Frequency analysis of loss of heat sink initiating events in nuclear power plants

Previous probabilistic safety assessments (PSA) of nuclear power plants have predominantly estimated the frequency of loss-of-heat-sink initiating events using generic data reported in the literature. Such data often fail to account for site-specific design characteristics and actual operational experience, raising concerns regarding their applicability and validity. In this study, a specific M310 nuclear power plant is selected for detailed analysis. The latest international Multiplier Method is applied to investigate potential causes of heat sink failure, including seawater intake blockage events. A fault tree model is developed to represent the plant’s design and operational characteristics, enabling evaluation of the loss-of-heat-sink initiating event frequency. The calculated frequency is compared with generic data to verify the results. Furthermore, the influence of extreme seawater quality on heat sink availability is assessed, providing valuable insights and recommendations.