Diffusion of technetium in dense bentonite

Sawatsky, N.; Oscarson, D. W.

doi:10.1007/bf00282908

Cited by 11 publications

(7 citation statements)

References 7 publications

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“…An exponential reduction in apparent diffusion coefficient with the effective dry density was observed, which is similar to the conclusion of Sawatsky and Oscarson (1991). The reduction in D a with increasing effective dry density was mainly attributed to an increase in the tortuosity as the effective dry density increased (Yu and Neretnieks 1997).…”

Section: Eu(iii) Concentration Profilessupporting

confidence: 71%

“…Increasing clay content in per unit-volume of the mixtures tends to enhance the adsorption ability of bentonite-sand mixtures, and decline the diffusion coefficient. Moreover, the reduction in D a with increasing in effective dry density was largely ascribed to an increase in the anion exclusion volume in the bentonite with increasing effective dry density, which likely decreases the effective size of the pores and so to influence the tortuosity or geometric factor (Sawatsky and Oscarson 1991). …”

Section: Eu(iii) Concentration Profilesmentioning

confidence: 99%

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Permeability and Migration of Eu(III) in Compacted GMZ Bentonite-Sand Mixtures as HLW Buffer/Backfill Material

Yan

Zhou

Chen

2014

Engineering Geology for Society and Territory - Volume 6

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Compacted GMZ bentonite-sand mixtures are studied as a feasible buffer/backfill material for high-level radioactive waste (HLW) disposal in China. This paper is concentrated on the hydraulic conductivity and the migration of Eu(III) in the compacted mixtures of Gaomiaozi bentonite added with quartz sand with various ratio from 0 to 50 %. Permeability tests were conducted using a flexible wall permeameter with the influent of distilled water and 2.0 × 10 −5 mol/l Eu(III) solution,respectively. Test results indicated that the hydraulic conductivities measured varied about 10 −10 cm/s, and no significant change was found with sand ratio increasing from 0 to 50 %. The migration of Eu(III) through compacted specimen was studied by effluent monitoring and Eu(III) extraction from specimen sections after permeability test. The apparent diffusion coefficients of Eu (III) estimated by Eu(III) concentration profile in the specimens varied at the level 10 −14 m 2 /s, when the compacted mixtures had a sand ratio ranging from 0 to 50 %.

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Section: Eu(iii) Concentration Profilessupporting

confidence: 71%

Section: Eu(iii) Concentration Profilesmentioning

confidence: 99%

Permeability and Migration of Eu(III) in Compacted GMZ Bentonite-Sand Mixtures as HLW Buffer/Backfill Material

Yan

Zhou

Chen

2014

Engineering Geology for Society and Territory - Volume 6

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“…6a for a stroke volume of 1.5 mL/s. The MRI measurements of 43 (cm/s)ũ ðtÞ ¼ P N n¼1 a n cos n xt þ b n sin n xt ð Þ * Flow outlet p exit ¼ 0; @ũ @n ¼ 0 Wall u ¼ 0; @p @n ¼ 0 Bolus infusion 35 the CSF flow in the spinal canal suggest that the CSF stroke volume could vary in the range of 0.1-2.5 mL/s in humans. 10 Figure 6b shows the effect of different pulsatile stroke volumes (0.5, 1.0, and 1.5 mL/s) on the speed of dye dispersion while keeping the pulse frequency at 1 Hz.…”

Section: Effect Of Oscillation Frequency and Stroke Volume On The Drumentioning

confidence: 99%

The Effect of Pulsatile Flow on Intrathecal Drug Delivery in the Spinal Canal

et al. 2011

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Clinical studies have shown that drugs delivered intrathecally distribute much faster than can be accounted for by pure molecular diffusion. However, drug transport inside the cerebrospinal fluid (CSF)-filled spinal canal is poorly understood. In this study, comprehensive experimental and computational studies were conducted to quantify the effect of pulsatile CSF flow on the accelerated drug dispersion in the spinal canal. Infusion tests with a radionucleotide and fluorescent dye under stagnant and pulsatile flow conditions were conducted inside an experimental surrogate model of the human spinal canal. The tracer distributions were quantified optically and by single photon emission computed tomography (SPECT). The experimental results show that CSF flow oscillations substantially enhance fluorescent dye and radionucleotide dispersion in the spinal canal experiment. The experimental observations were interpreted by rigorous computer simulations. To demonstrate the clinical significance, the dispersion of intrathecally infused baclofen, an anti-spasticity drug, was predicted by using patient-specific spinal data and CSF flow measurements. The computational predictions are expected to enable the rational design of intrathecal drug therapies.

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“…This resulted in the ion distribution coefficient increased thus the diffusion coefficient decreased (Muurinen and Lehikoinen 1995). (2) Elevated dry density decreases the effective porosity of the bentonite which results in a decrease in diffusion coefficient (Sawatsky and Oscarson 1991). (3) Changes of dry density affects the layer spacing.…”

Section: Effect Of Dry Density On the Diffusionmentioning

confidence: 99%

Diffusion of La3+ in Compacted GMZ Bentonite Used as Buffer Material in HLW Disposal

Chen

Niu

et al. 2014

Engineering Geology for Society and Territory - Volume 6

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It has been studied that the GMZ bentonite which has a chemical barrier property can play an important role in retarding the migration of radioactive nuclide. In order to understand the diffusion properties of nuclide in GMZ bentonite, a series of experiments were conducted to obtain the apparent diffusion coefficient of La 3+ in GMZ bentonite under different dry density and pH value conditions using a autonomous ion diffusion instrument. The results show that the apparent diffusion coefficient of La 3+ decreases significantly with the increasing dry density or pH value. The influence of dry density on the diffusion is very apparent for a low dry density, and the influence gradually slow down with the increase of dry density. At last the influence mechanism of the dry density and pH value on diffusion coefficient was also analyzed. KeywordsGMZ bentonite Á Diffusion property Á Lanthanum ion IntroductionThe deep geological disposal which based on a multi-barrier system is the most appropriate means for safe disposal of high-level radioactive waste (HLW). Bentonite has been chosen as the buffer/backfill material for this disposal because of good mechanical buffer resistance, low permeability, better swelling property and adsorption property (Wen 2006).The chemical barrier properties of bentonite are mainly manifested in retarding the migration of radioactive nuclide. Considering most of the nuclide uranium, thorium, plutonium in disposal repository are actinide elements, and lanthanide and actinide elements have similar electronic configuration inside and outside layer which determine their similar physical and chemical properties. Therefore the lanthanide ions are always selected instead of radionuclide in the study. In this work, effects of the dry density and pH value on the diffusion property of La 3+ in GMZ bentonite were studied. Experimental MaterialsThe GMZ bentonite derived from inner mongolia China was used in this experiment. Its major mineral is (Wang and Su 2006): montmorillonite 75.4 %, quartz 11.7 %, crystaballite 7 %, feldspar 4.3 %, calcite 0.5 %, kaolinite 0.8 %. It has been studied that GMZ bentonite has strong cation exchange capacity, hydration ability and strong adsorption ability.

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Diffusion of technetium in dense bentonite

Cited by 11 publications

References 7 publications

Permeability and Migration of Eu(III) in Compacted GMZ Bentonite-Sand Mixtures as HLW Buffer/Backfill Material

Permeability and Migration of Eu(III) in Compacted GMZ Bentonite-Sand Mixtures as HLW Buffer/Backfill Material

The Effect of Pulsatile Flow on Intrathecal Drug Delivery in the Spinal Canal

Diffusion of La3+ in Compacted GMZ Bentonite Used as Buffer Material in HLW Disposal

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