CORALUS: an integrated in situ test on the corrosion of α-active (SON68) HLW glass

Integrated in situ corrosion tests with α-doped SON68 (R7T7) glass samples have been performed in the HADES underground research facility in Mol, Belgium. The results on glass corrosion (effect of temperature, effect of addition of powdered glass frit, glass alteration mechanism) relate well to the expectations. Taking into account the loss of part of the alteration layer of the in situ corroded samples and the fact that the hypotheses in the model are not fully valid, the results agree also well with results from surface laboratory tests and modelling predictions with LIXIVER2. The α-doped glass samples showed slightly thicker alteration layers, and thickness seemed to increase with increasing αβγ-activity of the sample. In combination with the decreased glass alteration, the addition of powdered glass frit to a Ca-bentonite decreased the leaching of Np, Pu, and Am. In many cases, the migration profiles of these radionuclides showed a contribution of colloidal transport. Under the thermal gradient in the test tubes, the reaction of Ca-bentonite with the powdered glass frit resulted in the neo-formation of non-swelling 7Å minerals. The relevance of the results for the performance of a final repository for HLW glass is discussed.