.
14.4.3.3. Periodic testing
The safety classified parts of the DWK [FBVS] system is subject to periodic testing in accordance with the maintenance schedule in order to verify that the following SFRs are fulfilled:
closing operability of:
o isolation dampers of the fuel pool hall;
o isolation dampers of the HK [FB] building normal air supply / extraction system;
o isolation dampers of the air supply of the room facing the emergency airlock;
negative pressure in the HK [FB] building rooms;
electrical power of convectors and fan coil heaters;
correct operation of fire dampers;
start-up of local cooling units fans;
start-up of fan coil heaters; and
correct aspect of burst membrane.
14.4.3.4. Maintenance
The DWK [FBVS] system is subject to a maintenance programme. 14.5. FUNCTIONALAPPROVED DIAGRAM The functional diagram of the DWK [FBVS] system is shown in Section 9.4.14 – Figure 1 (for more details, see the detailed mechanical diagrams of the DWK [FBVS] system).
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15. VENTILATION SYSTEM FOR THE FIRE FIGHTING WATER BUILDING (DVJ)
The information reported in this section is, unless otherwise noted, consistent with the reference design, as referenced from Chapter 22.
15.0. SAFETY REQUIREMENTS
The UK EPR Safety Classification principles and the top-down functional approach are presented in Sub-chapter 3.2. These principles help to ensure that the plant is designed, manufactured, constructed, commissioned and operated so that the appropriate level of reliability and integrity is achieved for its Structures, Systems and Components (SSCs).
The HPC functional safety analyses and the application of these safety classification principles to the HPC reference design result in the identification of the safety requirements for all safety systems in accordance with the Safety Functional Requirements Notes (SFRNs) referenced from Sub-chapter 3.2.
This section summarises the results of these safety analyses and specifies the safety requirements that apply to the design of the Ventilation System for the Fire Fighting Water Building (DVJ) (Heating, Ventilation and Air Conditioning (HVAC) of the Fire Fighting Water Building (HOJ)).
The requirements described in the present section are consistent with safety functions to which the DVJ system contributes in Plant Condition Category (PCC) and Design Extension Conditions (DEC). Consistency with requirements inherited from the Design Basis Initiating Faults (DBIFs) should be checked when the list of DBIFs evolves (see Chapter 15).
15.0.1. Safety Functions
The three Main Safety Functions (MSFs) necessary to achieve the overall safety objective of protecting people and the environment from the harmful effects of ionising radiation are:
control of fuel reactivity,
fuel heat removal, and
confinement of radioactive material.
These three MSFs must be achieved during:
normal operating conditions (PCC-1), including duty functions, control of radioactive release during normal operating conditions, control of main plant parameters, fault initial conditions, Limiting Conditions of Operation (LCOs), limitations, monitoring functions, ProbabilisticAPPROVED Safety Assessment (PSA) significant functions as part of the preventive line of defence,
fault conditions (PCC-2 to PCC-4, DEC-A and any equivalent DBIFs) and DEC-B, and
hazard conditions.
15.0.1.1. Control of Fuel Reactivity
The DVJ system does not directly contribute to the MSF of control of fuel reactivity.
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15.0.1.2. Fuel Heat Removal
The DVJ system does not directly contribute to the MSF of fuel heat removal.
15.0.1.3. Confinement of Radioactive Material
The DVJ system does not directly contribute to the MSF of confinement of radioactive material.
15.0.1.4. Support Contribution to Main Safety Functions
The DVJ system contributes indirectly to the MSF of fuel heat removal as a support system of the Fire Fighting Water Supply System (JAC).
15.0.1.5. Specific Contribution to Hazards Protection
The generic Safety Feature (SF) [{ SCI removed }] dealing with SC2 requirements has the following function:
Preservation of SC1 SFs availability following a seismic event.
The DVJ system does not contribute to the safety functions that are part of the facility hazard protection.
15.0.1.6. Other Safety Functions to be performed in the Preventive Line of Defence
The DVJ system contributes indirectly to other safety functions to be performed as part of the preventive line of defence as follows:
Monitoring of room air temperature.
15.0.2. Safety Functional Requirements
15.0.2.1. Control of Fuel Reactivity
Not applicable.
15.0.2.2. Fuel Heat Removal
Not applicable.
15.0.2.3. Confinement of Radioactive Material
Not applicable. 15.0.2.4. SupportAPPROVED Contribution to Main Safety Functions In order to support its indirect contribution to the MSF of fuel heat removal, the DVJ system must satisfy the following Safety Functional Requirements (SFRs):
Ensure a room air temperature lower than maximum room air temperature in all fault conditions in order to ensure an air temperature compatible with safety classified equipment operation within JAC pumps and pipes rooms housing safety classified electrical and electro-mechanical equipment.
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Ensure a room air temperature higher than minimum room air temperature in all fault conditions in order to ensure an air temperature compatible with safety classified equipment operation within JAC pumps and pipes rooms housing safety classified electrical and electro-mechanical equipment.
15.0.2.5. Specific Contribution to Hazards Protection
In order to support its specific contribution to the safety functions that are part of the facility hazards protection, the DVJ system must satisfy the following SFRs:
Extreme low temperatures:
The DVJ system must maintain room conditions compatible with system operation in the event of extreme low temperatures.
Explosion:
The DVJ system must contribute to the limitation of a pressure wave inside the HOJ building in order to protect the safety classified equipment within this building.
Tornado:
The DVJ system must contribute to the limitation of a pressure wave and the non- propagation of missiles inside the HOJ building in order to protect the safety classified equipment within this building.
Wind:
The DVJ system must contribute to the non-propagation of wind generated missiles inside the HOJ building in order to protect the safety classified equipment within this building.
Fire:
The DVJ system must contribute to the prevention of spreading of fire through the ducts in case of fire event inside the HOJ building in order to protect the safety classified equipment within this building.
15.0.2.6. Other Safety Functions to be performed in the Preventive Line of Defence
In order to support its contribution to other safety functions to be performed as part of the preventive line of defence, the DVJ system must satisfy the following SFRs:
Monitoring of room air temperature The DVJAPPROVED system must monitor the air room temperature in order to alert control room staff if the temperature deviates outside the limits for correct function of safety classified JAC equipment.
15.0.3. Safety Features
Section 9.4.15 – Table 4 presents the SFs of the DVJ system, according to the contributions identified in section 15.0.1 and the SFRNs referenced in Sub-chapter 3.2.
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15.0.4. Classification and Architecture Requirements of Safety Features
15.0.4.1. Requirements arising from Safety Classification
Architecture requirements associated with SFs are essential for designing robust lines of defence consistent with their importance to nuclear safety (Sub-chapter 3.2). Such requirements strengthen the system design against:
single faults and associated consequences (Single Failure Criterion (SFC)) by requiring redundancy;
Loss Of Offsite Power (LOOP) by requiring a back-up power supply;
Common Cause Failures (CCF) by requiring, amongst others, physical separation;
earthquake by defining seismic requirements; and
accident conditions by qualification requirements.
Section 9.4.15 – Table 4 presents the requirements arising from safety classification for the DVJ system, according to the SFRNs referenced in Sub-chapter 3.2.
15.0.4.2. System Protection against Hazards
15.0.4.2.1. Internal Hazards
The SFs of the DVJ system must be protected against internal hazards if those hazards challenge the safety objectives, as defined in Sub-chapter 13.2.
15.0.4.2.2. External Hazards
The SFs of the DVJ system must be protected against external hazards if those hazards challenge the safety objectives, as defined in Sub-chapter 13.1.
15.0.4.3. Diversity
The DVJ system is not subject to the requirement for diversity.
15.0.5. Requirements defined at the Component Level
15.0.5.1. Generic Safety Requirements
15.0.5.1.1. Generic Mechanical, Electrical and I&C Requirements
The mechanical components of the DVJ system must comply with the mechanical requirements in accordanceAPPROVED with the rules laid out in Sub-chapter 3.2, section 7. The level of requirement is dependent upon whether or not it is a pressure retaining component, the safety class of the component, whether the component acts as an isolating device between interfacing SFs and on the role of the component as a barrier to the potential release of radioactivity as a result of failure of the component.
The electrical and Instrumentation and Control (I&C) components in the DVJ system must comply with the electrical and I&C requirements associated with their safety class, in accordance with the rules laid out in Sub-chapter 3.2.
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The mechanical, electrical and I&C components in the DVJ system must comply with Sub-chapter 9, section 4.1.
15.0.5.1.2. Seismic Requirements
The level of seismic requirements to be applied to DVJ system components is related to the Safety Feature Group (SFG) to which the component belongs, and the consequences on other classified components of its failure if it were not seismically qualified. The rules for defining the seismic requirements for a component are identified in Sub-chapter 3.2.
15.0.5.1.3. Qualification for Accident Conditions
The safety classified components of the DVJ system must be qualified for the operating conditions in which they are required, as specified in Sub-chapter 3.6.
15.0.5.2. Specific Safety Requirements
15.0.5.2.1. High Integrity Component (HIC) Requirements
The DVJ system is not subject to any High Integrity Components (HIC) requirements.
15.0.5.2.2. Specific I&C Requirements
The DVJ system has safety classified I&C and there will be specific reliability/availability requirements associated with the safety class of I&C architecture. It should further be clarified what is dedicated versus non-dedicated.
15.0.6. Examination, Maintenance, In-Service Inspection and Testing (EMIT)
15.0.6.1. Start-Up Tests
The DVJ system must be designed to enable the performance of start-up tests to ensure the adequacy of its design and performance under conditions as representative as possible of the different operating configurations, and in particular its compliance with the SFRs assigned to it in section 15.0.2.
15.0.6.2. In-Service Inspection
The DVJ system must be designed to enable surveillance under normal operation of the system characteristics necessary for the fulfilment of its safety-related tasks in order to ensure the performance of its components, and their availability under normal operation, or in the event of a fault or accident.
15.0.6.3. Periodic Testing The safety classifiedAPPROVED parts of the DVJ system must be designed to enable the performance of periodic tests in accordance with the maintenance schedule.
15.0.6.4. Maintenance
The DVJ system must be designed to enable the implementation of a maintenance schedule (see Sub-chapter 18.2).
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15.1. ROLE OF THE SYSTEM
The DVJ system performs the functions (or tasks) detailed in the following sections under the different plant operating conditions for which it is required.
15.1.1. Normal Plant Operation
The DVJ system provides the cooling support system for the rooms housing the classified systems contributing to heat removal and fire-fighting water production in the event of fire.
The DVJ system also contributes to the following non-classified functions:
air renewal required for occasional personnel intervention (comfort and hygiene) and more generally for purification of the rooms; and
cooling and heating of the rooms required to maintain acceptable room conditions (temperature) for good working order of the equipment.
The temperatures and humidity are listed in Sub-chapter 9.4, section 1.
15.1.2. Fault and Hazard Operating Conditions
The DVJ system provides the heating support system for the rooms housing the classified systems contributing to heat removal and fire-fighting water production in the event of fire.
It contributes to mitigating the effects of extreme low temperatures.
The DVJ system also contributes to the following non-classified functions:
in the event of fire, the DVJ system also ensures:
o isolation of fire in sector or zones limiting the fire propagation through ducts (SFI or ZFI);
o isolation of smoke transfer to the emergency exits and stairs, to facilitate safe means of escape for operators.
15.2. DESIGN BASIS
15.2.1. General Assumptions
The DVJ system provides air conditioning for the HOJ building and maintains room conditions compatible withAPPROVED the correct operation of the equipment, as defined in Sub-chapter 9.4, section 1 The DVJ system is used during normal operating conditions (plant states A to F) as well as during fault conditions and DEC-A and DEC-B.
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15.2.2. Design Assumptions
15.2.2.1. Control of Fuel Reactivity
Not applicable: the DVJ system does not directly contribute to the MSF of control of fuel reactivity.
15.2.2.2. Fuel Heat Removal
Not applicable: the DVJ system does not directly contribute to the MSF of fuel heat removal.
15.2.2.3. Confinement of Radioactive Material
Not applicable: the DVJ system does not directly contribute to the MSF of confinement of radioactive material.
15.2.2.4. Support Contribution to Main Safety Functions
In order to support the MSF of control of fuel reactivity, the DVJ system must satisfy the following SFRs:
Ensure a room air temperature lower than maximum room air temperature in all fault conditions in order to ensure an air temperature compatible with safety class 1 and class 2 equipment operation.
Ensure a room air temperature higher than minimum room air temperature in all fault conditions in order to ensure an air temperature compatible with safety class 1 and class 2 equipment operation.
15.2.2.5. Specific Contribution to Hazards Protection
The DVJ system contributes directly to the safety functions that are part of the facility hazard protection as follows:
maintaining room air temperature compatible with the correct operation of the safety classified equipment in the event of an “extreme low temperatures”,
protection against explosion,
protection against tornado,
protection against wind generated missiles, and
protection against fire events. 15.2.2.6. OtherAPPROVED Safety Functions to be performed in the Preventive Line of Defence In order to support other safety functions to be performed as part of the preventive line of defence, the DVJ system must satisfy the following SFRs:
Ensure a room air temperature lower than maximum room air temperature in all fault conditions in order to ensure an air temperature compatible with safety class 3 equipment operation.
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Ensure a room air temperature higher than minimum room air temperature in all fault conditions in order to ensure an air temperature compatible with safety class 3 equipment operation.
Monitor the air room temperature in order to prevent a failure of the DVJ equipment.
Other Assumptions
The DVJ system includes equipment which is resistant to a marine atmosphere C5M (to prevent corrosion).
15.2.3. Assumptions Associated with Extreme Situations resulting from Beyond Design Basis Hazards
15.2.3.1. Assumptions associated with Fukushima provisions
Studies regarding the DVJ system’s Fukushima provisions are ongoing. What follows are general assumptions regarding potential provisions:
Resistance to T7 tornado, and
Maintain inside temperature if the instantaneous temperature increases of { SCI removed } in summer, and decrease of { SCI removed } in winter.
15.2.3.2. Assumptions associated with other non–Fukushima provisions
The DVJ system is not subject to assumptions associated with non-Fukushima provisions.
15.3. SYSTEM DESCRIPTION AND OPERATION
15.3.1. Description
15.3.1.1. General System Description
For the purposes of describing the layout, the system can be divided up into the functions that it provides:
air renewal,
extraction,
heating, and monitoring.APPROVED These are discussed in detail below.
15.3.1.1.1. Air Renewal
Trains 1 and 4
Within trains 1 and 4 of the DVJ system, air is drawn in through an inlet plenum on the roof of the HOJ building and distributed simultaneously to the hall and intermediate levels.
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The supply of air to the hall area of the building also provides supply to the instrumentation room located on the same level. This supply is provided via ventilation grilles.
The supply of air to the intermediate level distributes air to the remainder of the building. This air is routed via a series of air transfer grilles from the intermediate level, through the staircase and associated lobbies, to the main JAC pump room for the associated train.
Trains 2 and 3
Within trains 2 and 3 of the DVJ system, air is drawn in through an inlet plenum on the roof of the building and distributed directly to the intermediate level of the HOJ building.
From the intermediate level this air is routed, via the staircase by ventilation grilles, to both the JAC pump room for the relevant train and the hall for the relevant train.
Water Tank
The water tank is naturally ventilated via dedicated ductwork.
15.3.1.1.2. Extraction
Trains 1 and 4
For the instrumentation room and the hall, air is extracted using a dedicated extraction fan located in the instrumentation room on the ground floor.
Air extracted directly from the intermediate and basement levels of the building is transported through extraction grilles and branching ductwork. Control valves located in this ductwork will be calibrated to ensure the appropriate air change rates throughout the building. The air is expelled to the environment via the outlet plenum on the roof of the HOJ building.
Trains 2 and 3
Trains 2 and 3 air extraction is provided by a single extraction fan located within the hall of the train ensuring an adequate air change rate for the building. Air is extracted directly from the 3 levels of the building via a series of branching ductwork. Control valves located in this ductwork will be calibrated to ensure the appropriate air change rates throughout the building. The air is expelled to the environment via the outlet plenum on the roof of the HOJ building.
