Diffusion behaviour of selenite and hydroselenide in compacted bentonite

Sato, Haruo; Miyamoto, Shinya

doi:10.1016/j.clay.2003.10.007

Cited by 32 publications

(15 citation statements)

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“…As evidenced below, this simplicity is instrumental in identifying the key trends associated with water and ion diffusion in clay materials. The diffusion of more complex or less extensively studied species such as oxyanions (Aertsens et al, 2003;Jansson and Eriksen, 2004;Sato and Miyamoto, 2004), actinides Joseph et al, 2013), lanthanides , trace metals (Lange et al, 2009), dissolved gases (Higashihara et al, 2004(Higashihara et al, , 2005, and organic molecules (Chapman and Parker, 2005;Martens et al, 2010) is not addressed here despite its interest in a range of areas. Diffusion in unsaturated conditionsdan important phenomenon in soils (Calvet, 1973;Nye, 1979) and, potentially, in HLRW repositories in certain conditions (Savoye et al, 2010)dis not discussed.…”

Section: Introductionmentioning

confidence: 98%

Self-Diffusion of Water and Ions in Clay Barriers

Bourg

Tournassat

2015

Developments in Clay Science

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Section: Introductionmentioning

confidence: 98%

Self-Diffusion of Water and Ions in Clay Barriers

Bourg

Tournassat

2015

Developments in Clay Science

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“…; [5][6][7][8] where selenite and selenate species are dominant, data obtained under reducing conditions are limited. 9,10) In particular, D e data for Se(-II) species are scarce.…”

Section: Introductionmentioning

confidence: 99%

Experimental and Modeling Study on Diffusion of Selenium under Variable Bentonite Content and Porewater Salinity

Iida

Yamaguchi

Tanaka

2011

Journal of Nuclear Science and Technology

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Effective diffusion coefficients of selenium through bentonite/sand mixtures were obtained by the through-diffusion method under reducing conditions where selenium was dissolved as HSe À and Se 4 2À . Experiments were carried out under variable bentonite content and porewater salinity. Bentonite contents in bentonite/sand mixtures varied from 20 to 70 wt%. The salinities of experimental solutions varied from 0.05 to 0.5 mol dm À3 , simulating brackish groundwater and seawater. Effective diffusion coefficients were also obtained under anaerobic conditions where the dominant selenium species was determined to be SeO 3 2À . The effective diffusion coefficients of selenium species decreased with increasing bentonite content and with decreasing salinity. This tendency is primarily due to anion exclusion that was caused by the negative surface charge of montmorillonite. A diffusion model for anionic species was developed based on the electric double layer theory and the pore diffusion model, to evaluate the diffusion behaviors of HSe À , Se 4 2À , and SeO 3 2À in bentonite porewater. In this model, pores in bentonite/sand mixtures are assumed to consist of two types of space; one is the space between mineral particles and the other is the space between layers of montmorillonite. The scope of application of this model is limited to less than or equal to 1,600 kg m À3 in dry density. The effective diffusion coefficients of selenium species predicted using this model showed good agreement with experimentally measured ones.

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“…While Se(re) 89) , U(re) 72) and Fe(re) 60) mean that those experiments were carried out under reducing conditions. For Se, also the apparent diffusion coefficients of 10 −12 m 2 /s order which is about one order of magnitude lower than plotted values have been reported under reducing conditions 35) , and its retardation is possible to be higher. …”

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confidence: 70%

Function for Controlling Nuclide Migration of Buffer Material in the Geological Disposal for High-Level Radioactive Waste

Sato

2009

Journal of the Mining and Materials Processing Institute of Jap

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Among the properties for controlling radionuclide migration of bentonite, used as a buffer material composing engineered barriers for the geological disposal of high-level radioactive waste, studies on the water penetration, swelling, chemical buffering and nuclide migration retardation properties were reviewed. For water penetration properties, the effects of bentonite dry density, silica sand mixture, temperature and salinity are approximately clear, and a model, applicable for various dry densities, silica sand contents and montmorillonite contents also has been developed. For swelling properties, the effects of bentonite dry density, silica sand mixture, salinity, interlayer cation, montmorillonite content and saturation degree are approximately clear, and a thermodynamic model, applicable for various dry densities, silica sand contents, salinities and montmorillonite contents has been developed. For chemical buffering properties, although data acquisition by a batch method and studies to directly measure pH and chemical component of the porewater of compacted bentonite have been conducted, data acquisition in compacted system and geochemical analysis have just started. Finding accumulation and data acquisition for various conditions such as high pH and saline groundwater are still needed. For nuclide migration retardation properties, the effects of bentonite dry density, salinity, silica sand mixture, montmorillonite content, particle size, interlayer cation, the charge of diffusion species and temperature on diffusion have been comprehensively studied. Data on the effect of interlayer cation on diffusion coefficient and activation energy and data on diffusion coefficient and activation energy for effective diffusion coefficient are however still insufficient. Inconsistency between batch sorption and retardation in diffusion should be additionally considered together with data setting method for safety assessment analysis.After the year 2000, studies for saline groundwater conditions have been powerfully conducted, and it is understood that saline groundwater conditions affect all properties described above. Continuing these studies, studies on the long-term behaviour considered the effect of alteration are necessary.

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Diffusion behaviour of selenite and hydroselenide in compacted bentonite

Cited by 32 publications

References 4 publications

Self-Diffusion of Water and Ions in Clay Barriers

Self-Diffusion of Water and Ions in Clay Barriers

Experimental and Modeling Study on Diffusion of Selenium under Variable Bentonite Content and Porewater Salinity

Function for Controlling Nuclide Migration of Buffer Material in the Geological Disposal for High-Level Radioactive Waste

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