Abstract

At present, probabilistic safety analysis (PSA) is widely used in the many fields of nuclear power plant (NPP), such as design, manufacture and etc. And PSA has gradually developed into the important tool of safety evaluation and decision making. With the development and improvement of PSA technology, the risk-informed safety management has also made great progress. The overhaul of NPP is an important work to keep safe and stable operation of NPP. During the overhaul, fuel replacement and maintenance of a large number of equipment will be carried out. Under different plant operation status (POS) in the overhaul process, several important equipment will exit operation at the same time, which will lead to the increase of core loss frequency of different degrees. At present, only few NPPs within the scope of China National Nuclear Power Co., Ltd (CNNP) has adopt qualitative PSA method to carry out the risk assessment of the overhaul, but there is no precedent to use quantitative PSA method to carry out the assessment. The paper will introduce how to use the risk-informed PSA method to assess the risk of the overhaul in a quantitative way. The higher risk stages in the overhaul will be identified through the assessment to optimize the work schedule of the overhaul to ensure that the work schedule will not lead to excessive increase in core damage frequency (CDF). And taking the fifth overhaul of unit one of Fangjiashan NPP (FJS NPP) (105 overhaul) as an example, to assess the work schedule of 105 overhaul and give reasonable Suggestions.

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