Risk-significant functional dependencies in PWRs

This report provides evidence that functional dependencies among nuclear plant systems, particularly those between frontline safety systems and support systems, are often major contributors to the calculated risks in completed PRAs. The study, furthermore, determines how the risk impact of functional dependencies could be reduced in future nuclear power plant designs. The risk reduction insights are summarized by a set of nine generalized design approaches, which the authors call design principles. These approaches, are not new to the nuclear industry nor are the dependencies that they address. The contribution made by PRAs that were combined with this study is in pointing out the relative importance of the dependencies in terms of their contributions to risk