Publications

Evaluation of used fuel disposition in clay-bearing rock

Jove Colon, Carlos F.; Hammond, Glenn E.; Kuhlman, Kristopher L.; Zheng, L.Z.; Kim, K.W.; Xao, H.X.; Rutqvist, J.R.; Caporuscio, F.A.; Norskog, K.E.; Maner, J.M.; Palaich, S.P.; Cheshire, M.C.; Zavarin, M.Z.; Wolery, T.J.; Atkins-Duffin, C.A.; Jerden, J.J.; Copple, J.M.; Cruse, T.C.; Ebert, W.E.

The R&D program from the DOE Used Fuel Disposition Campaign (UFDC) has documented key advances in coupled Thermal-Hydrological-Mechanical-Chemical (THMC) modeling of clay to simulate its complex dynamic behavior in response to thermal and hydrochemical feedbacks. These efforts have been harnessed to assess the isolation performance of heat-generating nuclear waste in a deep geological repository in clay/shale/argillaceous rock formations. This report describes the ongoing disposal R&D efforts on the advancement and refinement of coupled THMC process models, hydrothermal experiments on barrier clay interactions, used fuel and canister material degradation, thermodynamic database development, and reactive transport modeling of the near-field under non-isothermal conditions. These play an important role to the evaluation of sacrificial zones as part of the EBS exposure to thermally-driven chemical and transport processes. Thermal inducement of chemical interactions at EBS domains enhances mineral dissolution/precipitation but also generates mineralogical changes that result in mineral H2O uptake/removal (hydration/dehydration reactions). These processes can result in volume changes that can affect the interface / bulk phase porosities and the mechanical (stress) state of the bentonite barrier. Characterization studies on bentonite barrier samples from the FEBEX-DP international activity have provided important insight on clay barrier microstructures (e.g., microcracks) and interactions at EBS interfaces. Enhancements to the used fuel degradation model outlines the need to include the effects of canister corrosion due the strong influence of H2 generation on the source term.