Coupled thermo-hydro-chemical-mechanical models for the bentonite barrier in a radioactive waste repository

Resumen

Compacted bentonite is foreseen in several countries as a backfill and sealing material for high-level radioactive waste (HLW) disposal. The long-term performance assessment and the evaluation of the safety of a HLW repository requires the use of numerical models dealing with the thermal (T), hydrodynamic (H), chemical (C) and mechanical (M) processes and their interplays. This dissertation presents coupled THCM models of the bentonite barrier of HLW repositories in clay and granite. The models account for the geochemical processes taking place within the bentonite as well as the interactions of the bentonite with the concrete liner and the corrosion products of the metallic canister. The THCM code INVERSE-FADES-CORE has been updated, extended to deal with reactive gaseous phases, verified and benchmarked against other codes. Coupled THCM numerical models have been applied to: 1) Small-scale heating and hydration laboratory tests performed by CIEMAT on compacted FEBEX (Full-scale Engineer Barrier Experiment) bentonite and its interactions with corrosion products and concrete; 2) FEBEX mock-up and in situ tests; 3) Long-term reactive transport model predictions of HLW repositories in granite and clay rocks. The results of the numerical models of the lab and in situ tests show a good agreement with the measured data.