Fukushima accident is a tragic case that extreme external events (tsunami and seismic) threaten the safety of NPP and lead to large uncontrollable release of radioactive materials. Therefore, how to perform the study on external events Level 2 PSA has become a crucial problem needed to be considered deeply.
In this study, the main purpose is to describe an external events Level 2 PSA approach and apply it for a III generation PWR in China. This study consists of the following factors:
(1) Screening out external events.
(2) Focusing on the key technical elements of Level 2 PSA with special considerations on the characteristics of different external events.
(3) Building a detailed Level 2 PSA model for the screened events with software RiskSpectrum and obtaining the quantitative results of large release frequency (LRF).
(4) According to the analysis results, finding out the risk weaknesses and summarizing recommended proposals.