Particle Size Distribution of U308 Produced by Oxidation of Fuel in Air at 300-900OC

Abstract

Both unirradiated and irradiated UO, fuels were isothermally oxidized in air at temperatures between 300 and 900 degrees C During oxidation, the UO, samples fragmented and formed U30, particles. Sieving and sedimentation techniques were used to measure the size distribution of the particles. The median particle sizes of the unirradiated samples oxidized at 900, 700, 500 and 300 degrees were 600, 80, 16 and 7.5 um, respectively. The relative humidity of the environment during sieving did not affect the size distributions of particles from 900, 700 or 500 degrees oxidation. For the 300 degrees sample, increasing the humidity from 11% to 50% did not influence its size distribution, but when the humidity was increased to 98%, its median size increased from 7.5 um to about 100 um. The size distributions of the irradiated fuel (burnup457 MW*h/kgU) were similar to those of the unirradiated fuel.