Thermodynamic analysis of uranium oxides fluorination with HF(g) and F2(g)

Abstract

This paper presents a thermodynamic analysis of the fluorination of UO2(s) and UO3(s) with HF(g) and F2(g). The reaction mechanisms, intermediates and final products were analyzed using different thermodynamic calculations, including free energy change, phase stability and equilibrium composition diagrams. In the U–O–F system uranium oxyfluorides are necessarily formed between uranium oxides and fluorides. The effect of low pressure gaseous products was analyzed. The reaction between UO2F2(s) and HF(g) to produce UF4(s) is thermodynamically feasible at temperatures higher than 680, 320 and 160 °C for pO2(g) 10−3, 10−4 and 10−5 atm, respectively. This appears to be a potential yield loss mechanism during the fluorination in flow reactors.