Advances in nuclear power reactors include the use of mixed oxide fuel, containing uranium and plutonium oxides. The high-temperature behaviour and structure of PuO2-x above 1,800 K remain largely unexplored, and these conditions must be considered for reactor design and planning for the mitigation of severe accidents. Here, in this study, we measure the atomic structure of PuO2-x through the melting transition up to 3,000 +/- 50 K using X-ray scattering of aerodynamically levitated and laser-beam-heated samples, with O/Pu ranging from 1.57 to 1.76. Liquid structural models consistent with the X-ray data are developed using machine-learned interatomic potentials and density functional theory. Molten PuO1.76 contains some degree of covalent Pu-O bonding, signalled by the degeneracy of Pu 5f and O 2p orbitals. The liquid is isomorphous with molten CeO1.75, demonstrating the latter as a non-radioactive, non-toxic, structural surrogate when differences in the oxidation potentials of Pu and Ce are accounted for. These characterizations provide essential constraints for modelling pertinent to reactor safety design. The molten structure of plutonium oxide-a component of mixed oxide nuclear fuels-is measured, showing some degree of covalent bonding. Its atomic structure is similar to that of cerium oxide, which could be a non-radioactive structural surrogate.
Wilke, Stephen K., et al. "Plutonium oxide melt structure and covalency." Nature Materials, vol. 23, no. 7, Apr. 2024. https://doi.org/10.1038/s41563-024-01883-3
Wilke, Stephen K., Benmore, Chris J., Alderman, Oliver G., Sivaraman, Ganesh, Ruehl, Matthew D., Hawthorne, Krista L., Tamalonis, Anthony, Andersson, David A., Williamson, Mark A., & Weber, Richard (2024). Plutonium oxide melt structure and covalency. Nature Materials, 23(7). https://doi.org/10.1038/s41563-024-01883-3
Wilke, Stephen K., Benmore, Chris J., Alderman, Oliver G., et al., "Plutonium oxide melt structure and covalency," Nature Materials 23, no. 7 (2024), https://doi.org/10.1038/s41563-024-01883-3
@article{osti_2472836,
author = {Wilke, Stephen K. and Benmore, Chris J. and Alderman, Oliver G. and Sivaraman, Ganesh and Ruehl, Matthew D. and Hawthorne, Krista L. and Tamalonis, Anthony and Andersson, David A. and Williamson, Mark A. and Weber, Richard},
title = {Plutonium oxide melt structure and covalency},
annote = {Advances in nuclear power reactors include the use of mixed oxide fuel, containing uranium and plutonium oxides. The high-temperature behaviour and structure of PuO2-x above 1,800 K remain largely unexplored, and these conditions must be considered for reactor design and planning for the mitigation of severe accidents. Here, in this study, we measure the atomic structure of PuO2-x through the melting transition up to 3,000 +/- 50 K using X-ray scattering of aerodynamically levitated and laser-beam-heated samples, with O/Pu ranging from 1.57 to 1.76. Liquid structural models consistent with the X-ray data are developed using machine-learned interatomic potentials and density functional theory. Molten PuO1.76 contains some degree of covalent Pu-O bonding, signalled by the degeneracy of Pu 5f and O 2p orbitals. The liquid is isomorphous with molten CeO1.75, demonstrating the latter as a non-radioactive, non-toxic, structural surrogate when differences in the oxidation potentials of Pu and Ce are accounted for. These characterizations provide essential constraints for modelling pertinent to reactor safety design. The molten structure of plutonium oxide-a component of mixed oxide nuclear fuels-is measured, showing some degree of covalent bonding. Its atomic structure is similar to that of cerium oxide, which could be a non-radioactive structural surrogate.},
doi = {10.1038/s41563-024-01883-3},
url = {https://www.osti.gov/biblio/2472836},
journal = {Nature Materials},
issn = {ISSN 1476-1122},
number = {7},
volume = {23},
place = {United States},
publisher = {Springer Nature},
year = {2024},
month = {04}}
Argonne National Laboratory (ANL), Argonne, IL (United States)
Sponsoring Organization:
USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE Office of Science (SC), Office of SBIR/STTR Programs (SBIR/STTR); USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF); USDOE Office of Nuclear Energy (NE)
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 624, Issue 3https://doi.org/10.1016/j.nima.2010.09.125
Skinner, Lawrie B.; Benmore, Chris J.; Parise, John B.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 662, Issue 1https://doi.org/10.1016/j.nima.2011.09.031