Exploring diffusion and sorption processes at the Mont Terri rock laboratory (Switzerland): lessons learned from 20 years of field research

Leupin, Olivier X.; Loon, Luc R. Van; Gimmi, Thomas; Wersin, Paul; Soler, Josep M.

doi:10.1007/s00015-016-0254-z

Cited by 24 publications

(11 citation statements)

References 40 publications

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“…All this translated into initial bulk and EDL porosities in the rock equal to 0.0397 and 0.1103, respectively. Total porosity was fixed to 0.15, according to the findings in previous laboratory and field experiments. , …”

Section: Setup Dimensions and Model Parametersmentioning

confidence: 99%

“…Several diffusion experiments had already been performed at Mont Terri (DI, FM-C, DI-A1, DI-B, DI-A2, DR). − In those experiments, synthetic porewater at equilibrium with the rock and containing tracers was continuously circulated through a packed-off borehole interval and the decrease in tracer concentrations in the liquid phase was monitored. Subsequently, a volume of rock surrounding the borehole was overcored and the tracer profiles in the rock were analyzed.…”

Section: Introductionmentioning

confidence: 99%

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Modeling the Ionic Strength Effect on Diffusion in Clay. The DR-A Experiment at Mont Terri

Soler

Steefel

Gimmi

et al. 2019

ACS Earth Space Chem.

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Solute diffusion in compacted clays depends on ionic strength through its control on the thickness of the electrical double layer (EDL) on the charged clay surfaces. In the DR-A field experiment (Mont Terri, Switzerland), synthetic porewater was circulated through a borehole for 189 days, leading to the out-diffusion of a variety of tracers into the Opalinus Clay. The borehole solution was then replaced with a higher-salinity solution for an additional 540 days, leading to the diffusion of Cs + , Ca 2+ , Mg 2+ , and Sr 2+ back into the borehole and to an increase in the out-diffusion of anions (I-, Brand nd 3 H. The experimental results were interpreted using the CrunchClay code, which includes a mean electrostatic potential model for the EDL. The EDL corresponds to a second continuum in addition to bulk electrically neutral porewater. Species-specific diffusion (Nernst-Planck equation) occurs through both domains. A 1D radial model considered a single pore diffusion coefficient (D p = 10-9 m 2 /s) for cations and 3 H in the bulk porosity, and a smaller D p (3 × 10-10 m 2 /s) for anions. D p values in the EDL were smaller (10-11 m 2 /s), except for Cs + and K + (5 × 10-10 and 2 × 10-10 m 2 /s, respectively). The model reproduced well the experimental results and showed the capability to consider temporal changes in geochemical conditions affecting the transport and retention of potentially important radionuclide contaminants (e.g., 137 Cs + , 90 Sr 2+ , 129 I-) in underground geological nuclear waste repositories. Coupled multicomponent diffusion together with the electrostatic properties of the charged surfaces are essential in the development of predictive models for ion transport in clays.

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Section: Setup Dimensions and Model Parametersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Modeling the Ionic Strength Effect on Diffusion in Clay. The DR-A Experiment at Mont Terri

Soler

Steefel

Gimmi

et al. 2019

ACS Earth Space Chem.

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“…Countries like Switzerland, France, and Belgium have selected clayey rock as a candidate for geological disposal repositories of high-level radioactive waste. They conducted significant research and development on clayey rock site screening and feature evaluation and built underground clayey rock laboratories (Van Marcke et al, 2010;Jacops et al, 2015;Bossart et al, 2017;Leupin et al, 2017;Wigger et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

“…Van Loon et al (2005) studied the diffusion behavior of some key elements (e.g., tritiated water (HTO), Cl − , Na + ) in clayey rocks, e.g., Opalinus Clay, using the diffusion cell method and obtained many migration parameters. In another study, Leupin et al (2017) presented the research results of the Mont Terri Laboratory about material migration in Opalinus Clay in the last 20 years, which provided valuable data for the safety evaluation of underground laboratories and disposal repositories in Switzerland. Additionally, Jacops et al (2015;2017) studied the diffusion coefficients of dissolved gas and HTO in Boom clayey rocks by the diffusion cell method, providing a useful experimental basis for the construction of disposal repositories in Belgium.…”

Section: Introductionmentioning

confidence: 99%

Law of Nuclide Migration in Clayey Rocks considering Diffusion and Fluid Transport

Chen²,

Chen³

et al. 2022

Front. Earth Sci.

