Simulation of Expansive Clay Behavior under Simultaneous Heating-Hydration for Nuclear Waste Storage Applications

The storage of nuclear waste is still an unresolved problem of the nuclear industry, geological disposal being the most favored option. Most conceptual designs for the deep geological disposal of nuclear waste envisage placing the canisters containing the waste in horizontal drifts or vertical boreholes. The empty space surrounding the canisters is filled by an engineered barrier often made up of compacted swelling clay. A good understanding of thermo-hydro-mechanical (THM) issues is therefore necessary to ensure a correct performance of engineered barriers and seals. The conditions of the bentonite in a typical engineered barrier are being simulated in a mock-up heating test at almost full scale. The aim of the paper is to assess the capabilities of CODE_BRIGHT to analyze the evolution of the main Thermo-Hydro-Mechanical (THM) variables of this test; and also to study the unexpected slow hydration of the clay barrier observed at the advanced staged (i.e. after years) of the experiment. The inclusion of thermo-osmotic effects in the analysis has assisted to a better understanding of experiment.