Nuclear Waste Storage
Tools for the assessment of multi-barrier systems
Radioactive waste is planned to be safely stored, adopting an engineerd multibarrier system in deep geological formation. The disposal needs to ensure the isolation of the waste from the external environment for hundreds of thousands of years. The long term duration represents a major challenge for safety assessment. The metal canister containing the vitrified waste will be emplaced in a deep underground tunnel, excavated in a clayey geomaterial, and backfilled with bentonite clay.Several interacting physical phenomena take place simultaneously during the waste disposal life, making any prediction for the reservoir behaviour a challenging subject. In this sense, the understanding and modelling of the thermo-hydro-mechanical (THM) behaviour of these materials have to be accurately addressed.
Research Group for Nuclear Waste Storage:
Beacon – Bentonite mechanical evolution
The project aims at improving the numerical models for predicting the behaviour of bentonite seals, buffers and backfills in the context of deep nuclear waste disposal. The focus is on understanding the homogenisation of the material that will take place upon water uptake from the surrounding host rock. Robust numerical tools, able to predict the long term performance of such elements are key technical issues for the implementation of planned geological disposals.
Geomaterial behaviour in partially saturated conditions
In the concept of the nuclear waste repository, both the natural and the engineered barriers will come across unsaturated conditions. The partial saturation affects the mechanical response of the geomaterials. Understanding and characterising the behaviour of unsaturated geomaterials composing the multi-barrier system is, therefore, one of the main issues. Several advanced devices are available in our laboratory allowing to analyse experimentally swelling behaviour, mechanical response in unsaturated conditions, water retention behaviour and liquid and gas transfers.
Shale immersed in water: degradation over time
Thermo-Hydro-Chemo-Mechanical behaviour of Shales
Shales are not only considered as a suitable soil for the storage of high-level nuclear waste. They also provide perfect cap rocks for oil and gas reservoirs. This makes their behaviour an exciting subject of research for the civil and environmental engineer
During well boring pressures of tens of MPa and temperature up to 100°C are recorded. Such in-situ conditions are not easy to reproduce in the laboratory. Also, various fluids can be adopted to improve drilling efficiency. This fluid interacts with the shales with which it is in contact, inducing chemo-mechanical effects. LMS is currently researching the influence of salts on saturated soils and shales.
Thermo-hydro-mechanical constitutive modelling
A variety of phenomena occurs during wetting, drying, heating or mechanical loadings. The swelling behaviour, thermal collapse, wetting collapse, and the isothermal mechanical behaviour must all be included in a constitutive model. Based on concepts from the Cam-Clay model, our model, ACMEG, has been extended and tested to reproduce the key behaviours of unsaturated soils. It is currently expanded to other problems such as anisotropy or chemical couplings.
SKB Task Force on Engineered Barrier Systems
The objective of the International Task Force on Engineered Barriers, managed by the Swedish company SKB, is the development of general and effective tools for the advanced coupled THMC analysis of buffer and backfill for High-Level Waste repositories (https://www.skb.se/taskforceebs/). Our task focuses on the numerical modelling of gas flow in the compacted bentonite buffers. The scientific goal is to improve the predictive capabilities of the numerical tools to be used in the long-term safety assessment of the repository. Partners are Nagra (Switzerland), UPC (Spain), and Intera (Switzerland).
Thermo-Hydro-Mechanical 3D Modelling of the FE-Experiment in Mont Terri
The Full-scale Emplacement (FE) Experiment at the Mont Terri Underground Research Laboratory (URL) mimics the construction, waste emplacement, backfilling and early-stage evolution of a high-level waste repository tunnel, using heaters instead of canisters. In this context, Nagra has established an international modelling Task Force with the aim of validating and calibrate the available numerical Thermo-Hydro-Mechanical frameworks. The final aim is to assess the impact of repository induced effects on the long-term performance of the radioactive waste multibarrier storage system. Partners are Nagra (Switzerland), UPC (Spain), and BGR (Germany).
