Sorption effects on cation diffusion in compacted bentonite

Eriksen, Trygve E.; Jansson, Mats; Molera, Mireia

doi:10.1016/s0013-7952(99)00078-2

Cited by 54 publications

(38 citation statements)

References 4 publications

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“…[ ] Furthermore, in order to obtain the apparent diffusivity values and the implicit Kd values from the experimental concentration profiles in the clay plugs as well as from the breakthrough data (Cs + only) while at the same time taking the diffusive resistance of the end filters into account, a finite-difference code called ANADIFF was used, see (Eriksen et al, 1999) for details. The water content of all the SwyNaw and MX80 samples as controlled gravimetrically after termination of the in-diffusion experiment was 1.39±0.05 and 1.64±0.04 g/cm 3 , respectively.…”

Section: Diffusion Resultsmentioning

confidence: 99%

“…The rationale for using bentonite is its dense microstructure and swelling capacity in compacted form, rendering diffusion as the only way of transport from or to the canister holding the nuclear waste, as well as the high sorption capacity for many radionuclides. Previous studies have shown that the diffusive transport of radionuclides in water saturated compacted bentonite under ambient conditions is governed by several different parameters, such as compaction, smectite content, ionic strength and the specific interactions between the diffusants and montmorillonite, the main component of bentonite (Eriksen et al, 1999;Kozaki et al, 1998;2001;Molera and Eriksen, 2002;Van Loon et al, 2007). Under repository conditions however, the bentonite barrier will inevitably be exposed to ionizing radiation (mainly γ from Cs-137) under anoxic conditions.…”

Section: Introductionmentioning

confidence: 99%

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Effect of γ-radiation on radionuclide retention in compacted bentonite

Holmboe

Norrfors

Jönsson

et al. 2011

Radiation Physics and Chemistry

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Compacted bentonite is proposed as an engineered barrier in many concepts for disposal of high level nuclear waste. After the initial deposition however, the bentonite barrier will inevitably be exposed to ionizing radiation (mainly γ) under anoxic conditions. Because of this, the effects of γ-radiation on the apparent diffusivity values and sorption coefficients in bentonite for Cs + and Co 2+ were tested under different experimental conditions. Radiation induced effects on sorption were in general more noticeable for Co 2+ than for Cs + , which generally showed no significant differences between irradiated and unirradiated clay samples. For Co 2+ however, the sorption to irradiated MX80 was significantly lower than to the unirradiated clay samples regardless of the experimental conditions. This implies that γ-radiation may alter the surface characteristics contributing to surface complexation of Co 2+ . With the experimental conditions used however, the effect of decreasing sorption was not large enough to be reflected on the obtained Da values.

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Section: Diffusion Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of γ-radiation on radionuclide retention in compacted bentonite

Holmboe

Norrfors

Jönsson

et al. 2011

Radiation Physics and Chemistry

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“…Various studies have been carried out to examine different aspects of the sorption behavior of Sr on a variety of solid materials [2][3][4][5][6][7][8][9][10][11][12][13]. Whereas the sorption behavior of Sr 2+ on kaolinite was investigated in a limited number of studies [14][15][16][17], our literature survey did not yield information *Author for correspondence (E-mail: talalshahwan@iyte.edu.tr).…”

Section: Introductionmentioning

confidence: 99%

Characterization of Sr²⁺uptake on natural minerals of kaolinite and magnesite using XRPD, SEM/EDS, XPS, and DRIFT

Shahwan¹,

Erten²

2005

Radiochimica Acta

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Sr2+ / Kaolinite / Magnesite Summary. The sorption behavior of Sr 2+ ions on natural minerals rich in kaolinite and magnesite was studied using SEM/EDS, XPS, XRPD, AAS/AES and DRIFT techniques. Quantitative analysis of the XPS data shows that magnesite is more effective in Sr 2+ uptake than kaolinite. DRIFT spectra and XRPD patterns indicate that the structures of both minerals were not affected upon Sr 2+ sorption. Intercalation of DMSO in kaolinite lamellae aiming at increasing the interlayer space did not significantly enhance the sorption capacity of the clay towards Sr 2+ probably due to the lack of a negative charge on the accessible sites. EDS mapping indicated that while the sorbed Sr is equally distributed on surface of natural kaolinite, it was associated -to a larger extent -with the regions richer in Mg in the case of natural magnesite. Comparing the uptake mechanisms of natural magnesite with that of pure MgCO 3 , it was seen that while natural magnesite sorbed Sr 2+ mainly through an ion exchange type mechanism, the formation of SrCO 3 coprecipitate was detected on the surface of the MgCO 3 at higher loadings.

