| 摘要 |
In a liquid-liquid extraction process for recovering thorium and uranium values from a neutron-irradiated thorium composition by forming a nitrate ion-deficient aqueous solution from said composition and countercurrently contacting said solution with an aqueous immiscible organic solvent in a liquid-liquid extraction system containing a plurality of extraction stages divided into a first end extraction stage wherein said nitrate ion-deficient solution is introduced into said system, a plurality of intermediate extraction stages and a second end extraction stage for introduction of said organic solvent into said system, and a plurality of scrub stages preceding said first and extraction stage, the improvement consists in introducing an aqueous salting solution of nitric acid into any intermediate extraction stage of said system, countercurrently contacting said salting nitric acid solution with the solvent in said intermediate and succeeding extraction stages, passing thorium and uranium enriched solvent from each of said intermediate extraction stages to the first end extraction stage and thence to said scrub stages in countercurrent contact therein with an aqueous scrub to decontaminate said enriched solvent of residual amounts of fission products and protoactinium, cycling at least a portion of the thus contacted aqueous scrub to join the aqueous phase in said extraction stages and thereafter removing the decontaminated thorium and uranium enriched solvent from the scrub stages and the protoactinium and fission product-containing aqueous raffinate from said extraction stages. The aqueous scrub may be selected from the group consisting of water and an aqueous solution of nitric acid, the solution being no greater than 4 molar in nitric acid. Preferably the scrub solution contains a small amount of phosphate ions. The salting nitric acid solution should preferably be 13 to 16 molar. The organic extractant may be tributyl phosphate in a paraffinic hydrocarbon diluent. Specification 865,011 is referred to. |
