Lanthanide Tramex process—separation

Treatment of irradiated targets. The chemical operations relative to the production of transplutonium elements (americium 243, curium 244) are all performed using a nitric acid medium. The highly corrosive nature of the solutions concentrated with Cl" ions, which were used in the USA for the development of the Tramex process (JO, and the instability of SCN" ions to radiation (12), led us to select nitric acid solution to perform the chemical separations. Once the medium was selected, it was necessary to find an adequate additive which, in combination with a suitable extractant, would allow solution of the main problem namely separation of the trivalent actinides from triva-lent lanthanides. 

The Cleanex process was adapted from the DAPEX process described in Section 65.2.2.1 (iv) and also utilizes HDEHP to coextract the lanthanides and transplutonium elements. Subsequent separation of these two groups may then be carried out using, for example, the Tramex process. ... 

Amines can also be used to separate the trivalent actinides from the chemically similar trivalent lanthanides. In the Tramex process, a tertiary amine is used as the extractant from 10 to 12 M LiCl, 0.1 to 0.3 N A1C13, and 0.01 M HC1 (13,JA). The development... 

Distribution coefficients of Am and other trivalent transplutonium elements from concentrated LiCl solutions are from 150-fold to more than 1000-fold higher than those of trivalent lanthanides [55]. This phenomenon was used by Moore [56] in various analytical applications it was also exploited at ORNL in the development of the Tramex process for plant-scale separation of americium, curium, and other transplutonium elements from fission product lanthanides [7, 57]. 

Tertiary amines are poor extractants for lanthanides and actinides from dilute nitrate media, but extract these metal ions strongly from concentrated nitrate solutions of low acidity (as was true of TBP). Similar observations have been made for extraction from chloride media. Figure 1 indicates that for 30% Alamine 336/xylene/ll M LiCl group separations are good, some interactinide separations are possible, but lanthanide separation factors are small. Weaver briefly discusses the application of the TRAMEX (tertiary amine extraction) process for the purification of... 

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