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Diffusion Modeling in Compacted Bentonite Based on Modified Gouy-Chapman Model

Published online by Cambridge University Press:  03 July 2014

Kenji Yotsuji
Affiliation:
Japan Atomic Energy Agency, 4-33, Muramatsu, Tokai, Ibaraki, 319-1194, Japan
Yukio Tachi
Affiliation:
Japan Atomic Energy Agency, 4-33, Muramatsu, Tokai, Ibaraki, 319-1194, Japan
Yuichirou Nishimaki
Affiliation:
Visible Information Center, Inc., 440, Muramatsu, Tokai, Ibaraki, 319-1112, Japan
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Abstract

The integrated sorption and diffusion (ISD) model has been developed to quantify radionuclide transport in compacted bentonite. The current ISD model, based on averaged pore aperture and the Gouy-Chapman electric double layer (EDL) theory can quantitatively account for diffusion of monovalent cations and anions under a wide range of conditions (e.g., salinity, bentonite density). To improve the applicability of the current ISD model for multivalent ions and complex species, the excluded volume effect and the dielectric saturation effect were incorporated into the current model, and the modified Poisson-Boltzmann equations were numerically solved. These modified models had little effect on the calculation of effective diffusivity of Sr2+/Cs+/I. On the other hand, the model, modified considering the effective electric charge of hydrated ions, calculated using the Gibbs free energy of hydration, agreed well with the diffusion data including those of Sr2+.

Type
Articles
Copyright
Copyright © Materials Research Society 2014 

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References

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