Thermodynamics of the O–U system. IV – Critical assessment of chemical potentials in the U–UO 2.01 composition range

Abstract

A critical analysis of thermodynamic data available in the U–UO 2 system has been carried out with the twin aim of: (i) obtaining a reliable primary dataset for oxygen and uranium chemical potentials or partial Gibbs energies and, (ii) evaluating as realistically as possible the total uncertainties associated with these data. In order to perform this analysis, a array of regularly distributed values is built for sets of values, – ( G ¯ O 2 , O/U, T), – from which a direct comparison of different measurements can be undertaken within the evaluated uncertainty limits. The main conclusions of this analysis are (i) that major disagreements between different measurements are due to compositional uncertainties, (ii) and uncertainties associated with partial Gibbs energies are generally small except for those obtained by the isopiestic method of equilibrium with a given oxide. A set of selected data and proposed uncertainties is presented according to their distribution in our proposed array.