Use of reductants in the purification of uranium by purex process

Counter current extraction studies were carried out on a laboratory scale to assess the usefulness of reducing agents like hydrazine, ferrous sulfamate and uranous nitrate stabilized with hydrazine as scrubs in enhancing the uranium product purity during the final purification step by purex process. These experiments were conducted with depleted uranium solution containing plutonium and fission product impurities as aqueous feed and 30 % TBP in Shell Sol T as solvent, using a twelve stage mixer-settler unit. The extent to which parameters like feed acidity and organic uranium saturation would influence the product purity was also investigated. The capacity of the reductants as scrubs in giving the required uranium purity with respect to gross beta, gamma activities in the product decreased in the following order : uranous nitrate > ferrous sulfamate > hydrazine. Even under higher feed acidity and lower level of organic uranium saturation, uranous nitrate stabilized with hydrazine (when used as scrub) was capable of giving final product which was comparable to that obtained under low acid feed conditions. As for the plutonium removal, uranous nitrate and ferrous sulfamate were capable of giving uranium products with 0.05 μgPu/gmU when the feeds contained about 75 μgPu/gmU. Hydrazine scrub was suitable only for aqueous feeds having low plutonium content. (author)