Multi-state Risk-Based Maintenance Analysis of Redundant Safety Systems Using the Markov Model and Fault Tree Method

The risk-based maintenance strategy has received special attention in the safe operation of nuclear power plants. Simultaneous quantification positive and negative effects activities components degradation effect makes it possible to accurately evaluate risk criterion for safety systems However, is difficult integrate into standard reliability approaches. A straightforward approach considering different policies make use Markov models. In this article, effectiveness (including changes surveillance test intervals alteration policies) on unavailability with aging quantified using models then by coupling these fault tree method, measure upgraded from component level system level. proposed are applied two VVER-1000/V446 plants as case studies. results show that method due its multi-state nature effective conservative evaluation measures so computed process higher than original (calculated PSA data plants) all policies. addition, study illustrates developed could be large-scale whole plant provides a proper transition classical methods new techniques. This integrates strategies degradation. Also, practical more accurate tool determine technical specification real point view.