The POS Model For Common Cause Failure Quantification:Progress In Parameter Estimation And Comprehensive Documentation

摘要

The basic idea in the POS modelling approach is to assume some kind of CCF impact which, ata given point in time, affects all or a specified subset of the components belonging to the same commoncause component group (CCCG). As a consequence, the components affected by the CCF impact areassumed either to fail instantly – this is frequently termed a 'shock' – or else delayed. The followingsequence of stochastic variables is supposed to adequately describe the CCF process: time of CCF impact,simulated with a constant CCF impact rate, number of components within the component group of size raffected by the impact, times of failure of the impacted components, either immediately or delayed,controlled by model parameter Winst , the fraction of immediate failures, time of detection of the CCFprocess by inspection or functional testing. A number of different applications has been carried out withthe POS model to assess its possibilities and compare the POS results to those obtained with establishedmodels. The amount of different applications has advocated to document the model development statusreached including a detailed description of the model as well as of the approach to parameter estimation.This paper comprises an outline of this comprehensive report and highlights in addition a parameterestimation illustrated by an application to plate valves. The results are compared to data provided inGerman regulatory documents on this type of components.