Oxygen potential of (U_(0.88)Pu_(0.12))O _(2±x) and (U_(0.7)Pu_(0.3))O _(2±x) at high temperatures of 1673-1873 K

摘要

The oxygen potential of (U_(0.88)Pu_(0.12))O _(2±x) (-0.0119 < x < 0.0408) and (U _(0.7)Pu_(0.3))O_(2±x) (-0.0363 < x < 0.0288) was measured at high temperatures of 1673-1873 K using gas equilibrium method with thermo gravimeter. The measured data were analyzed by a defect chemistry model. Expressions were derived to represent the oxygen potential based on defect chemistry as functions of temperature and oxygen-to-metal ratio. The thermodynamic data, ΔGO_2, ΔHO2 and ΔSO2, at stoichiometric composition were obtained. The expressions can be used for in situ determination of the oxygen-to-metal ratio by the gas-equilibration method. The calculation results were consistent with measured data. It was estimated that addition of 1 wt.% Pu content increased oxygen potential of uranium and plutonium mixed oxide by 2-5 kJ/mol.