Global sensitivity analysis to rank parameters of stress corrosion cracking in the Spatio-Temporal Probabilistic Model of loss of coolant accident frequencies

This research conducts Global Sensitivity Analysis (Global SA) on the Spatio-Temporal Probabilistic methodology, developed for steam generator rupture caused by Stress Corrosion Cracking (SCC), to rank the physical causal factors with respect to their influence on the probability of rupture within the lifetime of a nuclear power plant (NPP). The Spatio-Temporal Probabilistic Methodology integrates two types of models: (1) Markov Model to depict the renewal processes associated with the physical degradation and periodic maintenance for repair, and (2) The Probabilistic Physics of Failure (PPoF) model to explicitly incorporate physical failure mechanisms into the estimation of rupture probability. The Spatio-Temporal Probabilistic Methodology enables the possibility for explicitly including the effects of location-specific causal factors such as operating conditions (e.g., temperature, pressure, pH), maintenance quality, and material properties (e.g., yield strength and corrosion resistance), on the probability of a rupture occurrence. The ranking obtained from Global SA could help guide resource allocation to reduce the probability of Loss of Coolant Accidents (LOCAs) in NPPs.