A thermodynamic study of fluorite/bixbyite equilibria in the UO2–PuO1.5–PuO2 system
Year: 2025
Type: article
Abstract: ABSTRACT Thermodynamic properties of U 1− z Pu z O 2+ δ fluorite (FCC) and U 1− z Pu z O 2+ δ bixbyite (BCC) in the UO 2 −PuO 1.5 −PuO 2 system are assessed by considering phase equilibrium constraints and data on the variation of oxygen to metal ratio ( O/M ) as a function of the chemical potential of O 2 . Thermodynamically, both BCC and FCC are described as ordered solid solutions allowing for a decrease in the configurational entropy of their oxygen/vacancy distributions at the specific values of δ = –0.5 and δ = –0.375 ( O/M = 1.5 and O/M = 1.625). With this approach, fluorite/bixbyite equilibria in PuO 1.5 –PuO 2 and in UO 2 –PuO 1.5 –PuO 2 are reproduced well with little effort. Moreover, we show that a large manifold of experimental data on the UO 2 –PuO 1.5 –PuO 2 system is consistent with the assumption that Pu/(Pu+U) ratios in individual phases remain equal to the total Pu/(Pu+U) ratio in the system, i.e., phase equilibration does not involve inter-phase U/Pu-partitioning.
Source: Journal of Nuclear Materials
Authors: Victor L. Vinograd, Romain Vauchy
Institutions: Forschungszentrum Jülich, Japan Atomic Energy Agency
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $2,640
OpenAlex ID: W4415541870