Numerical modelling of the Hydro-Mechanical behavior of shales in a real excavation context
In recent years, significant efforts have been made to characterize the hydromechanical response of Opalinus Clay shale. These data enable to improve the available numerical tools to better describe the real response of the formation in an excavation context. New features are being added to the theoretical approaches, and the calibration and validation of the models are enhanced by the analysis of the new laboratory and field data. Significant efforts are also devoted to the identification and interpretation of the site variability of the hydromechanical properties of Opalinus Clay. The main partner of these project is Nagra (Switzerland).
Hydro-mechanical behaviour of shallow Opalinus Clay shale
In Switzerland, Opalinus Clay shale has been selected as the host formation for radioactive waste disposal. The minimum required depth of the repository is related to the long-lasting isolation required for the disposal (1 million years). During this period, possible erosion scenarios affecting the repository need to be analysed. Opalinus Clay from shallow depths (< 70m) was sourced from a borehole in Northern Switzerland, where the formation was affected by a considerable exhumation process. This work aims to investigate the impact of the mentioned phenomenon on the hydro-mechanical behaviour of Opalinus Clay through one-dimensional consolidation and permeability measurements.
Jan 24 2019
Vol. 251 , p.214-227.
DOI : 10.1016/j.enggeo.2019.01.016
Consolidated-undrained triaxial testing of Opalinus Clay: Results and method validation
-An alternative procedure to “conventional” testing of clay shales is presented.
-The robustness and advantages of the procedure is demonstrated.
-The impact of inappropriate strain rate on test results is highlighted.
-The procedure decreases test complexity and rig time (10 to 20 days) significantly.
Geomechanics for Energy and the Environment
14, p. 16-28.
DOI : 10.1016/j.gete.2018.01.003
Anisotropic behaviour of Opalinus Clay through consolidated and drained triaxial testing in saturated conditions
This paper investigates the anisotropic hydro-mechanical behaviour of Opalinus Clay shale, the host material currently being considered for the construction of a nuclear waste repository in Switzerland. Consolidated and drained triaxial tests on Opalinus Clay from the Mont Terri URL have been conducted in order to derive information on its strength and stiffness properties. Opalinus Clay specimens were tested both parallel to bedding (P-specimens) and perpendicular to bedding (S7 specimens). The considered effective confining stress range (from 2 to 12 MPa) has been selected in order to reproduce possible in-situ stress conditions for the repository. In this work, particular attention has been paid to the experimental procedure in order to ensure consolidated conditions and avoid generation of unwanted excess pore water pressure during drained shearing.
Rock Mechanics and Rock Engineering,
DOI : 10.1007/s00603-017-1398-5
Favero, V., Ferrari, A., Laloui, L. (2016) International Journal of Rock Mechanics and Mining Sciences, 90, pp. 15-25.
Favero, V., Ferrari, A., Laloui, L. (2016) Engineering Geology, 208, pp. 128-135. DOI: 10.1016/j.enggeo.2016.04.030
Ferrari, A., Favero, V., Laloui, L. (2016) International Journal of Rock Mechanics and Mining Sciences, 88, pp. 286-300. DOI: 10.1016/j.ijrmms.2016.07.030
A. Minardi, E. Crisci, A. Ferrari and L. Laloui. (2016) Geotechnique Letters, vol. 6, p. 1-5,
Hydro-chemo-mechanical characterisation of sand/bentonite mixtures: with a focus on the water and gas transport properties
D. Manca, L. Laloui and A. Ferrari (Dirs.), Thèse EPFL, n° 6790, 2015
F. Parisio, S. Semat and L. Laloui. , International Journal of Solids and Structures, vol. 75-76, p. 88-98, 2015.
A. Ferrari, V. Favero, P. Marschall and L. Laloui. , International Journal of Rock Mechanics and Mining Sciences, vol. 72, p. 61-70, 2014.
