MEASUREMENT OF 2000-2100-DEGREES-C OXYGEN DIFFUSION-COEFFICIENTS IN HYPOSTOICHIOMETRIC UO2

The chemical diffusion coefficient of oxygen in UO2-x has been measure d using molten Zircaloy held in a UO2 crucible to establish the concen tration driving force. The oxygen-to-uranium distribution set up by th is method was determined by scanning electron microscopy/image analysi s of the number density and area fraction of uranium metal precipitate s that form when UO2-x disproportionates upon cooling. Oxygen diffusiv ities were determined by fitting the numerical solution of Fick's seco nd law to the O/U profiles. The diffusion coefficients are (3.3 +/- 0. 5) x 10(-8) m(2)/s at 2000 degrees C and (3.6 +/- 0.8) x 10(-8) m(2)/s at 2100 degrees C.