Common-mode/common-cause failure: a review

Common-mode/common-cause (CM/CC) failure and its prevention has been a serious concern in the nuclear safety community during the past few years. Since redundancy was first used in an attempt to achieve high reliability in systems, the CM/CC failure phenomenon has been inherent in system designs. The concern is that high-reliability systems are subject to compromise by human error and environmental factors. Potential CM/CC failures are the result of adding complexity to system designs. They are the product of a supersafe philosophy. The CM/CC failure phenomenon is reviewed. Classes of CM/CC failures are compiled, and the defenses against such failures and their weaknesses are surveyed. Some regulatory considerations, operating experiences, and reliability analysis methodology are touched upon. (author)