Abstract
It is nowadays a mainstream analysis method to use probability safety analysis (PSA) to support the nuclear power plants (NPPs) daily risk management and safety decision. In China, the NPPs are very experienced in doing PSA evaluation for different plant configurations such as equipment out of operation and failure, etc. In fact, however, the measures often used are not sufficient to reflect the real risk of the unit in such configurations, because there are numerous equipment degradation cases and few complete failure events in the NPPs. On this basis, the paper selects an event related to the main steam safety valve (MSSV) degradation in a domestic NPP as an example, collects failure data through experience feedback, and utilizes mathematical analysis and fitting function to determine the failure potential of the degraded equipment. By PSA calculation, the real unit risk under these configurations will be estimated finally. The purpose of this paper is to provide a new thinking and method for PSA analysis on degraded equipment in the NPPs.
