Oxygen potentials of (U,Nd)O2 ± x solid solutions in the temperature range 1000–1500°C

Charge compensation mechanisms in Nd-doped UO2 samples for stoichiometric and hypo-stoichiometric conditions: Lack of miscibility gap

“…It is clearly visible that the samples display a well crystallized single FCC structure with a small shift towards higher angles with increasing concentration of Nd, indicating a progressive lattice contraction but no symmetry change, see figure 1 (b). Numerous studies assessed the evolution of the lattice parameter, a, on stoichiometric samples (U 1y Nd y )O 2 [15], [27]- [30], [18]. Lee et al interpreted the evolution as a function of the Nd atomic concentration according to the following expression :…”

“…According to calculations employing the Thermo-Calc software, this stated value allows the reduction of the sample at 1473K. Similar analysis showing the evolution of the oxygen chemical potential for increasing temperatures on ternary systems can be seen in [15][16]. For the second stage, the oxygen atmosphere was set to the lowest achievable value of the equipment, reaching an oxygen partial pressure as low as 10 -29 bar.…”

Oxygen potential calculations for conventional and Cr-doped UO2 fuels based on solid solution thermodynamics

“…In a first step, attempts were made to determine the interaction parameter describing the interaction of Nd 3+ with U 4+ by fitting the oxygen potential data of Une and Oguma [51] for In order to shift the dashed curve in Fig. 4 to the right, so that O/M ratios only barely below 2.00 are obtained, one needs to assume a substitution mechanism that keeps more oxygen in the lattice, e.g.…”

Measurement of the oxygen partial pressure and thermodynamic modeling of the U–Nd–O system

“…Theconsidered U-Nd-O system consists of a gas phase, liquid phase, solid phases of the metals and their oxides, which include a fluorite solid solution phase and a rhombohedral oxide phase according to the surveyed literature [7,[11][12][13][14][15][16][17]. Thermodynamic values and models for all phases in the U-Nd-O system weredefined using the Gibbs energyapproach determinedby CALPHAD method [7,[21][22].Specifically, the CEF model for the fluorite solid solution phase and oxide rhombohedral phase was employed in this work.…”