Studies on the Electrodeposition of UO2 Production in UO2Cl2-LiCl-KCl Melt

Abstract

UO2 is an important nuclear fuel, also has potentials in the field of functional materials. In this work, the electrochemical behavior of UO2 2+ in LiCl-KCl molten salt (500 °C) and the effects of reduction potential (−0.1 to −1.0 V) and uranyl concentration (0.5 wt% to 4.0 wt%) on morphology and grain size of electrolytic products were studied. The reduction potential was found playing a decisive role in the morphology of cathodic products. When the potential was ≤−0.4 V (vs Pt(II)/Pt), dendritic and cracked characteristic of the UO2 crystal appeared. The average current density had a positive correlation with the grain size of cathodic products, and it increased first and then decreased with the increase of overpotential, having a maximum at −0.6 V (vs Pt(II)/Pt). On the other hand, the uranyl concentration also had a positive correlation with the grain size of the cathodic product without changing the integrity of grain morphology. For the preparation of large and granular UO2 crystal, the reduction potential of −0.2to−0.3 V (vs Pt(II)/Pt), as well as the uranyl concentration of greater than 2.0 wt% were recommended, and UO2 crystal with average grain size greater than 500 μm and high uniformity could be finally obtained.