HM Naval Base Devenport Report of Assessment of HAZARD IDENTIFICATION and RISK EVALUATION

~~_,.~~ -. ROYAL NAVY

AUGUST 2017

Radiation (Emergency Preparedness & Public Information) Regulations Regulation 6 & Schedule 5

Page 1 of 19 OFFICIAL Document Approval

Name Date Author Connor Ware

Checker I Richard Clark ~1/o-t/rl- App_roved for I Sheila Burrows I Naval Base 1ssue Emergency ~t . ~ .R Plannina A Hd

Page 2 of 19 OFFICIAL Contents 1. INTRODUCTION ...... 4 2. REPPIR SCHEDULE 5 : PARTICULARS TO BE INCLUDED IN AN ASSESSMENT REPORT ...... 4 2.1. CLAUSE (A)- NAME AND ADDRESS ...... 4 2.2. CLAUSE (B) - POSTAL ADDRESS ...... 4 2.3. CLAUSE (C)- COMMENCENT DATE ...... 5 2.4. CLAUSE (D)- GENERAL DESCRIPTION ...... 5 2.5. CLAUSE (E)- RADIOACTIVE SUBSTANCES (OPERATOR) ...... ? 2.6. CLAUSE (F)- RADIOACTIVE SUBSTANCES (CARRIER) ...... 9 2.7. CLAUSE (G)- PLAN AND SITE ENVIRONS ...... ~ ...... 9 2.8. CLAUSE (H)- PLANT DESCRIPTION ...... 9 ·2.9. CLAUSE (I)- MAJOR RELEASE ...... 10 2.1 0. CLAUSE (J)- CONTINUOUS RELEASE ...... 11 2.11. CLAUSE (K)- UNINTENDED SELF-SUSTAINING NUCLEAR CHAIN REACTION ...... 11 2.12. CLAUSE (L)- MANAGEMENT SYSTEMS AND STAFFING ...... 12 2.13. CLAUSE (M)- POPULATION ...... 14 2.14. CLAUSE (N) - RADIOACTIVE DISPERSAL...... 15 2.15. CLAUSE (0)- EXPOSURE ...... 16 2.16. CLAUSE (P)- REQUIREMENT FOR OPERATOR EMERGENCY PLAN 16 3. SUMMARY ...... 16 4. ANNEX A- HMNB DEVONPORT (NORTH YARD) ...... 18 5. ANNEX B- HAMOAZE AND THE SOUND ...... 19

Figure 1 -Schematic of a PWR ...... 10 Figure 2 - NPW Containment...... 10

Table 1 - HMNB Devenport Berths ...... 6 Table 2 - Population Data ...... 14 Table 3- Sectored Population Data (1 and 2 km) ...... 15

Page 3 of 19 OFFICIAL 1. INTRODUCTION

1.1. Regulation 4 of the Radiation (Emergency Preparedness and Public Information) Regulations 2001 (REPPIR) requires a Hazard Identification and Risk Evaluation (HIRE) to be undertaken for any premises or facilities containing more than the quantity of any radionuclide specified in Schedule 2 or, in the case of fissile material, more than the mass of that material specified in Schedule 3 of Reference 1.

1.2. Regulation 5 requires a review of the HIRE to be performed within 3 years of the date of the last assessment; or when a material change occurs~n the work with ionising radiation to which an assessment made pursuant to regulation 4(1) relates.

1.3. This document is the Report of Assessment (RoA) of the HIRE for HNMB Devon port.

1.4. This RoA, together with supporting documentation, will be presented to the Office for Nuclear Regulation (ONR) to satisfy Regulations 5 and 6 of REPPIR in order to enable ONR to assess the risk to the health or safety of persons who could be affected by the work with ionising radiation undertaken at HMNB Devenport.

