Benoit Garitte

Amberg (Czechia)

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Antonio Gens

Universitat Politècnica de Catalunya

Jean Vaunat

Universitat Politècnica de Catalunya

Gilles Armand

Agence Nationale pour la Gestion des Déchets Radioactifs

Tim Vietor

National Cooperative for the Disposal of Radioactive Waste (Switzerland)

S. Olivella

Universitat Politècnica de Catalunya

Klaus Wieczorek

Gesellschaft für Anlagen und Reaktorsicherheit

Thomas Trick

CryptoExperts (France)

Herwig Müller

National Cooperative for the Disposal of Radioactive Waste (Switzerland)

Juan Carlos Mayor

Empresa Nacional de Residuos Radiactivos

Alain Millard

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

Cooperative Institutions

National Cooperative for the Disposal of Radioactive Waste (Switzerland)

École Polytechnique Fédérale de Lausanne

Quintessa (United Kingdom)

Federal Institute for Geosciences and Natural Resources

Centre National de la Recherche Scientifique

Helmholtz Centre for Environmental Research

University of Liège

Universitat Politècnica de Catalunya

ETH Zurich

TU Dresden

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Observation of ventilation effects around a tunnel excavated in argillaceous materials

Antonio Gens Benoit Garitte

A full scale field test to evaluate the effects of ventilation in a tunnel excavated in Opalinus clay has been performed in the underground laboratory of Mont Terri in Switzerland. The test involved several stages of wetting and drying under controlled conditions. Coupled analyses have been performed taking into account the specific features of the test, especially the conditions in the boundary between air and clay. The results have revealed the existence of two different zones around the tunnel: a desaturation zone reaching only about 50 cm inside the clay and a larger zone, extending 2.5-3m from the tunnel wall, in which the Opalinus clay is under suction. Displacements are also small and the potential damaged zone very limited. Therefore, the observed ventilation effects on Opalinus clay have been modest and reduced to zones quite close to the tunnel.

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EBS Behaviour Immediately After Repository Closure in a Clay Host Rock: The HE-E Experiment (Mont Terri URL)

ASME 2011 14th International Conference on Environmental Remediation and Radioactive Waste Management, Parts A and B (2011)

Irina Gaus Klaus Wieczorek Juan Carlos Mayor Thomas Trick Jose ́-Luis Garcia` Sin ̃eriz

The evolution of the engineered barrier system (EBS) of geological repositories for radioactive waste has been the subject of many research programmes during the last decade. The emphasis of the research activities was on the elaboration of a detailed understanding of the complex thermo-hydro-mechanical-chemical processes, which are expected to evolve in the early post closure period in the near field. It is important to understand the coupled THM-C processes and their evolution occurring in the EBS during the early post-closure phase so it can be confirmed that the safety functions will be fulfilled. Especially, it needs to be ensured that interactions during the resaturation phase (heat pulse, gas generation, non-uniform water uptake from the host rock) do not affect the performance of the EBS in terms of its safety-relevant parameters (e.g. swelling pressure, hydraulic conductivity, diffusivity). The 7th Framework PEBS project (Long Term Performance of Engineered Barrier Systems) aims at providing in depth process understanding for constraining the conceptual and parametric uncertainties in the context of long-term safety assessment. As part of the PEBS project a series of laboratory and URL experiments are envisaged to describe the EBS behaviour after repository closure when resaturation is taking place. In this paper the very early post-closure period is targeted when the EBS is subjected to high temperatures and unsaturated conditions with a low but increasing moisture content. So far the detailed thermo-hydraulic behaviour of a bentonite EBS in a clay host rock has not been evaluated at a large scale in response to temperatures of up to 140°C at the canister surface, produced by HLW (and spent fuel), as anticipated in some of the designs considered. Furthermore, earlier THM experiments have shown that upscaling of thermal conductivity and its dependency on water content and/or humidity from the laboratory scale to a field scale needs further attention. This early post-closure thermal behaviour will be elucidated by the HE-E experiment, a 1:2 scale heating experiment setup at the Mont Terri rock laboratory, that started in June 2011. It will characterise in detail the thermal conductivity at a large scale in both pure bentonite as well as a bentonite-sand mixture, and in the Opalinus Clay host rock. The HE-E experiment is especially designed as a model validation experiment at the large scale and a modelling programme was launched in parallel to the different experimental steps. Scoping calculations were run to help the experimental design and prediction exercises taking the final design into account are foreseen. Calibration and prediction/validation will follow making use of the obtained THM dataset. This benchmarking of THM process models and codes should enhance confidence in the predictive capability of the recently developed numerical tools. It is the ultimate aim to be able to extrapolate the key parameters that might influence the fulfilment of the safety functions defined for the long term steady state.

Closure (psychology)

Shrinkage

10.1115/icem2011-59288

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mage Zone at High Depths: Field pled Analysis

Jean Vaunat Antonio Ge J. Girona Benoit Garitte

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Performance of the Opalinus Clay under thermal loading: experimental results from Mont Terri rock laboratory (Switzerland)

Swiss journal of geosciences. Supplement (2017)

Antonio Gens Klaus Wieczorek Irina Gaus Benoit Garitte Juan Carlos Mayor

10.1007/978-3-319-70458-6_14

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Applications of multiphysical geomechanics in underground nuclear waste storage

Revue française de génie civil (2009)

