Diffusion of Radionuclides in Brine-Saturated Backfill Barrier Materials

Nowak, E. J.

doi:10.1557/proc-15-735

Cited by 5 publications

(3 citation statements)

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“…Because of their high sorption capacity for cationic transuranic Clements and fission products clay minerals have been proposed as backfill material for the storage of radioactive waste [1,2,3]. However, most of the clays investigated exhibited very little or no retention capability for radioiodine [4,5,6], which exists predominantly as iodide in the terrestrial environment [7,8].…”

Section: Introductionmentioning

confidence: 99%

Sorption of Radioiodine in Organo-Clays and -Soils

Bors¹

1990

Radiochimica Acta

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Organo-clay / Radioiodine / Alkylammonium ions / Sorption / Migration / Rp-valuewith quaternary alkylammonium ions was investigated. AbstractIn the framework of investigations on the Sorption of radioiodine to natural and artificially altered soll components, a number of clay minerals and natural soils wäre treated with quaternary alkylammonium ions to replace the exchangeable metal cations. With help of batch experiments the resulting organo-clays were tested with respect to their sorption capability of radioiodine quantified by the distribution ratio (i?D-value).Treatment of bentonite, vermiculite and cretaceous clay as well as of samples from natural horizons of chernozem soil with hexadecylpyridinium (HDPY^) and benzethonium (BE^) exhibited sorption rates and amounts, which are several Orders of magnitude higher than those of the respective untreated samples. Moderate increases of the i?D-values were found after cation exchange with hexadecyltrimethylammonium (HDTMA^), while the applications of trimethylphenylammonium (TMPA"^) and tetramethylammonium (TM A ) were ineffecti ve. Considerable sorption of radioiodine was observed with the commercially available Bentone®.

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Section: Introductionmentioning

confidence: 99%

Sorption of Radioiodine in Organo-Clays and -Soils

Bors¹

1990

Radiochimica Acta

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“…Experimental studies of transport rates through packing materials have also been performed (Nowak, 1981;Jahnke, 1987;Jahnke & Radke, 1987;Torstenfelt et al, 1981). Results from these studies show that some cationic species experience an enhanced rate of transport through bentonite.…”

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confidence: 99%

Caesium and strontium diffusion through sodium montmorillonite at elevated temperature

Jensen

Radke

1988

Journal of Soil Science

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Counter ionic migration rates of dilute Cs' and Sr2+ against sodium in a Namontmorillonite gel are measured using a radially perfused diffusion cell. Enhanced or surface diffusion for caesium is observed both at ambient and elevated temperature. To quantify these surface diffusivities the ion-exchange properties of the diffusing species are required. Thus, exchange isotherms for caesium against sodium on montmorillonite at 22 and 90°C are given for lo-', lo-', and M background NaCl concentrations. Caesium counterion surface diffusivities at 22 and 90°C are 2.2 x and 8.0 x cm2 s-', respectively. These values are found to be essentially independent of background ionic strength over the range to lo-' M NaCI. Experimental evidence of enhanced transport through Na-montmorillonite for the divalent cation Sr2+ is also confirmed with a surface diffusivity of 2 x cm2 s-' at 22°C and in lo-' M NaCl. D E F I N I T I O N O F S Y M B O L S =gel cross-sectional area, cm2 =tank concentration, M =initial tank concentration, M =total gel concentration, M =interstitial gel concentration, M =inlet concentration to the diffusion cell, M =outlet concentration from the diffusion cell, M =overall diffusion coefficient, (D,/r2) (1 +(I -E) KDJED,), cm2 s -l =effective diffusion coefficient, D / a , cm2 s-' =molecular diffusion coefficient, cm2 s-' =radially perfused cell overall mass transfer coefficient, cm s-' =dimensionless ion-exchange isotherm slope =absolute permeability, m2 =length of gel sample, cm =volumetric flowrate, cm3 s-' = Laplace space variable, s =time, s =time of experiment, s =fluid volume of external tank, cm3 =cell dead volume, cm3 =axial position inside gel, cm =dimensionless axial position in gel, x / L = sorption retardation coefficient, (1 + (1 -E)K/E) = 4~~a D A l V k~, =porosity =clay density, g cm-3 = tortuosity ' 53

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“…For Ac no literature value is available. D, values for Eu in bentonite have been reported to be 2.0 Χ 10" 15 -1.0 Χ 10" 13 m 2 · s" 1 by Albinsson et al [14] and Nowak [15]. The D a for Cm has been reported to be 2.0 X 10" 15 m 2 · s" 1 for a density of 2000 kg · m~3 [14].…”

Section: Diffusion Of Smmentioning

confidence: 94%

Diffusion Behaviour of Se(-II) and Sm(III) in Compacted Sodium Bentonite

Sato

1998

Radiochimica Acta

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Diffusion / Sodium bentonite / Selenium / Samarium / pH dependence / Reducing conditions SummaryApparent diffusion coefficients (DJ for Se(-II) and Sm(III) in a compacted sodium bentonite, Kunigel-Vl®, were obtained for a range of dry densities from 800-1800 kg · m '. The D, values for Se were obtained under reducing conditions and those for Sm were obtained over a pH range of 8-11. The D, values for Se were between 6.1 X 10"" and 4.3 Χ 10" 10 m 2 · s" 1 and showed a tendency to slightly decrease with increasing dry density of bentonite. The dominant Se species in the porewater is predicted to be HSe~, and the D, values were approximately the same as those for TcOä, which has the same charge. The D, values obtained for Sm were between 8.0 Χ 10" 15 and 1.0 X 10" 13 m 2 · s" 1 and decreased with increasing dry density of bentonite. The dominant species of Sm in the porewater are predicted to be SmCO.i and Sm(C0 3 )2 at pH8 and 11, respectively. However, all D, values for the same bentonite density were approximately the same and no influence of the porewater pH on diffusivity was found. The D. values for Sm were similar to those for Eu, Am and Cm in the same range of bentonite density. Therefore, it is concluded that these trivalent elements show similar diffusion behaviour.

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Diffusion of Radionuclides in Brine-Saturated Backfill Barrier Materials

Cited by 5 publications

References 5 publications

Sorption of Radioiodine in Organo-Clays and -Soils

Sorption of Radioiodine in Organo-Clays and -Soils

Caesium and strontium diffusion through sodium montmorillonite at elevated temperature

Diffusion Behaviour of Se(-II) and Sm(III) in Compacted Sodium Bentonite

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