Research Activities

Radioactive waste arising from nuclear power generation, as well as from medicine, industry and scientific research, poses a potential hazard over extended periods of time and must therefore be isolated from the human environment. The disposal of such wastes in engineered caverns far below the Earth's surface fulfills this purpose. The Laboratory for Waste Management (LES), in co-operation with the National Cooperative for the Disposal of Radioactive Waste (Nagra) carries out experiments and develops models which contribute to safety assessments of disposal concepts for radioactive waste. The staff consists of more than 30 scientists, from a broad range of natural sciences, and technicians. Full experimental demonstrations of the safety case are not possible because of the long timescales associated with the disposal of radioactive waste. The release of radionuclides into the human environment occurs only on time scales of tens of thousands to millions of years after the wastes have been placed in the subterranean repositories. For this reason, safety analyses rely on extrapolations and computations based on a sufficient understanding of the events and processes which influence the long term performance of the repository, and which can affect the transport of radionuclides from the repository back to the human environment. The necessary information is obtained from laboratory experiments and investigations on appropriate natural systems e.g. natural analogues and field experiments in underground research laboratories. On the basis of the results from such investigations, LES develops mathematical models which allow the safety of the disposal system to be numerically assessed.

The principal areas of research carried out by LES can be conveniently partitioned into three main parts covering the most important issues i.e. geochemical in situ conditions and their temporal evolution, radionuclide retention/retardation and transport mechanisms.

Contact: Dr. Anke Neumann Jenal

The Clay Systems Group focuses on radionuclide behavior in clay-containing systems that are relevant in the near-field (bentonite) and far-field (Opalinus Clay) of deep geological repositories for radioactive waste. We combine experimental data, modelling, and synchrotron-based spectroscopic techniques to understand radionuclide sorption at a mechanistic and molecular level. Our sorption database and model, such as the widely known 2-Site Protolysis Non-Electrostatic Surface Complexation and Cation Exchange (2SPNE SC/CE) model, are integrated into GEMS and continuously updated. We further complement our understanding of sorption with redox processes at clay minerals – for which we use, among other techniques, Mössbauer spectroscopy – and expand this expertise from radionuclides to a wider range of environmentally relevant inorganic and organic compounds and contaminants. 

Contact: Dr. Nikolaos Prasianakis

Geosphere transport group uses interdisciplinary approach to merge experimental knowledge at the field and laboratory scale, geochemical and molecular modelling in order to assess geochemical and transport phenomena in geological repositories for radioactive waste. The major activities are focused on radionuclide transport modelling for needs of performance assessment, predictive modeling of the temporal and spatial evolution near- and far-fields in future underground repository. We combine simulation techniques at different scales to get mechanistic understanding of ion sorption and transport in heterogeneous porous materials.

Contact: Prof. Dr. Sergey Churakov

The activities in the “Diffusion Processes” group focus on i) understanding the diffusion mechanism(s) of radionuclides in compacted argillaceous materials and ii) measuring diffusion parameters (effective diffusion coefficients and rock capacity values) that can be used in performance assessment studies. For this purpose, laboratory experiments are performed on (i) compacted clay minerals and (ii) intact clay rock. In a recent laboratory measurement campaign (2019 – 2024), systematic diffusion measurements were carried out on an extensive series of rock samples from the deep-drilling campaign of Nagra at the potential siting areas in Northern Switzerland. These samples comprised representative sequences of Mesozoic sedimentary rock, including the Opalinus Clay and the under- and overlying Jurassic and Triassic formations. All these experiments are complemented by field studies carried out in the Underground Rock Laboratory at Mont Terri (North-West Switzerland) and by spectroscopic (e.g. neutron scattering and diffraction) or microscopic (e.g. X-ray tomography) techniques.

Diffusion experiments carried out using highly compacted clay minerals or intact clay rocks provide valuable information on retention mechanisms at high solid-liquid ratios. They thus contribute significantly to a deeper understanding of radionuclide uptake processes by the host rock material. The experience gained in these studies has clearly shown that an in-depth understanding of the processes governing mass transport in compacted argillaceous materials critically depends on the molecular dynamic properties of the diffusing species, the geometric features of the pore structure, and the physico-chemical properties of the pore solution, such as its chemical composition. Understanding the diffusion of charged substances in charged clay-containing media as a purely physical process would clearly fall short of the mark.
 

Contact: Prof. Dr. John Provis
 

The Cement Systems group carries out an experimental research programme focusing on the fundamental science and engineering cements. We investigate sorption of radionuclides by cementitious materials, and study other near field processes related to the safe disposal of radioactive waste in a cement-based repository, as well as the formation, thermochemistry, and durability of cementitious phases and phase assemblages. Experimental studies on the porewater and phase compositions of cementitious materials, and the fate of radionuclides under the conditions of a cementitious near field are aimed at improving our understanding of the geochemical processes and the in situ conditions in a cement-based repository. We also work to understand the reaction mechanisms and setting processes of cements, with a view toward supporting their more efficient and sustainable usage in service of society, and in improving and better understanding test methods for cement durability.