Formulation of A Risk Assessment Framework Capable of Analyzing Nuclear Power Multiunit Accident Scenarios

Abstract

During the 2011 Fukushima Daiichi and Daini accidents, the interactions of multiple units at the same nuclear power plant site made accident mitigation more difficult compared to single unit sites. The accidents revealed important multiunit risk factors that typically are not identified by risk assessments for single-unit sites. Therefore, in order to obtain an integrated risk evaluation for multiunit sites, it is important to analyze accident scenarios involving interactions of multiple reactor units. However, such analyses are difficult due to the complexity of potential multiunit interactions. In the work reported here, a framework for analyzing multiunit accident scenarios involving inter-unit interactions is presented. The major steps of the framework are illustrated using a simplified two-unit site. The framework is capable of providing accident mitigation suggestions based upon analysis results. In this work, accident scenarios inspired by the Fukushima Daiichi and Daini experiences are selected as analysis subjects. By analyzing these scenarios and providing corresponding accident mitigation suggestions, the capabilities of the framework are illustrated.