Water retention behaviour and microstructural evolution of MX-80 granular bentonite during wetting and drying cycles
A. Seiphoori, A. Ferrari and L. Laloui., Geotechnique, vol. 64, num. 9, p. 721-734, 2014.
F. Dupray and L. Laloui, Acta Geotecnica, pp. 1-15, 2014
P. Witteveen, A. Ferrari and L. Laloui, Bio- and Chemo- Mechanical Processes in Geotechnical Engineering, p. 32-43, 2014
Seiphoori, A., PhD Thesis 2014, EPFL Ecole polytechnique fédéral de Lausanne.
Ferrari, A., Seiphoori, A., Rüedi, J., Laloui, L. Engineering Geology -Amsterdam-, vol. 173, p. 10-18, 2014.
Dupray, F., Li, C., Laloui, L., Engineering Geology -Amsterdam-, vol. 163, p. 113-121, 2013.
L. Laloui, A. Ferrari, Springer, 2012.
Seiphoori, A., Ferrari, A. and Laloui L. Deformation Characteristics of Geomaterials, 2011, vol. 1, p. 396-403.
New experimental tools for the characterization of highly overconsolidated clayey materials in unsaturated conditions
Salager, S., Ferrari, A. and Laloui L. In: Mechanics of unsaturated geomaterials, Laloui, L. (ed.), John Wiley & Sons, 2010, p. 113-126.
ACMEG-T: Soil Thermo-Plasticity Model
Laloui L. and François B. Journal of Engineering Mechanics, vol. 135, num. 9, 2009, p. 932-944.
Hueckel T., Laloui L. and François B. Géotechnique, vol. 59, num. 3, 2009, p. 197-212.
François B., Laloui L. and Clément L. Computers and Geotechnics, vol. 36, 2009, p. 626-640.
Laloui L. and Nuth M. Computer and Geotechnics, vol. 36, num. 1-2, 2009, p. 20-23.
Nuth M. and Laloui L. Computer and Geotechnics, vol. 35, num. 6, 2008, p. 835-844.
Sanavia L., François, B., Bortolotto R., Luison L. and Laloui, L. Journal of Theoretical and Applied Mechanics, vol. 38, 2008, p. 7-24.
Experimental investigations of temperature and suction effects on compressibility and pre-consolidation pressure of a sandy silt
Salager S., François B., El Youssoufi S., Laloui L. and Saix C. Soils and Foundations, vol. 48, num. 4, 2008, p. 453-466.
François B. and Laloui L. International Journal of Numerical and Analytical Methods in Geomechanics, vol. 32, 2008, p. 1955–1988.
Laloui L. and Cekerevac C. Computers and Geotechnics, vol. 35, 2008, p. 729-745.
Nuth M. and Laloui L. Int. Journ. of Numerical and Analytical Methods in Geomechanics., vol. 32, 2008, p. 771-801.
Laboratoire Mont-Terri: Dr Alessio Ferrari’s interview with RTS
“The future of nuclear waste” – interview with Prof. Laloui
Alessio Ferrari, research associate at the LMS was interviewed by the Swiss radio television about the choice of the potential sites for the nuclear waste disposal.
Prof. Laloui gave a conference about nuclear waste storage in Sion on 19 January 2012:
Prof. Laloui was interviewed on January 19, 2012 on Radio Chablais about the Nuclear Waste Storage solutions investigated in Switzerland.
Burying the nuclear wastes
Interview with Prof. Laloui about the nuclear waste storage solution chosen in Switzerland.
The Gas-Permeable Seal Test (GAST) was initiated in 2010 and conducted at the Grimsel Test Site (GTS, Switzerland) to demonstrate the effective functioning of gas-permeable seals at realistic scales and under realistic hydraulic conditions.
FEBEX: Full-scale Engineered Barriers Experiment
Modelling of the bentonite and the repository design. Partners are ENRESA and UPC (Spain), NAGRA (Switzerland), SKB (Sweden).
SHARC2: Shale Research Centre consortium
This consortium unites the state-of-the-art knowledge and research on shales of both oil industries and nuclear agencies. The Shale Research Centre’s objectives are the experimental and theoretical characterisation of gas shales properties and the analysis of problems related to reservoirs performance. Partners are CSIRO (Australia), NAGRA (Switzerland), BP (U-K), Total (France), SINOPEC (China).