Reaction of native copper in contact with pyrite and bentonite in anaerobic water at elevated temperature

Abstract

ABSTRACTCopper pellets were reacted with different solutions, reference minerals, and well-characterised bentonites to investigate the effect of different bentonites on the stability of native copper in repository concepts for high-level radioactive waste. The reaction of Cu in contact with bentonite used as barrier material to store high-level radioactive waste was significantly affected by the presence of sulphides (e.g. pyrite) leading to a specific corrosion. Bentonites free of pyrite are not actively involved in a reaction with Cu. Nevertheless, slightly different Cu mass losses were found for different bentonites. For different bentonites, different coatings were found on the Cu surface. The characteristics of these coatings are probably responsible for different Cu mass losses of Cu in contact with different bentonites. As an example, particularly dense coatings led to a decrease in Cu mass loss. No relation of the Fe-corrosivity of different bentonites with Cu mass loss was found, which proves that the Fe-corrosion mechanism differs from the Cu-corrosion at the metal/bentonite interface. The experiments also demonstrated the importance of the presence even of traces of oxygen.