Peter Kaufholz

Laboratory-Scale Counter-Current Centrifugal Contactor Demonstration of an Innovative-SANEX Process Using a Water Soluble BTP

In this paper the development and laboratory-scale demonstration of a novel “innovative-SANEX” (Selective Actinide Extraction) process using annular centrifugal contactors is presented. In this strategy, a solvent comprising the N,N,N’,N’-tetraoctyldiglycolamide (TODGA) extractant with addition of 5 vol.-% 1-octanol showed very good extraction efficiency of Am(III) and Cm(III) together with the trivalent lanthanides (Ln(III)) from simulated Plutonium Uranium Refining by Extraction (PUREX) raffinate solution without 3rd phase formation. Cyclohexanediaminetetraacetic acid (CDTA) was used as masking agent to prevent the co-extraction of Zr and Pd. An(III) and Ln(III) were co-extracted from simulated PUREX raffinate, and the loaded solvent was subjected to several stripping steps. The An(III) were selectively stripped using the hydrophilic complexing agent SO3-Ph-BTP (2,6-bis(5,6-di(sulfophenyl)-1,2,4-triazin-3-yl)pyridine). For the subsequent stripping of the Ln(III), a citric acid based solution was used. A 32-stage process flow-sheet was designed using computer-code calculations and tested in annular miniature centrifugal contactors in counter-current mode. The innovative SANEX process showed excellent performance for the recovery of An(III) from simulated High Active Raffinate (HAR) solution and separation from the fission and activation products. ≥ 99.8% An(III) were recovered with only low impurities (0.4% Ru, 0.3% Sr, 0.1% Ln(III)). The separation from the Ln(III) was excellent and the Ln(III) were efficiently stripped by the citrate-based stripping solution. The only major contaminant in the spent solvent was Ru, with 14.7% of the initial amount being found in the spent solvent. Solvent cleaning and recycling therefore has to be further investigated. This successful spiked test demonstrated the possibility of separating An(III) directly from HAR solution in a single cycle which is a great improvement over the former multi-cycle strategy. The results of this test are presented and discussed.

Solvent Extraction and Fluorescence Spectroscopic Investigation of the Selective Am(III) Complexation with TS-BTPhen

ABSTRACT An americium(III) selective separation procedure was developed based on the coextraction of trivalent actinides (An(III)) and lanthanides (Ln(III)) by TODGA (N,N,N′,N′-tetraoctyl-diglycolamide), followed by Am(III) selective stripping using the hydrophilic complexing agent TS-BTPhen (3,3′,3ʺ,3ʺ′-[3-(1,10-phenanthroline-2,9-diyl)-1,2,4-triazine-5,5,6,6-tetrayl]tetrabenzenesulfonic acid). Distribution ratios were found at an acidity of 0.65 mol L−1 nitric acid that allowed for the separation of Am(III) from Cm(III) (DCm > 1; DAm < 1), giving a separation factor between curium and americium of SFCm/Am = 3.6 within the stripping step. Furthermore, Am(III) was readily separated from the lanthanides with the lowest selectivity for the Ln(III)/Am(III) separation being lanthanum with a separation factor of SFLa/Am = 20. The influence of the TS-BTPhen concentration on Am(III) distribution ratios was studied, giving a slope (logD vs. log[TS-BTPhen]) of approximately −1 for the stripping of An(III) with TS-BTPhen from the TODGA-based organic phase. Time-resolved laser fluorescence spectroscopy (TRLFS) measurements of curium(III) were used to analyze the speciation of Cm(III)-TS-BTPhen complexes. Both 1:1 and 1:2 complexes were identified in single-phase experiments. The formation of the 1:1 complex was suppressed in 0.5 mol L−1 nitric acid but it was significantly present in HClO4 at pH 3. Conditional stability constants of the complex species were calculated from the TRLFS experiments.

4-[18F]Fluorophenylpiperazines by improved Hartwig-Buchwald N-arylation of 4-[18F]fluoroiodobenzene, formed via hypervalent λ3-iodane precursors: application to build-up of the dopamine D4 ligand [18F]FAUC 316.

Substituted phenylpiperazines are often neuropharmacologically active compounds and in many cases are essential pharmacophores of neuroligands for different receptors such as D2-like dopaminergic, serotoninergic and other receptors. Nucleophilic, no-carrier-added (n.c.a.) 18F-labelling of these ligands in an aromatic position is desirable for studying receptors with in vivo molecular imaging. 1-(4-[18F]Fluorophenyl)piperazine was synthesized in two reaction steps starting by 18F-labelling of a iodobenzene-iodonium precursor, followed by Pd-catalyzed N-arylation of the intermediate 4-[18F]fluoro-iodobenzene. Different palladium catalysts and solvents were tested with particular attention to the polar solvents dimethylformamide (DMF) and dimethylsulfoxide (DMSO). Weak inorganic bases like potassium phosphate or cesium carbonate seem to be essential for the arylation step and lead to conversation rates above 70% in DMF which is comparable to those in typically used toluene. In DMSO even quantitative conversation was observed. Overall radiochemical yields of up to 40% and 60% in DMF and DMSO, respectively, were reached depending on the labelling yield of the first step. The fluorophenylpiperazine obtained was coupled in a third reaction step with 2-formyl-1H-indole-5-carbonitrile to yield the highly selective dopamine D4 ligand [18F]FAUC 316.

