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Effect of Carbonate on the Migration Behavior of Lanthanides in Compacted Bentonite

Published online by Cambridge University Press:  13 February 2018

Kazuya Idemitsu ,
Kazuyuki Fujii ,
Noriyuki Maeda ,
Yuki Kakoi ,
Noriya Okubo ,
Yaohiro Inagaki  and
Tatsumi Arima
Kazuya Idemitsu*
Affiliation:
Dept. of Applied Quantum Physics and Nuclear Engineering, Kyushu Univ., 744 Motooka, Nishi-ku, Fukuoka, Japan
Kazuyuki Fujii
Affiliation:
Dept. of Applied Quantum Physics and Nuclear Engineering, Kyushu Univ., 744 Motooka, Nishi-ku, Fukuoka, Japan
Noriyuki Maeda
Affiliation:
Dept. of Applied Quantum Physics and Nuclear Engineering, Kyushu Univ., 744 Motooka, Nishi-ku, Fukuoka, Japan
Yuki Kakoi
Affiliation:
Dept. of Applied Quantum Physics and Nuclear Engineering, Kyushu Univ., 744 Motooka, Nishi-ku, Fukuoka, Japan
Noriya Okubo
Affiliation:
Dept. of Applied Quantum Physics and Nuclear Engineering, Kyushu Univ., 744 Motooka, Nishi-ku, Fukuoka, Japan
Yaohiro Inagaki
Affiliation:
Dept. of Applied Quantum Physics and Nuclear Engineering, Kyushu Univ., 744 Motooka, Nishi-ku, Fukuoka, Japan
Tatsumi Arima
Affiliation:
Dept. of Applied Quantum Physics and Nuclear Engineering, Kyushu Univ., 744 Motooka, Nishi-ku, Fukuoka, Japan
*
*(Email: [email protected])
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Abstract

The apparent diffusion coefficients of La, Nd, Eu, Dy, Er, and Lu in compacted bentonites were investigated at various bicarbonate concentrations. The apparent diffusion coefficients of these lanthanides tended to decrease with increasing dry density. At bicarbonate concentrations below 0.25 M, lanthanum had the largest diffusion coefficient (ca. 10-13 m2/s) at 1.0 Mg/m3, and the diffusion coefficient decreased with increasing atomic number. On the other hand, at bicarbonate concentrations above 0.25 M, lutetium had the largest diffusion coefficient, and the diffusion coefficient decreased with decreasing atomic number. In particular, lanthanum and neodymium had diffusion coefficients below 10-14 m2/s, even at 1.0 Mg/m3. The diffusion coefficient of europium was around 10-13 m2/s at 1.0 Mg/m3 and was influenced less by the bicarbonate concentration. The diffusion coefficient of lutetium increased from 2 × 10-14 to 10-12 m2/s as the bicarbonate concentration was increased to 1.0 M. The concentration of carbonate ion in the pore water of bentonite is estimated to be much lower than that in solutions in contact with bentonite from the viewpoints of solubility and chemical species of lanthanides.

Keywords

diffusionLanthanidesolution deposition
Type
Articles
Information
MRS Advances , Volume 3 , Issue 21: Scientific Basis for Nuclear Waste Management XLI , 2018 , pp. 1155 - 1160
Copyright
Copyright © Materials Research Society 2018 

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References

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