Applications of Diglycolamide Based Solvent Extraction Processes in Spent Nuclear Fuel Reprocessing, Part 1: TODGA

ABSTRACT

Over the last decade there has been much interest in the applications of diglycolamide (DGA) ligands for the extraction of the trivalent lanthanide and actinide ions from PUREX high active raffinates or dissolved spent nuclear fuel. Of the DGAs, the N,N,N’,N’-tetraoctyldiglycolamide (TODGA) is the best known and most widely studied. A number of new actinide separation processes have been proposed based on extraction with TODGA. This review covers TODGA-based processes and extraction data, specifically focusing on how phase modifiers have been used to increase metal loading and thus enhance the operating process envelopes. Effects of third phase formation and the organic phase speciation are reviewed in this context. Relevant aspects of the extraction chemistry of important solvents (TODGA-modifier-diluent combinations) are described and their performances demonstrated by a consideration of the published flowsheet tests. It is seen that modifiers are successfully enabling the use of TODGA in actinide separation processes but to date the identification and testing of suitable modifiers has been rather empirical. There is a growing understanding of the fundamental chemistry occurring in the organic phase and how that affects extractant speciation and metal loading capacity but studies are still needed if TODGA-based flowsheets are to become an industrially deployable option for minor actinide (MA) recovery processes.

KEYWORDS:

• TODGA
• modifier
• third phase
• diglycolamide
• DGA
• extraction
• review

Supplemental data

Supplemental data for this article can be access on the publisher’s website.

Notes

¹ Tables of distribution ratios are summarized in the electronically available Supplementary Information (section 2).

² HAR/GANEX-1 product compositions and solvent dose rates used in testing TODGA-based processes are given in the electronically available Supplementary Information section 1. Data from flowsheet tests are given in the electronically available Supplementary Information section 3.

Additional information

Funding

The authors acknowledge the NNL Internal Strategic Research Program “ARIS: Advanced Recycling and Isotope Separations” and European Commission project SACSESS – Contract No. FP7-Fission-2012–323-282 – for financial support.