Partitioning of minor actinides from rare earths by solvent extraction with DI(2-ethyl hexyl) phosphoric acid

A flowsheet of the solvent extraction process to separate minor actinides(MA) from rare earths(RE) was devised and experimentally tested. The process is based on the high extractabilities of minor actinides and rare earths by di(2-ethyl hexyl) phosphoric acid at low nitric acid concentrations. The extraction process, composed of one extraction and three selective stripping in series, was installed with four miniature mixer-settler banks of a total of 44 stages in a glove box. The operation was performed by using a simulated waste solution containing 15 inactive compounds as the stands-in for rare earths and other fission products, and 241Am and 237Np as radioactive tracers for the minor actinides. For each element fed to the extraction bank, more than 99% of Am, Np, and rare earths were extracted by 1 M HDEHP/n-dodecane. Then each of the Am, Np, and RE was selectively back extracted into the aqueous phase by 0.05 M DTPA, 6 M HNO3, and 0.5 M H2C2O4, respectively, in consecutive stripping processes. In these steps, 99.8% of Am, 97 ∼ 99% of rare earths elements and 99.4% of Np were separated from one another. The Am and Np products, however, may require further purifications because of other impurities accompanied these elements into their respective product streams. (authors)