Kinetic models for the synthesis of (U, Pu)O2−y by hydrogen-reduction and carbothermic techniques

Three models have been developed that permit the calculation of the time necessary for the synthesis of hypostoichiometric oxide from (U, Pu)O₂. The models are based on the interrelation between oxygen potential, valence of plutonium, and temperature determined by Rand and Markin and on the experimental conditions for reduction. Two reduction techniques are considered: the flowing hydrogen system and the C-CO-CO₂ system. At the usual temperatures for reduction, the partial pressure of water, the hydrogen flow, and the total weight of plutonia are the most important factors in the hydrogen system, while in the C.CO-CO₂ system the important factors are the weight of the plutonia in each oxide pellet, the partial pressure of carbon monoxide, the proximity of the oxide and the carbon used for reduction, and the oxygen-to-metal ratio possible at the oxygen potential of the C-CO-CO₂ equilibrium.