Fire Risk Assessment of Transient Ignition Sources in Domestic Nuclear Power Plants

The fire risk of a nuclear power plant is evaluated using fixed and transient ignition sources. In terms of the overall fire risk, the proportion of transient ignition sources is very small. However, because the uncertainty due to the difference between the assumptions and the modeling method is relatively large, it is necessary to establish a methodology to address this. In this study, the new transient ignition source evaluation method presented in NUREG/CR-6850, the ignition source frequency revised in NUREG-2169, and the input parameters for transient fire modeling presented in NUREG-2233 were used to evaluate the fire risk assessment for transient ignition sources. In this new evaluation methodology, the fire ignition frequency is quantitatively evaluated based on the characteristics of the area, and an area-based scenario evaluation method considering the location of the transient ignition source is proposed for the evaluation within the area. As a result of applying the new methodology to the switchgear room of a reference nuclear power plant, an approximately 70% risk reduction was confirmed compared to the existing EPRI TR-105928 method. In the future, if fire risk assessment for transient ignition sources in nuclear power plants is applied using the results of this study, it is expected that areas whose control is important in the event of a fire can be determined, which should help reduce highly rated fire risks.