2. REPPIR SCHEDULE 5: PARTICULARS TO BE INCLUDED IN AN ASSESSMENT REPORT

2.1. CLAUSE (A)- NAME AND ADDRESS · The name and address of the operator or carrier;

2.1.1. Name of Operator: Naval Base Commander Devenport (NBC(D))

2.1.2. Address of Operator: Her Majesty's Naval Base Devenport, Plymouth, Devon, PL2 2BG.

2.2. CLAUSE (B) - POSTAL ADDRESS The postal address of the premises where the radioactive substance will be processed, manufactured, used or stored, or where the facilities for processing, manufacture, use or storage exist or, in the case of transport the postal address of the transport undertaking;

2.2.1. Postal Address: Her Majesty's Naval Base Devenport, Plymouth, Devon, PL2 2BG. ·

Page 4 of 19 OFFICIAL 2.3. CLAUSE (C)- COMMENCENT DATE The date on which it is anticipated that the work with ionising radiation will commence or, if it has already commenced, a statement to that effect;

2.3.1. HMNB Devenport has worked with ionising radiation to provide technical, logistical and administrative support to Nuclear Powered Warships (NPW) (Nuclear Submarines) since the Early 1970s. The Naval Base provides and operates a range of the required nuclear engineering and associated nuclear support facilities for NPWs.

2.4. CLAUSE (D)- GENERAL DESCRIPTION A general description of the premises or place including the geographical location, meteorological, geological, hydrographic conditions and, where material, the history of the premises, except that in the case of transport a general description shall be given of either -

(i) The starting and end points of the journeys and transhipment points, or

(ii) The criteria to be used for route selection;

Site purpose and Activities

2.4.1. The Devenport site which comprises the Dockyard site plus the Naval Base site, provides support and maintenance capabilities for surface ships and submarines as well as accommodation facilities for service personnel.

2.4.2. HMNB Devenport carries out the following operations in respect to the support of the NPWs and associated systems:

a. Operation of the Nuclear Steam Raising Plant (NSRP).

b. Movement and berthing of the vessels.

c. Testing, maintenance and repair of the NSRP and associated systems.

d. Lay up of Decommissioned submarines.

Geographical Location

2.4.3. HM Naval Base Devenport is part of the Naval Base site. It is located within the city of Plymouth, near the border of Devon and Cornwall. The Naval Base estate encompasses approximately 740 acres, with 3.5 miles of water frontage. HM Naval Base Devenport is situated on the Hamoaze, a reach of water stretching from Saltash to the Narrows, on the East bank of the river Tamar. The River Tamar is used extensively by a range of military, commercial and leisure craft. HM Naval Base Devenport is the operating and maintenance centre for the Submarine Flotilla South (SUBFLOT (S)). This work, and hence work with ionising radiation , is concentrated in the

Page 5 of 19 OFFICIAL North Yard area of the Naval Base. The adjacent dockyard carries out major refitting and refuelling of Nuclear Powered submarines.

2.4.4. Within the dockyard Port of Plymouth the MOD controls activities at the HMNB Devonport Berths and anchorages. At an 'X' Berth the activities allowed are maintenance, repair and ammunitioning. At a 'Z' Berth no nuclear related work is permftted without prior justification and Regulatory approval. Details of the HMNB Devonport berths and anchorages are provided in Table 1 below.

Table- 1 HMNB Devenport Berths

Berth Type Purpose 9 Wharf X (Tidal) Double Berth-Alongside. Maintenance. Ammunitioning position Lat: soc 23' 26.021 "N Long: 04c 11' 33.0S1"W 8 Wharf North X (Tidal) Double Berth-Alongside. Maintenance. Ammunitioning position Lat: soc 23' 23.1 07"N Long: 04c 11' 33.201"W , 8 Wharf X (Tidal) Double Berth-Alongside. South Maintenance. Ammunitioning position

' Lat: soc 23' 20.934"N Long: 04c 11' 29.0SS"W 7 Wharf X (Tidal) . · Double Berth-Alongside. Maintenance. Ammunitioning position Lat: soc 23' 14.892"N Long: 04 c 11' 24.368"W 'Delta' Buoy z Z Berth Anchorage Lat: soc 20' 1S.434"N Long: 04c 08' 29.21"W 'Echo' Buoy z Z Berth Anchorage Lat: soc 20' 34.318"N Long: 04 c 08' 38.31S"W Anchorage z Z Berth Anchorage 22* Lat: soc 19.22'N Long: 04c 09.29'W Anchorage z Z Berth Anchorage 23* Lat: soc 18.92'N Long: 04c

L__ 09.29'W

* These anchorages have never been used to berth NPWs and would require a specific safety justification in order for the anchorages to be used for this purpose ·

Meteorological Conditions

Page 6 of 19 OFFICIAL 2.4.5. The climate of the Plymouth area is temperate maritime, with the most active weather usually occurring as depressions approach the area from the South West, bringing strong winds and heavy rain. Snow fall in the Plymouth area occurs on average 10 to 15 days per year but is only deep enough for its depth to be measured on 2 or 3 days a year. Air frosts (air temp less than 0°C) are likely to be recorded on around 20 nights between October and May. Thunder occurs approximately around 10 days per year, with a slightly higher incidence recorded betw,een May and August than for the rest of the year.

