An electrochemical approach to predicting long-term localized corrosion of corrosion-resistant high-level waste container materials

Lifetime predictions of containers used for the disposal of high-level radioactive waste (HLW) are necessary to determine the overall performance of a HLW repository. Failure of the containers by localized corrosion and release of radionuclides into the accessible environment may occur if chloride-containing groundwater infiltrates the repository and interacts with the containers. To assess the repository performance, it is necessary to develop a methodology for predicting the long-term susceptibility of container materials to localized corrosion. Laboratory tests have demonstrated that pitting and crevice corrosion are initiated when the corrosion potential of the material exceeds the repassivation potential for localized corrosion. Once corrosion is initiated. the propagation of the localized attack will result in rapid penetration of the waste packages. However, no localized corrosion can be initiated, and all active corrosion sites repassivate when the corrosion potential of the material is lower than the repassivation potential. Results of this investigation demonstrated that the corrosion potential and repassivation potential are useful parameters to predict the long-term localized corrosion susceptibility of corrosion-resistant candidate container materials such as type 316L (UNS S31603) stainless steel and alloy 825 (UNS N08825).