Common Cause Multiparameter Models

Clearly, more parameters allow more freedom in representing common cause effects in svstem.s of complex redundancy. NUREG-1150 describes the Multiple Greek Letter Model (MGL), Parameter (BP) model and the Binomial Failure Rate (BFR) model. 

Fleming et al. (1985) define A, as the independent failure rate and higher order effects in order of the Greek alphabet (skipping a). The conditional probability that a CCF is shared by one 

Fleming et al. (1985) define this as similar to the model of Marshall and Olkin (1967) except that BPM is only for time-dependent failure rates. Equations 3.5.8-la-d are for four parameters, but the method may be generalized to n components. These parameters may be related to the MGL parameters as shown in equations 3.5.8-2a-d. 

X j = failure rate for one component tofail to run X - failure rate for two components tofail to run 

X j = failure ratefor three components to fail to run X, = failure ratefor four components to fail to run. 

---