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A Note on Radionuclide Transport by Gas Bubbles

Published online by Cambridge University Press:  03 September 2012

Ivars Neretnieks  and
Märta-Lena Ernstson
Ivars Neretnieks
Affiliation:
Department of Chemical Engineering and Technology, Royal Institute of Technology, S-100 44 Stockholm, SWEDEN
Märta-Lena Ernstson
Affiliation:
Department of Chemical Engineering and Technology, Royal Institute of Technology, S-100 44 Stockholm, SWEDEN
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Abstract

In a repository for spent nuclear fuel, gas generated by corrosion of the iron in the canister may form small bubbles that will escape and rise to the ground surface. Colloidal particles may attach to the surface of the bubbles and be carried by them. If the colloids are supplied by the montmorillonite clay of the buffer material surrounding the canister, the clay can be carried away. Nuclides sorbed in the clay can be carried with the bubbles. We have estimated the carrying capacity of the gas of the clay particles and the escape rate of nuclides carried by the gas bubbles. The latter is also compared to the escape rate by the conventional escape mechanisms from the near field. We have further estimated the detachment of the nuclides from the clay and their sorption onto the fracture surfaces of the rock as well as their uptake by diffusion into the rock matrix along the bubble transport paths.

The present paper is speculative and uses some hypothetical assumptions. Although the processes that are modelled are known to exist there is not enough known of several of them to quantify them accurately. The carrying capacity of the gas used in the calculations is an upper bound and probably very much exaggerated. Even so, the consequences are minor for the release of radionuclides.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 465: Symposium II – Scienfific Basis for Nuclear Waste Management XX , 1996 , 855
Copyright
Copyright © Materials Research Society 1997

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References

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