12th International Symposium on Symbiotic Nuclear Power ( ISSNP-2026)

The molten salt oxidation (MSO) process has significant potential for spent fuel reprocessing. In order to understand the oxidation reaction and product formation of UO₂ in molten carbonate，this study investigated the effects of temperature (450-650°C), KNO₃ dosage (0-22 mg) and molten salt composition (Li₂CO₃-Na₂CO₃, Li₂CO₃-K₂CO₃, Li₂CO₃-Na₂CO₃-K₂CO₃ eutectic melt) on the oxidation behavior of UO₂ in carbonate molten salt. By using characterization methods such as X-ray diffraction, infrared spectroscopy, and X-ray photoelectron spectroscopy, the changes of the oxidation products during the UO₂ oxidation process were studied. The results shows that increasing the temperature of molten salt can significantly increase the oxidation rate of UO₂; the amount of KNO₃ added has a significant impact on the degree of UO₂ oxidation, and when the potassium nitrate content is higher than 15 mg, complete oxidation of UO₂ can be achieved; for different compositions of molten salts, the oxidation rate of UO₂ in Li₂CO₃-K₂CO₃ eutectic molten salt is the fastest. The process of UO₂ molten salt oxidation mainly proceeds in two steps: first, UO₂ is oxidized to U₃O₈, and then further oxidized to K₂U₂O₇.
 

dry reprocessing;carbonate molten salt;uranium dioxide;molten salt oxidation