アルゴンヌの新たな研究により、核燃料の高温時の挙動が明らかに(When it’s hotter than hot, scientists know how nuclear fuel behaves, thanks to new research from Argonne)

2024-09-05 アルゴンヌ国立研究所(ANL)

＜関連情報＞

• https://www.anl.gov/article/when-its-hotter-than-hot-scientists-know-how-nuclear-fuel-behaves-thanks-to-new-research-from
• https://www.nature.com/articles/s41563-024-01883-3

プルトニウム酸化物のメルト構造と共有結合性 Plutonium oxide melt structure and covalency

Stephen K. Wilke,Chris J. Benmore,Oliver L. G. Alderman,Ganesh Sivaraman,Matthew D. Ruehl,Krista L. Hawthorne,Anthony Tamalonis,David A. Andersson,Mark A. Williamson & Richard Weber
Nature Materials  Published:26 April 2024
DOI:https://doi.org/10.1038/s41563-024-01883-3

Abstract

Advances in nuclear power reactors include the use of mixed oxide fuel, containing uranium and plutonium oxides. The high-temperature behaviour and structure of PuO_2–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, we measure the atomic structure of PuO_2–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 PuO_1.76 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 CeO_1.75, 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.