Geological Conditions

2.4.6. The Devenport Site is underlain by alluvium (associated with the River Tamar) above Upper Devonian Slates. The geology indicates that the slates have a cleavage dip mainly to the south in the vicinity of the site.

2.4.7. Groundwater is located at a depth of about 3.0m below ground level (about · 1.0 to 1.5m Above Ordnance Datum (AOD)). The groundwater conditions beneath the site are complicated by the presence of the dock walls, the emptying/filling of the docks and the influence of tidal fluctuations.

Hydrographical Conditions

2.4.8. The effects of tidal conditions, tsunami and groundwater on HMNB Devenport have been considered within site safety cases which have been used to inform the HMNB Devenport HIRE.

2.5. CLAUSE (E)- RADIOACTIVE SUBSTANCES (OPERATOR) In the case of an assessment by an operator, a description of any radioactive substance on the premises which is likely to exceed any quantity or mass specified in Schedule 2 or Schedule 3, as the case may be, which description shall where practicable include details of the radionuclides present and their likely maximum quantities;

Defiance Facility

2.5.1. The Defiance Facility is located on the Northern end of the Naval Base site, adjacent to Wharves 8 and 9. The facility consists of 2 different areas in which different operations involving work with ionising radiation are performed. This includes a sealed sources store and a sample counting room.

2.5.2. It is highlighted that the inventory in the facility does not exceed the limits in Schedule 2 of the regulations and the Defiance Facility is exempt from the requirements of REPPIR under regulation 3(1 )(a) .

Decommissioned, Defueled, Laid-up Submarines

Page 7 of 19 OFFICIAL 2.5.3. The De-equipped, Defueled, Laid-Up (DDLP) Submarines are nuclear submarines of the Royal Navy that have ceased commissioned service and have had the nuclear fuel removed from their reactors. A total of 4 DDLP Submarines are in the Naval Base. The decommissioned submarines are in No. 3 basin. COURAGEOUS which was located at 3 Dock is now also in No. 3 basin and is used as a public exhibit/museum. No.3 Basin is a non-tidal basin (except when the caisson is removed for vessel entry/exit) located in North Yard HMNB Devonport.

2.5.4. The vast majority of the radiological inventory, in the form of the spent fuel, associated with an operational Nuclear Steam Raising Plant (NSRP) has been removed during defueling in preparation for lay-up. The radioactive inventory associated with the submarines is in the form of activated reactor plant and pipework or activated corrosion and wear products which are in the form of particulate matter within associated reactor plant pipework. In the former case the radioactive material is in a non dispersible form and is therefore exempt from REPPIR under Regulation 3(4)(a). for the latter, the quantity of radioactive material does not exceed the levels in REPPIR Schedule 2 and is therefore exempt from REPPIR under Regulation 3(1) (a)

2.5.5. The nuclear hazards and risks associated with the presence of COURAGEOUS and the DDLP submarines are addressed in the Facility Safety Case for 3 Basin Authorised Activities. These documents demonstrate that although the inventory is above levels in Schedule 2 the activity is in a non-dispersible form and is exempt from REPPIR under regulation 3(4)(a).

Long Term Berthed (Fuelled) (L TB(F)) Submarines

2.5.6. A Maximum of 10 Fuelled decommissioned submarines could be berthed in 3 Basin. The basin currently houses 8 fuelled submarines alongside 4 DDLP submarines.

2.5.7. The hazards and risks associated with the Long Term Berthing of Fuelled submarines in 3 Basin are addressed in the Facility Safety Case for 3 Basin Authorised Activities. This Safety Case demonstrates that no reasonably foreseeable radiation emergency can result from the LTB submarines in 3 Basin.

