Oxygen self-diffusion in non-stoichiometric uranium dioxide

Abstract

Oxygen self-diffusion coefficients in UO_2+x were obtained using the nuclear reactions ¹⁸O(p, n)¹⁸F and ¹⁷O(d, n)¹⁸F followed by autoradiography. The activation energy for migration and the pre-exponential were 23·1 ± 3·8 kcal mole⁻¹ and 6·25 ± 5·03 × 10⁻⁴ cm² sec⁻¹, respectively, at x≃0·08. The functional dependence of the oxygen self-diffusion on composition could be semiquantitatively explained on the basis of a cooperative diffusion mechanism via a Willis 2 : 2 : 2 defect cluster subject to a very short-range defect–defect interaction.