Defensive strategies for reducing susceptibility to common-cause failures: Volume 1, Defensive strategies: Final report

This report presents the final results of EPRI Project RP2169-5. The study, begun in 1982, had three overall objectives: (1) develop a better method for understanding fault events, in general, and common cause failures (CCF) in particular; (2) develop a well focused data base for analyzing factors that describe or influence CCFs; (3) develop and assess defensive measures that might be employed against CCFs. In response to the first objective, a Classification System was developed as a logical and credible method for dissecting and understanding fault events, with special attention on the means to clearly identify and evaluate those events with multiple faults deriving from a common or shared cause. This system, which employs the concept of Linear and Branched Events, is briefly described herein with examples illustrating its use. A data base consisting of over 1700 events was compiled to meet the second objective, and a variety of analyses drawn from that data base are presented. The major portion of the report is devoted to the investigations conducted on defensive measures for CCFs. Analytically-based, data-based and expert-based approach are each discussed in detail, and provide a variety of guidelines that may be used to delineate specific defensive actions formore » both new plant designs as well as currently operating plants. 17 refs., 25 figs., 1 tab.« less