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A core concern in the research on deep geological disposal of high-level radioactive waste is the migration of radionuclides in geological bodies. Most studies on radionuclide migration consider the role of only the rock fissures without incorporating the influence of the rock matrix. In this paper, the rock mass for geological disposal of high-level radioactive waste is regarded as a fissure-pore medium. Considering the influences of radionuclide diffusion and fluid transport on radionuclide migration in the process of disposal, the governing equation of radionuclide migration and evolution in the pore-fissure medium is established. The numerical scheme of the governing equation is given based on the mixed finite volume method (FVM), using our program solution module written in C++. On this basis, the numerical test model with fissures was developed, which analyzed the radionuclide migration law in clayey rocks under various fissure and rock matrix diffusion coefficients and hydraulic conductivities. The simulation results are compared with finite element method results, revealing the superiority of the mixed FVM method in solving problems of radionuclide migration in discontinuous geological bodies containing hiatuses, mutations, and fissures. The study provides a theoretical basis for evaluating the safety, feasibility, and suitability of geological disposal repositories for high-level radioactive waste in terms of radionuclide migration.

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“…The retardation of radionuclide migration has been demonstrated for claystones, like the Swiss Opalinus Clay, in many laboratories as well as in-situ experiments, usually applying constant and homogeneous (geochemical) experimental conditions [2][3][4][5]. However, for many radionuclides it has been shown that sorption and migration are affected by geochemistry and can deviate by one or more orders of magnitude [6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Potential Uranium Migration within the Geochemical Gradient of the Opalinus Clay System at the Mont Terri

Hennig

Kühn

2021

Minerals

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Transport properties of potential host rocks for nuclear waste disposal are typically determined in laboratory or in-situ experiments under geochemically controlled and constant conditions. Such a homogeneous assumption is no longer applicable on the host rock scale as can be seen from the pore water profiles of the potential host rock Opalinus Clay at Mont Terri (Switzerland). The embedding aquifers are the hydro-geological boundaries, that established gradients in the 210 m thick low permeable section through diffusive exchange over millions of years. Present-day pore water profiles were confirmed by a data-driven as well as by a conceptual scenario. Based on the modelled profiles, the influence of the geochemical gradient on uranium migration was quantified by comparing the distances after one million years with results of common homogeneous models. Considering the heterogeneous system, uranium migrated up to 24 m farther through the formation depending on the source term position within the gradient and on the partial pressure of carbon dioxide pCO2 of the system. Migration lengths were almost equal for single- and multicomponent diffusion. Differences can predominantly be attributed to changes in the sorption capacity, whereby pCO2 governs how strong uranium migration is affected by the geochemical gradient. Thus, the governing parameters for uranium migration in the Opalinus Clay can be ordered in descending priority: pCO2, geochemical gradients, mineralogical heterogeneity.

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Exploring diffusion and sorption processes at the Mont Terri rock laboratory (Switzerland): lessons learned from 20 years of field research

Cited by 24 publications

References 40 publications

Modeling the Ionic Strength Effect on Diffusion in Clay. The DR-A Experiment at Mont Terri

Modeling the Ionic Strength Effect on Diffusion in Clay. The DR-A Experiment at Mont Terri

Law of Nuclide Migration in Clayey Rocks considering Diffusion and Fluid Transport

Potential Uranium Migration within the Geochemical Gradient of the Opalinus Clay System at the Mont Terri

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