Multiscale study of subsurface heterogeneity and its effects on contaminant transport in groundwater: The challenges posed by the realization of the national radioactive waste disposal facility.

The design and realization of radioactive waste disposal facilities (RWDF) requires a safety assessment, which is based also on a risk analysis related to dispersion of radioactive isotopes in the environment, after accidental leakage from the engineered barriers. Potential sites selected for the national RWDF and many of the present-day temporary repositories of low- and intermediate-level radioactive wastes, are located in areas characterized by thick alluvial deposits of fluvial and glacio-fluvial, porous sediments. Therefore, modeling of groundwater flow and solute transport in porous media is fundamental at different scales: adsorption phenomena, which occur at the pore/grain scale, are often studied with laboratory experiments and mathematical models; sediments' heterogeneity affects contaminant transport in aquifers from the near-field (the area near the point of release) to the far-field (even at large distance along the groundwater flow direction) and is studied by geological and geophysical surveys and mathematical simulations. This presentation gives a review of results from multi-disciplinary and multi-scale studies of these topics.