Heuristic for Binary Decision diagram Ordering to Assess Fault Tree in Probabilistic Safety Assessment

The most important safety functions in nuclear plants is Probabilistic safety assessment. This paper describes state of the development for the relatively new approach in the probabilistic safety analysis (PSA). This approach is based on the application of binary decision diagrams (BDD) representation for the logical function on the quantitative and qualitative analysis of complex systems that are presented by fault trees in the PSA applied for the nuclear power plants risk determination. The approach proposes a new variable ordering heurisuic that solve the shared events problem, improve the fault tree size, and minimize computation time.