Far-field process analysis and radionuclide transport modelling for saturated media

The differing roles of the geosphere in safety cases considering crystalline-basement and sedimentary-rock (clays, shales, marls) host formations for deep disposal of radioactive waste are discussed. These roles are then illustrated using the Swiss and Finnish programmes as examples. The analysis of relevant FEPs (features, events and processes) and scenarios provides the basis for the quantification of radionuclide transport. The key geosphere-related FEPs for Opalinus Clay in Switzerland and for crystalline rocks at Olkiluoto in Finland are compared and their effects on calculated radionuclide fluxes are evaluated. Further, the current status of the Swedish and Swiss site-selection programmes in crystalline and sedimentary rocks is summarised. Finally, recent developments in host-rock characterisation are discussed, including studies related to the chemical composition of pore water, to the microstructure of clay-rich rocks and to the understanding of microbial activity in the subsurface.