15.3.1.1.3. Cooling
Trains 1, 2, 3, and 4 of the DVJ system incorporate a single cooling unit within the hall at ground level. Train 2 incorporates a second cooler within the autocom room. Each cooler isAPPROVED connected to a condenser unit on the roof. 15.3.1.1.4. Heating
Both classified and non-classified heaters are installed as part of the DVJ system. Classified heaters are present in all rooms containing JAC pipes, pumps and instrumentation.
15.3.1.1.5. Monitoring
The JAC pump and instrumentation rooms for all trains are equipped with temperature monitoring.
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15.3.1.2. Description of Main Equipment
The DVJ system comprises the following main equipment items (see the functional diagram provided in section 15.5):
Air inlets and outlets:
o extraction or blower fans connected to inlet or outlet plenums, and
o ventilation grilles.
Cooling:
o extractor fan connected to hood, and
o air conditioning unit.
Heating:
o space heaters or convectors controlled by room thermostats.
Temperature monitoring:
o analogue measurements.
Fire protection:
o fire dampers.
External explosion:
o anti-blast dampers.
15.3.1.3. Description of Main Layout
The HOJ building is broken down into four adjacent independent trains. It houses the JAC system.
15.3.1.4. Description of System I&C
The DVJ system has safety classified I&C and there will be specific reliability/availability requirements associated with the safety class of I&C architecture. It should further be clarified what is dedicated versus non-dedicated. 15.3.2. OperationAPPROVED 15.3.2.1. System Normal Operation
The DVJ system operates independently of the plant state. During normal plant operating conditions, as well as fault conditions (PCC-2 to PCC-4, DEC-A and DEC-B), the operation of the DVJ system depends on the room temperature and the status of the actuators in the HOJ building:
the air renewal operates continuously;
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the air cooling ventilation and the heating operate automatically; operation is controlled by room temperature sensors;
the JAC heating operates in order to maintain the temperature requirements for the JAC system, and
the air conditioning units are in continuous service, and operate independently.
15.3.2.2. Air Exchange
Air exchange ventilation systems operate on a permanent basis and ensure a minimum air exchange rate of { SCI removed } for all rooms.
15.3.2.3. System Transient Operation
High Temperature within the Rooms housing Safety Classified Equipment
In the event of the maximum room temperature set point (Tmax) in a room which houses safety classified equipment being reached, an alarm is transmitted to the main control room.
Then manual shutdown of non-safety classified equipment should decrease the room temperature in the rooms housing safety classified equipment. Otherwise, the safety classified equipment will be manually switched to an available train.
Low Temperature within the Rooms housing Safety Classified Equipment
In the event of the minimum room temperature set point (Tmin) in a room which houses safety classified equipment being reached, an alarm is transmitted to the main control room.
Then manual shutdown of non-safety classified air renewal ventilation should increase the room temperature in the rooms housing safety classified equipment. Otherwise, the safety classified equipment will be manually switched to an available train.
Extreme Low Temperatures
The heating equipment is designed for extreme low temperatures.
Internal Fire
The closure of fire dampers to isolate each fire safety sector and zone is automatically triggered by a fire detection (JDT) signal. The fire dampers also have fusible links to passively close them, if required.
External Explosion The passive antiAPPROVED-blast dampers are automatically closed during shock waves. Once the shock wave has passed, the dampers reopen and the ventilation system resumes operation.
Loss Of Offsite Power (LOOP)
The non-safety classified equipment is not backed-up in event of LOOP. This operation condition should decrease the room temperature in the rooms housing safety classified equipment. Otherwise, the safety classified equipment is manually switched to an available train.
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The fire dampers in the fire safety sectors and zones (safety functions) are emergency supplied by the emergency diesel generators.
15.4. PRELIMINARY DESIGN SUBSTANTIATION
The level of detail of in terms of evidence of compliance with the safety requirements stated in section 0 will develop as the HPC project moves from basic design into detailed design since the PCSR3 sequence and system sequence are evolving in parallel. Therefore, the level of detail presented in this section reflects the level of information available at the time of issuing the system chapters.
15.4.1. Compliance with Safety Functional Requirements
15.4.1.1. Control of Fuel Reactivity
Not applicable: the DVJ system does not directly contribute to the MSF of control of fuel reactivity.
15.4.1.2. Fuel Heat Removal
Not applicable: the DVJ system does not directly contribute to the MSF of control of fuel reactivity.
15.4.1.3. Confinement of Radioactive Material
Not applicable: the DVJ system does not directly contribute to the MSF of control of fuel reactivity.
15.4.1.4. Support Contribution to Main Safety Functions
The design assumptions of the DVJ system stated in section 15.2.2 are consistent with the requirements of the corresponding systems/equipment items which it supports:
The maximum temperature to be maintained in the HOJ building, which has been used in the sizing of the system, corresponds to the maximum permissible temperature in which the safety classified systems will still be able to operate.
The minimum temperature to be maintained in the HOJ building, which has been used in the sizing of the system, corresponds to the minimum permissible temperature in which the safety classified systems will still be able to operate.
15.4.1.5. Specific Contributions to Hazards Protection
The hazard studies of Sub-chapters 13.1 and 13.2 involving functions of the DVJ system use values for the following parameters that are in keeping with the design assumptions stated in section 15.2.2:APPROVED Extreme low temperatures
For each hazard study concerned, these studies show that the design of these functions is such that they meet the acceptance criteria.
Extreme low temperatures:
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The minimum temperature to be maintained in the HOJ Building which has been used in the sizing of the system, corresponds to the minimum permissible temperature in which the safety classified systems will still be able to operate:
o All safety classified electrical or mechanical equipment within rooms with a freeze risk will be compatible with a minimum permissible temperature.
These elements ensure that the SFRs stated in section 15.0.2 are met.
15.4.1.6. Other Safety Functions to be Performed in the Preventive Line of Defence
Other safety functions to be performed in the preventive line of defence involving the DVJ system uses values for the following parameters that are in keeping with the design assumptions stated in section 2.2:
Monitoring:
The DVJ system provides continuous monitoring of the room air temperature and alerts main control room staff if an upper or lower temperature limit has been reached, to ensure that the temperature remains within the range for the correct functioning of the safety classified equipment housed within the pumping station and outfall structure rooms. Values for temperature alarm set points will be defined as part of the detailed design.
15.4.2. Compliance with Design Requirements
The DVJ system complies with the requirements stated in sections 15.0.4 and 15.0.5, particularly with respect to those detailed in the following sections.
15.4.2.1. Requirements arising from Safety Classification
15.4.2.1.1. Safety Classification
The compliance of the design and manufacture of DVJ system materials and equipment performing a safety-related function with requirements from the classification rules (in Sub-chapter 3.2, section 7) is presented in section 15.4.2.4.1.
15.4.2.1.2. Single Failure Criterion and Redundancy
The design of the DVJ system meets the requirements of the active SFC stated in section 15.0.4.1, in particular in respect of the following:
The physical separation of the ventilation system between four divisions allows the single failure criterion to be met for heating of safety equipment in the HOJ building for the JAC system.APPROVED 15.4.2.1.3. Robustness against LOOP
The design of the DVJ system complies with the emergency power supply requirement stated in section 15.0.4.1, in particular in respect of the following requirement.
Loss Of Offsite Power (LOOP)
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The HVAC systems with safety classified functions required to maintain temperatures for the availability and protection of safety classified equipment, which is backed-up by Emergency Diesel Generators, are also backed-up by the EDGs.
15.4.2.1.4. Physical Separation
The DVJ system is designed in accordance with the physical separation requirement stated in section 15.0.4.1, in particular in respect of the following:
The DVJ system is divided into four trains which are:
o segregated (i.e. geographically / physically independent);
o supplied from independent (geographically / physically) electrical boards;
o controlled from independent (geographically / physically) I&C cabinets.
15.4.2.2. System Protection against Hazards
15.4.2.2.1. Internal Hazards
The overall demonstration of the robustness of the plant to internal hazards is covered in Sub-chapter 13.2.
The design of the DVJ system complies with the internal hazard protection requirements stated in Sub-chapter 13.2.
SECTION 9.4.15 – TABLE 1 : INTERNAL HAZARD PROTECTION REQUIREMENTS FOR THE DVJ SYSTEM
Protection General protection Specific protection Internal hazards required in introduced in the design principle of the system Detailed verification of the system protection against these hazards will Ruptures of piping be performed as part of the detailed design. Failures of tanks, pumps and valves Internal missiles Dropped loads Detailed verification of the system protection against these hazards will be performed as part of the detailed design. Internal explosion Fire Internal floodingAPPROVED 15.4.2.2.2. External Hazards
The overall demonstration of the robustness of the plant to external hazards is covered in Sub- chapter 13.1.
The design of the DVJ system complies with the external hazard protection requirements stated in Sub-chapter 13.1.
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SECTION 9.4.15 – TABLE 1 : EXTERNAL HAZARD PROTECTION REQUIREMENTS FOR THE DVJ SYSTEM
Protection Specific protection introduced External hazards required in General protection in the design of the system principle Earthquake Aircraft crash External explosion External fire Detailed verification of the system protection against these hazards will External flooding be performed as part of the detailed design. Snow and wind Extreme cold Lightning and EMI UHS Hazards
15.4.2.3. Diversity
Not applicable.
15.4.2.4. Requirements defined at the Component Level
15.4.2.4.1. General Mechanical, Electrical and I&C Requirements
The components of the DVJ system equipment performing a safety-related function comply with the general mechanical, electrical, and I&C requirements stated in section 15.0.5.1 as detailed in Section 9.4.15 – Table 3.
SECTION 9.4.15 – TABLE 3 : SAFETY CLASSIFICATION AND DESIGN REQUIRMEENTS FOR COMPONENTS OF THE DVJ SYSTEM
Description Safety classification Design requirements Mechanical requirement for Highest Highest pressure retaining safety safety Seismic Electrical I&C components or function class of requirement requirement requirement leak-tightness category SFG requirement for HVAC component JAC pipes B 1 NT SC1 C1 C1 heaters APPROVED JAC pumps B 1 - SC1 C1 C1 heaters
15.4.2.4.2. Seismic Requirements
The DVJ system complies with the seismic qualification requirements listed in Section 9.4.15 – Table 3.
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15.4.2.4.3. HIC Requirements
Not applicable.
15.4.2.4.4. Specific I&C Requirements
Not applicable.
15.4.3. Examination, Maintenance, in-service inspection and testing (EMIT)
15.4.3.1. Start-Up Tests
The DVJ system is subject to a start-up test programme in accordance with the procedures set out in Chapter 20 serving to verify the fulfilment of the following SFRs:
Ensure an room air temperature higher than minimum room air temperature in all fault conditions in order to ensure an air temperature compatible with safety classified equipment operation:
o Start-up and minimum power of the heating equipment of the HOJ building.
Ensure an room air temperature lower than maximum room air temperature in all fault conditions in order to ensure an air temperature compatible with safety classified equipment operation:
o Start-up and minimum flow rate of the ventilation of the HOJ building.
The DVJ system must monitor the air room temperature in order to prevent a failure of the DVJ equipment.
o The DVJ room air temperature sensors will be subjected to start-up tests to check their availability.
15.4.3.2. In-Service Inspection
The following functions of the DVJ system are used during normal plant operation under conditions representative of the fault/hazard conditions in which they are required:
Safety classified heating.
Tests are carried out during plant operation. They are conducted on each train successively, rather than simultaneously.
The availability of these functions is thus verified as part of normal operation. 15.4.3.3. PeriodicAPPROVED Testing The safety classified parts of the DVJ system are subject to periodic testing in accordance with the maintenance schedule in order to verify that the following SFRs are fulfilled:
Ensure a room air temperature higher than minimum room air temperature in all fault conditions in order to ensure an air temperature compatible with safety classified equipment operation:
o start-up of heating equipment.
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Ensure a room air temperature lower than maximum room air temperature in all fault conditions in order to ensure an air temperature compatible with safety classified equipment operation:
o start-up and minimum flow rate of the ventilation.
The DVJ system must monitor the air room temperature in order to prevent a failure of the DVJ equipment:
o the DVJ room air temperature sensors will be subjected to periodic tests to check their availability.
15.4.3.4. Maintenance
The DVJ system is subject to a maintenance programme to ensure the availability of the main components, and the safety classified components.
Preventive maintenance of the heating equipment and air treatment units is carried out during "summer" load conditions and "winter" load conditions respectively. Maintenance of other ventilation equipment in the system is carried out at the same time as the maintenance of the associated JAC train.
15.5. FUNCTIONAL DIAGRAM
The functional diagram of the DVJ system is shown in Section 9.4.15 – Figure 1. This gives a schematic overview of the HOJ building.
16. VENTILATION OF THE TURBINE HALL (DVM)
The information reported in this section is, unless otherwise noted, consistent with the reference design, as referenced from Chapter 22.
16.0. SAFETY REQUIREMENTS
The UK EPR Safety Classification principles and the top-down functional approach are presented in Sub-chapter 3.2. These principles help to ensure that the plant is designed, manufactured, constructed, commissioned and operated so that the appropriate level of reliability and integrity is achieved for its Structures, Systems and Components (SSCs).
The Hinkley Point C (HPC) functional safety analyses and the application of these safety classification principles to the HPC reference design result in the identification of the safety requirements for all safety systems in accordance with the Safety Functional Requirements Notes (SFRNs) referenced from Sub-chapter 3.2.
This section APPROVED summarises the results of these safety analyses and specifies the safety requirements that apply to the design of the Turbine Hall Ventilation System (DVM).
The requirements described in the present section are consistent with safety functions to which the DVM system contributes in Plant Condition Category (PCC) and Design Extension Conditions (DEC). Consistency with requirements inherited from the Design Basis Initiating Faults (DBIFs) should be checked when the list of DBIFs evolves (see Chapter 15)
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16.0.1. Safety Functions
The three Main Safety Functions (MSFs) necessary to achieve the overall safety objective of protecting people and the environment from the harmful effects of ionising radiation are:
control of fuel reactivity,
fuel heat removal,
confinement of radioactive material.
These three MSFs must be achieved during:
normal operating conditions (PCC-1), including duty functions, control of radioactive release during normal operating conditions, control of main plant parameters, fault initial conditions, Limiting Conditions of Operation (LCOs), limitations, monitoring functions, Probabilistic Safety Assessment (PSA) signification functions as part of the preventive line of defence;
fault conditions (PCC-2 to PCC-4, DEC-A and any equivalent DBIFs) and DEC-B;
hazard conditions.
16.0.1.1. Control of Fuel Reactivity
The DVM system does not directly contribute to the MSF of control of fuel reactivity.
16.0.1.2. Fuel Heat Removal
The DVM system does not directly contribute to the MSF of fuel heat removal.
16.0.1.3. Confinement of Radioactive Material
The DVM system does not directly contribute to the MSF of confinement of radioactive material.
16.0.1.4. Support Contribution to Main Safety Functions
The DVM system does not contribute to the MSF of fuel heat removal.
16.0.1.5. Specific Contribution to Hazards Protection
The DVM system does not contribute to the safety functions that are part of the facility’s hazard protection. 16.0.1.6. OtherAPPROVED Safety Functions to be performed in the Preventive Line of Defence The DVM system must contribute indirectly to other safety functions to be performed as part of the preventive line of defence as follows:
Air conditioning of the Turbine Hall (HM [TH]).
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16.0.2. Safety Functional Requirements
16.0.2.1. Control of Fuel Reactivity
Not applicable: The DVM system does not directly contribute to the MSF of control of fuel reactivity.
16.0.2.2. Fuel Heat Removal
Not applicable: The DVM system does not directly contribute to the MSF of fuel heat removal.
16.0.2.3. Confinement of Radioactive Material
Not applicable: The DVM system does not directly contribute to the MSF of confinement of radioactive material.
