Unavailability of k-out-of-n Reactor Protection Systems in Consideration of CCF

Many safety-critical applications including nuclear power plants are equipped with k-out-of-n or specific voting- logic redundant safety signal generation systems for ensuring both safety and economy. In order to determine the configuration of these safety signal generation systems and to analyze the risk from these systems, common cause failures (CCF) must be considered carefully. It is known that CCF events are main contributors to unavailability of that kind of system, therefore CCFs should be considered carefully in calculating the unavailability