Effect of sodium nitrate on the diffusion of Cl and I in compacted bentonite

Takamitsu Ishidera, Shinya Miyamotoy, Haruo Sato

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

For safety assessment of TRU waste disposal, the effective diffusion coefficients (D, e) for Cl and I in compacted bentonite (Kunigel V1) were determined as a function of NaNO3 concentration, ranging from 0.01 to 5 mol/dm3. The De values for Cl and I increased from approximately 10−12 to 10−11 m2/s with increasing NaNO3 concentration. The capacity factor α, indicative of the effective porosity, also increased with increasing NaNO3 concentration. The maximum α values of 0.21 for Cl and 0.24 for I at 5 mol/dm3 NaNO3 concentration were lower than the total porosity of compacted bentonite (0.40), suggesting an anion exclusion effect. Therefore, the increases in the De values were interpreted in terms of the decrease in anion exclusion. The De values for Cl and I, normalized by their diffusivities in bulk water, were found to increase in proportion to the α values in a log-log plot, while the De values in porous media generally increase in proportion to the total porosity. This relationship between the logDe and the log α is considered to be derived from the lower effective porosities for Cl and I than the total porosity in compacted bentonite due to anion exclusion.

Original languageEnglish
Pages (from-to)610-616
Number of pages7
JournalJournal of Nuclear Science and Technology
Volume45
Issue number7
DOIs
Publication statusPublished - 2008
Externally publishedYes

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Keywords

  • Anion exclusion
  • Capacity factor
  • Chloride
  • Compacted bentonite
  • Diffusion
  • Iodide
  • Sodium nitrate
  • TRU waste

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Nuclear Energy and Engineering

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