Treatment of canister corrosion in Posiva's safety case for the operating licence application

Abstract

AbstractPosiva Oy have submitted an operating licence application to the Finnish government which, if approved, would permit the disposal of spent fuel in a deep geological repository at Olkiluoto. The license application is based on 40 years of site investigations, design and development work by Finnish, Swedish, and international experts. The canister is a key component of the overall multi‐barrier system and the treatment of the long‐term corrosion performance in the safety case is described in this paper. The importance of relating laboratory observations to the expected environmental conditions in the repository is highlighted, as is the use of complementary models to build confidence in long‐term predictions. Canister lifetime prediction is based on a combination of corrosion allowances for processes that will occur to a limited extent and mass‐transport calculations for the long‐term corrosion by sulphide. Examples of canister lifetime predictions for various scenarios and climate lines of evolution are given.