Research on the Quantitative Method for Seismic Common Cause Failures of Redundant Systems in Nuclear Power Plants

As a typical external disaster, earthquakes not only can trigger the failure of individual nuclear power equipment but may also lead to common-cause failures, thereby significantly increasing the risk of systemic failure. To assess seismic risk of multi-equipment common-cause failures, this paper constructs an integrated probabilistic analysis framework of “ground motion parameter-equipment response-system failure.” Based on a system failure probability modeling approach that considers failure dependencies, probabilistic risk parameters derived from seismic hazard analysis and seismic fragility assessments are integrated to achieve accurate quantification of multiequipment failures. Quantitative analysis of failure dependencies under varying ground motion intensities is conducted based on the α-factor model, revealing a significant nonlinear evolutionary pattern of failure correlation coefficients with respect to ground motion intensity. The rationality of the framework and methodology is validated through practical case studies. This research provides an analytical tool with both theoretical rigor and engineering applicability for seismic risk assessment in the nuclear engineering field, effectively enhancing the precision of probabilistic safety analysis for complex redundant systems.