Reliability Prediction of Passive Systems with Multiple Degradation Measures

This paper describes a modeling and analysis approach for reliability prediction based on degradation modeling, considering multiple degradation measures and with respect to the thermal-hydraulic passive systems.

Previous research on the topic has drawn attention to the susceptibility of passive systems to several modes of failure. In fact, it has been recognized that a system may have, in addition to component mechanism failures, multiple degradation paths, so it is necessary to simultaneously consider multiple degradation measures. Also, many research efforts on degradation analysis were initiated by making assumptions about the degradation mechanism. In reality, often there is very limited understanding about the concerned degradation mechanisms together with their interdependencies.

In this paper, an analysis procedure is developed to address this aspect. Simulated data have been used to illustrate the applicability of this approach. Results on the application of the methods to a simplified model of the passive residual heat transport system in water-cooled reactors is presented. It was verified that when the multiple degradation measures in a system are correlated, an incorrect independence assumption may overestimate the system reliability.