Tramex

Tramex [Transuranic metal (or amine) extraction] A process for separating transuranic elements from fission products by solvent extraction from chloride solutions into a tertiary amine solution. Developed at Oak Ridge National Laboratory, TN, for processing irradiated plutonium. 

Tramex. Trade name of a powdered NG-sensi-tized expl distributed in Switzerland by Vereinigung Schweizerischer Sprengstoff-Fabriken. Density, l.lg/cc wt strength, 77% Pb biock test, 335—340cc/10g... 

Tramex (Swiss). Trade name of a powdered NG-sensitized expl distributed in Switzerland by Vereinigung Schweizevischer Sprengstofffabri-ken. Itsd is l.lg/cc, wt strength 77%, and Pb block test 335-40cc/10g Ref R. Meyer, Explosives , Verlag Chemie, NY (1977), 296... 

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. 

In preparation for subsequent anion-exchange runs, the Tramex product solution is treated by a two-step clarification... 

The clarified Tramex product solution is divided into two or three batches (<35 g of curium or <19 g of 244 Qm pgr batch) and processed by LiCl-based anion exchange, which is discussed in detail in another paper at this symposium (10), to obtain further decontamination from rare earths and to separate curium from the heavier elements. In each run, the transplutonium and rare-earth elements are sorbed on Dowex 1-X10 ion exchange resin from a 12 hi LiCl solution. Rare earths are eluted with 10 hi LiCl, curium with 9 M LiCl, and the transcurium elements with 8 jl HC1. About 5% of the curium is purposely eluted along with the transcurium elements to prevent losses of 2498 which elutes immediately after the curium and is not distinguishable by the in-line instrumentation. The transcurium element fractions from each run are combined and processed in a second-cycle run, using new resin, to remove most of the excess curium. 

A second solvent extraction process (Pharex) was developed to partition the transcurium actinides from the americium and curium in the Tramex product ( 3) The Pharex process utilized 2-ethylhexyl phenylphosphonic acid as the extractant for the transcurium actinides. During early operations/ the selectivity of the Pharex extractant was found to be severely reduced by the presence of zirconium ions, which were introduced into the process solutions by corrosion of Zircaloy-2 equipment in TRU. At zirconium concentrations above 10 ppm, the achievable separation began to be diminished and, at 100 ppm, a practical separation could not be made (4). Thus, a replacement for the Pharex process was needed, and the LiCl AIX process was the most immediate alternative ... 

Temporary glass equipment was installed, and the LiCl AIX process was successfully scaled to a useful level (J3). Tramex product solutions containing from 4 to 10 g of 244Cm (11 to 28 W of decay heat) were processed initially, using a 38-mm-diam column containing 450 >n exchange resin. 

The process sequence now used is shown in Fig. 4. Since only about 5% of the fission products are disposed of in waste solutions from the Tramex batch extraction, that process serves primarily as a feed pretreatment for the LiCl AIX. The Tramex product contains about 98% of the transcurium elements and can be processed quickly to maximize the recovery of 253Es which has a 20-d half-life. As time permits, the "clean rework" can be processed to recover the remaining actinides. 

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. ... 

This involves the use of tertiary amine extraction of the An ions from acidic 11 M LiCl solutions. Spectroscopic studies have indicated that, in the cases of Am and Nd at least, the octahedral trianionic hexachloro complexes are extracted from 11 M LiCl. Stability constant data for the chloride complexing of Am , and Cfin media of ionic strength 1,0 have been reported. Tertiary amines also extract Pu and a study of extraction from nitrate media by trilaurylamine (TLA) in xylene has been reported. " This showed that the mass transfer rate was controlled by the reactions between Pu from the bulk phase and interfacially adsorbed TLA-HNOs. The separation of individual transplutonium elements from the Tramex actinide product may be achieved using ion exchange or precipitation techniques." ... 

To a limited extent, lanthanoids are separated from each other by tertiary amine extractants and by quaternary ammonium salts with long (Cg and Cio) alkyl groups. Tertiary amines in an organic phase preferentially extract the trivalent actinoids better than the lanthanoids by salting out (dehydrating) the cations from the aqueous phase with high LiCl concentration, e.g., the TRAMEX (tertiary amine extraction) process for Cm isolation . Recent developments in trivalent f-element separations, such as chelating and bifunctional extractants have been reviewed . 

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... 

This process, which has the advantage of being less corrosive than Tramex, has had widespread application since its development in 1964 (15,16). 

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