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Effect of sodium nitrate on the diffusion of Cl$$^{-}$$ and I$$^{-}$$ in compacted bentonite

Ishidera, Takamitsu ; Miyamoto, Shinya*; Sato, Haruo

For safety assessment of TRU waste disposal, the effective diffusion coefficients ($$D$$$$_{e}$$) for CO$$_{3}$$$$^{2-}$$, Cl$$^{-}$$ and I$$^{-}$$ ions in compacted bentonite (Kunigel V1) were determined as a function of NaNO$$_{3}$$ concentrations from 0.01 to 5 mol/dm$$^{3}$$. The $$D$$$$_{e}$$ values increased from 10$$^{-12}$$ to 10$$^{-11}$$ m$$^{2}$$/s with increasing NaNO$$_{3}$$ concentration. The rock capacity factor $$alpha$$, indicative of the effective porosity, were also increased with increasing NaNO$$_{3}$$ concentration. The maximum $$alpha$$ values of 0.21 for Cl$$^{-}$$ ion and of 0.25 for I$$^{-}$$ ion at 5 mol/dm$$^{3}$$ NaNO$$_{3}$$ concentration were lower than the net porosity of compacted bentonite (0.40). Therefore, the increases in the $$D$$$$_{e}$$ values were interpreted by the decrease of anion exclusion effect. The $$D$$$$_{e}$$ values for Cl$$^{-}$$ and I$$^{-}$$ ions normalized by the diffusivities for diffusants in the bulk water were found to increase in proportion to the $$alpha$$ values on the log-log diagram. The maximum $$alpha$$ value for CO$$_{3}$$$$^{2-}$$ ion was higher than the net porosity. The high concentration of CO$$_{3}$$$$^{2-}$$ ion was also found in the concentration profile in compacted bentonite. This retention of CO$$_{3}$$$$^{2-}$$ ion was possibly accounted for by isotopic exchange of $$^{14}$$C with inactive carbon of calcite in Kunigel V1.

Language

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English

Journal

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Journal of Nuclear Science and Technology

Volume

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45

Number

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7

Pages

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p.610 - 616

Publication Year/Month

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2008/07

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Held date

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Location (city)

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Location (country)

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Patent information

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PDF

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Paper URL

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https://doi.org/10.3327/jnst.45.610

DOI for research data

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Keywords

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no keyword

Research Facility

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QUALITY(地層処分放射化学研究施設)  

Press Release

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Article of JAEA R&D Review

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Cooperating Institute

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Accesses

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- Accesses

InCites™

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Percentile:59.16

Category:Nuclear Science & Technology

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