Seismic probabilistic risk assessment and its application to utility safety decisions

Abstract

Abstract The lack of complete field data, the current vague knowledge about the physical phenomena during and after an earthquake, and the extensive use of judgment have created several problem areas in the seismic probabilistic risk assessment (PRA). As a result, the estimated risk is usually characterized by great uncertainty, with the distributions of core melt frequency sometimes spanning more than several orders of magnitude. For the utility managers of nuclear power plants in which seismic risk cannot be overlooked (especially those located in areas of high seismicity), making risk management decisions which must be based on factors and assessments of great uncertainty is very challenging. Taiwan Power Company (TPC) has carried out PRA studies for Kuosheng and Maanshan; i.e. two of its three nuclear power plants. This paper presents a detailed discussion of risk management decisions faced by TPC managers based on their seismic PRA findings. It also discusses some sources of risk identified in the results of the two PRAs: these factors are significant only for plants located in areas of high seismicity.