16.0.2.4. Support Contribution to Main Safety Functions
Not applicable : The DVM system does not contribute to the MSF of fuel heat removal.
16.0.2.5. Specific Contribution to Hazards Protection
Not applicable: The DVM system does not contribute to the safety functions that are part of the facility’s hazard protection.
16.0.2.6. Other Safety Functions to be performed in the Preventive Line of Defence
With respect to its contribution to other safety functions to be performed as part of the preventive line of defence, the DVM system must satisfy the following Safety Functional Requirements (SFRs):
Ensure an inside air temperature lower than maximum inside air temperature in all fault conditions in order to ensure an air temperature compatible with safety class equipment operation.
Ensure an inside air temperature higher than minimum inside air temperature in all fault conditions in order to ensure an air temperature compatible with safety class equipment operation.
16.0.3. Safety Features
Section 9.4.16 – Table 2 presents the Safety Features (SFs) of the DVM system, according to the contributions identified in section 16.0.1 and the SFRNs referenced in Sub-chapter 3.2. 16.0.4. ClassificationAPPROVED and Architecture Requirements of Safety Features 16.0.4.1. Requirements Arising from Safety Classification
Architecture requirements associated with SFs are essential for designing robust lines of defence consistent with their importance to nuclear safety (see Sub-chapter 3.2). Such requirements strengthen the system design against:
single faults and associated consequences (Single Failure Criterion (SFC)) by requiring redundancy;
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Loss Of Offsite Power (LOOP) by requiring, among others, a back-up power supply;
Station Black-Out (SBO) by requiring a power supply by the Ultimate Diesel Generators (UDGs);
Common Cause Failures (CCFs) by requiring, amongst others, physical separation;
earthquake by defining seismic requirements; and
accident conditions by qualification requirements.
Section 9.4.16 – Table 2 presents the requirements arising from the safety classification for the DVM system according to the SFRNs references in Sub-Chapter 3.2.
16.0.4.2. System Protection against Hazards
Internal Hazards
The safety features of the DVM system must be protected against internal hazards if those hazards challenge the safety objectives, as defined in Sub-chapter 13.2.
External Hazards
The safety features of the DVM system must be protected against external hazards if those hazards challenge the safety objectives, as defined in Sub-chapter 13.1.
16.0.4.3. Diversity
The DVM system is not subject to the requirement for diversity.
16.0.5. Requirements Defined at the Component Level
16.0.5.1. Generic Safety Requirements
16.0.5.1.1. Generic Mechanical, Electrical and Instrumentation and Control (I&C) Requirements
The mechanical components within the DVM system must comply with the mechanical requirements in accordance with the rules laid out in Sub-chapter 3.2, section 7. The level of requirement is dependent upon whether or not it is a pressure retaining component, the safety class of the component, whether the component acts as an isolating device between interfacing SFs, and on the role of the component as a barrier to the potential release of radioactivity as a result of failure of the component.
The electrical and Instrumentation and Control (I&C) components in the DVM system must comply with APPROVED the electrical and I&C requirements associated with their safety class, in accordance with the rules laid out in Sub-chapter 3.2.
The mechanical, electrical and I&C components in the DVM system must comply with section 9.4.1.
16.0.5.1.2. Seismic Requirements
The DVM system is not subject to any seismic requirements.
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16.0.5.1.3. Qualification for Accident Conditions
The DVM system is not subject to the requirement for qualification in accident conditions.
16.0.5.2. Specific Safety Requirements
16.0.5.2.1. High Integrity Component (HIC) Requirements
The DVM system is not subject to any High Integrity Component (HIC) requirements.
16.0.5.2.2. Specific I&C Requirements
The DVM system dedicated I&C is subject to safety requirements applicable to Class 3 I&C systems.
The general approach to qualification of dedicated I&C systems in terms of Production Excellence (PE) and Independent Confidence Building Measures (ICBM) is set out in Chapter 7.
16.0.6. Examination, Maintenance, In-Service Inspection and Testing (EMIT)
16.0.6.1. Start-Up Tests
The DVM system must be designed to enable the performance of start-up tests to ensure the adequacy of its design and performance under conditions as representative as possible of the different operating configurations, and in particular its compliance with the SFRs assigned to it in section 16.0.2.
16.0.6.2. In-Service Inspection
The DVM system must be designed to enable surveillance under normal operation of the system characteristics necessary for the fulfilment of its safety-related tasks in order to ensure the performance of its components, and their availability under normal operation, or in the event of a fault or accident.
16.0.6.3. Periodic Testing
The safety classified parts of the DVM system must be designed to enable the performance of periodic tests in accordance with the maintenance schedule.
16.0.6.4. Maintenance
The DVM system must be designed to enable the implementation of a maintenance schedule (see Sub-chapter 18.2). 16.1. ROLEAPPROVED OF THE SYSTEM 16.1.1. Normal Operating Conditions
The DVM system performs the following functions (or tasks) under normal operating conditions, for which it is required.
It provides the heating, cooling and air conditioning support needed for the HM [TH] Building which houses classified systems.
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The DVM system also contributes to the following non-classified functions:
Air renewal required for occasional personnel intervention (comfort and hygiene) and more generally for purification of the rooms; and
Cooling and heating of the rooms required to maintain acceptable ambient conditions (temperature) for good working order of the equipment.
16.1.2. Fault and Hazard Conditions
The DVM system contributes to following non-classified functions:
In the event of fire (see chapter 3.8.5), the DVM system also ensures:
o isolation of fire zones,
o creation of overpressure in the access sectors and isolation of smoke ingress into the emergency exits and stairs, facilitating evacuation of personnel and emergency response activities, and
o natural smoke exhaust in the turbine hall and mechanical smoke exhaust in the Turbine Lubrication, Jacking and Turning System (GGR) and Generator Seal Oil System (GHE) rooms.
16.2. DESIGN BASIS
16.2.1. General Assumptions
The DVM system is designed to maintain ambient conditions compatible with the correct operation of the equipment, as defined in section 9.4.1.
16.2.2. Design Assumptions
16.2.2.1. Control of Fuel Reactivity
Not applicable: the DVM system does not directly contribute to the MSF of control of fuel reactivity.
16.2.2.2. Fuel Heat Removal
Not applicable: the DVM system does not directly contribute to the MSF of fuel heat removal.
16.2.2.3. Confinement of Radioactive Material
Not applicable: the DVM system does not directly contribute to the MSF of confinement of radioactive material.APPROVED
16.2.2.4. Support Contribution to Main Safety Functions
Not applicable: the DVM system does not contribute to the MSF of fuel heat removal.
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16.2.2.5. Specific Contribution to Hazards Protection
Not applicable: there is no quantitative safety-related design assumptions associated with the DVM system.
16.2.2.6. Other Safety Functions to be performed in the Preventive Line of Defence
With respect to its contribution to other safety functions to be performed as part of the preventive line of defence, the DVM system must satisfy the following SFRs:
Ensure an inside air temperature lower than maximum inside air temperature in all fault conditions in order to ensure an air temperature compatible with safety class equipment operation.
Ensure an inside air temperature higher than minimum inside air temperature in all fault conditions in order to ensure an air temperature compatible with safety class equipment operation.
16.2.3. Other Assumptions
The DVM system is not subject to any other assumptions.
16.2.4. Assumptions associated with Extreme Situations resulting from Beyond Design Basis Hazards
16.2.4.1. Assumptions associated with Fukushima Provisions
The DVM system is not subject to assumptions associated with Fukushima provisions.
16.2.4.2. Assumptions associated with other Non-Fukushima Provisions
The DVM system is not subject to assumptions associated with non-Fukushima provisions.
16.3. SYSTEM DESCRIPTION AND OPERATION
16.3.1. Description
Each turbine building has a covered footprint of approximately { SCI removed }. The lowest basement finished floor level is at { SCI removed } and the other floors are at various finished floor levels within the basement. A two storey office is located at the north east end of the halls at a finished floor level of { SCI removed }.
The HM [TH] are accessed by four external staircases, two on the east elevation and two on the west elevation. The staircases on the east elevation, one has a goods lift ({ SCI removed }) and the other a passenger lift ({ SCI removed }). Of the two staircases located on the west elevation, one only providesAPPROVED access ({ SCI removed }); the other ({ SCI removed }) is located within the Conventional Island Electrical Building (HF), which is not covered within the scope of this document. { SCI removed }
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16.3.1.1. General System Description
16.3.1.1.1. Cooling of the Hall
The cooling of the hall is performed by { SCI removed } which are operated in parallel. The makeup air is provided by the intake louvers which are located along the east and west facades of the facility at a level between { SCI removed } and { SCI removed } for the HM [TH] building. Air is drawn through these intake louvers, down a masonry duct and through wall openings at level { SCI removed } for the HM [TH] building (which is equivalent to the platform height { SCI removed }). It flows through the building and is extracted at level { SCI removed } for the HM [TH] building by the fans.
The HM [TH] Building is divided into three discrete areas: (basement, ground floor and turbine floor). The internal temperature to be maintained in defined in section 9.4.1.
Cooling will be required in summer and winter when the turbine is in operation.
16.3.1.1.2. Heating of the Hall
When the temperature entering the building drops below { SCI removed }, some of the { SCI removed }-mounted fans are switched off to decrease the airflow to { SCI removed }. The operating fans should be equally distributed across the { SCI removed }.
At the same time, air heaters (fan heaters fitted with electric batteries) mounted at an approximate level of { SCI removed } and { SCI removed } for the HM [TH] building to be as close as possible to the air intakes, shall be started to heat the incoming air as it is distributed within the building.
The air shall not be introduced to the upper level of the HM [TH] Building at a temperature lower than that prescribed in section 9.4.1, therefore when the incoming air drops below this temperature, the plant will operate in a heating cycle.
16.3.1.1.3. Basement Level { SCI Removed } for the HM [TH] Building Ventilation
To ensure an adequate distribution of fresh air at basement level { SCI removed } for the HM [TH] building it is necessary to transfer air from Level { SCI removed }. Supply fans draw air via transfer air grilles at level { SCI removed } for the HM [TH] building and discharge via supply air grilles at level { SCI removed }. Air is extracted naturally to the ground floor.
16.3.1.1.4. Smoke Control of the Turbine Hall
The smoke control of the HM [TH] Building is ensured by natural extraction of the smoke using vents { SCI removed }. These vents can be opened by an operator command located in the access points of the building or by heat triggering a thermal fuse.
16.3.1.1.5. Motor-driven Feedwater Pump System (APA [MFWPS]) pumps (Level { SCI RemovedAPPROVED } for the HM [TH] building)
Four pump housings are located at the { SCI removed } of the HM [TH] Building at level { SCI removed }. These housings are ventilated to remove excess heat generated by the pump motors and fluids contained within the inter-connecting pipework. The ventilation system draws air from the surrounding area via transfer grilles within the walls of the pump housings before discharging back into the HM [TH] building at level { SCI removed }.
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The extraction system will be required to provide a high level of reliability and availability and therefore the system will require { SCI removed } redundancy and this shall be achieved by the use of automatic changeover duty/standby fans.
16.3.1.1.6. Reagent Preparation (SIR) Room (Level { SCI Removed } for the HM [TH] building) and –Storage (SIR) Room (Level { SCI Removed } for the HM [TH] building)
In the unlikely event of a spill or leak from the process, it shall be possible for the volumetric flow rate for extraction to be increased by { SCI removed }. The emergency function of the system will operate if the detection equipment within either of the rooms detects the presence of reagent (hydrazine) above predetermined levels.
The extraction system will be required to provide a high level of reliability and availability and therefore the system will require { SCI removed } redundancy and this shall be achieved by the use of automatic changeover duty/standby fans.
In the unlikelihood of a spillage or leak from the process the normal extraction system volumetric flow rate shall be capable of being increased by { SCI removed }. Make up air shall be transferred from the HM [TH] building at levels { SCI removed } and { SCI removed } for the HM [TH] building to the rooms via transfer grilles. These grilles shall be fitted with automatic smoke/fire dampers.
Extracted air from the two areas shall be discharged to atmosphere via external louvres fitted at level { SCI removed } for the HM [TH] building in the east elevation wall. These louvres shall have security and bird guards fitted.
Each room shall be treated as a separate fire compartment and therefore will require a fire/smoke damper to be installed within the extract ductwork to maintain fire compartmentation between the room and the HM [TH] building.
16.3.1.1.7. Chemical Sampling (SIT) Room (Level { SCI Removed } for the HM [TH] Building)
The Chemical Sampling and Monitoring System (SIT) Chemical Sampling Room is split into two sections, one section shall be used as an Analytical Facility and the other as a Packaging Area.
A single extract fan with inter-connecting ductwork and grilles shall be used to provide a minimum of one air change rate per hour to both the areas. Make up air shall be cascaded through transfer grilles from the HM [TH] building to the Analytical Facility before being passed through another set of transfer grilles to the Packaging Area.
Extracted air shall be discharged to atmosphere via a louvre fitted at level { SCI removed } for the HM [TH] building in the east elevation wall.
The air transferred to the Analytical Facility will need to be cooled or heated to provide the required environmental temperature. This cooling/heating shall be provided from a reverse cycle split heating andAPPROVED cooling system. The condenser part of the split system shall be located within the HM [TH] building adjacent to the room.
16.3.1.1.8. Generator Seal Oil System (GHE) Room (Level { SCI Removed } for the HM [TH] Building)
The system shall consist of two extract fans installed in parallel with silencers, inter-connecting ductwork, extract grilles, non-return dampers, fire/smoke dampers and discharge louvre.
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During normal operations the extraction system shall be sized to provide the required number of air changes to remove the internal heat gains within the room and maintain the required operating temperature range.
A dedicated smoke extract fan shall provide smoke control in the event of a fire. Make up air shall be provided via transfer grilles fitted with fire/smoke dampers from the HM [TH] building to the GHE system room. Smoke extraction requires an air change rate of { SCI removed }.
The room shall be deemed to be a fire compartment and therefore the extract ductwork will require automatically operated fire/smoke dampers installed between the room and the HM [TH] building.
16.3.1.1.9. Turbine Generator Hydrogen Supply System (GRV) Area (Level { SCI Removed } for the HM [TH] Building)
The extraction system shall consist of two extractor fans duty/standby, inter-connecting ductwork, extractor hood and external discharge louvre. The extractor hood shall be of a sufficient size to remove any hydrogen leaking from the plant.
The extracted air shall discharge through an external louvre at level { SCI removed } for the HM [TH] building on the east elevation wall.
16.3.1.1.10. Autocom Room 01 & 02 (Level { SCI Removed } for the HM [TH] Building)
A local supply fan with intake louvre, inter-connecting ductwork and grilles shall provide air to the room in order to meet the requirement of { SCI removed }.
To achieve the required operating environmental temperature within the room a reverse cycle split heating and cooling system shall be installed. The condenser for this unit shall be located within the HM [TH] building at level { SCI removed } for the HM [TH] building.
The room shall be deemed to be a fire compartment and therefore the extraction ductwork will require automatically operated fire/smoke dampers installed between the room and the HM [TH] building.
16.3.1.1.11. Turbine Lubrication, Jacking and Turning System (GGR) – Oil Tank Room (Level { SCI Removed } for the HM [TH] Building)
The GGR system room is located on the ground floor of the HM [TH] building.
Air shall be extracted from the area through an extractor fan, inter-connecting ductwork, fire dampers and grilles. The extractor fan shall be configured to operate at three conditions:
Slow speed when the environmental temperature of the HM [TH] building is at { SCI removedAPPROVED } or below. High speed when the environmental temperature of the HM [TH] building is at a temperature above { SCI removed }.
High speed for the removal of smoke.
Supply air for smoke exhaust will be transferred directly from the outside, through a dedicated duct whose air intake louvre is located on the opposite side of the hall from the extraction louvre. This duct will be fitted with a smoke clearance damper.
