PREPARATION OF CARRIER-FREE Ra-228 (MsTh$sub 1$) AND Ac-228 (MsTh$sub 2$) BY ION EXCHANGE

An ion-exchange process was developed for the production of carrier-free Ra/sup 228/ and Ac/sup 228/ . The Ra/sup 228/ was produced from old Th(NO/sub 3/ )/sub 4/. After a tributyl phosphate extraction of about 95% of the Th, the residuals were separated from the Ra/sup 228/ on a Dowex 50 x 8 cation-exchange column in 0.5M NH/sub 4/-lactate solution. In the cation-exchange column, the Ra/ sup 228/ was bound. Rare earth impurities were removed from the column through elution by 0.7M NH/sub 4/-lactate The Ra/sup 228/ was eluated by 3M HNO/sub 3/ and after the solution was concentrated by evaporation, it was transferred through a 0.5 ml 0.05N HCl solution on a 0.3 x 8 cm cation-exchange column filled with Dowex 50 x 12 400 mesh resin. The Ac/sup 228/ can be regularly eluted from the column by 0.65M NH/sub 4/-lactate, since under such conditions the adsorption zone of the Ra/sup 228/ is shifting at a very low rate and the decomposition products Th/sup 228/, Pb/sup 212/, and Bi/sup 212/ are eluated in precedence to the Ac/sup228/. After acidification, the NH/sub 4/-lactate solution containing the Ac/sup 228/ was more » carried over to a cation-exchange column from which first the Pb/sup 212/ and B/sup 212/ were eluted through 2N HCl, and then the Ac/sup 228/ was eluted through 7N HCl. The radioactive contamination of Ac/sup 228/ amounts to 0.2%, and its yield is 70 to 80% related to the initial Ac/sup 228/ content of Th(NO/sub 3/)/sub 4/. (auth) « less