Level-1 Internal Fire PSA Study for Standard 220 MWe IPHWR (KGS-3&4)

KGS-3&4 is one of the Standardized 220 MWe IPHWR reactors which is in commercial operation since 2007. In this paper, details of the Level-1 Internal Fire PSA study carried out for this reactor is presented. Level-1 Internal Fire PSA was performed by the state-of-the-art methodology of Fire PSA as per NUREG-6850 V-II (NUREG-6850 Fire PSA methodology for Nuclear power facility V2). Level-1 Full Power Internal Event PSA study was used as a base case for this study. This study was carried out using Risk Spectrum software (version 1.1.3). A comprehensive Level-1 Full Power Internal Fire PSA study has been carried out for plant design to gain insights into the progression of severe accidents and various defenses in depth available. It identifies plant-specific vulnerabilities of the system, structure and components to Design Extension Conditions due to internal fire hazard and estimates the core damage frequency. The station-specific inputs i.e. Operation and Maintenance procedures, Fire Emergency Operating Procedures, Human actions, Fire brigade response time, and the drills, etc. are considered in the analysis. In this study, fire progression scenarios, fire hazard analysis and plant response with the above inputs were modeled. As per the analysis results, it was assessed that internal fire hazard contribution to Core Damage Frequency (CDF) is two to three orders lower in comparison to the CDF of Level-1 PSA for full power internal event of KGS-3&4. This paper presents the overall overview, methodology & important attributes of the level-1 internal fire PSA study.