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The room shall be deemed to be a fire compartment and therefore, in addition to the fire/smoke dampers installed on the air transfer grilles, automatically operated fire/smoke dampers shall be installed within the extraction duct, as it exits the room.
16.3.1.1.12. Turbine Valve Hydraulic Oil System (GFR) Room (Level { SCI Removed } for the HM [TH] Building)
The GFR system room is located on the ground floor of the HM [TH] building. Therefore, the temperature around it is lower than the temperature reached at the highest level (which is consistent with section 9.4.1). Filtered air shall be transferred from the HM [TH] building in order to maintain the room at the required temperature. The transfer air will enter the room via transfer grilles fitted with automatically operated fire/smoke dampers.
The ventilation ductwork will perform two functions, low and high speed ventilation, depending on whether temperature of the HM [TH] building is above or below { SCI removed }.
The room shall be deemed to be a fire compartment and therefore, in addition to the fire/smoke dampers installed on the air transfer grilles, automatically operated fire/smoke dampers shall be installed within the extraction duct, as it exits the room.
16.3.1.2. Description of Main Equipment
Cooling
The equipment inside the areas can be cooled using:
extractor fans, and
reverse cycle split heating and cooling system.
Heating
The heating is ensured by fan heaters fitted with electric heater batteries.
Intake louvres
The intake louvres are fitted with motorised isolation dampers, bird screens and security bars.
Attenuators
The silencers are installed in an accessible position within the concrete intake ducts and shall be designed to achieve the same sound insulation rating at the intake louvre as that for the cladding of the building. 16.3.1.3. DescriAPPROVEDption of Main Layout All the equipment is located within HM [TH] building.
16.3.1.4. Description of System I&C
Fire dampers and smoke controlled systems are controlled by the fire dedicated I&C (see Sub-chapter 9.5, section 1.5).
All the ventilation installations within each fire compartment are fitted with fire dampers at the air inlet and outlets.
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Other DVM system equipment is controlled by Heating, Ventilating and Air Conditioning (HVAC) dedicated I&C cabinets located within a dedicated room in the HM [TH] building.
16.3.2. Operation
16.3.2.1. System Normal Operation
The DVM system operates independently of the plant state. During normal plant operating conditions, as well as fault conditions (PCC-2 to PCC-4, DEC-A, and any equivalent DBIFs), the operation of the DVM system depends on the outside temperature:
the air renewal operates continuously;
the air cooling ventilation and the heating operate automatically; operation is controlled by the inside temperature sensors; and
the air conditioning units are in continuous service and operate independently.
16.3.2.2. System Transient Operation
Internal Fire
The closure of fire dampers to isolate each fire safety sector and zone is automatically triggered by a Fire Detection System (JDT [FDS]) signal.
The compartment can also be completely isolated in event of fire by activation of the thermal fuse.
16.3.2.3. Other Operating Conditions
16.3.2.3.1. Full or Partial System Failure
{ This section contains SCI-only text and has been removed }
16.3.2.3.2. Failures of Interfaced Systems
{ This section contains SCI-only text and has been removed }
16.4. PRELIMINARY DESIGN SUBSTANTATION
The level of detail of evidence and compliance with the safety requirements stated in section 16.0 will develop as the HPC project moves from basic design into detailed design since PCSR3 sequence and system sequence are evolving in parallel. Therefore, the level of details presented in this section depends on the information available at the time of issuing the system chapters. APPROVED 16.4.1. Compliance with Safety Functional Requirements
16.4.1.1. Control of Fuel Reactivity
Not applicable: the DVM system does not directly contribute to the MSF of control of fuel reactivity.
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16.4.1.2. Fuel Heat Removal
Not applicable: the DVM system does not directly contribute to the MSF of fuel heat removal.
16.4.1.3. Confinement of Radioactive Material
Not applicable: the DVM system does not directly contribute to the MSF of confinement of radioactive material.
16.4.1.4. Support Contribution to Main Safety Functions
Not applicable: the DVM system does not contribute to the MSF of heat removal.
16.4.1.5. Specific Contribution to Hazards Protection
Not applicable: the DVM system does not contribute to the safety functions that are part of the facility’s hazard protection.
16.4.1.6. Other Safety Functions to be performed in the Preventive Line of Defence
Other safety functions to be performed in the preventive line of defence involving the DVM system uses values for the following parameters that are in keeping with the design assumptions stated in section 16.2.2:
The target maximum temperature to be maintained in the HM [TH] building which has been used in the sizing of the system, corresponds to the maximum permissible temperature in which the safety classified systems will be able to operate:
o All safety classified electrical equipment will be compatible with a maximum permissible temperature.
The target minimum temperature to be maintained in the HM [TH] building which has been used in the sizing of the system, corresponds to the minimum permissible temperature in which the safety classified systems will still be able to operate:
o All safety classified electrical or mechanical equipment within rooms with a freeze risk will be compatible with a minimum permissible temperature.
These elements ensure that the SFRs stated in section 16.0.2 are met.
16.4.2. Compliance with Design Requirements
The DVM system complies with the requirements stated in sections 16.0.4 and 16.0.5, particularly with respect to those detailing in the following sections. 16.4.2.1. RequirementsAPPROVED arising from Safety Classification 16.4.2.1.1. Safety Classification
The compliance of the design and manufacture of the DVM system materials and equipment performing a safety-related function with requirements from the classification rules (in Sub-chapter 3.2, section 7) is presented in section 16.4.2.4.1.
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16.4.2.1.2. Single Failure Criterion and Redundancy
Not applicable: The DVM system is not subject to any requirements for SFC and redundancy requirements.
16.4.2.1.3. Robustness against LOOP
Not applicable: the DVM system is not subject to any robustness against LOOP requirements.
16.4.2.1.4. Physical Separation
Not applicable: the DVM system is not subject to any physical separation requirements.
16.4.2.2. System Protection against Hazards
16.4.2.2.1. Internal Hazards
The overall demonstration of the robustness of the plant to internal hazards is covered in Sub-chapter 13.2.
16.4.2.2.2. External Hazards
The overall demonstration of the robustness of the plant to external hazards is covered in Sub-chapter 13.1.
16.4.2.3. Diversity
Not applicable: the DVM system is not subject to the requirement for diversity.
16.4.2.4. Requirements defined at the Component Level
16.4.2.4.1. General Mechanical, Electrical and I&C Requirements
The components of the DVM system equipment performing a safety-related function comply with the general mechanical, electrical, and I&C requirements stated in section 16.0.5.1 as detailed in Section 9.4.16 – Table 1.
SECTION 9.4.16 – TABLE 1 : SAFETY CLASSIFICATION AND DESIGN REQUIREMENTS OF COMPONENTS OF THE DVM SYSTEM
Description Safety classification Design requirements Mechanical requirement for Highest Highest pressure retaining safety safety Seismic Electrical I&C components or function class of requirement requirement requirement leaktightness APPROVEDcategory SFG requirement for HVAC component Ventilation C 3 NT NR C3 C3 This table will be updated after the Safety Classification Component Lists (SCCLs) studies.
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16.4.2.4.2. Seismic Requirements
Considering that the HM [TH] building pipes, structures and component are not SC1 and considering the contribution of failsafe design implemented for the safety-related functions, no seismic requirements exist on component within the HM [TH] building.
16.4.2.4.3. HIC Requirements
Not applicable: the DVM system is not subject to any HIC requirements.
16.4.2.4.4. Specific I&C Requirements
The specific I&C requirements detailed in section 16.0.5.2.2 are the basis for the DVM system development and manufacturing. The DVM system will satisfy all these requirements.
16.4.3. Examination, Maintenance, In-Service Inspection and Testing (EMIT)
16.4.3.1. Start-Up Tests
The DVM system is subject to a start-up test programme in accordance with the procedures set out in Chapter 20 serving to verify the fulfilment of the following SFRs:
Ensure an inside air temperature lower than maximum inside air temperature in all fault conditions in order to ensure an air temperature compatible with safety class equipment operation:
o start-up of the ventilation; and
o start-up and minimum power of the air conditioning units.
Ensure an inside air temperature higher than minimum inside air temperature in all fault conditions in order to ensure an air temperature compatible with safety class equipment operation:
o start-up and minimum power of the heating equipment.
16.4.3.2. In-Service Inspection
The following functions of the DVM system are used during normal plant operation under conditions representative of the fault/hazard conditions in which they are required:
safety classified air conditioning units;
safety classified ventilation; and safety APPROVEDclassified heating. Tests are carried out during plant operation. They are conducted on each zone successively, rather than simultaneously.
Clogging of the filters is regularly checked.
The air conditioning units are serviced in accordance with the manufacturer's guidelines.
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16.4.3.3. Periodic Testing
The safety classified parts of the DVM system are subject to periodic testing in accordance with the maintenance schedule in order to verify that the following SFRs are fulfilled:
Ensure an inside air temperature lower than maximum inside air temperature in all fault conditions in order to ensure an air temperature compatible with safety class equipment operation.
o start-up of the ventilation; and
o start-up of air conditioning units.
Ensure an inside air temperature higher than minimum inside air temperature in all fault conditions in order to ensure an air temperature compatible with safety class equipment operation:
o start-up of heating equipment.
16.4.3.4. Maintenance
The DVM system is subject to a maintenance programme to guarantee requirements detailed in section 16.0.
16.5. FUNCTIONAL DIAGRAM
The functional diagrams of the DVM system “HM [TH] building” are shown in Section 9.4.16 – Figure 1.
The functional diagrams of the DVM system “APA [MFWPS] system pumps” are shown in Section 9.4.16 – Figure 2.
The functional diagrams of the DVM system “SIR/SIT system” are shown in Section 9.4.16 – Figure 3.
The functional diagrams of the DVM system “GHE, Autocom, DVM system cabinets” are shown in Section 9.4.16 – Figure 4.
The functional diagrams of the DVM system “GGR, GFR, GRV system” are shown in Section 9.4.16 – Figure 5.
This gives a schematic overview of the HM [TH] building (for more details, see the detailed mechanical diagram of the DVM system referenced in Chapter 22.3).
Note: this section does not provide a schematic overview of the offices because the DVM system only providesAPPROVED air renewal within these offices.
17. VENTILATION OF THE CONVENTIONAL ISLAND ELECTRICAL BUILDING (DVF)
The information reported in this section is, unless otherwise noted, consistent with the reference design, as referenced from Chapter 22.
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17.0. SAFETY REQUIREMENTS
The UK EPR Safety Classification principles and the top-down functional approach are presented in Sub-chapter 3.2. These principles help to ensure that the plant is designed, manufactured, constructed, commissioned and operated so that the appropriate level of reliability and integrity is achieved for its Structures, Systems and Components (SSCs).
The Hinkley Point C (HPC) functional safety analyses and the application of these safety classification principles to the HPC reference design result in the identification of the safety requirements for all safety systems in accordance with the Safety Functional Requirements Notes (SFRNs) referenced from Sub-chapter 3.2.
This section summarises the results of these safety analyses and specifies the safety requirements that apply to the design of the Ventilation System for the Conventional Island Electrical Building (DVF).
The requirements described in the present section are consistent with safety functions to which the DVF system contributes in Plant Condition Category (PCC) and Design Extension Conditions (DEC). Consistency with requirements inherited from the Design Basis Initiating Faults (DBIFs) should be checked when the list of DBIFs evolves (see Chapter 15).
17.0.1. Safety Functions
The three Main Safety Functions (MSFs) necessary to achieve the overall safety objective of protecting people and the environment from the harmful effects of ionising radiation are:
control of fuel reactivity,
fuel heat removal,
confinement of radioactive material.
These three MSFs must be achieved during:
normal operating conditions (PCC-1), including duty functions, control of radioactive release during normal operating conditions, control of main plant parameters, fault initial conditions, Limiting Conditions of Operation (LCOs), limitations, monitoring functions, Probabilistic Safety Assessment (PSA) signification functions as part of the preventive line of defence,
fault conditions (PCC-2 to PCC-4, DEC-A and any equivalent DBIFs) and DEC-B, and
hazard conditions. 17.0.1.1. ControlAPPROVED of Fuel Reactivity The DVF system does not directly contribute to the MSF of control of fuel reactivity.
17.0.1.2. Fuel Heat Removal
The DVF system does not directly contribute to the MSF of fuel heat removal.
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17.0.1.3. Confinement of Radioactive Material
The DVF system does not directly contribute to the MSF of confinement of radioactive material.
17.0.1.4. Support Contribution to Main Safety Functions
The DVF system must indirectly contribute to the MSF of control of fuel reactivity as a support system as follows:
Air conditioning of the rooms in the Conventional Island Electrical Building (HF) containing Class 1 and Class 2 systems.
17.0.1.5. Specific Contribution to Hazards Protection
The DVF system indirectly contributes to the hazard protection as a support system as follows:
Alarm on the loss of DVF system to { SCI removed } DC Power Production and Distribution (LA*) for modification of the operation of the batteries in forced floating mode ({ SCI removed }).
17.0.1.6. Other Safety Functions to be performed in the Preventive Line of Defence
The DVF system must contribute indirectly to other safety functions to be performed as part of the preventive line of defence as follows:
Air conditioning of Class 3 systems in the HF building (both HF-a, and HF-b parts).
Detection of the loss of air-conditioning of Class 1 and Class 2 systems in the HF building.
17.0.2. Safety Functional Requirements
17.0.2.1. Control of Fuel Reactivity
Not applicable: the DVF system does not directly contribute to the MSF of control of fuel reactivity.
17.0.2.2. Fuel Heat Removal
Not applicable: the DVF system does not directly contribute to the MSF of fuel heat removal.
17.0.2.3. Confinement of Radioactive Material
Not applicable: the DVF system does not directly contribute to the MSF of confinement of radioactive material.APPROVED 17.0.2.4. Support Contribution to Main Safety Functions
With respect to its contribution to the MSF of control of fuel reactivity, the DVF system must satisfy the following Safety Functional Requirements (SFRs):
Ensure an internal air temperature lower than maximum internal air temperature in all fault conditions in order to ensure an air temperature compatible with Safety Class 1 and Class 2 equipment operation.
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Ensure an internal air temperature higher than minimum internal air temperature in all fault conditions in order to ensure an air temperature compatible with Safety Class 1 and Class 2 equipment operation.
17.0.2.5. Specific Contribution to Hazards Protection
With respect to the facility’s hazard protection, the DVF system must satisfy the following SFRs:
Ensure an internal air temperature lower than maximum internal air temperature in all fault conditions in order to ensure an air temperature compatible with Safety Class 1 and Class 2 equipment operation.
Ensure an internal air temperature higher than minimum internal air temperature in all fault conditions in order to ensure an air temperature compatible with Safety Class 1 and Class 2 equipment operation.
Alarm on the loss of the DVF system to LA* for modification of the operation of the batteries in forced floating mode ({ SCI removed }).
17.0.2.6. Other Safety Functions to be performed in the Preventive Line of Defence
With respect to its contribution to other safety functions to be performed as part of the preventive line of defence, the DVF system must satisfy the following SFRs:
Ensure an internal air temperature lower than maximum internal air temperature in all fault conditions in order to ensure an air temperature compatible with Safety Class 3 equipment operation.
Ensure an internal air temperature higher than minimum internal air temperature in all fault conditions in order to ensure an air temperature compatible with Safety Class 3 equipment operation.
Detect the loss of air-conditioning of Class 1 and Class 2 systems in the HF building.
17.0.3. Safety Features and Instrumentation and Control (I&C) actuation modes
Section 9.4.17 – Table 2 presents the Safety Features (SFs) of the DVF system, according to the contributions identified in section 17.0.1 and the SFRNs referenced in Sub-chapter 3.2.
