Molten uranium dioxide structure and dynamics

Uranium dioxide (UO2) is the major nuclear fuel component of fission power reactors. A key concern during severe accidents is the melting and leakage of radioactive UO2 as it corrodes through its zirconium cladding and steel containment. Yet, the very high temperatures (>3140 kelvin) and chemical...

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Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 2014-11, Vol.346 (6212)
Main Authors: Skinner, L. B., Benmore, C. J., Weber, J. K. R., Williamson, M. A., Tamalonis, A., Hebden, A., Wiencek, T., Alderman, O. L. G., Guthrie, M., Leibowitz, L., Parise, J. B.
Format: Article
Language:English
Subjects:
NUCLEAR FUEL CYCLE AND FUEL MATERIALS
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Summary:Uranium dioxide (UO2) is the major nuclear fuel component of fission power reactors. A key concern during severe accidents is the melting and leakage of radioactive UO2 as it corrodes through its zirconium cladding and steel containment. Yet, the very high temperatures (>3140 kelvin) and chemical reactivity of molten UO2 have prevented structural studies. In this work, we combine laser heating, sample levitation, and synchrotron x-rays to obtain pair distribution function measurements of hot solid and molten UO2. The hot solid shows a substantial increase in oxygen disorder around the lambda transition (2670 K) but negligible U-O coordination change. On melting, the average U-O coordination drops from 8 to 6.7 +/- 0.5. Molecular dynamics models refined to this structure predict higher U-U mobility than 8-coordinated melts.
ISSN:0036-8075
1095-9203