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Romania Going To Double Its

Traian MAUNA Nuclear Energy Romanian Association – AREN 65 Polona, 010494, Bucuresti, , C.P. (PO Box) 22-102 [email protected]

ABSTRACT

Cernavoda NPP meeting IAEA safety standards in charge until 1980 is only one CANDU type reactor from Europe. The Cernavoda site was selected on the right side of the Danube River near the beginning point of the Danube – Black Sea Canal (CDMN), at the north side of it. The Cernavoda site was designed for 5 units CANDU type, the work on site began in 1979 and stopped in 1991 on different stage of erection. The work was only continued after some time for the first unit that was put in operation in 1996. The second unit was put in commercial operation in 2007. Now the Cernavoda NPP, operating two units of 706 MWe each, covers around 18% from annual electric power in Romania. The Romanian authorities decided last year to restart the work of units 3 and 4 from existing status on the new financing formula, having 51% of total estimated cost shared Romanian participation via Company. The remainder 49% is covered by 6 international private companies. The unit 3 and 4 will be equipped with CANDU 6 reactor type concept and GE turbine type via Ansaldo Nucleare. The 4 units in operation Cernavoda NPP from 2016 will cover a minimum 36% of Romania total electric power demand.

1 INTRODUCTION

Located at 180 km east of Bucharest, in Constantza County at about 2.5 km SE from Cernavoda town, on the north side of the Danube-Black Sea Channel, the site of Cernavoda

NPP equipped with CANDU 6 rector type and ANSALDO –GE turbine was designed for 5 units of 706.5 MWe maximum power per unit at 150 C cooling water temperature. First unit has been in commercial operation since middle of 1996 covers more than 10% from the national power demand reaching over 710 MWe maximum power in operation. In the cold time this unit supplies all heating Cernavoda town needs. In the middle of 2007 the second unit was connected to the national electrical grid and so around of 18% of total energy consumption are covered by nuclear. The operational performance of two units from Cernavoda NPP has largely complied with “Current Western European Nuclear Safety Objectives and Practices”. Also the IAEA mission safety recommendations and standards were met. The Unit 3-5 was in conservation more or less till 1990 when work stopped under new governmental decision. At the end of 2007, after Unit 2 successful put in operation, the Romanian government announced his decision to start again the work on site for Units 3+4 by private and state funds agreement. The estimated cost for the two reactors is 4 billion euro will be cover by a consortium constitute from Nuclearelectrica (51%), CEZ, GdF-Suez,

718.1 718.2 & RWE Power (9.15% each) and Arcelor Mittal & Iberdrola (6.2% each). The target is 2016 to be in operation. 2 CANDU 6 TYPE MAIN FEATURES

The nuclear island CANDU 6 concept has a reactor building, service building, D2O tower, emergency diesel underground room, spent fuel bay and other small structure. The reactor building has a cylindrical perimeter wall pre-stressed concrete structure, diameter around 41.00 m with a of 1.04 m thickness, a spherical cap 0.80 m pre-stressed concrete supported by annular upper beam. Reactor building epoxy lined is main parts of radionuclides retaining containment. Maximum design pressure of the containment is 124 kPa, which is higher than the pressure assessed to be caused by a large LOCA with heat sink dousing system. The test pressure is set at 143 kPa. All nuclear island structures and equipments are seismically qualified to the design basis earthquake (DBE). The PHWR horizontal reactor vessel called calandria operates having the following parameters: thermal output (PHTS) 2064 MWth, D2O coolant flow rate (PHTS) 7.7 Mg/s, temperature (RIH) 266° C and pressure (RIH) 11.75 MPa (abs). The fueling machine supplies the fuel bundles natural uranium concentration in U235 into 380 pressure tubes of calandria. This type of reactor uses D2O as coolant primary loops and as moderator. During operation D2O become TDO or T2O. The section from reactor building is shown in Fig. 1.

Fig. 1. The reactor building cross section

Proceedings of the International Conference Nuclear Energy for New Europe, Bled, Slovenia, Sept. 14-17, 2009 718.3 The calandria vessel is located in a steel plated concrete enclosure, filled with light water (the calandria vault), which serves as an additional shielding and an external cooling of the calandria vessel. The reactor is provided with a heat transport system with two independent loops which transfer the heat generated in the fuel during the controlled fission reaction to four steam generators with light water at the secondary side. The nuclear fuel is manufactured in a Romanian facility FCN Pitesti from national ore mining and yellow cake preparation at Feldioara factory.

