Corrosion of Potential Canister Materials During Oxic to Anoxic Transient in Compacted Bentonite

The long-term performance of the engineered barrier system is crucial for the safe, long-term disposal of high-level radioactive waste in a deep geological repository. This study examines the corrosion behavior of cast iron with spheroidal graphite and copper in contact with compacted bentonite under laboratory conditions, as well as that of copper in contact with compacted bentonite following exposure in an underground research laboratory (URL; MaCoTe experiment at Grimsel Test Site). In the laboratory experiments, bentonite was saturated with an artificial water composition from a crystalline rock and exposed for 1 and 4 months at 60°C under transient oxic conditions. The results indicate minor material degradation in the laboratory samples and suggest a redox-transient state at the metal–bentonite interface. Copper speciation in the bentonite from the MaCoTe experiment indicates a dependence on exposure time and bentonite dry density. Overall, the study highlights the importance of combining laboratory and URL studies to improve the understanding and prediction of long-term stability of metal–bentonite interactions for the safe disposal of HLW.