Talspeak process

Talspeak process, 6, 959,960 Tanabe-Sugano diagrams, 1, 238 Tannic acid in gravimetry, 1, 524 Tanning... 

Svantesson, I. 1984. A reversed TALSPEAK process for the separation of actinides from lanthanides. Thesis. Chalmers University of Technology, Goteborg. 

Nilsson, M., Nash, K.L. 2007. Review article A review of the development and operational characteristics of the TALSPEAK process. Solvent Extr. Ion Exch. 25 (6) 665-701. 

Collins, E.D., Benker, D.E., Bailey, P.D. etal. 2005. Hot test evaluation of the TALSPEAK process. Proc. GLOBAL 2005, Tsukuba, Japan, October 9-13. Paper No. 186. 

In the reverse TALSPEAK process, the An(III) + Ln(III) fraction is first coextracted from a feed, the acidity of which has to be reduced to 0.1 M by denitration or nitric acid extraction. An(III) are then selectively stripped using DTPA in citric acid (1 M) at pH 3 (hence the name reverse TALSPEAK process), and the Ln(III) are finally stripped by 6 M HN03. Attempts to apply this TALSPEAK variant to the treatment of actual UREX + raffinates are reported in the literature, but they involve several steps. The problematic Zr and Mo elements are first removed by direct extraction with HDEHP (0.8 M in di-iso-propylbenzene) from the high-acidity raffinate stream arising from the UREX + co-decontamination process (238). The remaining fission products and actinides can then be concentrated by acid evaporation and denitration processes. This concentrate is further diluted to a lower acidity (e.g., [HN03] = 0.03 M) to allow the coextraction of An(III) and Ln(III) by the TALSPEAK solvent. 

Di(2-ethylhexyl) phosphoric acid, used in the TALSPEAK process, which extracts trivalent metallic cations at low acidity by proton exchange. 

As in the SETFICS and TALSPEAK processes, the DIAMEX-SANEX/HDEHP process involves selectively back-extracting the trivalent actinides by a hydrophilic polyamino-carboxylate complexing agent, HEDTA, in a citric acid buffered solution (pH 3). However, the combination of HDEHP and DMDOHEMA at high acidity promotes the coextraction of some block transition metals, such as Pd(II), Fe(III), Zr(IV), and Mo(VI), which must be dealt with by specific stripping steps (as described on Figure 3.26) that increase the total volume of the output streams ... 

The same protective effect was observed in the TALSPEAK process, where the lactic acid added to the aqueous phase reduced the degradation of DTPA (161). 

The separation of transplutonium elements from the lanthanides constitutes the delicate phase of chemical treatment, owing to their comparable affinities for the usual extractants HDEHP, TBP and TLAHNO3. Among all the systems described in the literature and covered by a recently published critical compilation (JO), we selected those which appeared to be much suitable for adaptation to extraction chromatography the Talspeak process (7) and the... 

The Talspeak process and the CEN-FAR TBP process were transposed to extraction chromatography. European researchers (6) have adapted the Talspeak process for the final purification of 2l+1Am and 2l+,+ Cm at the scale of a few grams. Hence our intention is to use this experiment to treat hot targets. 

Since HDEHP is both a cation exchanger and a coordinator in most extraction situations, coordinated water must be removed from the metal ion in the extraction. Because this sometimes leads to a slow reaction step, the kinetics of HDEHP extraction is important. The kinetics of the Talspeak process (14,15) has been investigated (63) the kinetics of Am(III) and Th(IV) extraction by HDEHP in an unstirred system has also been studied (64). 

The aqueous strip solution will form directly the feed solution of the Am, Cm/RE countercurrent separation step, to be performed according to the operating conditions of the TALSPEAK process (15). The presence of a complexing agent like DTPA will prevent the extraction of Am and Cm whereas the RE will be more easily extracted by di(2-ethylhexyl)phosphoric acid (HDEHP) in n-dodecane (pH = 3). 

After the denitration, the process steps sequence of option 2 is similar to the "Reverse Talspeak Process" already developed on a cold laboratory scale at the KfK laboratories of Karlsruhe (19 for the recovery of actinides from HAW. It involves the coextraction of actinides with RE by HDEHP/TBP in n-dodecane at about pH2, the selective stripping of actinides by a Na5 DTPA-glycolic acid solution and the stripping of RE by 4 M HN03. In the case of option 2, the stripping of co-extracted... 

Also in the case of the TBP process, only simulated HAW solutions have been until now used to study the process feasibility. Results have already been reported (9), which indicated that separation yields of about 99.9% can be obtained for Am after three successive extraction stages operating with a concentrated HAW solution adjusted to 0.1 — 0.2 M HN03, 0.65 M AI(N03)3 and 1.3 M NaN03. The back-extraction of all the actinides and RE from loaded TBP (30% in n-dodecane) was carried out by means of Na5 DTPA-glycolic acid solution which can be then used directly to separate Am and Cm from RE according to the Talspeak process (15). 

The main purpose of the separation of Am-Cm from RE by the well known Talspeak process is to liberate the RE fraction from actinides. The acceptable resi-duel RE content in the actinide stream on the contrary will depend widely on the further destination of the latter. It is in any way not a critical point. Therefore, high A/O ratios and an efficient aqueous scrub section must provide for an as low as possible extraction of Am and Cm. For these operations mixer-settler batteries seem to offer the most convenient approach, taking into account radiation levels, flow rates and extraction (and back-extraction) kinetics. 

In the Talspeak process, the separation of trivalent actinides and lanthanides is accomplished by coextracting the two groups of elements into di(2-ethyl hexyl)phosphoric acid (HDEHP) from a carboxylic acid solution and then partitioning the acti-... 

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