Operational Submarines (NPWs)

2.5.8. The NSRP within a NPW contains more than the quantity of Radioactive Material (RAM) specified in Schedule 2 or 3 of REPPIR. Details regarding the maximum quantities of radionuclides within NSRP are detailed within the plant specific safety cases and the NSRP HIRE. Key fission products that may be released in the event of a severe accident include radioactive isotopes of iodine, caesium and krypton. The NSRP HIRE details all RAM which may be released into the environment in the event of a severe accident.

Page 8 of 19 OFFICIAL 2.6. CLAUSE (F) - RADIOACTIVE SUBSTANCES (CARRIER) In the case of an assessment by a carrier, a description of any radioactive substance which is likely to exceed any quantity or mass specified in Schedule 4 or Schedule 3, as the case may be, which description shall where practicable include details of the radionuclides present and their likely maximum quantities;

2.6.1 . This clause is applicable to carriers of RAM only.

2.7. CLAUSE (G)- PLAN AND SITE ENVIRONS Except in the case of an assessment relating to transport, a plan of the premises in question and a map of the environs to a scale large enough to enable the premises and any features which could affect the general risk in an emergency to be identified;

2.7.1. A map of North Yard showing the TXB locations and the submarines in 3 basin is provided in Appendix A. A map of the geographical location of the Devon port Site is provided in Appendix B. Table 1 gives locations for the wharfs.

2.8. CLAUSE (H)- PLANT DESCRIPTION A diagram and description of any single plant or enclosed system containing more than the quantity or mass of any radioactive substance specified in Schedule 2 or Schedule 3, as the case may be, or, in the case of the transport of more than the quantity or mass of any radioactive substance specified in Schedule 4 or Schedule 3, as the case may be, the nature of the containment for the radioactive substance, the type of vehicle and the means of securing the load within or on the vehicle;

2.8.1 . Within the NSRP, fission of uranium contained in the fuel elements takes place in the reactor core. The resulting fission products, including radioactive isotopes of iodine, caesium and krypton are contained within the fuel cladding. The heat generated by the fission process is removed from the core by water contained in a sealed circuit. This water is pumped through the steam generators where heat is transferred to a separate, secondary circuit to produce power.

2.8.2. The NPW containment is designed to confine RAM released during a reactor emergency within a limited and controlled volume. The containment and other barriers to fission product release in the event of an accident include:

a. The fuel cladding.

b. The reactor pressure vessel and primary circuit boundary.

c. The primary containment, which is normally, defined as the pressure hull and first pressure-tight bulkhead either side of the Reactor Compartment (RC).

Page 9 of 19 OFFICIAL 2.8.3. These multiple barriers provide defence in depth against accidental release of radioactivity .

...... ,...... o......

...... ,,.St"l v...-.1 .. w..,

.,.,eoa•'"*"' 5hlllctng

Figure 1 - Schematic of a PWR

Fue I Elemen Cla

Figure 2 - NPW Containment

2.9. CLAUSE (I)- MAJOR RELEASE Those factors which could precipitate a major release of any radioactive substance and the measures to be taken to prevent or control such release and information showing the maxi~um quantity of radioactive_ substance

Page 10 of 19 OFFICIAL which, in the event or major failure of containment, would be released to the atmosphere including, in respect of premises, the identification of plant and other activities anywhere on the premises which could precipitate such release;

2.9.1. The NSPR HIRE along with the Naval Base site specific Annex is a comprehensive assessment of the internal and external hazards associated with the submarine reactor plant and operations at HMNB Devenport. The majority of identified potential faults will not result in any release of RAM to the open environment, by the virtue of the prevention, mitigation and protection provisions installed and maintained in each NPW.

2.9.2. The NSRP HIRE concludes that a Radiation Emergency can result from an operational NPW. In accordance with the REPPIR requirements the HIRE provides assessment of the area which is likely to be affected by any release of RAM as a result of any radiation emergency, the period of time over which such dispersal is likely to take place and the likely exposures to ionising radiation to any person.

2.9.3. Information on the maximum quantity of radioactive substance that could be released to the atmosphere is excluded from this report for security reasons. This information has been made available to the ONR to enable their comprehensive review of HMNB Devenport's assessment.

2.9.4. The security arrangements at HMNB(D) are compliant with the relevant MOD standards such that an act of sabotage or terrorism, which results in an off-site release greater than that from the Reference Accident, is not reasonably foreseeable.

