Mont Terri project

Country / Region: Switzerland, Germany

Begin of project: July 1, 1997

End of project: December 31, 2025

Status of project: November 15, 2023

Map of the new experiments in Gallery 18 (green) at the Mont Terri rock laboratory, St. Ursanne in the Swiss Jura Mountains Source: swisstopo, www.mont-terri.ch

German Version

In the international Mont Terri rock laboratory located in northwestern Switzerland, BGR investigates the physical, chemical, and microbial processes taking place in argillaceous rocks, which are relevant for the safe disposal of radioactive waste in underground geological formations. Argillaceous rock is one of the three potential host rocks, alongside rock salt and crystalline rocks, selected for the final disposal of radioactive waste in Germany in accordance with the Site Selection Act (StandAG). In addition, investigations are being carried out into the barrier effect of the clay rock for the geological storage of CO₂.

The research activities carried out by BGR in the Mont Terri underground laboratory provide important information on the properties of argillaceous rocks as a potential host rock, relevant in the search for a German geological repository site. The following aspects are of primary importance:

• Keeping in close contact with international developments and their transferability to applications in Germany,
• Basic research for the comparative evaluation of potential host rocks for a geological repository.

BGR performs basic and location-independent research work in the Mont Terri project in close collaboration with international partners, this includes the following:

• Knowledge, experience and understanding of thermically, hydraulically, mechanically and chemically coupled processes in claystone
• Characterisation of argillaceous rock as a potential host rock,
• further development and adaptation of methods for exploration and monitoring measurements,
• Investigations into the realisation of geotechnical barriers and their optimisation,
• participation in demonstration experiments,
• Data analysis and data management,
• Application and further development of numerical simulations, especially for safety analyses.

The Mont Terri project in the Swiss canton of Jura was established in 1996 for fundamental research into clay rock and the development of investigation methods. The Swiss Federal Office of Topography (swisstopo) is the operator of the Mont Terri Rock Laboratory. The laboratory is owned by the Canton of Jura.

During the excavation of a motorway tunnel through the approximately 800-metre-high Mont Terri mountain, a layer of clay rock (Opalinus Clay) approximately 150 metres thick was exposed at a depth of around 300 metres. This Opalinus Clay is characterised by its comparatively low hydraulic permeability and also has the ability to close small cracks or fissures by self-sealing. Both of these characteristics are favourable for the safety of radioactive waste storage in clay rock.

Just one year after its foundation, BGR joined the international Mont Terri project in 1997. Currently (as of November 2023), 22 partners from ten countries are equally involved in the extensive research programme. Numerous universities and other research institutions as well as smaller companies are also involved as contractors.

In 2019, the expansion of the rock laboratory was completed with the construction of the new Gallery 18. This extension doubles the area available for experiments to a gallery and niche length of around 1200 metres. The BGR's new individual experiments include investigations into

• hydromechanical influences on the claystone formation through the excavation of mine workings,
• the influence of ventilation on the loosening zone,
• new geotechnical barriers for a deep geological repository
• the temporally and spatially high-resolution detection of deformations in clay rock,
• the storage of carbon dioxide in the geological subsurface with a view to the Opalinus Clay as a geological barrier.

Currently BGR either manages or participates as a partner in 19 of total 46 active experiments in the Mont Terri project. The measurements and investigations of the BGR in the rock laboratory focus on the mechanical behaviour of the Opalinus Clay, the rock permeability and preserving of the barrier effectiveness, the isolation capacity of geotechnical barriers and rocks, the quality of the isolation and the tendency to form fluid migration paths and the formation of gas.

The in-situ activities in the underground laboratory are supplemented in the Mont Terri project by small-scale laboratory work carried out at BGR, as well as comprehensive numerical modelling of the thermal, hydraulic, mechanical and chemically-coupled processes.

