Nature of the near-field environment in a deep geological repository and the implications for the corrosion behaviour of the container

Abstract

The corrosion behaviour of nuclear fuel waste containers depends on the near-field environmental conditions, which may differ significantly from those in the host rock, especially during the early thermal-saturation transient phase. Although it is widely accepted that, in broad terms, the repository evolves from initially warm and oxidising to cool and anoxic in the long term, it is important to understand the detailed nature of the near-field environment in order to predict the corrosion behaviour of the container with confidence. Available information about the near-field environment is briefly reviewed and the expected time dependence of various environmental parameters is defined for a bentonite-backfilled deep geological repository. Although the focus is on a Canadian repository design for copper-coated containers in crystalline or sedimentary host rocks, the discussion is broadly applicable to a variety of container materials and repository designs and locations. Some implications for the corrosion behaviour of the container are also considered. This paper is part of a supplement on the 6th International Workshop on Long-Term Prediction of Corrosion Damage in Nuclear Waste Systems.