Diffusion of HTO, 36Cl− and 125I− in Opalinus Clay samples from Mont Terri

Loon, Luc R. Van; Soler, Josep M.; Bradbury, Michael E.

doi:10.1016/s0169-7722(02)00114-6

Cited by 177 publications

(89 citation statements)

References 2 publications

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“…[37] It has been widely accepted in literature that the use of the time axis intercept in the TL solution (equation (5)) does not provide a reliable estimate of the effective porosity because the intercept is very sensitive to slight changes in the slope of the best fit line to the experimental data [Grathwohl, 1998;Van Loon et al, 2003a;Appelo and Wersin, 2007;Motellier et al, 2007]. This discrepancy can be seen in Table 2, where the effective porosities derived by this method vary substantially from both the bulk porosities and the effective porosities derived by the SA method.…”

Section: Discussionmentioning

confidence: 99%

Comparison of modeling methods for the determination of effective porosities and diffusion coefficients in through‐diffusion tests

Benning

Barnes

2009

Water Resources Research

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[1] Diffusion coefficients and effective, or transport, porosities are important parameters in the assessment of the fate and transport of contaminants in fractured rock systems and when contaminant transport needs to be considered in zones of low to negligible advective flows. This study presents and discusses various solutions, analytical and semianalytical, to Fick's law for the typical through-diffusion experiment and applies these solutions to the results of three through-diffusion experimental data sets. These through-diffusion experiments were conducted on two natural breccia samples, with bulk measured porosities of approximately 13.7% and 16.8%, and one manufactured porous plate sample with a bulk measured porosity of 40.9%, such that the samples displayed order of magnitude differences in their diffusivities. For each experiment, the derived effective porosities and intrinsic diffusion coefficients for each method are compared. It was shown that the semianalytical solution provides an improved method for reliably estimating the effective porosity from through-diffusion experimental data; however, there is little difference between methods in the derived intrinsic diffusion coefficients.

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Section: Discussionmentioning

confidence: 99%

Comparison of modeling methods for the determination of effective porosities and diffusion coefficients in through‐diffusion tests

Benning

Barnes

2009

Water Resources Research

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“…Sorption isotherms were either obtained at constant element concentration and varying solid-to-liquid ratio ( / ratio) of 2-20 g/L (Th(IV), Pu(III/IV/VI), Am(III)) or varying actinide concentration at constant / ratio (15 g/L) (U(VI) and Np(V)). All OPA suspensions were prepared in synthetic OPA pore water (pH ≈ 7.6, ≈ 0.4 M) [6] were contacted with the clay by shaking for 60 h. During this time, the pH of the solutions was checked twice, and, if necessary, readjusted. After the contact time, the solid and liquid phases were separated by centrifugation at 81 000 for one hour (Avanti J-30I Beckman Coulter, USA).…”

Section: Batch Experiments/sorption Isothermsmentioning

confidence: 99%

“…The clay used origi-nates from the rock laboratory Mont Terri (Switzerland). The distribution coefficients are determined from sorption isotherms using synthetic Opalinus Clay pore water (pH ≈ 7.6, ≈ 0.4 M) [6] as background electrolyte. In addition, the present work is part of an extensive study with the aim to combine macroscopic studies (batch experiments) with spectroscopic investigations to obtain molecular-level information on the sorption mechanisms, to define source terms, and to understand transport and retardation processes in a deep geological repository with clay formations as host rocks.…”

Section: Introductionmentioning

confidence: 99%

Distribution coefficients for the sorption of Th, U, Np, Pu, and Am on Opalinus Clay

Amayri

Fröhlich²,

Kaplan³

et al. 2015

Radiochimica Acta

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“…This controversy is linked (i) to the very low measured distribution coefficient (Kd) values, the uncertainty of which can be higher than the value itself, and (ii) to the potential mechanism(s) of I -sorption, if they exist. In order to avoid the first problematic point on Kd error bands, numerous studies have been devoted to the acquisition of the I -retardation factor in transport experiments (through-diffusion, outdiffusion, column experiments, (Van Loon et al, 2003;Descostes et al, 2008) where error bands are very low compared to batch sorption experiments (Bazer-Bachi et al, 2006). Until recently, these transport experiments conducted on different clay formation samples have systematically shown a low but significant retardation factor for iodide transport in comparison to the Cl -conservative tracer, thereby confirming a priori the effectiveness of a retention mechanism.…”

Section: Underground Nuclear Waste Disposal In Clayey Formations Is Umentioning

confidence: 99%

Natural iodine in a clay formation: Implications for iodine fate in geological disposals

Claret

Lerouge

Laurioux

et al. 2010

Geochimica et Cosmochimica Acta

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Iodine is one of the most problematic radioisotopes in the context of nuclear waste geological disposal due to its high mobility. Considerable effort has been dedicated to the measurement of its potential retardation during diffusive transport leading to conflicting results, from no retardation to significant retardation, leading in turn to considerable debate. The present study aims at providing new insights into this aspect of the iodine problem by careful quantification of iodine reservoirs in the Callovian-Oxfordian (COx) clay rock taken here as model material for these studies. The present study confirmed the ubiquitous presence of iodine at 1-5 mg kg -1 level in the COx clayey formation. The iodide concentration level in the porewater is also confirmed at a value in the range ~20-40 µmol L -1 , i.e. higher than the expected range of radio-iodine concentration in the far-field of the storage. Surprisingly, most of the iodine was found not to be associated with organic matter but rather in an inorganic form associated with carbonate minerals. This result has potentially significant implications for the fate of radio-iodine. In undisturbed far-field conditions, most natural iodine would not be accessible for isotopic exchange with radioactive iodine, reducing the effective Kd to negligible values. During laboratory experiments, good monitoring of the geochemical parameters (at least the Eh, pH, P CO2 , [Ca] and [Mg]) is mandatory to avoid iodine-bearing carbonate precipitation and to enable rigorous interpretation of the iodide diffusion/retention experiments.2

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Diffusion of HTO, 36Cl− and 125I− in Opalinus Clay samples from Mont Terri

Cited by 177 publications

References 2 publications

Comparison of modeling methods for the determination of effective porosities and diffusion coefficients in through‐diffusion tests

Comparison of modeling methods for the determination of effective porosities and diffusion coefficients in through‐diffusion tests

Distribution coefficients for the sorption of Th, U, Np, Pu, and Am on Opalinus Clay

Natural iodine in a clay formation: Implications for iodine fate in geological disposals

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