Analysis of oxygen potential of (U0.7Pu0.3)O2±x and (U0.8Pu0.2)O2±x based on point defect chemistry

Oxygen potential of (U0.88Pu0.12)O2± and (U0.7Pu0.3)O2± at high temperatures of 1673–1873 K

“…The calculated results are in good agreement with the data measured in this work and previous work [12] within r = 12.1 kJ/ mol and represented all data shown in Table 1 Analysis of the result of (U 0.7 Pu 0.3 )O 2±x was reported in a previous work [20] using the same method as in the current work, and the partial molar enthalpy DH O 2 and partial molar entropy DS O 2 of stoichiometric composition were estimated to be À552.5 kJ/mol and À149.7 J/mol, respectively. In the results of this analysis, however, data of both the hyper-and hypo-stoichiometry region was limited especially in near the stoichiometric composition.…”

“…It is known that x is proportional to P 1=n O 2 , where n is a characteristic number identifying the defect [20][21][22]. The relationships between x and P O 2 in (U 0.88 Pu 0.12 )O 2±x are shown in Figs.…”

“…In previous work [14,20], the defect reactions of Eqs. (7)-(13) were assumed to analyze the each region.…”

“…Eq. (7) was assumed to represent the data for (U 0.8 Pu 0.2 )O 2±x [20]. In the reducing region the value of n was À4 in both (U 0.88 Pu 0.…”

Thermal expansion measurement of (U,Pu)O2-x in oxygen partial pressure-controlled atmosphere

“…This measurement technique was used in previous works [19,23e25] and could control an oxygen potential within ± 10 kJ/mol. [23,24]. First the specimens were heated at 1923 K for 4 h in appropriate atmosphere to adjust target O/M ratio which were plotted in Fig.…”