Antonio Gens Benoit Garitte S. Olivella Jean Vaunat

Deep geological disposal in suitable host rocks is the favoured strategy for the storage and disposal of heat-emitting high level nuclear waste.A rational design of repositories requires a good understanding of the interacting thermo-hydro-mechanical phenomena that occur in the engineered barrier and adjacent rock.To this end, a multiphysical formulation is described that allows the performance of coupled THM analyses capable of reproducing observed phenomena.The formulation and computer code is applied to the simulation of two large scale tests: a mine-by test involving the excavation of a shaft in an argillaceous rock and a large-scale high-temperature heating test in fractured rock.RÉSUMÉ: La stratégie préconisée actuellement pour le stockage et le dépôt de déchets de haute radioactivité émettant de la chaleur est de les disposer dans des couches géologiques profondes appropriées.Un design rationnel des sites de stockage exige une bonne compréhension des phénomènes thermo-hydro-mécaniques interagissant au niveau de la barrière ouvragée et de la roche hôte proche.Pour y parvenir une formulation multiphysique, permettant de réaliser des analyses couplées THM et capable de reproduire les phénomènes observés, est décrite.La formulation est appliquée à la simulation de deux tests à échelle réelle : un essai dit « mine-by-test » concernant l'excavation d'un puits dans une roche argileuse et un test de chauffage à haute température dans une roche fracturée.

Geomechanics

Underground storage

10.3166/regc.13.937-962

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The FE-M Task Force: 3D modelling of THM repository induced effects in the Full-scale Emplacement Experiment (FE) – Mont Terri Rock Laboratory. Current status and the path forward.

Andrés Alcolea Ivan Puig Damians Berrak Firat-Lüthi Benoit Garitte Antonio Gens

The construction and operational phases of a deep geological repository imply potential perturbations of the host rock, so-called Repository Induced Effects (RIE). Amongst them, spent fuel and high level waste (SF/HLW) produce decay heat even after long times of cooling, which may impair the long-term safety of the Engineered Barrier System and of the geological barrier. The Opalinus Clay (OPA), is currently being assessed as host rock for the deep geological repository in Switzerland. OPA is an indurated clay of Jurassic age (ca. 180 My), whose main features are (1) a very low hydraulic conductivity, (2) an excellent retention capacity for dissolved radionuclides, and (3) a significant self-sealing capacity.The on-going Full-scale Emplacement (FE) Experiment at the Mont Terri Underground Rock Laboratory simulates, as realistically as possible, the construction, waste emplacement, backfilling and early-stage post-closure evolution of a single SF/HLW emplacement tunnel in OPA, using heaters instead of disposal canisters. The main goal of the FE experiment is the investigation of RIE on the host rock (and, to a lesser extent, on the the backfill material) at true scale and the validation of existing coupled thermo-hydro-mechanical (THM) models. In this context, Nagra has developed a new RD&D initiative, i.e., the FE modelling Task Force (FE-M TF), which involves three modelling teams with corresponding software packages (Code Aster, Code Bright and OpenGeoSys). So far, the TF has defined three main tasks:<ul><li>Code comparison and calculation verification: the TF designed a simplified (though realistic) 3D conceptual model of the FE experiment that includes the actual geometry of the main elements, materials and phases of the FE experiment, including tunnel excavation and ventilation. Such conceptual model was implemented by the modelling teams. Finally, code outputs were analysed and compared by the TF.</li> <li>Back-analyses of THM-observations in the host rock: monitoring data from radial and oblique boreholes around the backfilled FE tunnel are used for model calibration, including the derivation of parameter best estimates and inherent uncertainties, and model</li> <li>Model validation in the context of a prediction-evaluation exercise: the evolution of the THM conditions in the rock in response to a change of thermal loads (e.g., increase/decrease of heater output) will be predicted using the calibrated models. Finally, model predictions will be validated in the near future using the acquired measurements.</li> </ul>This presentation summarizes the current status of Tasks 1 and 2 and the path forward to Task 3.

Decay heat

High-level waste

10.5194/egusphere-egu22-13385

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Performance of the Opalinus Clay under thermal loading: experimental results from Mont Terri rock laboratory (Switzerland)

Swiss Journal of Geosciences (2017)

Antonio Gens Klaus Wieczorek Irina Gaus Benoit Garitte Juan Carlos Mayor

10.1007/s00015-016-0258-8

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Thermal Processes

Terrestrial environmental sciences (2016)

Shao Hua Tianyuan Zheng Philipp Hein Son Nguyen Benoit Garitte

Multiphysics

10.1007/978-3-319-29224-3_2

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HYDRAULIC RESPONSE TO A SHAFT EXCAVATION IN CALLOVO- OXFORDIAN CLAY

Benoit Garitte Antonio Gens Jean Vaunat Gilles Armand

Summary. This document presents a coupled hydro-mechanical (HM) numerical analysis, using Code_Bright, simulating the excavation of the main access shaft to the underground laboratory of Bure (France) in Callovo-Oxfordian Clay. The work consists in the description of the HM formulation using a specially developed constitutive law and in the discussion of the simulation results. The mechanisms at the origin of the water pressure response are analysed with special emphasis on the influence of the mechanical and hydraulic boundary conditions used for the shaft excavation. Shaft convergence and permeability evolution measured by ANDRA (Modex-REP mine-by-test, [1,2]) during the shaft excavation are compared with the modelling results to illustrate the model capability to reproduce excavation induced damage and to relate it to permeability increase. 1 HM FORMULATION AND CONSTITUTIVE MECHANICAL LAW The formulation used in the Finite Element code Code_Bright is based on a multiphase/multi-species approach [3]. In this work, two phases are considered, solid (s) and liquid (l) corresponding to the two species: mineral and water (w). The solution of the coupled HM problem requires the simultaneous solution of the mass balance of solid, the mass balance of water in saturated conditions and the balance of momentum (equation (1), (2) and (3), respectively).

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A DECOVALEX-2011 benchmark: laboratory drying test in opalinus clay

Benoit Garitte Antonio Gens Quansheng Liu Xiaoyan Liu Alain Millard

Laboratory test

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