Equilibrium Oxygen Pressures Over Solid Solutions of Urania‐Yttria and Urania‐Lanthana at 1100° to 14OO°C

Abstract

Using a thermobalance, the oxygen content of urania containing small amounts of yttria or lanthana was determined as a function of the oxygen partial pressure at 1100° to 1400°C. Values for the partial free enthalpy, the partial enthalpy, and partial entropy of oxygen were calculated. Equilibrium oxygen pressures over the solid solutions (U, Y, or La)O2+x were higher than for pure UO2+X. Both the partial enthalpy and partial entropy of oxygen decreased with the addition of yttrium and lanthanum, the change being larger in the latter case. The effects observed experimentally are discussed on the basis of differences in charge and size of the foreign cation relative to the uranium ion.