Determination of the oxygen coefficient for hyperstoichiometric uranium-plutonium mixed oxide by a solid-electrolyte-based coulometric technique

The cubic phase of the uranium-plutonium mixed oxide U1-zPuzO2+x has a wide range of homogeneity relative to x. The oxygen potential of the phase is a single value function of stoichiometry and temperature and is of importance in the use as nuclear fuel. For determination of the oxygen coefficients of hyperstoichiometric uranium-plutonium mixed oxide the solid-electrolyte-based coulometric technique has been used. The sample to be analysed is reduced in a Ar-H2-H2O gaseous mixture. The changes in hydrogen concentration according to the reaction U1-zPuzO2+x+xH2→U1-zPuzO2+xH2O are continuously measured by coulometric titration with a solid electrolyte cell. The standard deviation of the measurement was found to be Δx=±0.0004. During the storage of the powdered samples a slow oxidation occurs. (orig.)