DEFECT CONTRIBUTION TO EXCESS ENTHALPY OF URANIUM DIOXIDE-CALCULATION OF FRENKEL ENERGY

An equation for the enthalpy of UO2 was derived from earlier data. It is comprised of a lattice parabolic segment to which was added an enthalpy exponential term. Ht = -5601.5 + 17.78T + 1.02 × 10-3T2 + 71300 2exp 14.83 2Rexp -71300 2RT. This equation agrees well with the experimental data up to the melting point of UO2. The formation energy and entropy of Frenkel pairs in UO2 were derived from the high temperature data to be 71,300 ± 2.200 cal mole-1 and 14.83 ±0.84 cal mole-1 deg-1, respectively. The model is based upon the assumption that disordering occurs on the oxygen sublattice only and that oxygen Frenkel defects predominate. © 1969.