Application of Amine and Phosphonate Extractants to Transplutonium Element Production

The Tramex process, in which trivalent actinides are extracted into tertiary amine hydrochloride from concentrated lithium chloride solution, has been developed for isolation of transplutonium elements from irradiated High Flux Isotope Reactor targets. Tests made in laboratory scale mixer-settlers gave americium losses of about 0.01 % and fission product decontamination factors of equal to or greater than 10⁴. Nickel was the only contaminant that followed the transplutonium elements through the Tramex process. No serious radiation induced effects were noted in 1- to 10-ml batch extraction tests at activity levels up to the proposed processing level of 10 w/liter. A process was developed for splitting transplutonium elements into two fractions. Transcurium elements are extracted into mono-2-ethyl-hexyl phenyl phosphonic acid from dilute hydrochloric acid while americium-curium and nickel contaminant from the Tramex process remain in the aqueous phase. Demonstration in a 10-ml batch countercurrent extraction with simulated feed containing tracers gave a californium loss of about 0.1% and an americium decontamination factor of 10³. Important variables for both extraction processes are discussed.