Event-tree analysis using binary decision diagrams

This paper is concerned with ETA (event-tree analysis)where the branch point event causes are defined using faulttrees. Attention is on the nontrivial situation where there are dependenciesamongst the branch point events. The dependenciesare due to component-failures in more than one of the fault trees.In these situations the analysis methods based on traditional FTA(fault-tree analysis) are inaccurate & inefficient.The inaccuracies are not consistent across the outcome events. Iffrequency predictions calculated in this way are then used in a riskassessment then the relative riskswould be distorted and could leadto resources being used inappropriately to reduce the overall risk.A new approach using BDD (binary decision diagram) is describedwhich addresses these deficiencies.