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Distribution Coefficients and Apparent Diffusion Coefficients of Cesium in Compacted Bentonites

Published online by Cambridge University Press:  10 February 2011

Akiko Okamoto ,
Kazuya Idemitsu ,
Hirotaka Furuya ,
Yaohiro Inagaki  and
Tatsumi Arima
Akiko Okamoto
Affiliation:
Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Japan
Kazuya Idemitsu
Affiliation:
Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Japan
Hirotaka Furuya
Affiliation:
Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Japan
Yaohiro Inagaki
Affiliation:
Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Japan
Tatsumi Arima
Affiliation:
Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Japan
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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.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 556: Symposium QQ – Scientific Basis for Nuclear Waste Management XXII , 1999 , 1091
Copyright
Copyright © Materials Research Society 1999

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References

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