The oxidation behaviour of uranium in air at 348–765 K

Abstract

The oxidation behaviour of adjusted uranium has been examined in air, at atmospheric pressure, at 348–765 K. Particular emphasis has been directed to the role of swelling resulting from prior irradiation of the metal to a burn-up of 5600–9100 MWd/t and an addition of 2.5 × 10 4 vpm water vapour to the air. Pre-irradiation of uranium enhanced its attack by air at 348–523 K, the enhancement increasing progressively with percentage swelling. This effect resulted primarily from the break-up of the uranium surface during oxidation with the generation of a greater reaction surface area and was independent of the temperature of oxidation in dry air and also above 423 K in wet air. At lower temperatures, however, the water vapour addition increased the effective reaction rate, possibly by the transitory involvement of uranium hydride. The influence of the water vapour increased with swelling of the irradiated uranium and was greater than that exerted on the oxidation of unirradiated uranium at comparable temperatures. With increasing temperature above 623 K, swelling had a progressively decreasing influence upon the attack of irradiated uranium in both environments.