2009:30 A Review of Evidence for Corrosion of Copper by water

The planned spent nuclear fuel repository in Sweden relies on a copper cast iron canister as the primary engineered barrier. The corrosion behaviour of copper in the expected environment needs to be thoroughly understood as a basis for the post-closure safety analysis. It has been shown that corrosion may indeed be the primary canister degradation process during the utilised assessment period of 1 million years (this period is the longest time for which risk calculations will be needed according guidelines issued by the Swedish Radiation Safety Authority).

Previous analysis work has been based on that copper is corroded during the initial oxic environment as well as by sulphide in groundwater once reducing conditions have been restored. The quantitative analyses of these processes consider upperbound amounts of atmospheric oxidation as well as representative sulphide concentrations coupled with the transport limitation of the bentonite buffer and of the surrounding bedrock. A group of research-ers at the Royal Institute of Technology (Stockholm, Sweden) suggest, based on published experimental results, that disposed canisters will also be corroded by water itself under hydrogen evolution (Gunnar Hultqvist, Peter Szakalos, Gunnar Wikmark).

The purpose of the project is to evaluate the findings of the KTH research group based on an assessment of their experimental methods and chemical analysis work, thermodynamic models, and a discussion of reaction mechanisms as well as comparison with the analogue behaviour of native copper. As a background, the authors also provide a brief overview of other corrosion processes and safety assessment significance.