Isothermal Oxidation of Uranium Monocarbide Powder under Controlled Oxygen Partial Pressures

Abstract

The kinetics of isothermal oxidation of UC powder were studied at oxygen partial pressures between 7.0×10^-4 and 1.1×10^-2 atm in the temperature range from 400 to 1, 400°C with use made of thermogravimetric techniques. Oxidation rates at the initial stage were observed to be linear against the reaction time for all the cases studied, suggesting surface reaction. Different activation energies were found for three regions of temperature--1.6 kcal/mol for region I (below about 800°C), 4.9 kcal/mol for region II (about 8001, 200°C) and 23.0 kcal/mol for region III (above about 1, 200°C). The rate-determining step for each region is discussed from the experimental results.