3 CERNAVODA NPP UNITS 3&4 SITE AND STATUS

The site was selected taking into account the general requirements regarding the general characteristics of CANDU type reactor and Canadian Safety Regulations. Romanian specialists considered also the Romanian regulations regarding inhabitant radioprotection by calculating the exclusion area and low population area in connection with the maximum dose allowable in the case of 10-6 event probability. The exclusion area where a permanent resident not allowed, is a circular area of 1000 m radius from the reactor building central point so the maximum radioactivity at the boundary a less than accepted level by regulatory body. The low population area in a ring-shaped area includes a little number of Cernavoda town houses where the employers NPP families live.

3.1 Sitting requirements and technical solutions

The NPP Cernavoda Units 3&4 are aligned on Units 1&2 reactor building centreline. The first concept imposed by Romanian design project team of the NPP was to be separate units by a 160 m distance from the centres of reactors. The main buildings of Nuclear System of Plant and Balance of Plant were arranged to be at the middle of the rock platform level. The layout of whole buildings, roads, underground ducts, Unit 0, sewerage and others was disposed in connection of main buildings position. Every nuclear island unit is underground surrounded by tightened concrete wall as Romanian concept in order to prevent the radionuclide infesting of shallow water. 6 pits equipped with pumps control the underground water level. The other Romanian concept is relating to cooling pump house as a single building shared by equipments for each unit and single intake water basin. The Danube- Black Sea Navigable Canal short branch brings the cooling water from the Danube River. Every unit needs around 52 m3/s row water for heat exchangers of turbine and nuclear systems. The inlet systems satisfy the water needs at the medium Danube flow water, but for lowest level some upstream hydro technical work must be done. The outlet of cooling water to the Danube River needs the new tunnelling under the north side hill. The exclusion area and low population zone were assured at the beginning as approved site criteria. The site seismicity was established by scientists at the 0.204g for DBE.

3.2 Status of the buildings

The Unit 3 Reactor Building Structural concrete of the Containment Structure base slab, cylinder perimeter wall except the temporary 2 equipments gates, ring beam, lower dome and upper ring beam are finalized. The upper dome has some unconformity regarding the ducts positions of prestressing cables. The 90% of the Internal Structure concrete works has been completed excepting the temporary open of calandria vault. For the Service Building all foundation concrete and structural concrete of the superstructure have been completed. All

Proceedings of the International Conference Nuclear Energy for New Europe, Bled, Slovenia, Sept. 14-17, 2009 718.4 structural steel has been completed up to level 9.00 m above the 100.00 m standard reference level. The turbine building is almost ready close around estimating 90% of structural works. The Unit 4 Reactor Building Structural concrete of the Containment Structure; base slab, cylinder perimeter wall except the temporary 2 equipments gates and lower ring beam have been completed. Internal concrete structure was partially erected. The Service Building all foundation concrete has been completed. At the BOP main building the reinforced concrete base mat and underground perimeter wall and superstructures concrete wall, columns, lacing roof beam and others nonstructural elements, around 55% of structural work. There is no technical equipment for operation of the units inside the buildings. The Fig. 2 gets up the artistic picture of existing in operation 2 units and the actual status of Unit 3&4, ready for on site resumption.

Fig. 2 The artistic picture of four units Cernavoda NPP

The underground ducts for cooling water are carried out until the vicinity of main buildings for both units estimating 60% of work. The Preservation Program started for existing parts of both units after the works at the buildings was broken off.

4 ENVIRONMENTAL MONITORING

The Environmental Radioactivity Monitoring Program of Cernavoda NPP in operation was designed to provide a correct evaluation of the doses for a member of the critical group, by determining the increases of the radioactive levels in the specific environmental media, due to the NPP operation, a correct assessment of the effluents control and monitoring based on environmental measurements and an estimation of the doses to population in case of significant radioactive releases. The environmental radioactivity monitoring operational program in Cernavoda area was issued and approved in 1995, being implemented in March 1996. According to this program, Cernavoda NPP lab measures the radioactive concentrations of environmental samples (water, air, soil, vegetation) and food samples (milk, fish, meat, vegetables, fruits), taken from an area covering an approx. 25 km radius around the NPP site. The sampling analysis frequencies vary between daily and annually, depending on the sample type and the observed radionuclides. In most cases, these measurements did not revealed the presence of artificial radionuclides into the environment, except for the tritium detected in

Proceedings of the International Conference Nuclear Energy for New Europe, Bled, Slovenia, Sept. 14-17, 2009 718.5 several locations in the very vicinity of the plant, the detected values being comparable with the detection limits. The dose limits for the population are: ¾ 1 mSv per year of effective dose; in special situations, ¾ 15 mSv per year, equivalent dose for the lens of the eye, ¾ 50 mSv per year, equivalent dose for the skin. Regarding the radiation protection of the population, there is a lot of points for pick up the sample as show in the Fig. 3, according to monitoring program.

