An event sequence modeling method in multi-unit probabilistic risk assessment for high temperature gas-cooled reactor

The number of multi-unit nuclear power plants (NPPs) increases, so does the demand for multi-unit probabilistic risk assessment (MUPRA). Considering dependencies among multiple units on one site, conventional probabilistic risk assessment (PRA) for a single unit cannot meet requirements of the overall site risk analysis. Existing MUPRA studies mainly evaluate limited risk characteristics, such as core damage, or focus on a limited number of units, within the range of two to six units. This study proposes a multi-unit event sequence modeling method for MUPRA, and develops a corresponding computer-aided tool, making it possible to deal with considerable number of units. Furthermore, their application to high temperature gas-cooled reactor - pebble bed module (HTR-PM) was carried out, showing that the modeling method and computer-aided tool can be applied to address dependencies of function events (FEs) and provide a reference for the full risk spectrum.

Automated summary

The demand for multi-unit probabilistic risk assessment (MUPRA) has increased with the rise in the number of multi-unit nuclear power plants (NPPs). Conventional probabilistic risk assessment (PRA) for a single unit is insufficient in analyzing overall site risk due to dependencies among multiple units on one site. Existing MUPRA studies have mainly focused on limited risk characteristics or a small number of units. This study proposes a multi-unit event sequence modeling method and a corresponding computer-aided tool that can handle a larger number of units, and demonstrates its applicability to a specific type of reactor.