A comparative anion diffusion study on different argillaceous, low permeability sedimentary rocks with various pore waters

Wigger, Cornelia; Kennell-Morrison, Laura; Jensen, Mark; Glaus, Martin A.; Loon, Luc R. Van

doi:10.1016/j.apgeochem.2018.02.009

Cited by 8 publications

(3 citation statements)

References 33 publications

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“…The net surface charge of the clay minerals is compensated within the area of the DDL by the enrichment of counter-ions and repulsion of co-ions, which accordingly reduces their pore space and hampers their diffusive transport compared to counter-ions. In the case of negatively charged surfaces of the clay minerals, this effect is known as anion exclusion [36,38,43]. Therefore, the amount of water and hence the thickness of the DDL as well as the composition govern anion exclusion.…”

Section: Modelling Multi-component Diffusionmentioning

confidence: 99%

“…We use the fast and robust method of the Donnan approximation implemented in PHREEQC, that assumes a single potential for the DDL as entity, to calculate the composition within the DDL as average [17]. The thickness of the DDL is controlled by the ionic strength of the pore water [38,39,43]. With decreasing ionic strength according to the chloride concentration and the geochemical gradient towards the bounding aquifers, the thickness of the DDL increases.…”

Section: Modelling Multi-component Diffusionmentioning

confidence: 99%

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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 Such a homogeneous assumption is no longer applicable on the host rock scale as can be seen from the pore water profiles of the potential host rock Opalinus Clay at Mont Terri (Switzerland).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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Section: Modelling Multi-component Diffusionmentioning

confidence: 99%

Section: Modelling Multi-component Diffusionmentioning

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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“…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%

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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Diffusion of Re(VII) and Se (IV) in compacted GMZ bentonite in the presence of Bacillus spp.

Zhao

et al. 2019

J Radioanal Nucl Chem

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A comparative anion diffusion study on different argillaceous, low permeability sedimentary rocks with various pore waters

Cited by 8 publications

References 33 publications

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

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

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

Diffusion of Re(VII) and Se (IV) in compacted GMZ bentonite in the presence of Bacillus spp.

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