Severe Accident Mitigation Strategy for Operating and Advanced VVER-1000 Reactors

The author describes the general strategy of accident management adopted for the Russian VVER nuclear reactors. This strategy distinguishes some safety functions: sub-criticality, core cooling, primary coolant pressure boundary integrity, coolant inventory in the primary circuit, ultimate heat sink, containment integrity, restriction of radioactive releases. Then, he describes the accident management for existing VVER-1000. This management is based on some main measures which are described in two documents. The author illustrates this approach by discussing the cases of a small break LOCA (loss of coolant accident) with failure of ECCS (Emergency Core Cooling System ) active part, and of a nuclear power plant black out. He finally discusses the mitigation of severe accidents in advanced VVER reactor designs