APPLICATION OF PSA METHODOLOGY TO DESIGN IMPROVEMENT OF JAERI PASSIVESAFETY REACTOR (JPSR)

A probabilistic safety assessment (PSA) technique was applied to the d esign of JAERI Passive Safety Reactor (JPSR). A PSA was performed to c larify safety features and identify vulnerabilities of the original de sign. Based on the PSA results and considering thermal-hydraulic analy ses and experiments, the JPSR design was improved to enhance plant saf ety. The improved design was re-evaluated with the PSA. Initiating eve nts selected in this study were: large-break LOCA, medium- and small-b reak LOCAs, SGTR, main steam line break, loss of offsite power, loss o f feed water, and other transients. Fault tree analyses were used to e valuate the system unavailabilities. The total core damage frequency d ue to internal events was estimated to be less than 10(-7)/RY. The con tribution of high frequency non-LOCA events could be significantly red uced by the design modification. The dominant initiating event was the small break LOCA and the dominant sequence was the failure of residua l heat removal system. The present study indicated that the improved J PSR design has sufficient safety margin and the PSA methodology is ver y effective to improve reactor safety systems in a conceptual design p hase.