Time dependence of corrosion in steels for use in lead-alloy cooled reactors

Stability of the protective oxide layer is critical for the long-term performance of cladding and structural components in lead-alloy cooled nuclear systems. Measurements have shown that removal of the outer magnetite layer is a significant effect at higher temperatures in flowing lead–bismuth. Developing a predictive capability for oxide thickness and material removal is therefore needed. A model for the corrosion of steels in liquid lead-alloys has been employed to assist in materials development for application in the Generation IV Lead-cooled Fast Reactor (LFR). Data from corrosion tests of steels in Los Alamos National Laboratory’s DELTA Loop is used to benchmark the model and to obtain predictions of long-term material’s corrosion performance. The model is based on modifications of Wagner’s diffusion based oxidation theory and Tedmon’s equation for high-temperature oxidation with scale removal. Theoretically and experimentally obtained values for parabolic oxide growth rate, mass transfer corrosion rate, and long-term material thinning rates are presented and compared to the literature.