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Measurement of Dissolution Rates of UO2 Matrix with the Isotope Dilution Method

Published online by Cambridge University Press:  01 February 2011

K. Ollila  and
V. Oversby
K. Ollila
Affiliation:
VTT Processes, Technical Research Centre of Finland, PO Box 1608, FIN-02044 VTT, Finland
V. Oversby
Affiliation:
VMO Konsult, Karlavägen 70, SE-11459 Stockholm, Sweden
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Abstract

The objective of this work was to measure the actual rates of matrix dissolution of UO2 in synthetic groundwater by using an isotope dilution method to provide a quantitative estimate of precipitation effects. A preliminary series of tests was performed under oxidising conditions, in contact with air. The second series of tests was under reducing conditions produced by actively corroding iron. The solid phases were fragments of unirradiated fuel pellets and intact pellets. The aqueous phase was a dilute, synthetic groundwater - so-called modified Allard water that is buffered by sodium bicarbonate/carbonate. This paper gives results for the experiments under oxidising conditions and preliminary tests under reducing conditions. In contact with air, the U concentrations reached higher levels than measured in previous experiments with spent fuel or with UO2 pellets. The comparison of the U concentrations calculated from isotopicratios with the experimental results suggests precipitation has begun at later stages of restarted tests. The measurements in the presence of actively corroding iron gave very low concentrations in the aqueous phase. At contact times longer than one week, all U seemed to disappear from solution and sorb or precipitate on UO2 or Fe surfaces in the test vessel.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 807: Symposium Scientific Basis for Nuclear Waste Management XXVII , 2003 , 47
Copyright
Copyright © Materials Research Society 2004

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References

REFERENCES

1. Bruno, J., Cera, E., de Pablo, J., Duro, L., Jordana, S. and Savage, D., “Determination of radionuclide solubility limits to be used in SR 97”, SKB Technical Report 97–33, 1998.Google Scholar
2. Ollila, K., Ahonen, L., “Solubilities of uranium for TILA-99”, Posiva Report 98–13, 1998.Google Scholar
3. Allard, B., Larson, S.A., Albinsson, Y., Tullborg, E. L., Karlsson, M., Andersson, K. and Torstenfelt, B., in Near-Field Phenomena in Geologic Repositories for Radioactive Waste (NEA Workshop Proc, 1981), pp. 93–101.Google Scholar
4. Ollila, K., in Scientific Basis for Nuclear Waste Management XX, edited by Gray, W. J. and Triay, I. R. (Mater. Res. Soc. Proc, 1997), pp. 549–556.Google Scholar
5. Ollila, K., “Solubility of unirradiated UO2 fuel in aqueous solutions - Comparison between experimental and calculated (EQ3/6) data”, Report YJT-95–14, 1995.Google Scholar
6. Forsyth, R. S. and Werme, L. O., Journal of Nuclear Materials 190, 3 (1992).Google Scholar
7. Shoesmith, D.W. and Sunder, S., “An electrochemistry-based model for the dissolution of UO2”, SKB Technical Report 91–63, 1991.Google Scholar
8. Grenthe, I., Fuger, J., Konings, R. J. M., Lemire, R. J., Muller, A. B., Nguyen-Trung Cregu, C. and Wanner, H., in Chemical Thermodynamics of Uranium, edited by Wanner, H. and Forest, I. (North-Holland Elsevier Science Publishers B.V. ), 1992.Google Scholar
9. Ollila, K., “Dissolution of unirradiated UO2 fuel in synthetic groundwater - Final report (1996–1998)”, Posiva Report 99–24, 1999.Google Scholar
10. Vuorinen, U. and Snellman, M., “Finnish reference waters for solubility, sorption and diffusion studies” Posiva Working Report 98–61, 1998.Google Scholar