Corrosion issues in relation to copper canisters for disposal of spent nuclear fuel

Spent nuclear fuel in Finland and Sweden will be disposed in deposition holes excavated in granitic bedrock at a depth of about 400 to 500 m. The release of activated products is prevented by a multi-barrier concept. A copper canister with 50 mm wall thickness will be the main corrosion shield, expected to last un-perforated for over 100 000 years. There are several different corrosion mechanisms that in principle may threaten the integrity of the copper canister. Likewise, there are several different scenarios which may expose the copper canister to these corrosion phenomena. During the years, most of the corrosion related concerns have been satisfactorily dealt with, leaving a few to be further researched. This paper gives an overview of the corrosion related issues with regard to the integrity of the copper canister, as well as the main approaches developed by the share holders to ensure the integrity for the duration needed. A more detailed description of the few remaining ongoing corrosion related research items is also included. (orig.)