STEAM OXIDATION KINETICS AND OXYGEN DIFFUSION IN UO2 AT HIGH TEMPERATURES

Results of steam oxidation measurements of UO2 cylinders from 885° to 1835°C may be expressed by the equations: (Formula Presented.) for the parabolic rate of oxidation and (Formula Presented.) for the chemical oxygen diffusion coefficient. Kp and Dc, obtained from thermobalance measurements to 1500° C and from pre‐ and post‐test weights for the higher temperatures, were independent of sample weight from 10 to 149 g and of surfaceto‐volume ratios from 2.34 to 18.74 cm‐1. Dc varied as the 0.65 power of the final average excess oxygen (x in UO2+x). The oxidation was accompanied by considerable grain growth. A bulk diffusion mechanism was verified by analyses of partially oxidized samples using both X‐ray diffraction and analytical chemistry; an oxygen gradient was demonstrated by each technique. Copyright © 1969, Wiley Blackwell. All rights reserved