17.0.4. Classification and Architecture Requirements of Safety Features
17.0.4.1. Requirements Arising from Safety Classification
Architecture requirements associated with SFs are essential for designing robust lines of defence consistent with their importance to nuclear safety (see Sub-chapter 3.2). Such requirements strengthenAPPROVED the system design against: single faults and associated consequences (Single Failure Criterion (SFC)) by requiring redundancy;
Loss Of Off-site Power (LOOP) by requiring, among others, a back-up power supply;
Station Black-Out (SBO) by requiring a power supply by the Ultimate Diesel Generators (UDGs);
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Common Cause Failures (CCFs) by requiring, amongst others, physical separation;
earthquake by defining seismic requirements; and
accident conditions by qualification requirements.
Section 9.4.17 – Table 2 presents the requirements arising from the safety classification for the DVF system according to the SFRNs references in Sub-Chapter 3.2.
17.0.4.2. System Protection against Hazards
Internal Hazards
The SFs of the DVF system must be protected against internal hazards if those hazards challenge the safety objectives, as defined in Sub-chapter 13.2.
External Hazards
The SFs of the DVF system must be protected against external hazards if those hazards challenge the safety objectives, as defined in Sub-chapter 13.1.
17.0.4.3. Diversity
The DVF system is not subject to the requirement for diversity.
17.0.5. Requirements Defined at the Component Level
17.0.5.1. Generic Safety Requirements
17.0.5.1.1. Generic Mechanical, Electrical and I&C Requirements
The mechanical components within the DVF system must comply with the mechanical requirements in accordance with the rules laid out in Sub-chapter 3.2, section 7. The level of requirement is dependent upon whether or not it is a pressure retaining component, the safety class of the component, whether the component acts as an isolating device between interfacing SFs, and on the role of the component as a barrier to the potential release of radioactivity as a result of failure of the component.
The electrical and Instrumentation and Control (I&C) components in the DVF system must comply with the electrical and I&C requirements associated with their safety class, in accordance with the rules laid out in Sub-chapter 3.2.
The mechanical, electrical and I&C components in the DVF system must comply with the section 9.4.1. 17.0.5.1.2. SeismicAPPROVED Requirements The DVF system is not subject to any seismic requirements.
17.0.5.1.3. Qualification for Accident Conditions
The safety classified components of the DVF system must be qualified for the operating conditions in which they are required, as specified in Sub-chapter 3.6.
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17.0.5.2. Specific Safety Requirements
17.0.5.2.1. High Integrity Component (HIC) Requirements
The DVF system is not subject to any High Integrity Component (HIC) requirements.
17.0.5.2.2. Specific I&C Requirements
The DVF system dedicated I&C is subject to safety requirements applicable to Class 3 I&C systems.
The general approach to qualification of dedicated I&C systems in terms of Production Excellence (PE) and Independent Confidence Building Measures (ICBM) is set out in Chapter 7.
17.0.6. Examination, Maintenance, In-Service Inspection and Testing (EMIT)
17.0.6.1. Start-up Tests
The DVF system must be designed to enable the performance of start-up tests to ensure the adequacy of its design and performance under conditions as representative as possible of the different operating configurations, and in particular its compliance with the SFRs assigned to it in section 17.0.2.
17.0.6.2. In-Service Inspection
The DVF system must be designed to enable surveillance under normal operation of the system characteristics necessary for the fulfilment of its safety-related tasks in order to ensure the performance of its components, and their availability under normal operation, or in the event of a fault or accident.
17.0.6.3. Periodic Testing
The safety classified parts of the DVF system must be designed to enable the performance of periodic tests in accordance with the maintenance schedule.
17.0.6.4. Maintenance
The DVF system must be designed to enable the implementation of a maintenance schedule (see Sub-chapter 18.2).
17.1. ROLE OF THE SYSTEM
17.1.1. Normal Operating Conditions
The DVF system performs the following functions (or tasks) under normal operating conditions, for which it is required:APPROVED It provides the heating, cooling and air conditioning support system for the rooms housing the classified systems contributing to control of fuel reactivity.
The DVF system also contributes to the following non-classified functions:
Air renewal required for occasional personnel intervention (comfort and hygiene) and more generally for purification of the rooms.
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Cooling and heating of the rooms required to maintain acceptable ambient conditions (temperature) for good working order of the equipment.
17.1.2. Fault and Hazard Conditions
The DVF system contributes to following non-classified functions:
In the event of fire, the DVF system also ensures:
o isolation of fire sectors,
o creation of overpressure in the access sectors and isolation of smoke ingress into the emergency exits and stairs, facilitating evacuation of the personnel and emergency response activities, and
o smoke control in rooms containing electrical equipment.
17.2. DESIGN BASIS
17.2.1. General Assumptions
The DVF system is designed to maintain internal conditions compatible with the correct operation of the equipment, as defined in section 9.4,.1.
17.2.2. Design Assumptions
17.2.2.1. Control of Fuel Reactivity
Not applicable: the DVF system does not directly contribute to the MSF of control of fuel reactivity.
17.2.2.2. Fuel Heat Removal
Not applicable: the DVF system does not directly contribute to the MSF of fuel heat removal.
17.2.2.3. Confinement of Radioactive Material
Not applicable: the DVF system does not directly contribute to the MSF of confinement of radioactive material.
17.2.2.4. Support Contribution to Main Safety Functions
With respect to its contribution to the MSF of control of fuel reactivity, the DVF system must satisfy the following SFRs:
EnsureAPPROVED an internal air temperature lower than maximum internal air temperature in all fault conditions in order to ensure an air temperature compatible with Safety Class 1 and Class 2 equipment operation.
Ensure an internal air temperature higher than minimum internal air temperature in all fault conditions in order to ensure an air temperature compatible with Safety Class 1 and Class 2 equipment operation.
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17.2.2.5. Specific Contribution to Hazards Protection
With respect to the facility’s hazard protection, the DVF system must satisfy the following SFRs:
Ensure an internal air temperature lower than maximum internal air temperature in all fault conditions in order to ensure an air temperature compatible with Safety Class 1 and Class 2 equipment operation.
Ensure an internal air temperature higher than minimum internal air temperature in all fault conditions in order to ensure an air temperature compatible with Safety Class 1 and Class 2 equipment operation.
Alarm on the loss of the DVF system to LA* for modification of the operation of the batteries in forced floating mode ({ SCI removed }).
17.2.2.6. Other Safety Functions to be performed in the Preventive Line of Defence
With respect to its contribution to other safety functions to be performed as part of the preventive line of defence, the DVF system must satisfy the following SFRs:
Ensure an internal air temperature lower than maximum internal air temperature in all fault conditions in order to ensure an air temperature compatible with Safety Class 3 equipment operation.
Ensure an internal air temperature higher than minimum internal air temperature in all fault conditions in order to ensure an air temperature compatible with Safety Class 3 equipment operation.
Detect the loss of air-conditioning of Class 1 and Class 2 systems in the HF building.
17.2.3. Other Assumptions
The DVF system is not subject to any other assumptions.
17.2.4. Assumptions associated with Extreme Situations resulting from Beyond Design Basis Hazards
17.2.4.1. Assumptions associated with Fukushima Provisions
The DVF system is not subject to assumptions associated with Fukushima provisions.
17.2.4.2. Assumptions associated with other Non-Fukushima Provisions
The DVF system is not subject to assumptions associated with non-Fukushima provisions.
17.3. SYSTEMAPPROVED DESCRIPTION AND OPERATION
17.3.1. Description
The HF building and the Turbine building (HM [TH]), are structures within the Conventional Island (CI) and are positioned such that the HF building adjoins the HM [TH] building as well as being located near the power-transmission platform.
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The CI systems have electrical supplies that originate from normal and secured electrical distribution panels. These, together with the instrumentation and control system which manages and monitors these systems, are all housed within the HF building.
The { SCI removed } electrical supplies to the HF building come from the step-down transformers and auxiliary transformers.
The HF building delivers the permanent { SCI removed } supply to the nuclear island’s four electrical buildings.
In order to minimize the risks of loss of power from an external source, the HF building is divided into two fire compartments referenced Zone A and Zone B. Each zone has its own independent ventilation system that is referenced hereon as the DVF system.
17.3.1.1. General System Description
The DVF system is consistent with the fire protection requirements listed in Sub-chapter 3.8 section 5.
17.3.1.1.1. Ventilation and Air-Conditioning System
Each of the HF building zones will be provided with two standalone Air Handling Units (AHU).
In some cases (rooms with important heat loads), the heating and cooling power supplied by the AHUs may not be sufficient to maintain the rooms at the requested temperature. Therefore, additional cooling and heating shall be provided via local equipment.
There is no intention to provide redundancy in the event of heating failure on an AHU. However, as temporary cooling is not as easy to provide as heating, it is intended that the AHU units are sized to provide two thirds of the total cooling duty. During normal operations, each unit shall operate at { SCI removed } of the total duty leaving approximately { SCI removed } in reserve as extra cooling capacity if needed.
The DVF system shall only provide supply air to the battery rooms. An independent sub-system shall provide extraction. It is sized to ensure that the hydrogen concentration levels within the battery room are maintained at a level below { SCI removed } volume of hydrogen in air (Lower Explosion Limits (LEL)).
17.3.1.1.2. Chilled Water System
Air cooled water chillers shall provide chilled water at the required flow rate to the cooling coils within the AHU’s. In order to provide a level of redundancy for the chilled water system serving the two zones, an additional standby chiller shall be supplied. This chiller shall be sized to operate at the maximum design duty for one zone and have pipework configured so that in the event of one of the designated zone chillers failing, the third chiller can be brought into service to replace the failedAPPROVED one. 17.3.1.1.3. Supplementary Cooling and Heating
Supplementary heating and cooling shall be installed in some rooms where the supply of warm air by the AHUs is not sufficient to maintain the requested temperatures.
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17.3.1.1.4. Battery Discharge Bench
An independent supply and extract sub-system shall be provided to remove the heat source during the electrical discharging of the batteries.
17.3.1.1.5. Battery Extraction System
The battery room will have an independent extraction sub-system. An extraction fan, supplied with emergency power and housed in the ventilation plant room of each HF building (HFA and HFB), extracts the acidic vapours from the lower parts of the room and hydrogen gas from the upper parts then routes outside the building. There are two extractor fans in backup of each other.
The supply air to the Battery Room shall be provided by the central AHU.
17.3.1.1.6. Smoke Control System
A smoke exhaust sub-system, independent from the air conditioning system, shall provide an air change rate of { SCI removed } in each floor of the building.
17.3.1.2. Description of Main Equipment
Ventilation and Air-Conditioning System
The equipment inside the areas can be cooled using:
AHUs;
fans; and
local air-conditioning units.
Heating
Space heaters or convectors controlled by room thermostats.
Chilled Water System
A single air cooled water chiller and associated equipment shall be provided for each zone. A third chiller is provided as a backup for both zones.
Intake Louvres
In order to minimize water droplets entering the system, the Heating, Ventilating and Air Conditioning (HVAC) air intake shall be fitted with a louvre / filter / coalescent assembly to reduce the salt.APPROVED A screen or mesh sized to provide protection against birds shall also be fitted to the air intake louvre.
Attenuators
Attenuators shall be installed on the inlet and outlet side of each of the AHU to provide the required level of attenuation.
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17.3.1.3. Description of Main Layout
All the equipment is located within HF building.
17.3.1.4. Description of System I&C
Fire dampers and smoke controlled systems are controlled by the fire dedicated I&C (see Sub-chapter 9.5, section 1.5)
All the ventilation installations within each fire compartment are fitted with fire dampers at the air inlet and outlets.
Other DVF system equipment is controlled by the HVAC dedicated I&C cabinets located within a dedicated room in the HF building.
17.3.2. Operation
17.3.2.1. System Normal Operation
The DVF system operates independently of the plant state. During normal plant operating conditions, as well as fault conditions (PCC-2 to PCC-4, DEC-A, and any equivalent DBIFs), the operation of the DVF system depends on the internal temperature:
The air renewal operates continuously.
The air cooling ventilation and the heating operate automatically; operation is controlled by internal temperature sensors.
The air conditioning units are in continuous service and operate independently.
17.3.2.2. System Transient Operation
Internal Fire
The closure of fire dampers to isolate each fire safety sector and zone is automatically triggered by a Fire Detection System (JDT [FDS]) signal. The compartment can also be completely isolated in event of fire by activation of the thermal fuse.
17.3.2.3. Other Operating Conditions
17.3.2.3.1. Full or Partial System Failure
{ This section contains SCI-only text and has been removed } 17.3.2.3.2. FailuresAPPROVED of Interfaced Systems { This section contains SCI-only text and has been removed }
17.4. PRELIMINARY DESIGN SUBSTANTATION
The level of detail of evidence and compliance with the safety requirements stated in section 17.0 will develop as the HPC project moves from basic design into detailed design since PCSR3 sequence and system sequence are evolving in parallel. Therefore, the level of details presented in this section depends on the information available at the time of issuing the system chapters.
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17.4.1. Compliance with Safety Functional Requirements
17.4.1.1. Control of Fuel Reactivity
Not applicable: the DVF system does not directly contribute to the MSF of control of fuel reactivity.
17.4.1.2. Fuel Heat Removal
Not applicable: the DVF system does not directly contribute to the MSF of fuel heat removal.
17.4.1.3. Confinement of Radioactive Material
Not applicable: the DVF system does not directly contribute to the MSF of confinement of radioactive material.
17.4.1.4. Support Contribution to Main Safety Functions
The design assumptions of the DVF system stated in section 17.2.2 are consistent with the requirements of the corresponding systems / equipment items which it supports.
Indirect Contribution to the Main Safety Function of Control of Fuel Reactivity:
The target maximum temperature to be maintained in the HF building which has been used in the sizing of the system, corresponds to the maximum permissible temperature in which the safety classified systems will be able to operate:
o All safety classified electrical equipment will be compatible with a maximum permissible temperature.
The target minimum temperature to be maintained in the HF building which has been used in the sizing of the system, corresponds to the minimum permissible temperature in which the safety classified systems will still be able to operate:
o All safety classified electrical or mechanical equipment within rooms with a freeze risk will be compatible with a minimum permissible temperature.
17.4.1.5. Specific Contribution to Hazards Protection
The design assumptions of the DVF system stated in section 17.2.2 are consistent with the requirements of the corresponding systems/equipment items which it supports:
Indirect Contribution to the Hazard Protection:
The target maximum temperature to be maintained in the HF building which has been used inAPPROVED the sizing of the system, corresponds to the maximum permissible temperature in which the safety classified systems will be able to operate:
o All safety classified electrical equipment will be compatible with a maximum permissible temperature.
The target minimum temperature to be maintained in the HF building which has been used in the sizing of the system, corresponds to the minimum permissible temperature in which the safety classified systems will still be able to operate:
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o All safety classified electrical or mechanical equipment within rooms with a freeze risk will be compatible with a minimum permissible temperature.
An alarm must connect the DVF system to the LA* to ensure that the loss of the DVF system leads to the switch to forced floating mode of the batteries.
17.4.1.6. Other Safety Functions to be performed in the Preventive Line of Defence
Other safety function to be performed in the preventive line of defence involving the DVF system use values for the following parameters that are in keeping with the design assumptions stated in section 17.2.2:
The target maximum temperature to be maintained in the HF building which has been used in the sizing of the system, corresponds to the maximum permissible temperature in which the safety classified systems will be able to operate:
o All safety classified electrical equipment will be compatible with a maximum permissible temperature.
The target minimum temperature to be maintained in the HF building which has been used in the sizing of the system, corresponds to the minimum permissible temperature in which the safety classified systems will still be able to operate:
o All safety classified electrical or mechanical equipment within rooms with a freeze risk will be compatible with a minimum permissible temperature.
These elements ensure that the safety functional requirements stated in Section 17.0.2 are met.
17.4.2. Compliance with Design Requirements
The DVF system complies with the requirements stated in sections 17.0.4 and 17.0.5, particularly with respect to those detailed in the following sections.
17.4.2.1. Requirements arising from Safety Classification
17.4.2.1.1. Safety Classification
The compliance of the design and manufacture of the DVF system materials and equipment performing a safety-related function with requirements from the classification rules (see Sub-chapter 3.2, section 7) is presented in section 17.4.2.4.1.
