Analysis of the oxygen potential of Th1−yUyO2+x

Oxygen potentials of UO2–ThO2 solid solutions (Th1−yUyO2+x) were retrieved from the literature and analyzed. For each datapoint the oxygen pressure pO2, the nonstoichiometry x, the temperature T and the uranium concentration y was specified. The data were analyzed using the valency control model and the thermochemical model of Lindemer and Besmann for UO2+x which was extended for the analysis of the Th1−yUyO2+x data. The solid solution is regarded as an ideal ternary solution of UO2, ThO2 and a hypothetical compound UaOb. The thermodynamic properties of this compound UaOb were determined in two oxygen pressure ranges of the database. In this thermochemical approach ThO2 is treated as an inert solvent that does not participate in any of the chemical equilibria describing the oxygen potential.