Modelling of crevice chemistry in nuclear reactor environments

A corrosion model has been developed to predict the water chemistry and electrochemical potentials that may be present in crevices and bulk water environments in a BWR reactor core and to relate these environments to the materials and operating conditions necessary to initiate SCC. Principal features include: transport in crevices due to diffusion, ion migration and cyclic stress; geometry of the crevice; cathodic reductions of hydrogen ions and water; dissolution of manganese sulfide; reactions of an extensive list of radiated water species; and provision for transient effects. The model was applied to the study of cracking at the bottom of a 2 ft-long crevice between a nozzle and a safe end and to predict hydrogen, oxygen and hydrogen peroxide concentrations in the core. Both normal water chemistry and hydrogen water chemistry were considered