Risk Informed In-Service Inspection of PWR Nuclear Power Plant Piping Components Subjected to Erosion-Corrosion Using Markov Chain Model

A Markov Chain (MC) model for failure probability assessment of power plant piping components against erosion-corrosion is proposed. In the MC model, the state space is the degradation state of the system represented by the ratio of the loss in wall thickness due to erosion-corrosion to the original wall thickness of the pipe, and the index space is the time. The use of the proposed MC model is illustrated through an example problem. The model proposed by Abdulsalam and Stanley is used for determining the rate of erosion-corrosion in the example, and, the pipe diameter, pipewall thickness, temperature, pH value, flow velocity, and model error are considered as random variables. From the results obtained, it is noted that there is a need to consider the correlation between degradation at two successive times for obtaining conservative estimates of failure probability against rupture.