Fig. 3 Selected sample ingather points around Cernavoda NPP

The environmental monitoring lab use the ingathered sample from water, soil, milk, grass in order to calculate the real radioactive pollution from Cernavoda NPP released gaseous or liquid effluents. Until now overcoming of approved limit was not registered. So there is basic environmental monitoring experience for develop new methods and improve the existing program.

5 SAFETY ASPECTS

The is circulated through the moderator system for cooling, for purification, and for control of the substances used for reactivity adjustment. The heavy water in the calandria functions as a heat sink in the unlikely event of a loss of coolant accident coincident with failure of emergency core cooling.

Proceedings of the International Conference Nuclear Energy for New Europe, Bled, Slovenia, Sept. 14-17, 2009 718.6 The shutdown cooling system is provided to cool the heat transport system and keep it at low temperature for an indefinite period of time. Initial cooling is provided by blowing off steam from the main boilers. The safety systems include two totally independent, redundant and diverse Shut Down Systems, the Emergency Core Cooling System and the Containment System. Thus the moderator system backs up both the regular and emergency core cooling systems for added safety. Multiple static barriers that prevent the release of radioactive emissions into the atmosphere as Reactor Containment prestressed, posttensioned concrete structure, designed to withstand the pressure reached in large loss of coolant accidents (LOCA) and dousing system for heat sink.

6 CONCLUSIONS

Roughly speaking the conservation procedures was for too long time and many repairs works are need. The status of all steel structures are rusted more or less, like service building column, beams, joints, lacing, prestressing concrete ducts, cooling water ducts, penetrations. IAEA draft safety guide on evaluation of seismic hazards for existing NPPs published in 2007 is not obligatory to apply for Cernavoda NPP Units 3&4. The improvements of safety systems from last CANU 6 NPP projects from Korea and China can and must to be applied. The monthly dose for human in the critical group caused by the radioactive emissions released from NPP is around 100 times less than average monthly dose released by the natural background. The average annual dose is only 0.8 % from 1000 μSv legal dose limit. In Romania responsibilities in the field of environmental radioactivity monitoring (including the surveillance of food stuffs) regulations and limits are of: ¾ Ministry of Environment and Sustainable Development, which organizes the Environmental Radioactivity Monitoring Network on the Romanian territory, ¾ Ministry of Public Health, which organizes the epidemiological monitoring system of the health condition of the occupationally exposed personnel and of the hygiene conditions in nuclear installations, follows up the influence of nuclear activities on the population health, ¾ National Commission for Nuclear Activities Control (CNCAN).

REFERENCES

[1] I. Rotaru, “The Private Sector Involvement In Financing ”, The future of Nuclear Power in Central and Eastern Europe, Budapest, 2006 October 19

[2] A. Wenisch, R. Kromp, “NPP Cernavoda ¾, Bilateral Consultation ", REP-0149, Wien, 2008.

[3] A. Wenisch, R. Kromp, G. Mraz, P. Seibert, “Construction of NPP Cernavoda Unit 3 & 4 - Environmental Impact Assessment “, REP-0126, Wien, 2007

[4] A. Carabulea, I.D. Gheorghiu, S.C. Valeca, I. Rotaru, ” On nuclear ” Int. J. Nuclear Governance, Economy and Ecology, Vol. 1, No. 3, 2007, pp. 322 – 334

Proceedings of the International Conference Nuclear Energy for New Europe, Bled, Slovenia, Sept. 14-17, 2009 718.7 [5] E. Bobric, C. Bucur, I. Popescu, V. Simionov, ” Environmental Radiological Impact Assessment After 12 Years of Operation at Cernavoda ” Bucharest July 8, 2009 - Seminars organized on the occasion of the State Visit of Their Majesties the King and Queen of the Belgians,

[6] S. S. Doerffer,” Enhanced CANDU 6 – EC6 Overview”, Atomic Energy of Canada Limited, Seminar on CANDU TECHNOLOGY, Warsaw, Poland, January 23rd, 2007.

Proceedings of the International Conference Nuclear Energy for New Europe, Bled, Slovenia, Sept. 14-17, 2009