Severe Accident Sequence Screening Criteria for Nuclear Power Plant

Severe accidents prevention and mitigation is an important safety issue for new generation Nuclear Power Plant (NPP). This paper mainly focuses on the severe accident dominant sequences screening criteria when performing NPP severe accident management and study,including qualitative and quantitative criteria and their understanding. On this basis,a set of severe accident dominant sequence screening criteria is recommended for Chinese nuclear power plant severe accident study. Using this set of criteria to Advanced Passive Pressurized water reactor (AP1000) standard design is also attempted to show criteria's applicability. It is shown that severe accident sequence screening criteria should be described both qualitatively and quantitatively. From the qualitative point of view,the selection of severe accidents should be based on nuclear power plant state definition. Sequences which may lead to core damage or containment bypass and have most serious consequences in the range of beyond design basis accidents should be selected. From the quantitative point of view,absolute and relative values corresponding to severe accidents risk should be identified. At the same time,steep side effect combined with the outcomes of deterministic analysis and engineering experience should be considered. The screening results derived from the proposed screening criteria application on advanced reactor AP1000 are basically consistent with that given in AP1000 probabilistic safety assessment report.