Predicting failures in light water nuclear reactors which have not yet been observed —microprocess sequence approach (MPSA)

An approach, microprocess sequence approach (MPSA), for predicting failures, utilizes sets of elements from the environments and materials where these elements can be identified and quantified, and connected sequentially or in parallel, to provide a scenario leading to the initiation of failure. The idea of microprocesses focuses on specific processes that occur within the domains and have been shown to be critical processes in the nucleation, initiation, and growth of stress corrosion cracking (SCC). The domains provide an intellectual framework for identifying explicitly the sequence of events and for organizing the microprocesses. One of the domains, “Global Domain,” is intended to include microprocesses that apply to all the domains. Another domain, “Bulk Environment Domain,” refers to the primary water, the secondary water, tertiary water, ambient inside the containment or outside, and similar fluids to which components, and materials are exposed. The “Near-Surface Environment Domain” consists mainly of deposits, flow gradients, and electrochemical cells. The “Bulk Metal Domain,” is the “semi-infinite region” of the metal, which, on a gross scale, is homogeneous but on a microscopic and microprocess scale is quite heterogeneous. These local heterogeneities provide paths or influences that affect the development and propagation of corrosion damage.