Probabilistic Risk Assessment (PRA) is a comprehensive, structured and logical analysis method, which aims at identifying risks in complex systems to improve its safety and operation performance.With the development of PRA methods, some key issues had already been solved nonetheless some new ones have been identified. Among them, the external events are one of the special type that could destroy the redundant systems and lead to uncontrollable release of radioactive materials.&nbsp;Level 2 PRA focuses on the severe accident phenomenon and progression, release of source terms to overall evaluate the containment response when facing the risk of severe accident.&nbsp;Therefore, the study on external events Level 2 PRA has become a crucial problem needed to be deeply considered during the design and safety review phase. In this study, the main purpose is to develop an external events Level 2 PRA approach and apply it for a PWR in China. This paper consists of the following critical factors:&nbsp;(1) Screening out the external events and finding out the ones (including seismic, internal flood and internal fire, etc.) needed to be analyzed in detail.(2) Developing an external events Level 2 PRA approach which could be used in any types of PWRs. The analysis methodology is based on the internal events Level 2 PRA.(3) Focusing on the key technical elements of Level 2 PRA with special considerations on the characteristics of different external events, such as the influences on the interfaces, list of SSCs, failure modes of equipment, system responses, etc.(4) Developing a detailed Level 2 PRA model for the screened external events with the commercial software RiskSpectrum. Obtaining the quantitative results and special insights of large release frequency (LRF) for NPPs.(5) According to analysis results, finding out the risk weaknesses and summarizing some recommended proposals for the future design or operation.The analysis approach of external events Level 2 PSA could also be applied to other types of reactors for the further study. Furthermore, it could also improve the safety management of NPPs in aspects of external events.

Level 2 Probability Risk Assessment for External Events: Approach and Application for Npps in China

Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE28/volume/85246

2021 28th International Conference on Nuclear Engineering (ICONE28)

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