Construction and Application of Mitigation System Performance Index (MSPI) Platform for a China Nuclear Power Plant

The mitigation system performance index is used to evaluate the ability of the safety-related system to be put into operation to mitigate the accident when an accident occurs in the nuclear power plant (NPP). This index can effectively monitor the status of the safety system and reasonably reflect the impact of equipment performance on the safety level of the nuclear power plant. Typical pressurized water reactor (PWR) nuclear power plant mitigation systems include emergency alternating current (AC) power system, high pressure safety injection system, auxiliary feedwater system, residual heat removal system and cooling water support system. Based on the probabilistic safety assessment (PSA) model, this paper develops a nuclear power plant MSPI computing platform to monitor and judge the risk level of the mitigation system, and guide the nuclear power plant to carry out production activities such as risk-informed preventive maintenance, corrective maintenance and production planning. This paper takes the Essential Service Water System (SEC) of a nuclear power plant in China as an example to verify the proposed method, and conducts the trend analysis of MSPI in the 8 quarters of 2020–2021. The results show that MSPI can timely reflect the influence of the unavailability and unreliability of system equipment on the overall safety status of the power plant from the perspective of risk.