Geohydrological research in relation to radioactive waste disposal in an argillaceous formation

Since 1974, the Belgian Nuclear Research Establishement (SCK/CEN) at Mol has been studying the suitability of the Boom clay formation as a potential host formation for wastes arising from the Belgian nuclear power production. This paper presents the method developed to evaluate, from the point of view of the regional hydrology, the capacity of the Boom clays for confining radioactive waste products. This method consist of four successive steps: (1) a reconnaissance of the geological and hydrogeological structure; (2) the development of a numerical model to interpret the field observations; (3) the construction of an appropriate migration model that uses the results obtained by the hydrodynamic model; and finally (4) the simulation of the consequences of possible changes in the hydrogeological system due to natural geological evolution. The analysis also stresses the role of confining layers in multilayered aquifer systems and the importance of leakage flow on a regional scale.