A computer code for common-cause failure analysis

COMCAF, a computer code for the common-cause failure analysis, is developed to treat the common-cause failures in nuclear power plants. In the treatment of common-cause failures, the minimal cut sets of the system are obtained first without changing the fault-tree structure. The occurrence probabilities of the minimal cut sets are then calculated accounting for the common-cause failures between components in the same and/or in the different minimal cut sets. The basic parameter model is used to model the common-cause failures between similar or identical components. The top event probability is evaluated using the inclusion-exclusion method. This study applied this common-cause failure analysis to the PWR auxiliary feedwater system. The results in the top event probability for the system are compared with those of no common-cause failures