Quantification of Fault Tree Models for Initiating Events

The computation of initiating event frequencies has received much attention in recent years. This attention reflects the importance of support system failures in the computation of core damage frequencies from internal events for nuclear power plants. Multi-train support system failures, such as a total loss of service water or a total loss of component cooling water, potentially represent significant impacts for many nuclear plant designs. The contribution to basic event importance from such initiator models has also been recognized, especially as part of the Mitigating Systems Performance Index (MSPI) program; Reference 1.