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High-Temperature Annealing of Natural UO2+x

Published online by Cambridge University Press:  28 February 2011

J. Janeczek  and
R. C. Ewing
J. Janeczek
Affiliation:
Department of Geology, University of New Mexico, Albuquerque, NM 87131.
R. C. Ewing
Affiliation:
Department of Geology, University of New Mexico, Albuquerque, NM 87131.
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Abstract

Four powdered samples of natural UO2+x (uraninite) were annealed in a reducing atmosphere up to 1200°C. The initial unit cell parameters ranged from ao=0.5463 to 0.5385 nm. Small amounts of UO2.25 occur in all samples after annealing. Annealing curves show the effects of recovery of point defects in the oxygen sublattice, ordering of U4+ and U6+, vacancy migration in the cation sublattice, and second order phase transformations. The difference in the annealing behavior of UO2+x with x < 0.15 as compared to x = 0.25 between 400 and 700°C is due to ordering of U4+ and U6+. Density increased after annealing except for one sample in which a large number of cavities (1–2 μm in size) formed. Oxidation and chemical composition have a more dramatic effect on the structural state of natural UO2+x than self-irradiation caused by a-decay damage.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 212: Symposium P – Scientific Basis for Nuclear Waste Management XIV , 1990 , 235
Copyright
Copyright © Materials Research Society 1991

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References

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