The TRUEX process separates the lanthanides and transuranic actinides from the other components in the CCD-PEG, FPEX or NPEX raffinates, notably zirconium and noble metals. Two TRUEX flowsheets have been tested in the demonstrations. The first TRUEX flowsheet is shown in Fig. 7.8 (Pereira, 2007a). Americium, curium and the lanthanide elements are extracted by the TRUEX solvent, which consists of CMPO and TBP diluted by n-dodecane. When the NPEX step is omitted, plutonium and neptunium are also extracted. Lesser amounts of other fission products are also extracted and must be scrubbed from the solvent. The first TRUEX flow­sheet is unique to the UREX+ process by having three scrub sections. In the first scrub section the impurities are removed from the solvent using oxalic acid. Moderately concentrated nitric acid scrubs oxalic acid from the solvent in the second scrub section. In the third scrub section, addition of dilute nitric acid lowers the acid concentration in the solvent to allow effective stripping. The transuranic actinides and lanthanide elements are stripped from the solvent using a lactate buffer containing a complexant which becomes the feed to TALSPEAK. An acetate solution was used when the Cyanex 301 based process followed. In the simplified TRUEX flowsheet shown in Fig. 7.9 (Pereira, 2007b), the three scrub sections were reduced to a single scrub section by adding oxalic acid to the feed directly. The single

scrub section is used to adjust the acidity of the organic phase prior to entering the strip section.

The raffinate of the NPEX process can be fed directly to the extraction section of the TRUEX segment with no feed adjustment. To serve as the TRUEX feed, the CCD-PEG or FPEX raffinate compositions were adjusted by addition of concentrated nitric acid. Just prior to introduction of the feed, a reductant was added to reduce Np(V) to extractable Np(IV).