Evaluation of the B and W Owners Group BAW-10182 topical report: Justification for increasing the engineered safety features actuation system on-line test intervals. Technical evaluation report

摘要

This Technical Evaluation Report provides an evaluation of the Babcock and Wilcox Owners Group (B&WOG) Technical Specifications Committee Topical Report BAW-10182, entitled, ''Justification for Increasing Engineered Safety Features Actuation System (ESFAS) On-Line Test Intervals.'' This evaluation was performed by the Idaho National Engineering Laboratory in support of the Nuclear Regulatory Commission. The BAW-10182 report presents justification for the extension of on-line test intervals from the existing one-month interval to a three-month interval for the ESFAS system. In the BAW-10182 report, the B&WOG stated that ''(hor ellipsis)the B&WOG proposes to increase the ESFAS test interval from one to three months and concludes that the effect on plant risk is insignificant.'' The proposed extension was based upon risk-based (i.e., probabilistic risk assessment (PRA)) methods such as reliability block diagrams, uncertainty analyses, and time-dependent system availability analyses. This use of PRA methods requires a detailed evaluation to determine whether the chosen methods and their application are valid in the context of the proposed test interval extension. The results of the evaluation agreed that the effect on plant risk is small if the ESFAS test interval is extended to three months for the ESFAS designs that were evaluated.