Solution of trivalent cations into uranium dioxide

Abstract

The accommodation of trivalent oxides (M 2O 3) in uranium dioxide has been investigated using atomic scale simulation. Calculations suggest that all trivalent oxides studied preferentially enter UO 2 by associating the substitutional ion with an oxygen vacancy, larger cations forming the cluster { 2 M U ′ : V O } × . Solution into hyper-stoichiometric UO 2+ x was accompanied by the formation of the { M U ′ : U U } × cluster and smaller solution energies than into stoichiometric UO 2. Solubility is a particularly strong function of hyper-stoichiometry for smaller cations such as Cr 3+, which has implications for the use of Cr 2O 3 as a grain enlarger but not so for larger cations such s Gd 3+.