Influence of dose rate on the radiolytic stability of a BTBP solvent for actinide(III)/lanthanide(III) separation

Abstract

Irradiation / Dose rate / Solvent extraction / Partitioning / Actinides / Lanthanides / Distribution ratio / Separation factorSummary. The recently developed ligand MF2-BTBP dissolved in cyclohexanone is a promising solvent for the group separation of trivalent actinides(III) from the lanthanides(III). Its high stability against nitric acid has been demonstrated recently. Since the solvent is also exposed to a continuously high radiation level in the counter current process, the radiolytic stability of the solvent was examined in this study. Irradiation experiments were carried out up to an absorbed dose of 100 kGy and the effect of the dose rate was investigated. The extraction behaviour for An(III)/Ln(III) separation was studied after radiolysis for evaluation. It was found that during high dose rate irradiation the extraction efficiency for both Am(III) and Eu(III) decreased significantly with increasing absorbed dose, whereas during the low dose rate irradiation the extraction efficiencies remained more or less at the same level.

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.…”

Synthesis and Evaluation of Lipophilic BTBP Ligands for An/Ln Separation in Nuclear Waste Treatment: The Effect of Alkyl Substitution on Extraction Properties and Implications for Ligand Design

“…The tert-butyl-substituted derivative 2 [12] (Figure 1) posesses a higher solubility than CyMe 4 -BTBP 1 in suitable diluents such as 1-octanol and cyclohexanone, [13] although its solvent extraction kinetics are slower than those of 1. More recently, a symmetrical BTP ligand derived from camphor has shown both improved solubility and fast extraction kinetics compared to related BTP ligands.…”

“…[10] Recently, it has been shown that the extraction properties of ligands such as 1 can be improved considerably if the ligand is pre-organized for metal binding with a phenanthroline moiety, which locks the ligand into the required cis conformation. [11] The tert-butyl-substituted derivative 2 [12] ( Figure 1) posesses a higher solubility than CyMe 4 -BTBP 1 in suitable diluents such as 1-octanol and cyclohexanone, [13] although its solvent extraction kinetics are slower than those of 1. More recently, a symmetrical BTP ligand derived from camphor has shown both improved solubility and fast extraction kinetics compared to related BTP ligands.…”

Radiation chemistry in solvent extraction: FY2010 Research

“…Recently, it was reported that the use of varying J-dose-rates for the irradiation of 0.01 M 4-t-butyl-6,6'-bis (5,5,8,8,-tetramethyl-5,6,7,8-tetrahydro-benzo[1,2,4]triazin-3-yl)-bypyridine (MF2-BTBP) in cyclohexanone resulted in different effects on D Am and D Eu (Fermvik et al 2009). The solvent extraction efficiency of americium and europium was unchanged when the solutions were irradiated at 15 Gy h -1 , while distribution ratios decreased to about 60% of their initial value when the solutions were irradiated to the same absorbed dose at 1.2 kGy h -1 .…”