Corrosion rate of pure copper in an oxic bentonite/saline groundwater environment

The principal strategy for high level radioactive waste disposal in Sweden is to enclose the spent fuel in copper canisters that are embedded in bentonite clay similar to 500 m down in the Swedish bedrock. At this depth, the groundwater is reducing. However, oxic conditions are initially established in the repository during emplacement. The corrosion rate of pure copper in an oxic bentonite/saline groundwater environment has been followed by thin electrical resistance sensors placed in a bentonite test package that was kept at room temperature for 3 years. The corrosion potentials of the sensors have verified oxic conditions in the test package. The corrosion rate of pure copper in this environment has been found to slowly decrease to quite low but measurable values; from above 15 mu m/year down to similar to 1 mu m/year after 3 years of exposure. The measurements have verified a desired behaviour of copper in the environment.