(GRS 261) BET - Barrier Integrity of the Isolating Rock Zone in Clay Formations

In a high-level radioactive waste repository in a clay host rock formation which is under discussion in several European and non-European countries, gases will be produced, mainly as a consequence of corrosion of the metallic waste containers. Enough water will be available for corrosion of all metals present. Corrosion is a slow process and will continue when engineered barriers and excavation damaged zones are fully re-saturated. Gas production may then result in a gas pressure increase, since gas flow paths in unsaturated parts of the repository are no longer available. Could the pressure exceed the minimum stress in the host rock formation, this might lead to impairment of the geological barrier by fracturing. Therefore, the mechanism of gas transport in the saturated host rock is important for predicting the long-term behaviour of the repository. The gas transport issue at elevated gas pressure was the subject of the BET project performed by GRS between 2006 and 2010. A combined approach involving in-situ experiments, laboratory testing, and numerical simulation was chosen.