PURPOSE: To easily recover high-purity U components without contaminating an org. phase after extraction by extracting U components in an aqueous soln. into an org. solvent and shifting the U components into an aqueous phase using an aqueous soln. contg. NH4F, NH4HF2, KF or KHF2.

CONSTITUTION: U components in an aqueous soln. are extracted with an org. solvent prepared by diluting ≥1 kind of extracting reagent selected from alkylphosphoric acids, alkylarylphosphoric acids, alkyldithiophosphoric acids, aryldithiophosphoric acids, neutral phosphoric esters and alkylamines with petroleum hydrocarbon. The org. solvent contg. the U components is brought into contact with an aqueous soln. contg. ≥1 kind of compound selected from NH4F, NH4 HF2, KF and KHF2. Thus, sexivalent U and quadrivalent U in the org. solvent are shifted into the aqueous phase in accordance with equationsIWV, and crystals of uranium ammonium fluoride, etc. are formed. Each of these double salts has a high crystallization rate, the purity can be easily enhanced by recrystallization, and by heating the crystals in water, O2, H2 or an inert gaseous flow, UF4 and UO2 can be recovered at a relatively low temp. The decomposed gas can be utilized.