Fluorination reaction of UO3 and electrochemical preparation of UO2

In this work, a technique was proposed to prepare UO 2 from UO 3 by the two processes of fluorination reaction of UO 3 with NH 4 HF 2 and electrochemical reduction of UO 2 2 + for the recycle uranium. The feasibility of fluorination reaction was firstly confirmed using thermodynamic calculation; then, the products were analyzed using XRD, Raman and fluorescence to be UO 2 F 2 . The fluorination mechanism was inferred to be UO 3 (s) + NH 4 HF 2 → (NH 4 ) 3 UO 2 F 5 → NH 4 (UO 2 ) 2 F 5 → UO 2 F 2 . The redox behavior of UO 2 2 + on W electrode was investigated by cyclic voltammetry and square wave voltammetry, which indicated that UO 2 2 + was reduced to UO 2 via a two-step single electron transfer with diffusion-controlled. The diffusion coefficient of UO 2 2 + was calculated to be 6.22 × 10 −5 cm 2 /s. The disproportionation reaction of UO 2 + was observed, and the relationship between the disproportionation reaction and scan rate was discussed. Moreover, the electrochemical fabrication of UO 2 was conducted by electrolysis at −0.8 V, and the product was analyzed by XRD, SEM and EDS to be UO 2 . ICP-AES results showed that the extraction efficiency of UO 2 could reach 98.53%. UO 3 obtained by high-temperature oxidation of spent fuel is first fluorinated to produce UO 2 F 2 , and then UO 2 F 2 is electrochemically reduced to the oxide fuel UO 2 in LiCl-KCl molten salt.