Method based on directed graph and binary decision diagram to break logic loops

摘要

In the probabilistic safety analysis (PSA) of nuclear power plants (NPP), fault tree analysis is often taken as a useful way for reliability evaluation. Logic loops due to mutual dependencies among systems may emerge in fault trees. Logic loops or circular logics can make it complex to get the minimum cut sets. This paper presents a method based on directed graphs and Binary Decision Diagram (BDD) to break logic loops and get the minimum cut sets consistent to previous attempting methods. The paper illustrates this method by giving one linear actual case in nuclear field and non-linear case presented by Vaurio. Utilizing directed graphs and Binary Decision Diagram is effortless for reliability analysts and concerned people in a nuclear field to have an intuitive comprehension for correlations among systems without logic loops. What's more, directed graphs and BDD can express the minimum cut sets of systems that can be understood intuitively. In addition, this present method is able to solve non-linear logic loops that is hard to operate in fault tree analysis. This proposed non-iterative method is also helpful to design good reliability engineering systems.