2.10. CLAUSE (J)- CONTINUOUS RELEASE Those factors which could precipitate a smaller but continuing release of any radioactive substance and the measures to be taken to prevent or control such releases to atmosphere;

2.10.1. The NSRP HIRE details modelling of many of the reasonably foreseeable accident sequences, and sensitivity studies indicate the possibility of very low but continuing release of RAM over a period of more than 24 hours.

2.1 0.2. Information on the maximum quantity of radioactive substance that could be released to the atmosphere is excluded from this report for security reasons. This information has been made available to the ONR to enable their comprehensive review of HMNB(D)'s assessment.

2.11. CLAUSE (K)- UNINTENDED SELF-SUSTAINING NUCLEAR CHAIN REACTION Those factors which could give rise to an incident involving the initiation of an unintended self-sustaining nuclear chain reaction or the loss of

Page 11 of 19 OFFICIAL control of an intended self-sustaining nuclear chain reaction and, in either case, the measures to be taken to prevent or control any such incident;

2.11.1. No hazards have been identified which could, under reasonably foreseeable conditions, result in an unintended self-sustaining nuclear chain reaction from NSRP operations at HMNB Devonport.

2.12. CLAUSE (L)- MANAGEMENT SYSTEMS AND STAFFING Information concerning the management systems and staffing arrangements by which the radioactive substance is controlled and by which the procedures are controlled;

Internal Regulation and Approval

2.12.1. HMNB Devonport, as a MOD establishment, is not subject to licensing under the Nuclear Installations Act 1965. The MOD operates an internal nuclear regulatory regime that mirrors the Office for Nuclear Regulation (ONR) licensing approach. The MOD internal regulator is the Defence Nuclear $afety Regulator (DNSR), who uses a similar framework to the ONR licensing approach by assessing the site's organisation and arrangements against 36 Authorisation Conditions (ACs) and 4 Further Authorisation Conditions (FACs). The site complies with these conditions through Authorisation Condition Compliance Statements(ACCSs) which set out the sites policy and processes for compliance.

Safety Management Arrangements

2.12.2. HMNB Devonport has a Safety Management System with suitable and ,. sufficient arrangements in place to meet the requirements of the Nuclear Site Authorisation. These arrangements include the fundamental requirements of radiological safety for doing all that is reasonably practicable to minimise operational doses, risks and the initiation of abnormal events, particularly those which could escalate to major accidents.

2.12.3. Conditions for the safe operation of individual facilities are derived from detailed risk and safety assessments of each facility, reported in the relevant safety case, thus complying with Nuclear Site ACs. All safety related Structures, Systems and Components are subject to appropriate examination, inspection, maintenance and testing. Key operational requirements necessary for safe operation are highlighted in formally approved Operator Instructions. In addition, processes are in place to ensure scrutiny and control of changes, whether these are to engineered systems, site services, procedures, organisational structures or resources.

2.12.4. NBC(D) as Authorisee is responsible for the safe operation of HMNB Devonport. This includes having overall responsibility for ensuring that adequate numbers of staff are present on site to operate the plants and ancillary plant in a safe manner, and that these staff are suitably qualified and experienced. This process is supported by appropriate Safety Committees.

Page 12 of 19 OFFICIAL Engineering Controls

2.12.5. The containment arrangements for the NSRP are described in section 2.8 of this report. In addition, there are engineered and procedural safeguards to prevent and mitigate any accident scenario. All equipment is designed and constructed to a high specification, and undergoes thorough examination, testing and regular planned maintenance. Operation of all equipment is conducted according to operating procedures, by Suitably Qualified and Experienced Persons (SQEP). The safety justifications for the equipment, its operation and any changes to these are subject to review.

Staffing arid Training Requirements

2.12.6. Personnel who have direct and indirect responsibility for nuclear safety (not including operators) are defined in the HMNB Devenport Nuclear Baseline. The nuclear training requirements (qualifications and experience) for each role with direct nuclear safety responsibilities are managed through the Nuelear Training Requirements Plan (NTRP). This ensures personnel at HMNB Devenport, are SQEP for the work that they are expected to perform.

2.12.7. All operators of the NSRP are SQEP and undergo a thorough training and requalification process set out through the Standing Committee on the Training and Qualification of Naval Nuclear Propulsion Plant Operators: This includes examination, simulations, boards and a process of trainee development. These requirements are managed through a process of audit and review ensuring that operator training remains current and effective.

