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Diffusion of Plutonium in Compacted Bentonites in the Reducing Condition With Corrosion Products of Iron

Published online by Cambridge University Press:  10 February 2011

K. Idemitsu ,
X. Xia ,
T. Ichishima ,
H. Furuya ,
Y Inagaki ,
T. Arima ,
T. Mitsugashira ,
M. Hara  and
Y. Suzuki
K. Idemitsu
Affiliation:
Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Japan
X. Xia
Affiliation:
Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Japan
T. Ichishima
Affiliation:
Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Japan
H. Furuya
Affiliation:
Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Japan
Y Inagaki
Affiliation:
Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Japan
T. Arima
Affiliation:
Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Japan
T. Mitsugashira
Affiliation:
The Oarai Branch, Institute for Materials Research, Tohoku University, Japan
M. Hara
Affiliation:
The Oarai Branch, Institute for Materials Research, Tohoku University, Japan
Y. Suzuki
Affiliation:
The Oarai Branch, Institute for Materials Research, Tohoku University, Japan
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Abstract

In a high-level waste repository, a carbon steel overpack will corrode after the repository is closed. This will create a reducing environment in the vicinity of the repository. Reducing conditions are expected to retard the migration of redox-sensitive radionuclides such as plutonium.

The apparent diffusion coefficients of plutonium were measured in compacted bentonites (Kunigel V1® and Kunipia F®, Japan) in contact with carbon steel and its corrosion products under a reducing condition and, for comparison, without carbon steel under an oxidizing condition. Gas bubbles were observed in some bentonite specimens which had low dry densities after contact with carbon steel for approximately two years. This observation suggests hydrogen generation during corrosion of the carbon steel. The apparent diffusion coefficients measured were approximately 10−14 m2/s under the reducing condition and less than 1015 m2s under the oxidizing condition. There was a significant effect of redox conditions on the apparent diffusion coefficients. The effects of dry density (0.8 to 2.0 Mg/m3) and montmorillonite contents (50% for Kunigel V1 or 100% for Kunipia F), however, were not observed clearly. The chemical species of plutonium were expected to be PuOH2+ for the reducing condition and Pu(OH)4 for the oxidizing condition, respectively.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 608: Symposium QQ – Scientific Basis for Nuclear Waste Management XXIII , 1999 , 261
Copyright
Copyright © Materials Research Society 2000

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References

REFERENCES

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