Three dimensional analysis of combined gas, heat and nuclide transport in a repository in clay rock including coupled thermo-hydro-geomechanical processes

To study the coupled thermo-hydrologic-geomechanical processes and their influence on gas and nuclide transport in a two phase flow configuration in a porous medium, a coupling of the thermo-hydrodynamic code TOUGH2 and the thermo-mechanic code FLAC3D is described and applied to analyze three dimensional gas, heat and nuclide transport in a repository for heat generating nuclear waste in a plastic clay rock. According to stress or strain dependent hydrological properties, like, porosity, permeability and capillary pressure, the influence of coupled processes on two phase flow can be relevant. The present procedure can be applied to quantify safety margin related to hydro-fracturing due to pressure build-up caused by gas generation and to define bounding analyses, if the hydrological properties, such as porosity, permeability, and capillary pressure, depending on mean effective normal stress or volumetric strain are applied.