(A) study on the safety systems reliability analysis for a 2000 MWe pressureized water reactor

Abstract

Reliability analysis is an activity that determines, from a product design, how resistant the product is to failure. The outputs of a reliability analysis are the probability of system failure, calculated from the analysis tools and probabilities of component failures, and an enumeration of minimal cut sets. This study deals with the reliability analysis for the conceptually designed safety systems for 2,000 MWe class advanced pressurized water reactor, named PWR-2000, which could be suitable to serve as the domestic energy source after APR1400. As a part of the reliability analyses, an independent six-train Safety Injection System (SIS) with Direct Vessel Injection (DVI) and three-division Auxiliary Feedwater System (AFWS), which are representative of the accident mitigation systems, are suggested in this study. As a part of Level 1 PSA, quantitative analysis of the reliability and unavailability was performed for the proposed SIS, and AFWS for PWR-2000 by using the quantification code, KIRAP of Korea Atomic Energy Research Institute (KAERI). The results of the quantification show that the proposed design concepts of the PWR-2000 promote a low risk and the Common Cause Failures (CCF) of check valves and pumps are significant contributors to the core damage frequency and system reliability. As a result, the system reliability can be improved due to the system redundancy even though the CCF critically affects the redundancy, so it turns out to be a dominant factor for system reliability and core damage frequency. It is concluded from this study that the independent six-train SIS and three-division AFWS concepts do not represent a significant contributor to the overall core damage frequency, these can be an option of applicable design concepts for PWR-2000. However, since the quantification results are highly dependent on reliability data, it is recommended that several sensitivity studies on the reliability data, such as CCF, are needed to improve the relia...