The oxidation behaviour of highly irradiated uranium in dry carbon dioxide at 375–500°C and in dry air at 200–300°C

Abstract

The influence of irradiation of adjusted uranium, to a burn-up of 6400 MWd/t, has been studied upon its reactivity out-of-reactor in carbon dioxide at 375–500° C and in air at 200–300° C. In the absence of appreciable swelling, the irradiation increased the attack in carbon dioxide and air by factors of only 1–8 and 1–2 respectively. With swollen metal, the attack increased with swelling, without there being any notable dependence of the enhancement factor on the environment. Thus, the enhancement factor was ≈100 with a swelling of 50% and had a maximum value of 1000–2000 for 120% swollen material. The pore structure of swollen uranium was established by BET surface area and density measurements to be primarily closed. Consequently, the enhanced reactivity was not due to access of the gas to the internal surface area and is attributed to break-up of the metal surface during oxidation.