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

Abstract

Summary. The selective partitioning (P) of long-lived minor actinides from highly active waste solutions and their transmutation (T) to short-lived or stable isotopes by nuclear reactions will reduce the long-term hazard of the high-level waste and significantly shorten the time needed to ensure their safe confinement in a repository. The present paper summarizes the on-going research activities at Forschungszentrum Jülich (FZJ), Karlsruher Institut für Technologie (KIT) and Institute for Transuranium Elements (ITU) in the field of actinide partitioning using innovative solvent extraction processes. European research over the last few decades, i.e. in the NEWPART, PARTNEW and EUROPART programmes, has resulted in the development of multi-cycle processes for minor actinide partitioning. These multi-cycle processes are based on the co-separation of trivalent actinides and lanthanides (e.g. by the DIAMEX process), followed by the subsequent actinide(III)/lanthanide(III) group separation in the SANEX process. The current direction of research for the development of innovative processes within the recent European ACSEPT project is discussed additionally. This paper is focused on the development of flow-sheets for recovery of americium and curium from highly active waste solutions. The flow-sheets are verified by demonstration processes, in centrifugal contactors, using synthetic or genuine fuel solutions. The feasibility of the processes is also discussed.

The structures of CyMe4-BTBP complexes of americium(iii) and europium(iii) in solvents used in solvent extraction, explaining their separation properties

“…Recent studies have shown that poly-aromatic nitrogen compounds, N-PAHs, acting as tetradentate chelating ligands to the metal ions in the extraction, have the ability to sufficiently separate An(III) from Ln(III). [7][8][9][10] One of these N-PAHs, 6,6'-bis (5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-benzol [1,2,4]triazin-3-yl) [2,2]bipyridine, CyMe4-BTBP (Figure 1), has promising process potential, [11][12][13][14][15][16] as it has proven to be resistant towards acidic environments [17][18][19] and strong radiation from radioactive decomposition 13,20 Qualitative reasoning concerning the Lewis basicity of the extractant and the somewhat softer character of the actinoid(III) ions compared to the lanthanoid(III) ones has been used to explain the An(III)/Ln(III) separation capacity of N-PAH ligands. 32,33 An(III)/Ln(III) separation by CyMe4-BTBP has also been observed to vary with the solvent used.…”

A Complexation Study of 2,6-Bis(1-(p-tolyl)-1H-1,2,3-triazol-4-yl)pyridine Using Single-Crystal X-ray Diffraction and TRLFS

“…The minor actinides are recovered from a PUREX raffinate by selective extraction. 3,4 The implications of this strategy are the subject of several studies. 5,6 These strategies at some point require separating trivalent actinides, An(III) = Am(III), Cm(III) from the chemically similar lanthanides, Ln(III), generated by nuclear fission.…”

Reprocessability of molybdenum and magnesia based inert matrix fuels

“…The processes that have been developed over the past 20 years, are mainly based on the co-extraction of trivalent actinides and lanthanides and their subsequent separation [2,11]. The separation of An(III) + Ln(III) from PUREX raffi nate in a process called DIAMEX (diamide extraction) was proposed in the 1980s [12].…”

“…Plutonium and MA (especially americium) are of particular concern with respect to long-term radiotoxicity, heat load issues and proliferation risks. The partitioning and transmutation (P&T) of MA in accelerator driven systems (ADS) is one possibility to cope with this problem [1][2][3].…”