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Direct alpha-recoil as a process to generate U-234/U-238 disequilibrium in groundwater

Published online by Cambridge University Press:  21 March 2011

Kari Rasilainen ,
Henrik Nordman ,
Juhani Suksi  and
Nuria Marcos
Kari Rasilainen
Affiliation:
Technical Research Centre of Finland, P.O. Box 1608, FI-02044 VTT, Finland
Henrik Nordman
Affiliation:
Technical Research Centre of Finland, P.O. Box 1608, FI-02044 VTT, Finland
Juhani Suksi
Affiliation:
University of Helsinki, P.O. Box 55, FI-00014 University of Helsinki, Finland
Nuria Marcos
Affiliation:
Helsinki University of Technology, P.O. Box 6200, FI-02015 TKK, Finland
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Abstract

We discuss quantitatively the capability of direct α-recoil to create observable radioactive disequilibrium (U-234/U-238 activity ratio > 1) in flowing groundwater. Coupled equations for radioactive decay chain are formulated for the solid U source and for the corresponding groundwater receiving the recoiling U-234 atoms. U-rich fracture coating material and the water flowing in the fracture are discussed in detail.

The novel modelling approach worked well and provides a useful tool for more detailed site-specific studies with more detailed input data. The approach appears feasible because the equations are based on straightforward mass balance considerations.

α-recoil -induced enrichment of U-234 in groundwater is a slow process: the increase of U-234/U-238 activity ratio to notable values above unity will take hundreds to thousands of years. Strong groundwater flow prevents any local recoil-induced U-234 enrichment in the water.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 932: Symposium – Scientific Basis for Nuclear Waste Management XXIX , 2006 , 4.1
Copyright
Copyright © Materials Research Society 2006

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References

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