INVESTIGATION OF NUCLEAR MIXED-OXIDE FUEL GAS INTERACTION BY A SOLID ELECTROLYTE BASED COULOMETRIC TECHNIQUE

The general reaction UyMe1-yO2+x + delta-H2 --> UyMe1-yO2+x-delta + delta-H2O (Me = Pu, rare earths) was investigated by a solid electrolyte based coulometric technique in a carrier gas mode. The changes in the hydrogen concentration and the oxygen potential during the reaction were registered continuously by coulometric titration and potentiometric measurement, respectively. These investigations were used to deal with the following problems: (1) Thermodynamic measurement of p - T - x - y diagrams of these oxides: especially the near stoichiometric range of Pu-, Ce-, Pr- and Gd-mixed oxide has been investigated. Mathematical fit and modelling in the setup of p - T - x diagrams are discussed. (2) Determination of oxygen-metal ratio in hyper- and hypostoichiometric oxides: a well defined redox state as the result of the above reaction is an essential condition for a precise analysis in oxygen stoichiometry. (3) Preparation of mixed oxides with a defined oxygen stoichiometry. (4) Measurement of the kinetics of gas-mixed oxides interaction. (5) Measurement of fuel-water interaction.