Abstract: In a process for converting UF.sub.6 into UO.sub.2, the UF.sub.6 is brought into contact with an aqueous aluminum nitrate solution. The resultant product is solvent extracted with tributyl phosphate to remove uranyl nitrate. The raffinate has a fluorine/aluminum (F/Al) weight ratio within the range of from about 0.5 to about 1.2. A sufficient quantity of hydrofluoric acid is added to the raffinate to minimize the solubility of aluminum fluoride (AlF.sub.3) therein and thereby maximize the precipitation potential of AlF.sub.3. Generally this occurs when sufficient hydrofluoric acid has been added to cause the F/Al weight ratio to be within the range of from about 1.8 to about 2.2. As a result of this treatment, the raffinate is divided into an uranium-containing aqueous solution and an AlF.sub.3 precipitate which contains substantially no uranium.

Abstract: An improved Purex wet recovery process including the step of extracting and separating uranium and plutonium simultaneously from the fission products in the presence of nitric acid and nitrous acid by using a multistage extractor unit having an extracting section and a washing section is provided for separating and recovering neptunium simultaneously with uranium and plutonium contained in spent nuclear fuel. The improved method comprises the steps of maintaining the nitrous acid concentration in said extracting section at a level suited for effecting oxidation of neptunium from (V) to (VI) valence, while lowering the nitrous acid concentration in said washing section so as to suppress reduction of neptunium from (VI) to (V) valence, and maintaining the nitric acid concentration in said washing section at a high level.