Ensuring Safety in Nuclear Power: Radiation Protection, Chain Reaction Control, and Suppression of Accidents

1. INTERNATIONAL CONFERENCEON FIFTY YEARS OF NUCLEAR POWER – THE NEXT FIFTY YEARS27 June – 2 July 2004 NUCLEAR POWER SAFETY: THE PRESENT AND ASSURANCE FOR THE FUTURE Asmolov V.G., Sidorenko V.A.

2. Lines of Safety Ensuring • Radiation protection; • Chain reaction control; • Prevention (limitation) of radioactive material spreading (suppression of radiation accidents).

3. Radiation Protection State Regulatory Documents(the initial period) 1960-“Sanitary rules for the operation with radioactive materials and other sources of ionizing radiation” (SP-333.60); 1968- “Sanitary rules for designing of nuclear power plants”; 1969- “Radiation safety standards” (NRB-69).

4. Elimination of an Uncontrolled Chain Reaction 1962 - “Rules of nuclear safety ensuring for reactors” (the first edition).

5. Suppression of Radiation Accidents • Special requirements imposed on materials and structures: - the equipment quality; • Conservatism in solutions; • Location of power plants: - a far distance from large settlements.

6. Conservatism in SolutionsBy the Example of the VVER Reactor First Generations • Reduced power density in the core; • Significant thermal margins ranging up to the limiting values; • Stability of spatial power distributions; • Negative values of reactivity coefficients at operating parameters; • Coolant stable natural circulation without running beyond the design parameters up to 10% of thermal power; • High redundancy of the basic equipment (six loops of the reactor cooling) with the opportunity for a long-duration operation at reduced power (up to three loops); • A large amount of water storage above the core and in the circulation loop mitigating the processes taking place during the accident with loss of coolant;

7. Conservatism in SolutionsBy the Example of the VVER Reactor First Generations(cont’d) • Horizontal steam-generators with a large water storage providing the removal of residual heat-generation up to five hours on the power plant complete block-out; • Chrome-molybdenum-vanadium pearlitic steel of improved radiation resistance was used as the reactor vessel material; • The reactor vessel was manufactured from the forged ferrule without longitudinal joints; • The vessel lower part where the core was located had neither joining pipes nor other openings; • Austenitic stainless steel allowing to realize the concept “leakage before the breakdown” was used as the equipment material for the first loop.

8. Formation of a Combined ApproachUnification with International Requirements • Entering into the west market: - the contract with Finland; • 1971-The first edition of the “General regulations for safety ensuring of nuclear power plants on designing, construction and operation”; • 1973-“OPB-73”; • 1982-“OPB-82”; • 1972-“Rules for the arrangement and safe operation of the equipment at nuclear power plants, test and research nuclear reactors and facilities”; • “Standards for the strength calculations of the elements of reactors, steam-generators, vessels and pipelines for nuclear power plants, and so on”; • “General provisions for welding and surfacing of units and structures of nuclear power plants… and so on”. (OP-1513-72); • “Rules for the control of welding joints, surfacing of units and structures of nuclear power plants… and so on”. (PK-1514-72); • 1972-“Basic sanitary rules for the operation with radioactive materials and other sources of ionizing radiation” (OSP-72); • 1974 - “Regulations for nuclear safety of nuclear power plants” (PBYa-04-74).

9. Formation of New Approaches1977-1978 • Development of district-heating power plants; • Reduction of the entity initial danger: the priority of inherent safety properties and passive technical means; • Elimination of the far distance factor: October 1978.Addition to OPB-73: “Requirements imposed on the location of nuclear district-heating power plants and nuclear combined heat power plants with regard to the radiation safety conditions”, requirements on nuclear district-heating power plant (NHDPP) safety.

10. Establishment of the State Regulatory Body in the Field of Nuclear Safety • October 1970-Decree of the CPSU Central Committee and USSR Council of Ministers “On the establishment of the State regulatory bodies for the technological and nuclear safety ensuring on the construction and operation of nuclear power plants, test and research reactors and facilities”. • Duties were imposed on the following bodies: • State City Technology Inspection (“Gosgortechnadzor”) - technological safety; • Ministry for Medium-Scale Engineering - nuclear safety; • Ministry of Health – radiation safety and sanitary inspectorate;

11. Establishment of the State Regulatory Body in the Field of Nuclear Safety (cont’d) February 1972-The establishment of the Department for Nuclear Power Engineering Inspection in “Gosgortechnadzor”; October 1972 – The establishment of the State Atomic Inspectorate (“Gosatomnadzor”) under the Ministry for Medium-Scale Engineering (the chain reaction safety; from 1980 – heat removal from the core was included); July 1983-The establishment of the USSR State Committee for the inspection of safe performance of works in nuclear power engineering.

12. 1985 год The code of regulations and rules on the NPP safety 190 documents

13. 1986 – 1997 April 1986-Accident at the 4th power unit of the Chernobyl NPP; July 1990-Putting in force of OPB-88 (OPB-82 + the accident management); October 1995-Adoption of the Federal statute “On the use of atomic energy” OPB-88/97.

14. Participation in the International Cooperation for Studies of the NPP Safety • Participation in the west international programmes; • The initiation of studies for Russia in the west facilities; • The arrangement of studies on general problems in Russia attracting west assets; • International programme on thermal hydraulics – ICAP; on severe accidents – CSARP; • International standard problems – ISP; • Agreements with: France (IPSN); Germany (GRS); USA (DOE and NRC); Japan (JAERI);

15. Studies for the Accident ManagementDevelopment of the Knowledge Base • Programme АСЕ (USA): • comparative studies of the Russian filtering system; • studies of Russian concrete (melt-concrete interaction); • The facility ВЕТА (Germany) • - melt-concrete interaction; • The facility CORA (Germany) • - the VVER reactor fuel assemblies under the conditions of a severe accident with loss of coolant;

16. The FA View after the Tests and the CORA Facility

17. Facilities KOPER and RUTInvestigations of Hydrogen Inflammation and Detonation 62.69 m 1 480 m3 Russia with participants: the USA, Germany, France

18. Programmes RASPLAV and MASCAMelt-Vessel Interaction Russia + 11 countries under OECD NEA aegis

19. The Facility RASPLAV RCW

20. Studies of Reactivity-Initiated Accidents Limits for fuel rod failures under the conditions of design-basis and beyond the design basis accidents up to 60000 MW/t burnup Participants: • I.V. Kurchatov Institute of Atomic Energy; • PSRTI test site in Semipalatinsk; • SRIAR; • SIA “Lutch”; • RDIPE; • SRIIM; • SRIPP.

21. THE BASIS FOR SAFETY ENSURING IS THE DANGER MANAGEMENT BASED ON THE KNOWLEDGE BASE

22. The Regulation System • Laws interaction and responsibility of participants; • Principles uniform approaches to the achievement of goals; • Regulations and rules efficiency and completeness of technical statements; • Quality provision assurance of the conformity to the regulations and rules.

23. Technology Concept Principles - Defence in depth protection: • Prevention of accidents priority of safety inherent characteristics ; • Suppression of accidents priority of passive emergency systems; • Mitigation of consequences accident management;

24. Technology Concept The basis-the base of knowledge about the processes at all possible stages of the facility and equipment behaviour

25. The Implementation of the Accident Management The Illustration forthe VVER Reactor The Tyanvan NPP Schematics of the arrangement for the core melt localization