Bench-scale study of the reduction and hydrofluorination reactions in the catalysed fluorox process

Abstract

Catalysed reduction of U02F2 by hydrogen and the hydrofluorina-tion of the UO2 produced were investigated in separate and simultaneous reactions. The production of UO2F2 by hydrofluorination of UO3 was also studied. Some catalysed reduction of UO2F2 occurred at temperatures as low as 375ºC. However, with particles of 100 to 300 ym diameter, only 50 per cent conversion was achieved at the catalysed rate for temperatures up to 460ºC. Recombination of the active hydrogen atoms before they penetrated to the core of individual UO2F2 particles prevented the reduction from proceeding further at the catalysed rate. Hydrofluorination of UO2 produced from U02F2 yielded 75 per cent conversion to OFt* at 375 ºC and 50 per cent at 460ºC, the low yields being due to sintering of the UF^ which prevented further reaction. With UO2F2 particles of 100 to 300 Vim diameter, the maximum conversion to UFu in simultaneous reduction and hydrofluorination experiments was 32 per cent at 365ºC over 3 hours. The low yield was due to the size of the U02F2 particles which limited the amount of catalysed reduction, and also to the sintering of UF^. Production of UO2F2 with a low surface area (1.6 m g~ ) was achieved by hydrofluorination between 300 and 400ºC of denitrator U03 which was activated by vapour phase hydration over 10 per cent nitric acid.