COMPUTER-SIMULATION OF URANIUM OXIDE PHASES

Results are presented of computer simulation studies of some uranium o xide phases, using two contrasting methods to calculate defect paramet ers. The first is based on the Mott-Littleton approach, which assumes defects to be in infinite dilution in an otherwise perfect lattice, an d the second allows finite defect concentrations to be modelled, using a supercell approach. Two groups of uranium oxide compounds are studi ed; firstly the mixed oxide reactor fuel (U,Pu)O-2, where lattice and defect properties are obtained as a function of Pu concentration, and secondly the alkaline earth metal uranates M(3)UO(6), where the calcul ation of a complete set of structural data and defect parameters is de scribed, and the dominant mode of intrinsic disorder proposed.