TS-BTPhen as a promising hydrophilic complexing agent for selective Am(III) separation by solvent extraction

Abstract The novel hydrophilic back-extraction agent TS-BTPhen (3,3ʹ,3ʺ,3ʹʺ-[3-(1,10-phenanthroline-2,9-diyl)-1,2,4-triazine-5,5,6,6-tetrayl]tetrabenzenesulfonic acid) was tested for its selectivity towards Am(III) over Cm(III) and Eu(III) with a TODGA (N,N,Nʹ,Nʹ-tetraoctyldiglycolamide) based solvent. Batch experiments were carried out using TS-BTPhen dissolved in aqueous nitric acid solution with tracers of 152Eu, 241Am and 244Cm. A significant increase of the separation factor for Cm over Am from SFCm/Am = 1.6 up to SFCm/Am = 3.3 was observed compared to the use of a TODGA-nitric acid system alone. Furthermore, stripping was possible at high nitric acid concentrations (0.6-0.7 mol/L) resulting in a low sensitivity to acidity changes. The influence of the TS-BTPhen concentration was analyzed. A slope of -2 was expected taking into account literature stoichiometries of the lipophilic analogue CyMe4BTPhen. However, a slope of -1 was found. Batch stripping kinetics showed fast kinetics for the trivalent actinides. As an alternative organic ligand the methylated TODGA derivate Me-TODGA (2-methyl-N,N,Nʹ,Nʹ-tetraoctyldiglycolamide) was tested in combination with the hydrophilic TS-BTPhen. The Am(III) separation was achieved at even higher nitric acid concentrations compared to TODGA.

Process Development and Laboratory-Scale Demonstration of a Regular-SANEX Process Using C5-BPP (2,6-Bis(5-(2,2-dimethylpropyl)-1H-pyrazol-3-yl)pyridine)

An optimized solvent comprising 0.01 mol/L C5-BPP + 0.5 mol/L 2-bromo-hexanoic acid in TPH with 10% 1-octanol was developed for the selective extraction of trivalent actinides from lanthanides. Equilibrium extraction data and kinetics of the system in extraction, scrubbing and stripping modes were evaluated and a 16-stage flow-sheet was successfully tested in a spiked centrifugal contactor demonstration. It turned out that 16 stages were insufficient for a complete recovery of An(III), although a clean An(III) product was obtained. The high selectivity of C5-BPP for An(III) was shown. The results of the spiked centrifugal contactor test are presented and discussed.

Complexation of Actinide(III) and Lanthanide(III) with H4TPAEN for a Separation of Americium from Curium and Lanthanides

Previous studies have identified the TPAEN ligand as a potentially appropriate complexing agent in solvent extraction processes for the separation of americium (Am(III)) from the fission products including lanthanide (Ln(III)) and curium (Cm(III)) ions, a challenging issue for advanced nuclear fuel recycling. To get insight into the selectivity of this ligand, the complexation of selected trivalent Ln(III) and actinide (An(III)) cations with TPAEN was investigated in solution. First, the structure and stoichiometry of the TPAEN complex with Am(III) were characterized by extended X-ray absorption fine structure spectroscopy (EXAFS). Then complexation constants and thermodynamics data were acquired for the complexes using different methods: microcalorimetry for the Ln(III) cations, time-resolved laser fluorescence spectroscopy (TRLFS) for Eu(III) and Cm(III), and UV-visible spectroscopy for Nd(III) and Am(III).

Optimization and Single-Stage Centrifugal Contactor Experiments with the Novel Hydrophilic Complexant PyTri-Diol for the i-SANEX Process

ABSTRACT The applicability of 2,6-bis[1-(propan-1-ol)-1,2,3-triazol-4-yl)]pyridine (PyTri-Diol) in the innovative Selective ActiNide EXtraction (i-SANEX) process as water-soluble complexing agent was studied. Preliminary batch experiments were aimed at identifying the optimal formulation of the PyTri-Diol solution and at preparing the ground for single-stage centrifugal contactor experiments. A N,N,N′,N′ tetraoctyl diglycolamide (TODGA)-based solvent loaded using a spiked synthetic Plutonium and Uranium Reduction EXtraction raffinate and the optimized PyTri-Diol aqueous phase were contacted in a single-stage annular centrifugal contactor setup with three different flow-rate conditions. No hydrodynamic problems were encountered, and promising minor actinide separation from other cations was achieved with satisfactory kinetics and stage efficiency. The flow sheet of a TODGA–PyTri-Diol-based i-SANEX process was designed exploiting batch and single-stage data, promoting the CHON compliant PyTri-Diol as excellent alternative to the formerly used SO3–Ph–BTP.