The structure of liquid UO2-x in reducing gas atmospheres
Abstract
High energy X-ray diffraction experiments performed on hypostoichiometric UO2-x liquids in reducing gas mixtures of 95%Ar:5%CO and 95%Ar:5%H2 are compared to that conducted in a pure Ar atmosphere [Skinner et al., Science 346, 984 (2014)]. The measurements are pertinent to severe accident scenarios at nuclear reactors, where core melts can encounter reducing conditions and further shed light on the oxide chemistry of the low valence states of uranium, particularly U(III), which become stable only at very high temperatures and low oxygen potentials. The radioactive samples were melted by floating small spheres of material using an aerodynamic levitator and heating with a laser beam. In the more reducing environments, a 1.7% shift to lower Q-values is observed in the position of the principal peak of the measured X-ray structure factors, compared to the more oxidizing Ar environment. This corresponds to an equivalent elongation in the U-U nearest neighbor distances and the U-U periodicity. The U-O peak (modal) bond-length, as measured from the real-space total correlation functions, is also observed to expand by 0.9–1.6% under reducing conditions, consistent with the presence of 15–27% U3+ cations, assuming constant U-O coordination number. The slightly larger U-U elongation, as compared to the U-O elongation, ismore »
- Authors:
-
[1];
[1];
[3];
- Materials Development Inc., Arlington Heights, IL (United States); Argonne National Lab. (ANL), Argonne, IL (United States). X-ray Science Division
- Argonne National Lab. (ANL), Argonne, IL (United States). X-ray Science Division
- Argonne National Lab. (ANL), Argonne, IL (United States). X-ray Science Division; Stony Brook Univ., NY (United States). Mineral Physics Inst.
- Materials Development Inc., Arlington Heights, IL (United States)
- Materials Development Inc., Arlington Heights, IL (United States)A
- Argonne National Lab. (ANL), Argonne, IL (United States). Nuclear Engineering
- Publication Date:
- Research Org.:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- OSTI Identifier:
- 1389313
- Alternate Identifier(s):
- OSTI ID: 1349361
- Grant/Contract Number:
- AC02-06CH11357
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Applied Physics Letters
- Additional Journal Information:
- Journal Volume: 110; Journal Issue: 8; Journal ID: ISSN 0003-6951
- Publisher:
- American Institute of Physics (AIP)
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 54 ENVIRONMENTAL SCIENCES; X-ray diffraction; Liquid metals; X-ray absorption near edge structure; Uranium; Atmospheric temperature
Citation Formats
Alderman, O. L. G., Benmore, C. J., Weber, J. K. R., Skinner, L. B., Tamalonis, A. J., Sendelbach, S., Hebden, A., and Williamson, M. A. The structure of liquid UO2-x in reducing gas atmospheres. United States: N. p., 2017.
Web. doi:10.1063/1.4977035.
Alderman, O. L. G., Benmore, C. J., Weber, J. K. R., Skinner, L. B., Tamalonis, A. J., Sendelbach, S., Hebden, A., & Williamson, M. A. The structure of liquid UO2-x in reducing gas atmospheres. United States. https://doi.org/10.1063/1.4977035
Alderman, O. L. G., Benmore, C. J., Weber, J. K. R., Skinner, L. B., Tamalonis, A. J., Sendelbach, S., Hebden, A., and Williamson, M. A. Wed .
"The structure of liquid UO2-x in reducing gas atmospheres". United States. https://doi.org/10.1063/1.4977035. https://www.osti.gov/servlets/purl/1389313.
@article{osti_1389313,
title = {The structure of liquid UO2-x in reducing gas atmospheres},
author = {Alderman, O. L. G. and Benmore, C. J. and Weber, J. K. R. and Skinner, L. B. and Tamalonis, A. J. and Sendelbach, S. and Hebden, A. and Williamson, M. A.},
abstractNote = {High energy X-ray diffraction experiments performed on hypostoichiometric UO2-x liquids in reducing gas mixtures of 95%Ar:5%CO and 95%Ar:5%H2 are compared to that conducted in a pure Ar atmosphere [Skinner et al., Science 346, 984 (2014)]. The measurements are pertinent to severe accident scenarios at nuclear reactors, where core melts can encounter reducing conditions and further shed light on the oxide chemistry of the low valence states of uranium, particularly U(III), which become stable only at very high temperatures and low oxygen potentials. The radioactive samples were melted by floating small spheres of material using an aerodynamic levitator and heating with a laser beam. In the more reducing environments, a 1.7% shift to lower Q-values is observed in the position of the principal peak of the measured X-ray structure factors, compared to the more oxidizing Ar environment. This corresponds to an equivalent elongation in the U-U nearest neighbor distances and the U-U periodicity. The U-O peak (modal) bond-length, as measured from the real-space total correlation functions, is also observed to expand by 0.9–1.6% under reducing conditions, consistent with the presence of 15–27% U3+ cations, assuming constant U-O coordination number. The slightly larger U-U elongation, as compared to the U-O elongation, is interpreted as a slight increase in U-O-U bond angles. Difficulties concerning the determination of the hypostoichiometry, x, are discussed, along with the future directions for related research.},
doi = {10.1063/1.4977035},
journal = {Applied Physics Letters},
number = 8,
volume = 110,
place = {United States},
year = {2017},
month = {2}
}
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