Development of a TODGA based Process for Partitioning of Actinides from a PUREX Raffinate Part I: Batch Extraction Optimization Studies and Stability Tests

Abstract

The extractant, N,N,N 0 ,N 0 -tetraoctyl diglycolamide (TODGA) has been evaluated for the separation of actinides(III) and lanthanides(III) from a high active raffinate (HAR). The effect of oxalic acid and HEDTA complexant on the extraction of actinides(III), lanthanides(III), and important fission products (e.g. Mo, Pd, Sr, Zr, Ru etc.) from synthetic HAR has been studied with 0.2 mol/L TODGA in TPH.With an extractant mixture of TODGA and tributyl phosphate (TBP) the amount of oxalic acid can be reduced to less than 0.3 mol/L for the effective complexation of zirconium, whereas the distribution ratios of actinides(III) and lanthanides(III) are still high for the separation from HAR. Furthermore the maximum loading of lanthanides (e.g. Nd) can be significantly increased by adding TBP to the extractant. However, the extraction of oxalic acid and nitric acid also increased by the addition of TBP, which can lead to problems during back extraction of the loaded extractant. Extraction studies after radiolysis and hydrolysis reveal that the TODGA þ TBP mixture is a sufficient stable extraction system suited for further process development studies.

A review of the demonstration of innovative solvent extraction processes for the recovery of trivalent minor actinides from PUREX raffinate

“…Following this, Modolo et al optimized the partitioning process and suggested a new continuous process in which the extractant was a mixture of 0.2 mol/L TODGA and 0.5 mol/L TBP in TPH [28]. The addition of TBP not only improved the hydrodynamic properties but also increased the loading capacity of the extractant and reduced the tendency to third-phase formation.…”

“…using TODGA (Fig. 3) as extracting agent [23,28,29]. A hydrophilic complexing agent selective for An(III) over Ln(III) such as DTPA (diethylenetriaminepentaacetic acid) is used for back-extracting An(III) from the loaded organic phase.…”

Reprocessability of molybdenum and magnesia based inert matrix fuels

“…N,N-dimethyl-N,N-dioctylhexylethoxymalonamide (DMDOHEMA) has become the reference molecule for the DIAMEX processs [13,14] enhancing the extractive properties towards trivalent elements and shortening the degradation compounds formed by acidic hydrolysis and radiolysis [15]. Recently, a new process for recovery of trivalent actinides from PUREX-type raffinate utilizing N,N,N,N--tetraoctyldiglycolamide (TODGA) was developed [16][17][18][19][20][21][22]. In a fi rst step a very effi cient extraction of An(III) and Ln(III) from acidic medium is performed, followed by their stripping using diluted nitric acid [19].…”

A study of cerium extraction by TBP and TODGA using a rotating diffusion cell

“…To facilitate this, a rotating diffusion cell (RDC) [4] apparatus has been established to enable the study of coupled interfacial-mass transfer kinetics of several organic extractant molecules which are to be studied including TBP, TODGA [5,6], CyMe 4 -BTBP [7] and CyMe 4 -BTPhen [8]. The RDC is derived from the Lewis cell but whereas the Lewis design comprises two directly interfaced liquid phases within a single container and utilizes individual stirrers within each phase to generate interfacial fl ux, the RDC includes two separate compartments into which the two solution phases are placed.…”