Radionuclide migration in the geosphere - Swiss research activities in laboratory and field experiments and in model validation

In the multibarrier system of a nuclear waste repository, the geosphere represents an important component. For performance assessments, predictive modelling of radionuclide transport in the geosphere is one of the main tasks. Such models need to be based on a sound understanding of important mechanisms affecting radionuclide migration. Correspondingly, in Switzerland an extensive programme is underway aimed at validation of models for geosphere transport. The activities can be broken up into three different topics: laboratory experiments, including static sorption experiments of various radionuclides on fracture infill material and on fluviatile sediments as well as dynamic column experiments and bore core infiltration under pressure; field experiments, in a near-surface quaternary aquifer at the Grimsel Rock Laboratory; and natural analogues, to help to understand radionuclide transport on a long term scale. 29 refs.; 5 figs.; 3 tabs