Modelling the interaction of the alkaline plume with Boom Clay at different scales

The supercontainer in the concept of the Belgian geological disposal of high level radioactive waste produces a high pH plume in the Boom Clay. This studies assess both the extend of the alkaline plume perturbation and the effect of the Boom Clay pore water on the geochemical concrete properties. At the laboratory scale, long-term column experiments were modeled using a reactive transport model incorporating cation exchange reactions and surface complexation. Long term modeling at the scale of the geological disposal facility was also performed with the reactive transport model PHREEQC. Parameter and model sensitivity were tested with respect to the spatial extend of the alkaline perturbation. The disturbed zone is limited up to 2 m after 25000 y.