| 摘要 |
<p>Plutonium or uranium or both are extracted from an aqueous nitric acid solution containing fission products by treating the solution, in which the plutonium is in the tetravalent or higher state and the uranium is in the hexavalent state, with tributyl phosphate which forms a water-immiscible phase containing the plutonium or uranium. For extraction of both uranium and plutonium, the aqueous nitric acid solution treated should be at least normal in nitric acid, preferably 2-7 N. The tributyl phosphate may be diluted with an inert liquid, e.g. kerosene or benzene. Uranium and plutonium present in the water-immiscible phase may be separated (a) by contacting the solvent phase with an aqueous N-SN nitric acid solution containing a reducing agent, e.g. ferrous sulphamate, hydroxylamine, or hydrazine in a concentration of 0.05 N, when the plutonium is reduced to the trivalent state and transfers to the aqueous phase, leaving the uranium in the solvent phase; or (b) by contacting the solvent phase repeatedly with 0.1-0.3 N nitric acid, when the plutonium passes preferentially into the aqueous phase. Plutonium or uranium may be removed from the solvent phases by washing with water. In an alternative process, the initial solution is made 0.1-0.3 normal in nitric acid and extracted with tributyl phosphate; only the uranium is extracted, the plutonium remaining in the aqueous phase, from which it may be obtained by increasing the acidity to 2-7 N and contacting with tributyl phosphate.</p> |
