Research Areas
Clay Sorption Mechanisms Group
Contact: Dr. Anke Neumann Jenal
Radionuclide uptake on the materials in the near-field and the host rock is one of the main pillars upon which the safety case for a deep geological repository is built. The research activities aim at improving the understanding of the retention mechanisms and processes. One of the primary tasks of the Sorption Mechanism Group is to develop (and update) sorption data bases (SDBs) for the near-field (bentonite) and far-fields (Opalinus Clay, ‘Brauner Dogger’, Effingen Member and Helvetic Marl) for safety analyses. At the present time the SDBs consist of "smart" distribution ratios tailored to specific geochemical conditions. By definition the SDBs must be "state-of-the-art". The "bottom up" strategy currently followed for the high clay mineral content argillaceous rocks is a key activity. The concept is to carry out experimental investigations on the major clay mineral near- and far-field repository components, elucidate the sorption mechanisms, and apply the “in house” developed 2 Site Protolysis Non Electrostaic Surface Complexation and Cation Exchange (2SPNE SC/CE) sorption model which can quantitatively describe the uptake of radionuclides over a wide range of conditions (pH, Eh, water chemistry, concentration). Since clay minerals are the main sorbing phases in the systems under consideration, the premise is that the sorption on argillaceous rocks and bentonite can be calculated by using the sorption models for the individual clay minerals modified by their modal compositions. This essentially wet chemistry/modelling approach is supported by surface spectroscopic techniques, e.g. X-ray absorption spectroscopy (XAS) which provide on a molecular level information on the sorbed species (coordination numbers, bond distances and system disorder). Such a mechanistic modelling approach to sorption has the goal of developing a thermodynamic based sorption data base (TD-SDB). Such a TD-SDB readily lends itself to porting into a coupled code which can then be used to calculate radionuclide migration in PA studies without having to use Kd values directly.
Transport Mechanisms Group
Diffusion Processes Group
Contact: Dr. Martin Glaus a.i.
Cement Systems Group
Contact: Prof. Dr. John Provis