Kinetic Measurements for the Carbothermic Synthesis of UN, PuN, and (U,Pu)N

Abstract

A kinetic study of the synthesis of nitrides using carbothermic reduction of UO2 and PuO2 in flowing N2 was conducted. Reactio n rate constants as functions of the reaction temperature and N2 flow rate were determined. The measured rate constants varied with temperature according to the Arrhenius equation at constant N2 flow rates. In logarithmic form, the measured rate constants also varied linearly with N2 flow rate at constant temperature, up to a flow rate of 120 cm3/min-g of reactant. The rate constant for a particular reaction temperature and N2 flow rate can be calculated from the logarithmic form of the Arrhenius equation by adding a flow- rate term, F. The expression ln k = (-86,000/ RT) + 18.1 + 0.021F fits the kinetic data from 1430 to 1625 deg C. Close agreement was obtained between calculated and experimenta rate constants determined for 50-g batch production runs. The reaction rates measured are considered rapid enough for an economical nitride process.