17.4.2.1.2. Single Failure Criterion and Redundancy
Not applicable: the DVF system is not subject to any requirements for SFC and redundancy requirements. APPROVED 17.4.2.1.3. Robustness against LOOP
Not applicable: the DVF system is not subject to any robustness against LOOP requirements.
17.4.2.1.4. Physical Separation
Not applicable: the DVF system is not subject to any physical separation requirements.
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17.4.2.2. System Protection against Hazards
17.4.2.2.1. Internal Hazards
The overall demonstration of the robustness of the plant to internal hazards is covered in Sub-chapter 13.2.
17.4.2.2.2. External Hazards
The overall demonstration of the robustness of the plant to external hazards is covered in Sub-chapter 13.1.
17.4.2.3. Diversity
Not applicable: the DVF system is not subject to the requirement for diversity.
17.4.2.4. Requirements defined at the Component Level
17.4.2.4.1. General Mechanical, Electrical and I&C Requirements
The components of the DVF system equipment performing a safety-related function comply with the general mechanical, electrical, and I&C requirements stated in section 17.0.5.1 as detailed in Section 9.4.17 – Table 1.
SECTION 9.4.17 – TABLE 1 : SAFETY CLASSIFICATION AND DESIGN REQUIREMENTS OF COMPONENTS OF THE DVF SYSTEM
Description Safety classification Design requirements Mechanical requirement for Highest Highest pressure retaining safety safety Seismic Electrical I&C components or function class of requirement requirement requirement leaktightness category SFG requirement for HVAC component Ventilation C 3 NT NR C3 C3 Air heater C 3 NT NR C3 C3 Air conditioning A 3 NT NR C3 C3 unit
17.4.2.4.2. Seismic Requirements
Considering that the HF building structures and components are not SC1 and considering the contribution of failsafe design implemented for the safety-related functions, no seismic requirements existAPPROVED on component within the HF building.
17.4.2.4.3. HIC Requirements
Not applicable: the DVF system is not subject to any HIC requirements.
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17.4.2.4.4. Specific I&C Requirements
The specific I&C requirements detailed in section 17.0.5.2.2 are the basis for the DVF system development and manufacturing. The DVF system will satisfy all these requirements.
17.4.3. Examination, Maintenance, In-Service Inspection and Testing (EMIT)
17.4.3.1. Start-up Tests
The DVF system is subject to a start-up test programme in accordance with the procedures set out in Chapter 20 serving to verify the fulfilment of the following SFRs:
Ensure an internal air temperature lower than maximum internal air temperature in all fault conditions in order to ensure an air temperature compatible with Safety Class 3 equipment operation:
o Start-up and minimum flow rate of the ventilation;
o Start-up and minimum power of the air conditioning units.
Ensure an internal air temperature higher than minimum internal air temperature in all fault conditions in order to ensure an air temperature compatible with Safety Class 3 equipment operation:
o Start-up and minimum power of the heating equipment.
17.4.3.2. In-Service Inspection
The following functions of the DVF system are used during normal plant operation under conditions representative of the fault/hazard conditions in which they are required:
Safety classified air conditioning units;
Safety classified extract ventilation; and
Safety classified heating.
Tests are carried out during plant operation. They are conducted on each zone successively, rather than simultaneously.
Clogging of the filters is regularly checked.
The air conditioning units are serviced in accordance with the manufacturer's guidelines. 17.4.3.3. PeriodAPPROVEDic Testing The safety classified parts of the DVF system are subject to periodic testing in accordance with the maintenance schedule in order to verify that the following SFRs are fulfilled:
Ensure an internal air temperature lower than maximum internal air temperature in all fault conditions in order to ensure an air temperature compatible with Safety Class 3 equipment operation:
o Start-up and minimum flow rate of the ventilation; and
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o Start-up of air conditioning units.
Ensure an internal air temperature lower than maximum internal air temperature in all fault conditions in order to ensure an air temperature compatible with Safety Class 1 and Class 2 equipment operation:
o Start-up of air conditioning units, monitored by { SCI removed }.
Ensure an internal air temperature higher than minimum internal air temperature in all fault conditions in order to ensure an air temperature compatible with Safety Class 3 equipment operation:
o Start-up of heating equipment.
17.4.3.4. Maintenance
The DVF system is subject to a maintenance programme to guarantee requirements detailed in section 17.0.
17.5. FUNCTIONAL DIAGRAM
The functional diagrams of the DVF system “Level -11.000 and -6.000” are shown in Section 9.4.17 – Figure 1.
The functional diagrams of the DVF system “level 0.000 and 4.600” are shown in Section 9.4.17 – Figure 2.
The functional diagrams of the DVF system “level 8.800 and 13.000” are shown in Section 9.4.17 – Figure 3.
This gives a schematic overview of Zone A of the HF building (for more details (e.g. Zone B), see the detailed mechanical diagram of the DVF system).
Note: this section does not provide a schematic overview of the Technical Galleries (HGT, HGJ, HGK, HGU) and the HTE basement because the DVF system only provides air renewal within these galleries.
18. VENTILATION SYSTEM FOR THE VVP AND ARE VALVE ROOMS (DVE)
The information reported in this section is, unless otherwise noted, consistent with the reference design, as referenced from Chapter 22. 18.0 SAFETYAPPROVED REQUIREMENTS The UK EPR Safety Classification principles and the top-down functional approach are presented in Sub-chapter 3.2. These principles help to ensure that the plant is designed, manufactured, constructed, commissioned and operated so that the appropriate level of reliability and integrity is achieved for its Structures, Systems and Components (SSCs).
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The Hinkley Point C (HPC) functional safety analyses and the application of these safety classification principles to the HPC reference design result in the identification of the safety requirements for all safety systems in accordance with the Safety Functional Requirements Notes (SFRNs) referenced from Sub-chapter 3.2.
This section summarises the results of these safety analyses and specifies the safety requirements that apply to the design of the DVE system.
The requirements described in the present section are consistent with safety functions to which the DVE system contributes in Plant Condition Category (PCC) and Design Extension Conditions (DEC). Consistency with requirements inherited from the Design Basis Initiating Faults (DBIFs) should be checked when the list of DBIFs evolves (see Chapter 15).
18.0.1 Safety Functions
The three Main Safety Functions (MSFs) necessary to achieve the overall safety objective of protecting people and the environment from the harmful effects of ionising radiations are:
control of fuel reactivity,
fuel heat removal, and
confinement of radioactive material.
These three main safety functions must be achieved during:
normal operating conditions PCC-1), including duty functions, control of radioactive release during normal operating conditions, control of main plant parameters, fault initial conditions, Limiting Conditions of Operation (LCOs), limitations, monitoring functions, Probabilistic Safety Assessment (PSA) significant functions as part of the preventive line of defence;
fault conditions (PCC-2 to PCC-4, DEC-A and any equivalent DBIFs) and DEC-B; and
hazard conditions.
18.0.1.1 Control of Fuel Reactivity
The DVE system does not directly contribute to the MSF of control of fuel reactivity.
18.0.1.2 Fuel Heat Removal
The DVE system does not directly contribute to the MSF of fuel heat removal. 18.0.1.3 ConfinementAPPROVED of Radioactive Material The DVE system does not directly contribute to the MSF of confinement of radioactive material.
18.0.1.4 Support Contribution to Main Safety Functions
The DVE system does not indirectly contribute to the three MSFs.
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18.0.1.5 Specific Contribution to Hazards Protection
The DVE system must contribute directly to the safety functions that are part of the facility's hazards protection against the consequences of fire (see Sub-chapter 13.2, section 7), earthquake (see Sub-chapter 13.1, section 2) and external explosion (see Sub-chapter 13.1, section 4) as follows:
Contribution to the containment and prevention of spread of fire to maintain intervention fire compartment (SFI) integrity in the Nuclear Auxiliary Building (HN [NAB]);
Preservation of Seismic Requirement levels (SC1) Safety Features (SFs) availability following a seismic event;
Limit the effects of an explosion pressure wave inside the Safeguard Buildings (HL [SB]) in the case of external explosion.
Moreover, the DVE system must be protected against internal / external hazards (see section 18.0.4.2).
18.0.1.6 Other Safety Functions to be performed in the Preventive Line of Defence
The DVE system must contribute directly to other safety functions to be performed as part of the preventive line of defence as follows:
Avoid an overpressure event inside the Main Feed Water System (ARE [MFWS]) and the Main Steam Supply System (VVP [MSSS]) rooms inside the HL [SB] buildings.
18.0.2 Safety Functional requirements
18.0.2.1 Control of Fuel Reactivity
Not applicable: the DVE system does not directly contribute to the MSF of control of fuel reactivity.
18.0.2.2 Fuel Heat Removal
Not applicable: the DVE system does not directly contribute to the MSF of fuel heat removal.
18.0.2.3 Confinement of Radioactive Material
Not applicable: the DVE system does not directly contribute to the MSF of confinement of radioactive material.
18.0.2.4 Support Contribution to Main Safety Functions Not applicable:APPROVED the DVE system does not indirectly contribute to the three MSFs. 18.0.2.5 Specific Contribution to Hazards Protection
With respect to its specific contribution to the safety functions that are part of the facility’s hazards protection, the DVE system must satisfy the following Safety Functional Requirements (SFRs):
Fire:
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o Ensure containment of fire in rooms by closure of fire dampers to maintain SFI integrity in order to protect safety classified systems from the propagation of smoke or fire in the HN [NAB] building (passively and actively).
Earthquake:
o Ensure the integrity or stability of the DVE system components to avoid damage to higher classified components and ensure that it does not adversely impact the availability of SC1 SFs following a seismic event.
External explosion:
o Limit the effects of an Explosion Pressure Wave (EPW) in order to protect safety classified components housed inside the HL [SB] buildings steam and feedwater valve rooms.
18.0.2.6 Other Safety Functions to be performed in the Preventive Line of Defence
With respect to its contribution to other safety functions to be performed as part of the preventive line of defence, the DVE system must satisfy the following SFRs:
Overpressure event:
o Avoid overpressure event in the ARE [MFWS] / VVP [MSSS] system rooms in case of a Main Steam Line Break (MSLB) or a Main Feed Water Line Break (MFWLB).
18.0.3 Safety Features and Instrumentation & Control (I&C) Actuation Modes
Section 9.4.18 – Table 2 presents the SFs of the DVE system, according to the contributions identified in section 18.0.1 and the SFRNs referenced in Sub-chapter 3.2.
18.0.4 Classification and Architecture Requirements of Safety Features
18.0.4.1 Requirements arising from Safety Classification
Architecture requirements associated with SFs are essential for designing robust lines of defence consistent with their importance to nuclear safety (see Sub-chapter 3.2). Such requirements strengthen the system design against:
single faults and associated consequences (Single Failure Criterion (SFC)) by requiring redundancy;
Loss Of Off-site Power (LOOP) by requiring, among others, a back-up power supply; StationAPPROVED Black-Out (SBO) by requiring a power supply by the Ultimate Diesel Generators (UDGs);
Common Cause Failures (CCFs) by requiring physical separation;
earthquake by defining seismic requirements; and
accident conditions by defining qualification requirements.
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Section 9.4.18 – Table 2 presents the requirements arising from safety classification for the DVE system, according to the SFRNs referenced in Sub-chapter 3.2.
18.0.4.2 System Protection against Hazards
18.0.4.2.1 Internal Hazards
The SFs of the DVE system must be protected against internal hazards, if those hazards challenge the safety objectives as defined in Sub-chapter 13.2.
18.0.4.2.2 External Hazards
The safety features of the DVE system must be protected against external hazards, if those hazards challenge the safety objectives as defined in Sub-chapter 13.1.
18.0.4.3 Diversity
The DVE system is not subject to the requirement for diversity.
18.0.5 Requirements Defined at the Component Level
18.0.5.1 Generic Safety Requirements
18.0.5.1.1 Generic Mechanical, Electrical and I&C Requirements
The mechanical components within the DVE system must comply with the mechanical requirements in accordance with the rules laid out in Sub-chapter 3.2, section 7. The level of requirement is dependent upon whether or not it is a pressure retaining component, the safety class of the component, whether the component acts as an isolating device between interfacing SFs, and on the role of the component as a barrier to the potential release of radioactivity as a result of failure of the component.
The electrical and Instrumentation and Control (I&C) components in the DVE system must comply with the electrical and I&C requirements associated with their safety class, in accordance with the rules laid out in Sub-chapter 3.2.
18.0.5.1.2 Seismic Requirement
The level of seismic requirements to be applied to the DVE system components is related to the Safety Feature Group (SFG) to which the component belongs, and the consequences on other classified components of its failure if it were not seismically qualified. The rules for defining the seismic requirements for a component are identified in Sub-chapter 3.2.
18.0.5.1.3 Qualification for Accident Conditions The safety classifiedAPPROVED parts of the DVE system must be qualified for the operating conditions in which they are required, as specified in Sub-chapter 3.6.
18.0.5.2 Specific Safety Requirements
18.0.5.2.1 High Integrity Component (HIC) Requirements
The DVE system is not subject to any High Integrity Component (HIC) requirements.
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18.0.5.2.2 Specific I&C Requirements
The DVE system is not subject to any specific I&C requirements; the DVE system does not have any dedicated I&C. However, DVE fire dampers are actuated by the Fire Detection System (JDT [FDS]) dedicated I&C (see Sub-chapter 9.5, section 1.2).
The general approach for I&C systems is set out in Chapter 7.
18.0.6 Examination, Maintenance, (In-Service) inspection and Testing (EMIT)
18.0.6.1 Start-up Tests
The DVE system must be designed to enable the performance of start-up tests to ensure the adequacy of its design and performance under conditions as representative as possible of the different operating configurations, and in particular its compliance with the SFRs assigned to it in section 18.0.2.
18.0.6.2 In-Service Inspection
The DVE system must be designed to enable surveillance under normal operation of the system characteristics necessary for the fulfilment of its safety-related tasks in order to ensure the performance of its components, and their availability under normal operation, or in the event of a fault or accident.
18.0.6.3 Periodic Testing
The safety classified parts of the DVE system must be designed to enable the performance of periodic tests in accordance with the maintenance schedule.
18.0.6.4 Maintenance
The DVE system must be designed to enable the implementation of a maintenance schedule (see Sub-chapter 18.2).
18.1 ROLE OF THE SYSTEM
The DVE system performs the functions (or tasks) (detailed in the following sections) under the different plant operating conditions for which it is required.
18.1.1 Normal Operating Conditions
During normal operating conditions, the role of the DVE system is to:
Within the ARE [MFWS], VVP [MSSS] systems and the Steam Generator Blow-down SystemAPPROVED APG [SGBS] valve rooms (HL [SB] buildings): o Maintain minimum (during plant outage in winter conditions) and maximum room temperatures in the temperature range limit defined in section 1.
Within the Operational Chilled Water System (DER [OCWS]) chillers rooms (HN [NAB] building):
o Maintain minimum (during plant outage in winter conditions) and maximum room temperatures in the temperature range limit defined in section 1; and
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o Ensure minimum flow rate to avoid a potential asphyxiation risk associated with the leakage of refrigerant gas into chiller rooms.
18.1.2 Fault and Hazard Operating Conditions
Under fault and hazards conditions, the DVE system must:
Ensure active and / or passive fire compartmentation in the HN [NAB] building;
Ensure stability or integrity to not impact the availability of SC1 SFs following a seismic event;
Limit the effects of an explosion pressure wave inside the HL [SB] buildings; and
Avoid an overpressure event in the case of a MSLB or a MFWLB in the ARE [MFWS] and VVP [MSSS] systems valve rooms.
18.2 DESIGN BASIS
18.2.1 General Assumptions
The DVE system is designed with the following assumptions:
Local Cooling Units (LCUs) are used to remove the heat loads in order to maintain the required temperatures (see section1) within the HL [SB] and the HN [NAB] buildings.
