Distribution coefficients and apparent diffusion coefficients of cesium in compacted bentonites

Akiko Okamoto, Kazuya Idemitsu, Hirotaka Furuya, Yaohiro Inagaki, Tatsumi Arima

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Abstract

Distribution coefficients and apparent diffusion coefficients of cesium in some compacted bentonites were determined by the penetration profile method. Cylindrical compacted bentonites with the dry density of 0.8 to 1.6 Mg/m3 were contacted with tracer solutions containing 1000, 100 or 10 ppm of cesium. The apparent diffusion coefficients were obtained from the concentration profiles of cesium in compacted bentonites. The distribution coefficients were obtained concurrently by dividing the intercepts of the profiles by the concentration of the tracer solution. The apparent diffusion coefficients of cesium in compacted bentonite were obtained in the range of 0.42 to 9.6·10-12 m2/s. The apparent diffusion coefficients in the compacted bentonite contacted with three different concentrations of cesium tended to decrease with increasing dry density of the specimen; but, they had no dependence on cesium concentration within a factor of 3 at the same dry density. The distribution coefficient of cesium for the specimens contacted with three different concentrations of cesium were obtained in the range of 0.3 to 90 L/kg and had little dependence on dry density. The distribution coefficients obtained in the compacted bentonites were dependent on pH of the solution rather than concentration of cesium. These distribution coefficients obtained in the compacted bentonites were 10 to 1000 times smaller than those obtained by batch experiments. The data suggest that not all sorption sites for cesium are available in highly compacted bentonite. It is necessary to consider surface diffusion as a significant migration mechanism of cesium through the compacted bentonites at very high pH condition such as 12.

Original languageEnglish
Pages (from-to)1091-1098
Number of pages8
JournalMaterials Research Society Symposium - Proceedings
Volume556
Publication statusPublished - Dec 1 1999
EventProceedings of the 1998 MRS Fall Meeting - Symposium 'Scientific Basis for Nuclear Waste Management XXII' - Boston, MA, USA
Duration: Nov 30 1998Dec 4 1998

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All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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