Scientific basis for corrosion of copper in water and implications for canister lifetimes

Abstract

The Swedish Nuclear Fuel and Waste Management Company has developed a method for safely disposing spent nuclear fuel, which involves encapsulation of the waste in copper canisters and burying it deep in the stable crystalline rock of the Fenno-Scandian shield. The design life of the canisters in the so called KBS-3 design is in excess of 100 000 years. These long canister lifetimes are a consequence of a number of factors involving the properties of the material and the nature of the near field environment in the KBS-3 repository. One of these factors, namely the thermodynamic stability of copper in O2 free water in the absence of sulphide, has been questioned. This paper critically reviews the evidence for and against the claim that water oxidises copper, and discusses the implications for canister lifetimes even if the proposed mechanism is correct. Even though the evidence presented in support of the proposed mechanism is not compelling, the Swedish Nuclear Fuel and Waste Management Company is actively engaged in ongoing research and development on the topic.