Operational Chillers rooms in the HN [NAB] building are ventilated by a full fresh air unit to ensure minimum flow rate in case of refrigerant leak.
Convectors are used to ensure minimum required temperature in all rooms in order to be consistent with the general design criteria applicable to Heating, Ventilation and Air- Conditioning (HVAC) systems, as described in section 1, in particular with regards to:
o requirement for ambient (indoor) temperatures; and
o taking into account outdoor temperatures (including extreme cold conditions).
Although not subject to a redundancy requirement, redundancy is provided for fans and LCUs of the ventilation system of operational chillers rooms in the HN [NAB] building to maximise the availability and to ensure maintenance during operations.
18.2.2 Design Assumptions 18.2.2.1 ControlAPPROVED of Fuel Reactivity Not applicable: the DVE system does not directly contribute to the MSF of control of fuel reactivity.
18.2.2.2 Fuel Heat Removal
Not applicable: the DVE system does not directly contribute to the MSF of fuel heat removal.
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18.2.2.3 Confinement of Radioactive Material
Not applicable: the DVE system does not directly contribute to the MSF of confinement of radioactive material.
18.2.2.4 Support Contribution to Main Safety Functions
Not applicable: the DVE system does not indirectly contribute to the three MSFs.
18.2.2.5 Specific Contribution to Hazards Protection
Fire:
Not applicable: there are no quantitative safety-related design assumptions with this safety function.
Earthquake:
Not applicable: there are no quantitative safety-related design assumptions with this safety function.
External explosion:
The burst membranes must satisfy the criteria defined in Sub-chapter 13.1, section 4.
18.2.2.6 Other Safety Functions to be performed in the Preventive Line of Defence
Overpressure event:
The burst membranes in the ARE [MFWS] / VVP [MSSS] systems rooms are designed to open at a pressure (after a MSLB or a MFWLB) of { SCI removed } in the ARE [MFWS] system rooms, and { SCI removed } in the VVP [MSSS] system rooms.
18.2.3 Other Assumptions
The DVE system is also subject to the following assumptions:
The ventilation system of the DER [OCWS] system chillers rooms in the HN [NAB] building must ensure minimum flow rate in case of refrigerant leak to ensure operator’s security. The DVE system minimum ventilation flow rate must be as follows:
o { SCI removed } with m, the mass of refrigerant contained inside the chiller circuits (kg).
DVE system design is consistent with RCC-M requirements as described in Sub-chapterAPPROVED 3.8, section 2. DVE system design is consistent with fire requirements as described in Sub-chapter 3.8, section 5.
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18.2.4 Assumptions Associated with Extreme Situations Resulting from beyond Design-basis Hazards
18.2.4.1 Assumptions associated with Fukushima Provisions
The DVE system is not subject to assumptions associated with Fukushima provisions.
18.2.4.2 Assumptions associated with non-Fukushima Provisions
The DVE system is not subject to assumptions associated with non-Fukushima provisions.
18.3 SYSTEM DESCRIPTION AND OPERATION
18.3.1 Description
18.3.1.1 General System Description
The main task of the DVE system is to maintain required ambient (indoor) conditions (see section 1 of this sub-chapter) in the VVP [MSSS] / ARE [MFWS] and APG [SGBS] systems valve rooms in the HL [SB] buildings and in the DER [OCWS] system chillers rooms in the HN [NAB] building.
In the HL [SB] buildings, the DVE system ventilates the VVP / ARE and APG systems valve rooms.
In order to comply with the safety and operational requirements, for each valve room the DVE system architecture in these rooms is as follows:
An LCU ensuring the cooling of the room by recirculating air through a cooling coil supplied with chilled water by the DER [OCWS] system;
Convectors to ensure minimum temperature during extreme cold and LOOP or outage under winter conditions;
Burst membranes ensuring protection against EPW and limitation of overpressure in case of MSLB or MFWLB, only for VVP [MSSS] and ARE [MFWS] systems rooms; and
Fire dampers ensuring passive (thermal fuse) or active (activation order from the JDT [FDS] system) fire compartmentation, only for ARE [MFWS] system rooms.
In the HN [NAB] building, the DVE system ventilates the DER [OCWS] chillers room. The DVE system architecture in the HN [NAB] building is as follows:
An Air Handling Unit (AHU) which supplies both DER [OCWS] system chiller rooms ensuring filtering and thermal conditioning of air supply. This AHU is provided with two redundantAPPROVED fans (2 x 100% capacity) to enable in-service maintenance.
An exhaust network which extracts the air from both DER [OCWS] system chiller rooms. This network is provided with two redundant fans (2 x 100% capacity) to enable in- service maintenance;
LCUs providing additional cooling power to cope with temperature requirements (see section 1) under all design conditions:
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o two LCUs (2 x 100% capacity); and
o two LCUs (2 x { SCI removed } capacity);
Convectors to ensure minimum temperature during extreme cold and LOOP or outage under winter conditions;
Fire dampers ensuring passive (thermal fuse) or active (activation order from the JDT [FDS] system) fire compartmentation.
18.3.1.2 Description of Main Equipment
The DVE system comprises the following main equipment items (see the functional diagram provided in section 18.5):
LCUs:
o Cooling Coils: used to cool down the air. Droplet separators and drains are provided if necessary. They are served with chilled water from the DER [OCWS] system.
o Recirculation Fans: they ensure the air flow through the cooling coil. The air flow rate is calculated based on the heat loads inside the rooms.
Air Handling Unit (AHU):
o Heating Coil: used to heat the air intake with hot water supplied by the Electrically Heated Hot Water System (SEL).
o Filters: a two stage filtration (pre-filter and filter) is provided to ensure the removal of atmospheric dust.
o Cooling coil: used to cool down the air. Droplet separator and drain are provided if necessary. They are served with chilled water from the DER [OCWS] system.
o Supply Fans: they are redundant (2 x 100%) fans. Required air flow rate is defined to meet the requirements of industry standards in case of refrigerant leak (see section 18.2.3).
Exhaust fans: they are redundant (2 x 100%) fans. Required flow rate is defined to meet the requirements of industry standards in case of refrigerant leak (see section 18.2.3).
Convectors: they are used to ensure minimum temperatures in rooms. Fire dampeAPPROVEDrs whose closure ensures the fire compartment isolation. Burst Membranes whose rupture limits the pressure inside the rooms in case of MSLB or MFWLB.
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18.3.1.3 Description of Main Layout
The ventilation system of the APG [SGBS], ARE [MFWS] and VVP [MSSS] systems valve rooms housed in the supplied rooms, located in the upper part of the Main Steam Valve bunker (Train 1) (HLK), Main Steam Valve bunker (Train 2) (HLL), Main Steam Valve bunker (Train 3) (HLM) and Main Steam Valve bunker (Train 4) (HLN), from level { SCI removed } to level { SCI removed }.
The supply and exhaust units of the DER [OCWS] system chiller rooms, including external air intake and exhaust, are located at the level { SCI removed } of the HN [NAB] building supplying both DER [OCWS] system chiller rooms of the level { SCI removed }, { SCI removed } and { SCI removed }. LCUs are provided in each DER [OCWS] system chiller rooms at levels { SCI removed } and { SCI removed }.
18.3.1.4 Description of system I&C
Not applicable: the DVE system does not have any dedicated I&C.
18.3.2 Operation
18.3.2.1 System Normal Operation
In normal operation of the plant, the DVE system is used to maintain acceptable temperature (see section 1) within the steam valve rooms and the DER [OCWS] system chiller rooms.
The LCUs and convectors are in automatic operation, operated in on / off mode based on the room’s temperature.
The DER [OCWS] system chiller rooms supply and exhaust units are in continuous operation to ensure minimum air flow rate in case of refrigerant leak.
The burst membranes of the DVE system must fulfil their function under any plant condition.
18.3.2.2 System Transient Operation
18.3.2.2.1 System Operation during Hazards
The fire dampers must be closed actively and passively in case of fire in steam valve rooms or DER [OCWS] system chiller rooms.
18.3.2.2.2 Full or Partial System Failure
18.3.2.2.2.1 Failure of DVE system in the HL buildings { This section APPROVEDcontains SCI-only text and has been removed } 18.3.2.2.2.2 Failure of DVE system in the HN [NAB] building
{ This section contains SCI-only text and has been removed }
18.3.2.2.3 Failures of Systems in Interface (Server or Served)
18.3.2.2.3.1 Failures of Server Systems
{ This section contains SCI-only text and has been removed }
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18.3.2.2.3.2 Failure of Served Systems
{ This section contains SCI-only text and has been removed }
18.4 PRELIMINARY DESIGN SUBSTANTATION
The level of detail of evidence of compliance with the safety requirements stated in section 18.0 will develop as the HPC project moves from basic design into detailed design since the PCSR3 sequence and the system sequence are evolving in parallel. Therefore, the level of detail presented in this section depends on the information available at the time of issuing the system chapters.
18.4.1 Compliance with Safety Functional Requirements
18.4.1.1 Control of Fuel Reactivity
Not applicable: the DVE system does not directly contribute to the MSF of control of fuel reactivity.
18.4.1.2 Fuel Heat Removal
Not applicable: the DVE system does not directly contribute to the MSF of fuel heat removal.
18.4.1.3 Confinement of Radioactive Material
Not applicable: the DVE system does not directly contribute to the MSF of confinement of radioactive material.
18.4.1.4 Support Contribution to Main Safety Functions
Not applicable: the DVE system does not indirectly contribute to the three MSFs.
18.4.1.5 Specific Contribution to Hazards Protection
The hazard studies of Sub-chapters 13.1 and 13.2 involving functions of the DVE system use values for the following parameters that are in keeping with the design assumptions stated in section 18.2.2:
Fire:
o Contribution to the containment and prevention of spread of fire in the HN [NAB] building by the closure of fire dampers is ensured by active (automation by the JDT [FDS] system) or ultimately passive (fusible device inside and outside the duct) means: APPROVED. fire damper qualification; and . fire damper closure monitored by position status.
Earthquake:
o Ensuring the stability or integrity of all components:
. DVE system components will be seismically qualified to confirm their stability or integrity is maintained following a seismic event.
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External explosion:
o The burst membranes pressure resistance to EPW.
For each hazard concerned in Sub-chapters 13.1 and 13.2, these studies show that the design of these functions is such that they meet the acceptance criteria.
These elements ensure that the SFRs stated in section 18.0.2 are met.
18.4.1.6 Other Safety Functions to be performed in the Preventive Line of Defence
Other safety functions to be performed in the preventive line of defence involving the DVE system use values for the following parameters that are in keeping with the design assumptions stated in section 18.2.2:
Overpressure event:
o The burst membranes opening pressure.
These elements ensure that the SFRs stated in section 18.0.2 are met.
18.4.2 Compliance with Design Requirements
The DVE system complies with the requirements stated in sections 18.0.4 and 18.0.5, particularly with respect to those detailed in the following sections.
18.4.2.1 Requirements arising from Safety Classification
18.4.2.1.1 Safety Classification
The compliance of the design and manufacture of the DVE system materials and equipment performing a safety-related function with requirements from the classification rules (see Sub-chapter 3.2, section 7) is presented in section 18.4.2.4.1.
18.4.2.1.2 Single Failure Criterion and Redundancy
Active single failure:
Not applicable: the DVE system is not subject to active single failure.
Passive single failure:
The design of the DVE system must comply with the requirements of the passive SFC stated in section 18.0.4.1, in particular in respect of the following: ProtectionAPPROVED of the ARE [MFWS] and VVP [MSSS] systems rooms against overpressure in case of a MSLB or a MFWLB.
This requirement is not met by physical redundancy of membranes but by their design, in particular as membranes are simple, robust and reliable components and conservatisms are taken in associated studies.
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18.4.2.1.3 Robustness against loss of power
The design of the DVE system complies with the emergency power supply requirement stated in section 18.0.4.1, in particular in respect of the following:
Fire compartmentation (fire dampers).
Furthermore, while not subject to an emergency power supply requirement, the room heating function of the DVE system is provided with a backed-up power supply in the form of an emergency electrical power supply to the DVE equipment items using Emergency Diesel Generators (EDGs).
18.4.2.1.4 Physical Separation
The design of the DVE system must comply with the requirements of the physical separation stated in section 18.0.4.1, in particular in respect of the following:
Protection of the ARE [MFWS] and VVP [MSSS] system rooms against overpressure in case of a MSLB or a MFWLB.
18.4.2.2 System Protection against Hazards
18.4.2.2.1 Internal Hazards
The overall demonstration of the robustness of the plant to internal hazards is covered in Sub-chapter 13.2.
18.4.2.2.2 External Hazards
The overall demonstration of the robustness of the plant to external hazards is covered in Sub-chapter 13.1.
18.4.2.3 Diversity
Not applicable: the DVE system is not subject to the requirement for diversity.
18.4.2.4 Requirements defined at the Component Level
18.4.2.4.1 General Mechanical, Electrical and I&C Requirements
The components of the DVE system equipment performing a safety-related function comply with the general mechanical, electrical, and I&C requirements stated in section 18.0.5.1 as detailed in Section 9.4.18 – Table 1.
SECTION 9.4.18 – TABLE 1 : CLASSIFICATION OF MAIN MECHANICAL AND ELECTRICAL APPROVEDCOMPONENTS ASSOCIATED TO THEIR SAFETY FEATURES Safety classification Design requirements Highest Highest Description Safety Safety Leaktightness Seismic Electrical I&C function class of Requirement Requirement Requirement Requirement category SFG Burst A 1 M3 SC1 - - membranes
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Safety classification Design requirements Highest Highest Description Safety Safety Leaktightness Seismic Electrical I&C function class of Requirement Requirement Requirement Requirement category SFG Fire dampers in the HN C 3 NT NR C3 C3 [NAB] building Other components C 3 NT/NR SC2 NR NR in HL [SB] building The table will be updated after the Safety Classification Component Lists (SCCLs) studies.
18.4.2.4.2 Seismic Requirements
The DVE system complies with the seismic qualification requirements listed in Section 9.4.18 – Table 2.
18.4.2.4.3 HIC Requirements
Not applicable: the DVE system is not subject to any HIC requirements.
18.4.2.4.4 Specific I&C requirements
Not applicable: the DVE system does not have any dedicated I&C.
The demonstration of compliance with the specific I&C requirements stated in section 18.0.5.2.2 is provided in the JDT [FDS] system chapter (see Sub-chapter 9.5, section 1.2).
18.4.3 Examination, Maintenance, (In-Service) Inspection and Testing (EMIT)
18.4.3.1 Start-up Tests
The DVE system is subject to a start-up test programme in accordance with the procedures set out in Chapter 20 serving to verify the fulfilment of the SFRs.
The start-up test programme will verify:
Correct operation of fire dampers.
As the DVE system SFR associated to the burst membranes cannot be directly verified on site due to the fact that the test conditions are different to the fault and hazards conditions under which it is requiredAPPROVED to be fulfilled, it must be verified in an indirect manner as follows:
Justification of the qualification of the burst membranes by testing and calculations performed by the supplier.
18.4.3.2 In-Service Inspection
Not applicable: the DVE system is not subject to in-service inspection.
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18.4.3.3 Periodic Testing
The safety classified parts of the DVE system are subject to periodic testing in accordance with the maintenance schedule in order to verify that the following SFRs are fulfilled:
Correct operation of fire dampers; and
Correct aspect of burst membranes.
18.4.3.4 Maintenance
The DVE system is subject to a maintenance programme.
18.5 FUNCTIONAL DIAGRAM
The functional diagrams of the DVE system are shown in Section 9.4.18 – Figure 1 and Figure 2 (for more details, see the detailed mechanical diagram of the DVE system).
APPROVED
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19. REFERENCES
[1] Engineering rules ENG2.83 (MD2): Ventilation System Functional Requirements, Sizing & Material Selection – ECEF040074 B1 BPE.
