Uranium Release and Secondary Phase Formation during Unsaturated Testing of UO2 at 90°C
Experimental results indicate that UO2 will readily react after being exposed to dripping oxygenated ground water at 90°C. A pulse of rapid U release, combined with the formation of dehydrated schoepite characterizes reactions between one to two years. Rapid dissolution of intergrain boundaries and spallation of UO2 granules appears to be responsible for the rapid U release. Less than 5% of the U is released in a soluble or suspended form. After two years, U release rates decline and a more stable assemblage of uranyl silicate phases form by incorporating cations from the leachant. Uranophane, boltwoodite, and sklodowskite are the final solubility-limiting phases for U in these tests. This observed paragenetic sequence (from uraninite to schoepite to uranyl silicates) is identical to those observed in weathered uraninite deposits. Dispersion of particulate matter may be an important release mechanism for U and other radionuclides in spent nuclear fuel.
D. J. Wronkiewicz et al., "Uranium Release and Secondary Phase Formation during Unsaturated Testing of UO2 at 90°C," Journal of Nuclear Materials, vol. 190, no. C, pp. 107-127, Elsevier, Aug 1992.
The definitive version is available at https://doi.org/10.1016/0022-3115(92)90081-U
Geosciences and Geological and Petroleum Engineering
Keywords and Phrases
Fission products; Leaching; Phase transitions; Spent fuels; Uranium release; Uranium dioxide
International Standard Serial Number (ISSN)
Article - Journal
© 1992 Elsevier, All rights reserved.