Diffusion coefficients and accessible porosity for HTO and 36Cl in compacted FEBEX bentonite

Garcı́a-Gutiérrez, Miguel; Cormenzana, J.L.; Missana, Tiziana; Mingarro, M.

doi:10.1016/j.clay.2003.09.012

Cited by 79 publications

(26 citation statements)

References 3 publications

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“…The accessible porosity for water and other dissolved species may be close to the total porosity. García-Gutiérrez et al [57] also report that the accessible porosity for HTO is almost close to the total porosity which is about 0.40 for FEBEX bentonite. Here, a porosity of 0.128 was adopted for the macro-pores which was taken from Sánchez et al [56].…”

Section: Model Uncertaintiesmentioning

confidence: 87%

“…The quantification of the micro-and macro-porous domains requires knowing the porosity of the macro-porous domain which is hard to measure. It is often assumed to be equal to the Cl − throughdiffusion accessible porosity which has been reported for FEBEX [57] and MX-80 [10] bentonites. Bradbury and…”

Section: Model Uncertaintiesmentioning

confidence: 99%

“…García-Gutiérrez et al [57] derived a porosity of 0.022 for Cl − from through-diffusion tests performed on compacted FEBEX bentonite at a dry density of 1.65·10 3 kg/m 3 . This porosity may be lower than the porosity of the macro-pores because Cl − suffers from anion exclusion.…”

Section: Model Uncertaintiesmentioning

confidence: 99%

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Dual-continuum multicomponent reactive transport with nth-order solute transfer terms for structured porous media

Zheng

Samper

2015

Comput Geosci

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The dual-continuum model (DCM) is a type of modeling approach often used to interpret anomalous and non-ergodic solute transport in which the breakthrough curve cannot be explained by the classical advection-dispersion equation. Experimental studies show that bentonites have a macro-porous domain containing free water and a microporous domain containing double-layer and interlayer water. Therefore, a DCM could be needed to describe water flow, solute transport, and chemical reactions through compacted bentonite. In most DCMs, the mass exchange between domains is based on a lumped first-order solute transfer term which is not always accurate. An nth-order solute transfer term for dual-continuum flow and reactive transport model for structured porous media is proposed here. The value of n is derived from the approximation of the analytical solution of diffusion through a thin slab. The parameters of DCMs are obtained by an inverse methodology. Solute transfer terms for compacted bentonite have been evaluated for 1-D and 2-D synthetic cases by solving the inverse problem for several values of n. The best results are obtained with an n of 0.72 and a scale term of 2.5. The reactive transport DCM has been tested with data from a permeability test conducted on a sample of full-scale engineered barrier experiment (FEBEX) bentonite. By accounting for the solute flux across the micromacro interface, the DCM overcomes the limitations of the single-continuum model (SCM) which fails to reproduce the long tails of the breakthrough curves of most chemical species of this test. The exponent n and the scaling factor were estimated from Cl − data. They are similar to those obtained from the 2-D synthetic case, thus indicating that the exponent and the scaling factor derived for the FEBEX bentonite could be used for other compacted bentonites.

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Section: Model Uncertaintiesmentioning

confidence: 87%

Section: Model Uncertaintiesmentioning

confidence: 99%

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Dual-continuum multicomponent reactive transport with nth-order solute transfer terms for structured porous media

Zheng

Samper

2015

Comput Geosci

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“…The model considers a steady state condition with constant influent flux. An aqueous phase effective diffusion coefficients, D* of 1×10 −9 m 2 /s was adopted (Bourg et al, 2007;García-Gutiérrez et al, 2004;Shackelford and Daniel, 1991a;1991b;Iversen and Jorgensen, 1993). The advective and diffusive equivalency was then investigated separately.…”

Section: Case 1: Qualitative Comparison Of Barriers Performancementioning

confidence: 99%

Hydraulic Flow through Engineering Bentonite-Based Containment Barriers

Loh¹,

Wijeyesekera²

2015

American Journal of Applied Sciences

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This paper presents the use of software modelling as a tool to study the impact of hydraulic "resistivity" on the contaminant transport through bentonite-based containment barriers. A sensitivity analysis on the predicted data was carried out by varying the boundary conditions as well as the hydraulic resistance to flow through varying contaminant transport parameters. Accordingly, both advective and diffusive flow processes are considered as that which resists the flow. In particular, the effect on the contaminant migration due to desiccation cracking is explored. Laboratory evidence is provided and discussed to show how the initial microstructure of the clay influences the development of subsequent macro structural features such as shrinkage crack patterns. The effect of these cracks and the intensity of cracking on the contaminant migration are modelled and pragmatically discussed. Additionally, the effect on the hydraulic conductivity of bentonite-based barriers, when permeated with non-standard liquids is discussed and a typical analytical output is presented.

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“…with regard to cationic, anionic and neutral species, in a given system). ) (Muurinen et al, 1986;Sato et al, 1992;Kozaki et al, 1996Kozaki et al, , 1998aChoi and Oscarson, 1996;Kozaki et al, 1999a;b, 2001, 2008Lee et al, 1996;Nakajima et al, 1997;Nakashima, 2000Nakashima, , 2002Nakashima, , 2003Nakashima, , 2006Molera, 2002;Molera and Eriksen, 2002;Molera et al, 2003;Sato and Suzuki, 2003;Van Loon et al, 2003a;b, 2004a;b, 2005a;b, 2007;Wang, 2003;Jansson and Eriksen, 2004;García-Gutiérrez et al, 2004;Sato and Miyamoto, 2004;Suzuki et al, 2004;García-Gutiérrez et al, 2009;Wang and Liu, 2004;Wang and Tao, 2004;Melkior et al, 2005Melkior et al, , 2007Melkior et al, , 2009Nakashima and Mitsumori, 2005;Wang et al, 2005;Appelo and Wersin, 2007;Glaus et al, 2011Glaus et al, , 2013Motellier et al, 2007;Glaus et al, 2007Glaus et al, , 2008Glaus et al, , 2010…”

Section: Introduction and Research Motivationmentioning

confidence: 99%

Laboratory Experiments on Bentonite Samples: FY15 Progress

Tinnacher¹,

Davis²

2015

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Diffusion coefficients and accessible porosity for HTO and 36Cl in compacted FEBEX bentonite

Cited by 79 publications

References 3 publications

Dual-continuum multicomponent reactive transport with nth-order solute transfer terms for structured porous media

Dual-continuum multicomponent reactive transport with nth-order solute transfer terms for structured porous media

Hydraulic Flow through Engineering Bentonite-Based Containment Barriers

Laboratory Experiments on Bentonite Samples: FY15 Progress

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