Methods for the treatment of common cause failures in redundant systems

Dependent failures are extremely important in reliability analysis and must be given adequate treatment so as to minimize gross underestimation of reliability. German regulatory guidance documents for PSA stipulate that model parameters used for calculating frequencies should be derived from operating experience in a transparent manner. Progress has been made with the process oriented simulation (POS) model for common cause failure (CCF) quantification. A number of applications are presented for which results obtained from established CCF models are available, focusing on cases with high degree of redundancy and small numbers of observed events.