Reactive transport modeling of the interaction between a high-pH plume and a fractured marl: the case of Wellenberg

摘要: Abstract In the context of proposed low- and intermediate-level radioactive waste repository at Wellenberg (Switzerland), calculations simulating interaction between hyperalkaline solutions a fractured marl, 25 °C, have been performed. The aim these is to evaluate possible effects mineral dissolution precipitation on porosity permeability changes in such their impact performance. Solute transport chemical reaction are considered both high-permeability zone (fracture), where advection important, wall rock, diffusion dominant mechanism. reactions promoted by derived from degradation cement (a major component engineered barrier system repository) host rock. Both diffusive/dispersive advective solute taken into account calculations. Mineral described kinetic rate laws. fluid flow under consideration two-dimensional porous medium (marl, 1% porosity), with fracture (10% porosity) crossing domain. dimensions domain 6 m per 1 m, width 10 cm. field updated during course simulations. Permeabilities according Kozeny's equation. composition entering modeling studies conditions underground Wellenberg. Two different cases These 2 representative stages process (pH 13.5 pH 12.5). cases, velocity diminishes time, due decrease porosity. This caused calcite (replacement dolomite calcite) other secondary minerals (brucite, sepiolite, analcime, natrolite, tobermorite). However, much more pronounced lower case. extent alteration along also limited reduction fractures would be highly beneficial for performance, since it mean that coming potentially carrying radionuclides solution through low-conductive rock before they able get higher-conductive features. biggest uncertainty rates used arises surface areas primary minerals. Additional making use smaller results show (and therefore rates) result reactivity changes.