A comprehensive framework for evaluation of piping reliability due to erosion-corrosion for risk-informed inservice inspection

Risk-Informed In-Service Inspection (RI-ISI) aims at prioritizing the components for inspection within the permissible risk level thereby avoiding unnecessary inspections. The two main factors that go into the prioritization of components are failure frequency and the consequence of the failure of these components. The study has been focused on piping component as presented in this paper. Failure frequency of piping is highly influenced by the degradation mechanism acting on it and these frequencies are modified as and when maintenance/ISI activities are taken up. In order to incorporate the effects of degradation mechanism and maintenance activities, a Markov model has been suggested as an efficient method for realistic analysis. Emphasis has been given to the erosion-corrosion mechanism, which is dominant in Pressurized Heavy Water Reactors. The paper highlights an analytical model for estimating the corrosion rates and also for finding the failure probability of piping, which can be further used in RI-ISI