Hydrogeological modeling of radionuclide transport in low permeability media: a comparison between Boom Clay and Ypresian Clay

Safe disposal of nuclear waste is an important environmental challenge. Several countries are investigating deep geological disposal as a long-term solution for their high-level waste. In Belgium, the Oligocene Boom Clay is the reference host formation for research purposes and for the safety and feasibility assessment of the deep disposal of high-level and/or long-lived radioactive waste. The Mol-Dessel zone (province of Antwerp) is the reference site for research, development and demonstration studies on the Boom Clay (Fig. 1). The clay layers of the Eocene Ieper Group (the Kortrijk Formation and Kortemark Member) are an alternative host formation for the research and assessment of a deep disposal solution for high-level and/or long-lived radioactive waste in Belgium. The Doel nuclear zone (province of Antwerp) is an alternative reference site for methodological studies regarding the Ypresian Clays (ONDRAF/NIRAS 2002). In previous studies, the fate of radionuclides released from a potential repository in the Boom Clay was calculated under different assumptions. Mallants et al. (2001) examined radionuclide migration from the vitrified waste through the Boom Clay into the surrounding aquifers, assuming that the clay layer was homogeneous. In two later studies (Huysmans and Dassargues 2005a, b), the effect of fractures and spatial variability of hydraulic conductivity and the effect of spatial variability of the diffusion parameters, respectively, was Marijke Huysmans Alain Dassargues Hydrogeological modeling of radionuclide transport in low permeability media: a comparison between Boom Clay and Ypresian Clay