Phase equilibrium studies in the UO2ZrO2 system

Progress in understanding fission-product behaviour in coated uranium-dioxide fuel particles

“…At lower temperature, this solubility strongly decreases where Romberger et al [28] measured at the eutectoid temperature of the UO 2 -ZrO 2 phase diagram (1383 K) a content of 0.38 mol.% of ZrO 2 in UO 2 . On this experimental basis, zirconium is assumed, in the thermodynamic models, to precipitate as a separate phase and its presence at the grain boundaries usually results in the preferential formation of zirconate-type compounds since these compounds are more thermodynamically stable than uranates.…”

“…It is well known that zirconium dioxide (ZrO 2 ) is highly soluble in uranium dioxide at high temperature (i.e., >1700 K) [28]. At lower temperature, this solubility strongly decreases where Romberger et al [28] measured at the eutectoid temperature of the UO 2 -ZrO 2 phase diagram (1383 K) a content of 0.38 mol.% of ZrO 2 in UO 2 .…”

“…The solution energy includes a term corresponding to the dissociation of zirconium dioxide. Through this term, this energy is representative of the ability of zirconium dioxide to be soluble in urania as it can be measured in classical thermodynamic experiments (e.g., [28]). In the situation of cations produced inside irradiated fuel, the pertinent energy is more likely the incorporation energy of the cation in the UO 2 matrix in a pre-existing defect.…”

Development of Thermodynamic Database for U-Zr-Fe-O-B-C-FPs System

“…Table 2 shows the parameters we assessed for the liquid phase of the U-Zr-Fe-O-C-B system. The references of the fitted diagrams are included in the 25) were used. Recently, Chevalie 17) and Gueneau 26) have developed U-Zr-O associate model and U-O ionic two-sublattice model for liquid, respectively.…”

“…34) Romberger's estimation of the eutectoid temperature, 1;383AE5 K, 35) based on their experiments of the three equilibrium solid solutions, ZrO 2 , ZrO 2 and MO2, is well simulated as in Chevalie's because his parameters are used for the interaction between ZrO 2 and UO 2 of ZrO 2 .…”