Oxygen potential and lattice parameter studies in (U, Ce)0_2X

Abstract

Studies have been carried out on (U, Ce)O_2-x to assist the understanding of oxygen behaviour in the fast reactor fuel (U, Pu)O_2-x . Oxygen potentials at 1123 K and lattice parameters after rapid cooling to room temperature have been determined as functions of oxygen content for Ce/(U + Ce) ratios of 0.148 and 0.282. The results are discussed in terms of the lattice defects by which oxygen deficiencies are accommodated. Simple models based on clusters either of the (Ce³⁺ O_vac) or of the (2Ce³⁺ O_vac) type with U⁴⁺ ions as an inert matrix are inconsistent with the experimental data. Complex cluster models devised for (U, Pu)O_2-x require further development before they can account for the oxygen potential behaviour of (U, Ce)O_2-x.