Derivation of Seismic Risk Estimates from Seismic Margin Assessments

摘要

The objective of this study has been to ascertain whether certain risk-type safety insights can be extracted from arnSeismic Margin Assessment (SMA) performed for a nuclear power plant, and to identify any limitations to the applicability ofrnsuch insights. The approach has been to use as case studies the seismic analyses done by two nuclear power plants (SurryrnUnit 1 and Nine Mile Point Unit 2). NMP-2 possesses both an SMA and a Seismic Probabilistic Risk Assessment (SPRA),rnwhereas Surry possesses only an SPRA. The notion tested was whether, given only an SMA, it is feasible to developrnelements of a pseudo-SPRA and obtain results and safety insights typical of a full SPRA, such as seismic-initiated coredamagernfrequency. The conclusion of the project is that this is feasible if certain prescribed procedures are followed, but thernsafety insights are not as robust as could be obtained from a full SPRA. The implications of this finding for the new standardrnfor SPRA methodology being developed by the American Nuclear Society are also explored, and requirements that might bernincorporated into that standard are proposed.