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“…Compacted bentonite has been proposed as backfill material in many of the European repositories, because of its very low permeability (Kim et al, 1993;Muurinen, 1994;Pusch, 2001;Molera and Eriksen, 2002;Bourg et al, 2003) and its strong sorptive properties (Eriksen et al, 1999;Ochs et al, 2001), both of which will limit the release of radionuclides. The low permeability of bentonite is largely due to the fact that it contains a high percentage of Namontmorillonite, a clay that swells in water.…”

Section: Reactive-diffusive Transport In the Ebsmentioning

confidence: 99%

Disposal systems evaluations and tool development : Engineered Barrier System (EBS) evaluation.

Rutqvist¹,

Liu²,

Steefel³

et al. 2011

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Eric Sonnenthal (LBNL) Engineered Barrier System (EBS) Evaluation This page is intentionally left blank Engineered Barrier System (EBS) Evaluation 5 Executive SummaryKey components of the nuclear fuel cycle are short-term storage and long-term disposal of nuclear waste. The latter encompasses the immobilization of used nuclear fuel (UNF) and radioactive waste streams generated by various phases of the nuclear fuel cycle, and the safe and permanent disposition of these waste forms in geological repository environments. The engineered barrier system (EBS) plays a very important role in the long-term isolation of nuclear waste in geological repository environments. EBS concepts and their interactions with the natural barrier are inherently important to the long-term performance assessment of the safety case where nuclear waste disposition needs to be evaluated for time periods of up to one million years. Making the safety case needed in the decision-making process for the recommendation and the eventual embracement of a disposal system concept requires a multi-faceted integration of knowledge and evidence-gathering to demonstrate the required confidence level in a deep geological disposal site and to evaluate longterm repository performance.The focus of this report is the following:• Evaluation of EBS in long-term disposal systems in deep geologic environments with emphasis on the multi-barrier concept;• Evaluation of key parameters in the characterization of EBS performance;• Identification of key knowledge gaps and uncertainties;• Evaluation of tools and modeling approaches for EBS processes and performance.The above topics will be evaluated through the analysis of the following:• Overview of EBS concepts for various NW disposal systems;• Natural and man-made analogs, room chemistry, hydrochemistry of deep subsurface environments, and EBS material stability in near-field environments;• Reactive Transport and Coupled Thermal-Hydrological-Mechanical-Chemical (THMC) processes in EBS;• Thermal analysis toolkit, metallic barrier degradation mode survey, and development of a Disposal Systems Evaluation Framework (DSEF).This report will focus on the multi-barrier concept of EBS and variants of this type which in essence is the most adopted concept by various repository programs. Empasis is given mainly to the evaluation of EBS materials and processes through the analysis of published studies in the scientific literature of past and existing repository research programs. Tool evaluations are also emphasized, particularly on THCM processes and chemical equilibria. Although being an increasingly important aspect of NW disposition, short-term or interim storage of NW will be briefly discussed but not to the extent of the EBS issues relevant to disposal systems in deep geologic environments. Interim storage will be discussed in the report Evaluation of Storage Concepts FY10 Final Report (Weiner et al. 2010). Engineered Barrier System (EBS) Evaluation 6This page is intentionally left blank Engineered Barrier System (EBS) Eva...

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Sorption effects on cation diffusion in compacted bentonite

Cited by 54 publications

References 4 publications

Effect of γ-radiation on radionuclide retention in compacted bentonite

Effect of γ-radiation on radionuclide retention in compacted bentonite

Characterization of Sr²⁺uptake on natural minerals of kaolinite and magnesite using XRPD, SEM/EDS, XPS, and DRIFT

Disposal systems evaluations and tool development : Engineered Barrier System (EBS) evaluation.

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Sorption effects on cation diffusion in compacted bentonite

Cited by 54 publications

References 4 publications

Effect of γ-radiation on radionuclide retention in compacted bentonite

Effect of γ-radiation on radionuclide retention in compacted bentonite

Characterization of Sr2+uptake on natural minerals of kaolinite and magnesite using XRPD, SEM/EDS, XPS, and DRIFT

Disposal systems evaluations and tool development : Engineered Barrier System (EBS) evaluation.

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Characterization of Sr²⁺uptake on natural minerals of kaolinite and magnesite using XRPD, SEM/EDS, XPS, and DRIFT