Probabilistic Safety Assessment to the 1000 MWe NPP During Shutdown Conditions

For nuclear power plant, probabilistic safety assessment (PSA) is an effective tool for risk evaluating, risk recognizing and risk managing. This paper initiate a study focused on shutdown safety for NPP as well as the related PSA approaches. Especially, a PSA preliminary analysis and estimation on shutdown operation to the 1000 MWe NPP are performed. The first part of this thesis presents the methods used in the classification of plant operation state (POS), the identification of initiating event and the quantification of initiating event frequency. The second part centers on configuration of shutdown model used in PSA. Based on the design and operation features during shutdown conditions of NPPs, event trees for the shutdown model are constructed and Human Reliability Analysis (HRA) is performed. The last part is the quantification of the integrated shutdown model by means of Risk Spectrum software. System analysis is based on FuQing nuclear power plant PSA report. Component failure data and initiating event frequencies are largely based on EPS900 or NUREG./CR-6144. Overall point estimation of core damage frequency (CDF) during shutdown is assessed; the most important risk contributors of plant operational states, the dominant initiating events and their contribution to CDF are described respectively.