Systematic Analysis

2.12.8. The Design Authority for the Naval Pressurised Water Reactor (PWR), Rolls Royce, is charged with producing a Though Life Safety Case (TLSC) covering all classes. This safety case is based on deterministic and probabilistic safety assessment of the PWR and its associated systems (making the totality of the NSRP). The TLSC is independently peer reviewed and then subjected to Independent Nuclear Assurance (INA) by AMEC (formally part of SERGO Assurance). They produce a Nuclear Safety Clearance Document for each NPW, which is formally reviewed by DNSR. When satisfied, DNSR issues a Safety Clearance Letter to the Authorisee, who authorises the operation of each NPW.

2.12.9. HMNB Devenport take benefit from the NSRP safety justifications in the production of Naval Base site safety justification which are presented in facility safety cases.

Detection and Mitigation 2.12.1 0. Key Parameters of the NSRP (identified through the systematic analysis) are continuously monitored to ensure the NSRP is operating within its limits. There are multiple and diverse means to detect that a fault

Page 13 of 19 OFFICIAL condition has been initiated, with the detection mechanism then prompting operator intervention to remedy the situation.

2.12.11. If the National Grid electricity supply to HMNB Devenport fails there are alternative power sources available which can maintain safe supplies to high priority facilities and systems. Uninterruptible Power Supply equipment is connected to those electrical systems considered essential to safety and temporary supplies are provided by local generators.

Access Control. Security and Prevention of Malicious Intent

2.12.12. The security arrangements at HMNB Devenport are compliant with the relevant MOD standards and compliance with those standards is checked by bodies independent of the operator on a periodic basis. Compliance is achieved by the principle of multi-layered defence in depth where levels of protection are set by the strategic value of the asset, its vulnerability to perceived threats and the current threat assessment. In general this protection falls into two main areas, access control and training/control of persons undertaking work.

2.12.13. Further details on access contrQI, security and prevention of malicious intent are excluded from this report for security reasons. This information has been made available to the ONR to enable their comprehensive review of HMNB Devenport's assessment.

2.13. CLAUSE (M)- POPULATION Except in the case of an assessment relating to transport, information about the size and distribution of the population in the vicinity of premises to which the report relates;

2.13.1. The population distribution around HMNB Devenport is detailed below. This is taken from the most recent UK population census in 2011. There are minimal seasonal variations in permanent residents in this data. The local population surrounding the Naval Base is substantial. Table 2 below shows the population numbers related to each berth. There is significant overlapping. Table- 2 Population Data

Berth No of Residents No of Residents No of Residents No of Residents within 550m within 2km within 10km within 20km 9 Wharf 472 33826 278067 368721 8 Wharf North 0 34557 277617 368515 8 Wharf South 0 35268 277676 368296 7 Wharf North 0 39047 278108 367018 7 Wharf South 0 38624 278163 366600 Delta Buoy 0 25 273823 335667 Echo Buoy 0 111 285738 337243

22 Anchorage 0 0 . 200692 329631 I

23 Anchorage 0 0 180093 327031 I

Page 14 of 19 OFFICIAL 2.13.2. Table 3 below illustrates the population in the 30 degree sectors for 7 Wharf, 8 and 9 Wharfs to distances of 1 and 2 km .

Table- 3 Sectored Population Data (1 and 2 km)

1 km 2km 8 8 7 8 8 7 Sector 9 Wharf Wharf Wharf 9 Wharf Wharf Wharf (degrees) Wharf North south North · Wharf North South North 0-30 1420 1429 1084 357 4631 4855 4800 4762 30-60 124 0 0 453 3914 3395 3132 2910 60-90 656 722 1026 1483 4147 4930 4871 4904 90-120 424 433 383 508 7111 6915 7133 7679 120-150 75 0 0 130 4510 4339 4516 5395 150-180 0 0 0 0 355 472 721 1709 180-210 0 0 0 0 2473 2891 2808 2226 210-240 0 0 0 0 761 1170 1589 2784 240-270 8 8 8 8 194 194 152 219 270-300 0 0 0 0 13 13 42 83 300-330 0 0 0 0 37 14 0 0 330-360 444 688 688 733 2057 2089 2315 2704

2.14. CLAUSE (N)- RADIOACTIVE DISPERSAL An assessment of the area which is likely to be affected by the dispersal of any radioactive substance as a result of any radiation emergency and the period of time over which such dispersal is likely to take place;

2.14.1. The NSRP HIRE has identified a Reference Accident which is the bounding case reasonably foreseeable accident sequence. The reference accident is a Loss of Coolant Accident (LOCA) where core damage occurs but the containment remains intact therefore there is only a very small release of RAM into the environment. For this accident sequence, the consequence is dominated by gamma shine from the submarine hull , with a 5mSv dose contour (unmitigated) extending approximately 870m.