[2] Position paper on the treatment of extreme high external air temperature – NNB-202- PAP-000073 Version 1.0.
[3] An Aid to the design of Ventilation of Radioactive Areas Issue 1 – January 2009 – NVF/DG001.
[4] BS EN 50272−2: Safety requirements for secondary batteries and battery installations — Part 2: Stationary batteries.
[5] RCC-E 2012 and UK EPR Book of Project Data Supplementary to Requirements of RCC-E 2012 – ENSEMD120096 B BPE.
[6] ALARP analysis regarding HVAC ductwork components leak tightness – UK: UKX- SEPTEN-AU-ALL-NOT-000282 - D305914000379 A BPE.
[7] Basis of Safety Case: DVL – HPC-CNENXX-AU-DVL-RES-200511, Revision B, June 2016.
[8] UK EPR – Safety Functional Requirements Note for RC1.2 – BNI Scope. HPC- ECESNX-XX-ALL-NOT-000160, Revision E, December 2016.
[9] RC1.2 BNI Safety Features List UKX-CNENXX-XX-ALL-NOT-200142, Revision C, July 2016.
[10] UK EPR – Safety Functional Requirements Note for CI/BOP Scope RC1.2 – HPC- ETSEEX-XX-ALL-NOT-000036, Revision D, October 2016.
[11] SFRN UKX-UK1401-AU-ALL-STU-005309, Revision E, September 2016.
[12] List of RC1.1 Frontline Safety Features and associated actuation modes. UKX-UK1401- AU-ALL-NOT-005869, Revision B, April 2015.
[13] Technical Specification – Diesel Buildings (HD). UKX-ECEIGX-AU-HDX-SPT-000011, Revision B. March 2013.
[14] Safety Requirements for batteries and battery installations Part 2: Stationary batteries. EN 50272-2. AFNOR. June 2001.
[15] Basis of Safety Case: DEL HPC-CNENXX-AU-DEL-RES-200550, Revision B, June 2016. APPROVED [16] HPC-CNENXX-XX-000-NOT-200750, D305116091141, rev. A BPE AF-UKEPR-FS-103 – Analysis of the consequences of a total loss of DER chillers in normal operation.
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SECTION 9.4.1 – TABLE 1 : TEMPERATURE AND RELATIVE HUMIDITY IN PCC-1 CONDITIONS
In PCC-1 conditions, HVAC systems are sized to maintain the following internal conditions.
Safety Case Commitment: target temperatures listed in Section 9.4.1 – Tables 1, 2 and 3 which are not in the current generic temperature ranges [Ref. 5] will be clearly identified in a dedicated document which will be used for equipment contract specifications.
Minimum Maximum Areas Temperature Temperature Reactor buildings (HRA): Service area In-Core Instrumentation System (RIC) rooms { SCI removed } { SCI removed } Other rooms inside service area (during access) { SCI removed } { SCI removed } Equipment compartment Average value { SCI removed } { SCI removed } Maximum local admissible temperature { SCI removed } { SCI removed } Annulus (HRB): Presence of pipework containing { SCI removed } { SCI removed } { SCI removed } boric acid) Non-controlled areas of Safeguard Buildings
(HLA/B/C/D [SB (E)]): Main Control Room 2 DCL trains mode { SCI removed } { SCI removed } Main Control Room 1 DCL train mode { SCI removed } { SCI removed } Offices, kitchen { SCI removed } { SCI removed } Bathrooms, cloakrooms { SCI removed } { SCI removed } Computer rooms, Instrumentation and Control { SCI removed } { SCI removed } rooms, Remote Shutdown Station Electrical rooms { SCI removed } { SCI removed } Cable decks { SCI removed } { SCI removed } Battery rooms { SCI removed } { SCI removed } HVAC technical rooms { SCI removed } { SCI removed } Nuclear Auxiliary Building (HN [NAB]), Fuel Building (HK [FB]), Controlled Areas of Safeguard Buildings
(HLF/G/H/IAPPROVED [SB (M)]), Controlled Areas of Effluent Treatment Building (HQ [ETB]): Electrical rooms { SCI removed } { SCI removed } Cable decks { SCI removed } { SCI removed } Computer rooms, Instrumentation and Control rooms { SCI removed } { SCI removed } Laboratory { SCI removed } { SCI removed }
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Minimum Maximum Areas Temperature Temperature Frequent and long occupation (green zone) { SCI removed } { SCI removed } Frequent and short or infrequent and long occupation { SCI removed } { SCI removed } (yellow zone) Infrequent and short occupation (orange and red { SCI removed } { SCI removed } zones) Exceptions: Fuel handling hall { SCI removed } { SCI removed } Minimum admissible temperature for “boron” rooms { SCI removed } { SCI removed } (Bo1, Bo2, Bo3) HVAC technical rooms { SCI removed } { SCI removed } Gaseous Waste Processing System (TEG [GWPS]) { SCI removed } { SCI removed } delay beds Diesel Generator Buildings (HD [DB]) Diesel hall { SCI removed } { SCI removed } Main Fuel Tank room { SCI removed } { SCI removed } Mechanical rooms { SCI removed } { SCI removed } Computer rooms, Instrumentation and Control rooms { SCI removed } { SCI removed } Battery rooms { SCI removed } { SCI removed } Switchboards/transformers rooms { SCI removed } { SCI removed } Diesel electrical rooms { SCI removed } { SCI removed } HVAC technical rooms { SCI removed } { SCI removed } Main Steam Valve rooms (HLK/L/M/N) { SCI removed } { SCI removed } Pumping Station (HP): Electrical rooms { SCI removed } { SCI removed } Mechanical rooms { SCI removed } { SCI removed } Stairs, lobbies and Circulation Water Filtration { SCI removed } { SCI removed } System (CFI [CWFS]) cells Outfall Building (HCA): Essential Service Water System (SEC [ESWS]) and { SCI removed } { SCI removed } Circulation Water System (CRF [CWS]) release APPROVEDrooms and diversification rooms Classified Galleries (HGA/B/C/D/E/F/G/H/I/Z): { SCI removed } { SCI removed } Galleries Fire Fighting Water Building (HOJ): Electrical rooms (autocom) { SCI removed } { SCI removed } Mechanical rooms { SCI removed } { SCI removed } Stairs and lobbies { SCI removed } { SCI removed }
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Minimum Maximum Areas Temperature Temperature Conventional Island Electrical Buildings (HF) Electrical rooms { SCI removed } { SCI removed } Battery rooms { SCI removed } { SCI removed } HVAC technical rooms { SCI removed } { SCI removed } Other rooms { SCI removed } { SCI removed } Turbine Hall (HM-): Motor-driven FeedWater Pump System (APA { SCI removed } { SCI removed } [MFWS]) area Electrical rooms { SCI removed } { SCI removed } Other rooms { SCI removed } { SCI removed }
For electrical equipment, the humidity requirement [Ref. 5] is applied.
{ SCI removed }
There are three types of “boron” rooms considered for HVAC systems design:
Bo1 ({ SCI removed } and safety-classified)
Conservatively, a boron concentration of { SCI removed } has been considered which is higher than the maximum concentration of boron within systems housed in Bo1 rooms, which is { SCI removed }. In fault conditions, a minimum temperature of 18°C is required to prevent from boron crystallisation at { SCI removed } (see Section 9.4.1 – Table 2).
Bo2 ({ SCI removed } and not safety-classified)
Conservatively, a boron concentration of { SCI removed } has been considered (same as for Bo1 rooms). In normal operating conditions, a minimum temperature of { SCI removed } is ensured only when the HVAC system is operating normally.
Bo3 ({ SCI removed } and safety-classified)
Conservatively, a boron concentration of { SCI removed } has been considered which is higher than the maximum concentration of boron within systems housed in Bo3 rooms, which is { SCI removed }. In fault conditions, a minimum temperature of { SCI removed } is required to prevent from boron crystallisation at { SCI removed } (see Section 9.4.1 – Table 2). In Bo1, Bo2 andAPPROVED Bo3 rooms, a minimum temperature of { SCI removed } (same as normal operating conditions) has to be ensured during maintenance of HVAC systems.
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SECTION 9.4.1 – TABLE 2 : MINIMUM SAFETY TEMPERATURES AND RELATIVE HUMIDITY TO BE MAINTAINED IN FAULT CONDITIONS AND EXTREME COLD CONDITIONS
In fault conditions and extreme cold conditions, HVAC systems are designed to guarantee the following minimum temperatures. Therefore this table does not deal with qualification under accident conditions (see Sub-chapter 3.6).
Safety Case Commitment: target temperatures listed in Section 9.4.1 – Tables 1, 2 and 3 which are not in the current generic temperature ranges [Ref. 5] will be clearly identified in a dedicated document which will be used for equipment contract specifications.
Equipment / Areas Min. Temperature
Pure water system { SCI removed }
Fire detection equipment { SCI removed }
{ SCI removed } borated water system { SCI removed } (without margin on the temperature) { SCI removed } borated water system { SCI removed } (with margin on the temperature)
{ SCI removed } safety classified borated water system { SCI removed }
Pump with oil tank { SCI removed }
Main Control Room { SCI removed }
Instrumentation and Control equipment { SCI removed }
Electrical equipment – transformers – rectifiers – inverters { SCI removed }
Computer rooms and adjacent rooms { SCI removed }
HD [DB] feed tank rooms { SCI removed }
Battery rooms { SCI removed }
APPROVEDBattery rooms in HD [DB] Building { SCI removed }
EVU [CHRS] sodium hydroxide tank with a concentration range { SCI removed } of { SCI removed }
Other equipment { SCI removed }
For electrical equipment, the humidity requirement [Ref. 5] is applied.
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SECTION 9.4.1 – TABLE 3 : MAXIMUM SAFETY TEMPERATURES AND RELATIVE HUMIDITY TO BE MAINTAINED IN FAULT CONDITIONS
In fault conditions, HVAC systems are designed to guarantee the following maximum temperatures. Therefore this table does not deal with qualification under accident conditions (see Sub-chapter 3.6).
Safety Case Commitment: target temperatures listed in Section 9.4.1 – Tables 1, 2 and 3 which are not in the current generic temperature ranges [Ref. 5] will be clearly identified in a dedicated document which will be used for equipment contract specifications.
Equipment / Areas Max. Temperature
Main Control Room { SCI removed }
Instrumentation and Control equipment { SCI removed }
Instrumentation and Control rooms in HL [SB] buildings Non- { SCI removed } controlled Areas, during { SCI removed } Electrical equipment – transformers – rectifiers – inverters – { SCI removed } switchboards Switchgears rooms in HL [SB] buildings Non-controlled Areas { SCI removed } during { SCI removed }
Computer rooms and adjacent rooms, during { SCI removed } { SCI removed }
Battery rooms { SCI removed }
HK [FB] Controlled Areas green and yellow zones without global { SCI removed } ventilation including safety related component(s) HK [FB] Controlled Areas orange and red zones without global { SCI removed } ventilation including safety related component(s)
HLF/G/H/I [SB (M)] Non-controlled Areas mechanical rooms { SCI removed }
HLF/G/H/I [SB (M)] Controlled Areas mechanical rooms { SCI removed }
Reactor pit (concrete surface temperature) { SCI removed }
APPROVEDDiesel halls { SCI removed }
Diesel electrical rooms { SCI removed }
Daily fuel tank rooms { SCI removed }
Diesel HVAC technical rooms { SCI removed }
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Equipment / Areas Max. Temperature
Other equipment { SCI removed }
For electrical equipment, the humidity requirement [Ref. 5] is applied.
{ SCI removed }
Safety Case Commitment: the maximum temperature allowed in the reactor pit in the most restrictive events is under consolidation.
{ SCI removed }
APPROVED
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SECTION 9.4.1 - TABLE 4 : LEAK TIGHTNESS REQUIREMENTS FOR HVAC COMPONENTS [REF. 6]
Airtight component Internal leakage rate
Isolation damper (or non-return damper with { SCI removed } isolation function) T2
Isolation damper T3 { SCI removed }
Non-return damper T2 or T3 { SCI removed }
Filter or iodine adsorption unit housing T2 or T3 { SCI removed }
External leak tightness is defined as follows (see [Ref. 6] for more details):
On whole T2 ductwork (including components): { SCI removed } external area,
On whole T3 ductwork (including components): { SCI removed } external area and,
For external leak tightness requirements of HVAC components such as fire dampers and isolation dampers for example [Ref. 6].
For internal and external leak tightness tests, the air reference conditions are { SCI removed }, temperature of { SCI removed } and P of { SCI removed }.
APPROVED
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SECTION 9.4.2 – TABLE 1 : DWN [NABVS] SAFETY FEATURES
{ This table contains SCI and has been removed }
SECTION 9.4.3 - TABLE 2 : EVR [CCVS] SYSTEM SAFETY FEATURES TABLE
{ This table contains SCI and has been removed }
SECTION 9.4.4 – TABLE 2 : EVF SYSTEM SAFETY FEATURES
{ This table contains SCI and has been removed }
SECTION 9.4.5 – TABLE 2 : EBA [CSVS] SYSTEM SAFETY FEATURES
{ This table contains SCI and has been removed }
SECTION 9.4.6 – TABLE 1 : DWL [CSBVS] SYSTEM SAFETY FEATURES
{ This table contains SCI and has been removed }
SECTION 9.4.7 - TABLE 2 : DVL [SBVSE] SYSTEM SAFETY FEATURES
{ This table contains SCI and has been removed }
SECTION 9.4.8 – TABLE 2 – DCL [CRACS] SYSTEM SAFETY FEATURES
{ This table contains SCI and has been removed }
SECTION 9.4.9 – TABLE 3 : DVD SAFETY FEATURES [REF. 8] TO [REF. 12]
{ This table contains SCI and has been removed }
SECTION 9.4.10 - TABLE 2 : DEL [SCWS] SAFETY FEATURES
{ This table contains SCI and has been removed }
SECTION 9.4.11 – TABLE 2 – DER [OCWS] SAFETY FEATURES
{ This table contains SCI and has been removed }
SECTION 9.4.12 – TABLE 4 : DVP SYSTEM SAFETY FEATURES { This table containsAPPROVED SCI and has been removed } SECTION 9.4.13 – TABLE 1 : 9DWQ [ETBVS] SYSTEM SAFETY FEATURES
{ This table contains SCI and has been removed }
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SECTION 9.4.14 – TABLE 2 : DWK [FBVS] SYSTEM SAFETY FEATURES
{ This table contains SCI and has been removed }
SECTION 9.4.15 - TABLE 4 : DVJ SYSTEM SAFETY FEATURES
{ This table contains SCI and has been removed }
SECTION 9.4.16 - TABLE 2 : DVM SAFETY FEATURES
{ This table contains SCI and has been removed }
SECTION 9.4.17 - TABLE 2 : DVF SYSTEM SAFETY FEATURES
{ This table contains SCI and has been removed }
SECTION 9.4.18 - TABLE 2 : DVE SYSTEM SAFETY FEATURES
{ This table contains SCI and has been removed }
SECTION 9.4.2 – FIGURE 1 : { SCI REMOVED }
{ This figure contains SCI and has been removed }
SECTION 9.4.2 – FIGURE 2 { SCI REMOVED }
{ This figure contains SCI and has been removed }
SECTION 9.4.2 – FIGURE 3 : { SCI REMOVED }
{ This figure contains SCI and has been removed
SECTION 9.4.2 – FIGURE 4 : { SCI REMOVED }
{ This figure contains SCI and has been removed } APPROVED
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HPC PCSR3 – Sub-Chapter 9.4 – Heating, Reference: Ventilation and Air Conditioning Systems HPC-NNBOSL-U0-000-RES-100053
SECTION 9.4.2 – FIGURE 5 : DWN [NABVS] BUFFER TANK AND PRESSURE REFERENCE PIPEWORK PRINCIPLE
APPROVED
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SECTION 9.4.3 TO 9.4.18 – ALL FIGURES
{ These figures contain SCI and have been removed }
APPROVED
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