More than 170 experiments have been carried out so far in the research laboratory, of which around 130 have already been successfully concluded. BGR is focusing primarily on the first two phases of a geological repository for radioactive waste, namely:

• The period before the emplacement of the radioactive waste - investigating the initial conditions prior to the construction of the geological repository and the determination of changes in the rock mass due to the construction of a deep geological repository,
• The initial phase after emplacement of the radioactive waste - investigating the changes in the rock and and the geotechnical barriers during storage operation of the geological repository.

View of the new Gallery 18 in May 2019 Source: D. Rebscher

In addition to the temporal categorisation, the scientific-technical studies also differentiate between the spatial situations, i.e. between the undisturbed zones in the rock mass, and the excavation damaged zone. For this purpose, BGR performs rock-mechanical and rock-hydraulic in-situ investigations, for instance, to determine the permeability of the clay stone. Another of BGR's foci is on the development of methods, e.g., the development of geomechanical, geohydraulical or geophysical measuring techniques, which are also applied successfully in the investigation of other rock types as well as in other areas of application in underground geological formations. These research activities in the context of the final disposal of radioactive waste are supplemented by investigations into the storage of CO₂ underground.
Computer-supported modelling of the thermal, hydraulic, mechanical, and chemically coupled processes are intensely utilised for the design of an experiment, supporting the experimental measurements, and in the evaluation and interpretation of examination results and other findings.

References:

Bossart, P., Bernier, F., Birkholzer, J., Bruggeman, C., Connolly, P., Dewonck, S., Fukaya, M., Herfort, M., Jensen, M., Matray, J.M., and Mayor, J.C., (2018): Mont Terri rock laboratory, 20 years of research: introduction, site characteristics and overview of experiments. In: Mont Terri rock laboratory, 20 Years, pp. 3-22. Birkhäuser, Cham.

Schuster, K., Furche, M., Shao, H., Hesser, J., Hertzsch, J.M., Gräsle, W. and Rebscher, D. (2019): Understanding the evolution of nuclear waste repositories by performing appropriate experiments–selected investigations at Mont Terri rock laboratory. Advances in Geosciences, 49, pp.175-186.

Project website: www.mont-terri.ch

Partner:

• ANDRA Agence nationale pour la gestion des déchets radioactifs, France
• BASE Federal Office for the Safety of Nuclear Waste Managment, Germany
• BGE Federal Company for radioactive waste disposal, Germany
• BGR Bundesanstalt für Geowissenschaften und Rohstoffe, Germany
• CHEVRON Chevron Energy Technology Company, USA
• CRIEPI Central Research Institute of Electric Power Industry, Japan
• ENSI Eidgenössische Nuklearsicherheitsinspektorat, Switzerland
• ENRESA Empresa Nacional de Residuos Radiactivos, S.A., Spain
• ETH Federal Institute of Technology Zurich
• FANC Federaal agentschap voor nucleaire controle, Belgium
• GRS Gesellschaft für Anlagen- und Reaktorsicherheit gGmbH, Germany
• Helmholtz-Association UFZ, GFZ, FZJ, HZPR und KIT, Germany
• IRSN Institute for Radiological Protection and Nuclear Safety, France
• NAGRA National Cooperative for the Disposal of Radioactive Waste, Switzerland
• NWMO Nuclear Waste Management Organization, Canada
• OBAYASHI Obayashi Corporation, Japan
• RWM Radioactive Waste Management, Great Britain
• SCK CEN Belgian Nuclear Research Centre, Belgium
• Shell, Netherlands
• swisstopo Federal Office of Topography, Switzerland
• TotalEnergies SE, France
• U.S. DOE Department of Energy, USA

Cooperation with partners including:

• BGS British Geological Survey, Great Britain
• BGRM, Bureau de Recherches Géologiques et Minières, France
• CEE Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, USA
• CHYN, Université de Neuchâtel, Switzerland
• CIEMAT, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, Spain
• CMM-KIT Competence Center for Material Moisture of the "Karlsruher Institut für Technologie", Germany
• CSIC Consejo Superior de Investigaciones Científicas, Spain
• Edi Meier + Partner, Schwitzerland
• Hydroisotop, Germany
• University of Bern, Institute of Geological Sciences, Switzerland
• University of Ottawa, Canada