Kinetics of the Dissolution Reaction of the U₃O₈ Powder in Nitric Acid after Oxidation Volatilization at 850 °C

Abstract

Due to a series of factors such as variations in powder preparation methods, the kinetic parameter data for its dissolution in nitric acid solution exhibit dispersion. This study investigates the U 3 O 8 powder which underwent oxidation and volatilization at 850 °C. The particle size of the U 3 O 8 powder prior to dissolution was measured, and the surface area during dissolution was calculated under certain assumptions. By comparison of unit area dissolution rates at different temperatures and acidities, apparent kinetic parameters were derived. Results indicate an escalation in the dissolution rate of the U 3 O 8 powder with increasing temperature and acidity. The initial stage of the reaction period reaction order was raised to n 1 = 2.12, while the rapid reaction period exhibited a reaction order of n 2 = 1.40, and the reaction end period showed a reaction order of n 3 = 1.50. The apparent activation energy during the initial stage of the reaction period, rapid reaction period, and the reaction end period was measured as 98.93, 99.39, and 99.13 kJ/mol, respectively.