A cause-coupling-defense approach to common cause failures

The status and recent history of common cause failures (CCF) research are briefly reviewed. Current US Nuclear Regulatory Commission research in the area of CCFs is described with emphasis on the remaining problem areas. These include deficiencies in data and the need to more completely understand the characteristics of CCFs. The concepts and relationships of root cause, coupling, and defensive mechanisms are discussed. Key definitions and some in-depth analysis of these concepts are included. An overview of the recent research to be published is presented. This research includes (1) the cause-defense methodology for analyzing CCFs, (2) guidelines for identifying potential CCFs as part of a nuclear power plant walkdown and procedures review, and (3) requirements for an industry-wide data base, including documentation of failure events and additional component failure and failure mode data requirements to support future PRAs. 5 refs