2.14.2. The consequences of a range of accidents which have a lower probability of happening have also been analysed (sensitivity studies). The bounding case sensitivity study has a slightly greater atmospheric release of RAM with a 5mSv dose contour (unmitigated) extending to 1170m. In this accident sequence, the radiation dose beyond 500m is dominated by the release of radioactive fission products. ONR have used this accident sequence ·to determine the Detailed Emergency Planning Zone (DEPZ) for HMNB Devonport berths.

2.14.3. The release duration of both accident sequences is greater than 24 hours with most of the RAM being released into the environment in the first few hours following core damage.

Page 15 of 19 OFFICIAL 2.15. CLAUSE (0)- EXPOSURE An assessment of the likely exposures to ionising radiation of any person or class of persons as a result of any radiation emergency

2.15.1. The consequences in terms of radiation exposures to members of the public from the full range of accident sequences have been analysed in the HIRE and Supporting information. Information has been provided to the Local Authority to enable them to review and revise their ott-site emergency plans. This information is based upon the HSE/ONR determination that the ott-site emergency plan is required to a distance of not less than 1.5km from an NWP berth. This is based upon the consequences of the bounding case sensitivity study.

2.15.2. A number of site personnel and NSRP operators could potentially receive a radiation exposure while performing either their emergency operating procedures to secure containment or an intervention. Radiation exposures would be monitored and maintained below the emergency exposure levels that have been agreed by ONR.

2.16. CLAUSE (P)- REQUIREMENT FOR OPERATOR EMERGENCY PLAN An assessment of the necessity for an emergency plan to be prepared by the operator or carrier.

2.16.1. HMNB Devenport has concluded that, in order to protect personnel on-site and undertake mitigation activities to minimise the risk of any radiological consequences ott-site, an Operator's emergency plan is required.

2.16.2. The On-Site Emergency Plan DEVNUSAFE includes mechanisms tor alerting, protection of personnel, assessing the actual and potential coAsequences of any emergency, on-site actions to mitigate those consequences, and tor notifying the authorities responsible tor activation of the Devenport Ott-Site emergency plan (DOSE~).

3. SUMMARY

3.1. This Report of Assessment fulfils HMNB Devenport's duty under REPPIR Regulation 6 tor the site. · It confirms REPPIR is applicable to HMNB Devenport as the quantities of radiological materials on the site exceed those specified in the REPPIR schedules 2 and 3.

3.2. HMNB Devenport has conducted a Hazard Identification and Risk Evaluation tor its work with ionising radiation. This has assessed Naval Base Facility Safety Cases and safety documentation, and the MOD Generic submarine HIRE.

3.3. HMNB Devenport has determined that a radiation emergency is reasonably foreseeable at the Devenport site from the NSRP. The 5mSv dose contour

Page 16 of 19 OFFICIAL from a reasonably foreseeable radiation emergency at HMNB Devenport extends to a distance of approximately 0.87 km.

3.4. ONR's determination for the Off-Site Emergency Planning Area (DEPZ) extends to a distance of not less than 1.5km based upon sensitivity studies. This information has been supplied to Plymouth City Council to enable them to review and revise their off-site Emergency Plan, in consultation with other Local Authorities, Emergency Services and other supporting Agencies.

Page 17 of 19 OFFICIAL 4. ANNEX A- HMNB DEVONPORT (NORTH YARD)

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• Autlrrised Site Autlrrised Activities .licensed Site

Page 18 of 19 OFFICIAL 5. ANNEX B - HAMOAZE AND THE SOUND

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Dockyard Port Of Plymouth ,J NUCLEAR A UTHORISED ACTIVITIES

NOT TO BE USED FOR NAVIGATION This chart has been produced in consultation with Queen's Harbour Master Plymouth.

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IS Longilude4• 10 West from Greenwich OS '

Page 19 of 19 OFFICIAL