Vaporization of thoria-urania solid solution

In order to elucidate the vaporization behavior of thoria-urania solid solution, its vapor species identification and partial vapor pressure measurement have been made in a high temperature mass spectrometer. Partial vapor pressure of $\text{UO}{}_3$(g) over $\text{Th}{}_1\text{-}{}_{\mathrm{y}}\text{U}{}_{\mathrm{y}}\text{0}{}_2$ was observed to remarkably change with time and this behavior can be explained from the extended Blackburn's thermochemical model. Activities of $\text{U0}{}_2$(s) and $\text{Th0}{}_2$(s) in $\text{Th0}{}_2\text{-U0}{}_2$ show positive deviation from Raoult's law. Absolute vapor pressures of $\text{U0}{}_2$(g) and $\text{UO}{}_3$(g) over $\text{Th}{}_1\text{-}{}_{\mathrm{y}}\text{U}{}_{\mathrm{y}}\text{0}{}_2$ are evaluated.