NEHRP Clearinghouse
 Title
 The Effect of a Certain Class of Potential Common Mode Failures on the Reliability of Redundant Systems.
 File

PB289714.pdf
 Author(s)
 Apostolakis, G. E.
 Source

National Science Foundation, Washington, DC. Office of Energy R and D Policy.,
November 1975,
42 p.
 Identifying Number(s)
 UCLAENG7528
 Abstract
 A theoretical investigation of the importance of common mode failures on the reliability of redundant systems is given. These failures are assumed to be the result of fatal shocks (e.g., from earthquakes, explosystem is given. These failures are assumed to be the result of fatal shocks (e.g., from earthquakes, explosions, etc.) which occur at a constant rate. The method presented allows analytical prediction of results obtained in the past which showed that the probability of a common mode failure of the redundant channels of the protection system of a typical nuclear power plant was orders of magnitude larger than the probability of failure from chance failures alone. Furthermore, since most reliability analyses of redundant systems do not include potential common mode failures in the probabilistic calculations, criteria are established which can be used to decide either that the commonmodefailure effects are indeed insignificant or that such calculations are meaningless, and more sophisticated methods of analysis are required, because common mode failures cannot be ignored.
 Keywords
 Statistical analysis; Failure; Mathematical models; Nuclear reactor safety; Risk; Birth and death processes; Nuclear power plants; Common mode failures; Reliability; Redundancy; Nuclear reactor accidents