The long-term evolution of the geochemical conditions in a geological repository system, the release of radionuclides from the emplaced wastes, and the radionuclide migration behaviour in the repository near- and far-field are governed by various strongly coupled thermo-hydraulical-mechanical-chemical-biological (THMCB) processes. The radionuclide transport driven either by diffusion and/or advection involves multi-phase flow phenomena under hydraulic and geochemical gradients. The transport phenomena are affected by various complex processes including dissolution, (co)precipitation and adsorption, redox processes, and gas evolution, which are partly induced and catalysed by microbial activity. Reactive Transport Modelling (RTM) entails the integration of hydrogeology and geo-chemistry and the prediction of chemical reactions along transport pathways in space and time. It is extensively various energy related subsurface applications (e.g. e.g., for geothermal energy extraction, CO2 sequestration, H2 storage or even nuclear waste disposal). However, for a rigorous comparative analyses of long-term safety aspects of geological repository systems an in-depth understanding and close to reality description of the strongly coupled THMCB processes that affect the radionuclide transport on different time and length scales is required – a so far largely unresolved scientific challenge.
Research on Reactive transport at IEK-6 focuses on the development of cross-scale experimental and computational approaches to generate spatio-temporal insights into radionuclide release and transport in the near- and far-field of geological repositories for radioactive wastes. We develop innovative lab-on-a chip approaches integrating AI based tools to understand and rationalize pore scale hydrogeochemical processes which are further integrated into larger scale models (upscaling). These models are validated by laboratory scale experiments. We also investigate radionuclide release and transport in the near- and far-field of geological repositories for radioactive wastes on repository scales, employing the high performance computing (HPC) environment provided by the Jülich Supercomputing Centre (JSC) where required. This work aims at an enhanced process and system understanding across scales as well as at the reduction of uncertainties and conservatisms in performance assessments (PA), contributing thus to the scientific basis for an in-depth comparison of different repository concepts and sites as required for the German site selection procedure