New Procedural Path for F&B Operation and Its Risk Impact on a Nuclear Power Plant

Although a feed and bleed (F&B) operation is an important emergency task having a significant effect on the risk of a pressurized water reactor–type nuclear power plant, there is a high uncertainty regarding its modeling and analysis in a probabilistic safety assessment (PSA). This paper introduces a study on the design of an operational strategy for an F&B operation based on human reliability analysis (HRA) with plant-specific thermal-hydraulic (TH) and human performance time (PT) analyses. The emergency operating procedures (EOPs) of a reference plant were modified by adding a new procedural path for the F&B operation to reduce its effect on the plant’s risk. To support the modification of the procedure, an intensive TH analysis was conducted to evaluate the plant’s behavior in diverse accident conditions and to revise the success criteria for the HRA of the F&B operation. In addition, an empirical analysis of PT required to carry out the F&B operation was conducted based on plant-specific simulator records. The PSA model of the reference plant was revised by reflecting the modified EOPs and new success criteria for the HRA of the F&B operation, which showed that core damage frequency of the revised PSA was about 50% lower than that of the original PSA.