Electron probe microanalysis of UO₂ for stoichiometry determination

Abstract Oxygen-metal ratios are important to the study of irradiated nuclear oxide fuel. Critical performance metrics such as thermal conductivity, constituent redistribution, and melting temperature depend on the degree of departure from UO 2.00 stoichiometry and in which direction (hyper- or hypo-stoichiometric) the departure has occurred. This study examined three sintered pellets with compositions of UO 2.00 , UO 2.02 , UO 2.21 and one un-sintered pellet with a composition of UO 2.16 . When analysed via electron probe microanalysis, Al-coated pellet accuracy ranged from −1.0 % to 19.4 % while Ir-coated pellet accuracy ranged from −0.5 % to 4.6 %. For both analysis sets the un-sintered pellet exhibited the largest accuracy error. While some pellet heterogeneity contributed to lower-than-expected precision, this method appears suitable for characterising oxygen-metal ratios in irradiated uranium oxide fuels.