Risk-informed time margin analysis for operators in main control room of nuclear power plant

Nuclear reactor safety is crucial for the sustainable development of nuclear energy and the utilization of clean energy. This paper proposed a comprehensive framework for analyzing nuclear power plant accidents by integrating Risk-Informed Safety Margin Characterization (RISMC) with Human Reliability Analysis (HRA). It dynamically assessed Human Error Probability(HEP) by considering the continuous distribution of factors such as required time and available time for tasks. Unlike the static appr oach of the Standardized Plant Analysis Risk-Human Reliability Analysis (SPAR-H), this study introduced the concept of time margin to replace available time and established a distribution function for time margin-PSF. The integrated approach of coupling HRA with the RISMC method was applied to analyze Medium Break Loss of Coolant Accident (MLOCA). It utilized RELAP5 program for system simulation and risk analysis of key parameters within discrete intervals, combined with HEP, to evaluate Probability Safety Margin (PSM).The results indicated that, compared to existing safety analysis methods, the approach proposed in this paper adequately characterizes the distribution characteristics of available time for personnel actions and the time req uired for these actions. The probability of accident sequences, risk levels, and sequence consequences will significantly change with time margin, thereby affecting probabilistic safety margin. By incorporating human factor uncertainties into the PSM value, it is possible to reduce the reliance on expert judgment and conduct risk analysis from a more realistic perspective.