Radiation resistant ionic liquids for the separation of minor actinides

The project foresees the synthesis of novel radiation-resistant hydrophobic ionic liquids to be used for the extraction of minor actinides from acidic aqueous solutions. The importance of elaborating a separation scheme based on ionic liquids is substantiated by the fact, that currently the presence of the long-lived minor actinides pose a major obstacle in finding a soothing method for final disposal of reprocessed nuclear fuel waste. In the framework of the MYRRHA-project launched by SCK·CEN, accelerator-driven spallation experiments on target materials composed of heavy elements (including minor actinides as well) shall be conducted. The idea of using minor actinides as spallation targets for the purpose of neutron generation has long been fostered by Prof. Carlo Rubbia. A successful demonstration could open new ways to reduce the scale of the problem posed by spent nuclear fuel. In the light of the above, the scope of the present project is clear; elaborating a separation method tailored for the treatment of effluents left after the PUREX process. Such method should be based on a novel ionic liquid for the efficient separation of trivalent minor actinide ions (i.e. Am3+) from mono- or divalent fission products. The ionic liquid needs to remain stable under high doses of absorbed radiation and in highly acidic environment. For the purpose of electrochemical reduction of separated ions, it would be beneficial, that the ionic liquid also has a broad electrochemical window. The project aims to embrace a research during which the target compound is approached on the basis of systematic study of radiation and coordination chemistry of selected candidate compounds. Ionic liquids that show outstanding resistance against radiation-induced decomposition shall be functionalized to enhance extracting properties. In order to demonstrate the extraction properties of the ionic liquids on minor actinide ions, aqueous solution of 241Am3+-ions shall be used in the hot labs of SCK·CEN.status: publishe

Synthesis of gadolinium-doped thorium dioxide via a wet chemical route: Limitations of the co-precipitation method

A wet chemical route (oxalate precipitation) was chosen to prepare gadolinium-doped thoria powders as a feed for pellet fabrication. The oxalate and derived oxide powders were characterized by thermogravimetric analysis coupled to evolved gas analysis, BET, XRD and SEM. Dilatometry was used to study the sintering behavior. From homogeneous solutions containing selected mixtures of gadolinium (III) and thorium (IV) nitrates solid precipitates were obtained, that were composed of two phases. Calcination at 700 °C or 1000 °C was insufficient to obtain single phases for any of the compositions. Rietveld analysis of calcined powders confirmed the presence of both a Th-rich phase (ThxGd1−xO2−x/2) and a Gd-rich phase ((GdyTh1−y)2O3+(1−y)) in which limited substitution of the foreign element (Gd or Th, respectively) occurred. A fluorite-type solid solution formed during sintering at 1750 °C. The unit cell parameters of sintered pellets were determined for ThxGd1−xO2−(1−x)/2 mixed oxides in the composition range: 0 ≤ x ≤ 0.30 and agree with reported values.status: publishe

Beyond U/Pu separation: Separation of americium from the highly active PUREX raffinate

This review provides a comprehensive overview of published hydrometallurgicalchemical processes capable of separating americium from curium and the lanthanides.A search for highly-selective and robust americium separation methods is motivated bythe fact that americium isotopes contribute significantly to the long-term heat load andresidual radiotoxicity of high level waste originating from the PUREX process,nowadays still the key reprocessing technology to recycle uranium and plutonium fromspent nuclear fuel. The separation (partitioning) and subsequent nuclear transmutation(or burning) of americium would allow a substantial cost saving in the construction ofan underground final repository and provide safety benefits – highly relevant for theexploitation of such a facility over extended periods of time. Besides the discussion ofbasic properties of the various separation methods, an evaluation of their compatibilitywith upstream and downstream processes as well as the treatment of secondary wastestreams is provided

Purification of medical 153Sm using radiation-resistant ionic liquids

Poster presentation by Michiel Van de Voordestatus: publishe

Selective Extraction of Americium from Curium and the Lanthanides by the Lipophilic Ligand CyMe4BTPhen Dissolved in Aliquat-336 Nitrate Ionic Liquid

The feasibility of separating americium from curium and the lanthanides was studied in batch solvent extraction experiments using an organic solvent composed of 0.01 mol L-1 2,9-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-1,10-phenanthroline (CyMe4BTPhen) in the ionic liquid Aliquat-336 nitrate [A336][NO3] from feed solutions containing N,N,N’,N’-tetraethyl diglycolamide (TEDGA), stable lanthanide ions and tracers of 241Am, 244Cm and 152Eu. The combined use of a lipophilic and a hydrophilic ligand with opposite selectivity for Am(III) vs. Cm(III) and Ln(III) allowed the separation of Am(III) from Cm(III) and Ln(III) from moderate acidic feed solutions (1 mol L-1 HNO3, SFAm/Cm = 3.1 - 3.9, SFAm/La > 75, SFAm/Eu ≥ 3000)

Solvent extraction of Am(III), Cm(III) and Ln(III) ions from simulated highly active raffinate solutions by TODGA diluted in Aliquat-336 nitrate ionic liquid

The extraction behaviour of americium(III), curium(III) (minor actinides, MA), fission products (lanthanides (Ln(III)), Mo, Ru, Pd, Rh) and corrosion products (Zr, Fe) was studied in batch solvent extraction experiments using the room-temperature ionic liquid Aliquat-336 nitrate ([A336][NO3]) and a solvent composed of 0.05 M TODGA in [A336][NO3]. From acidic, dilute Ln(III) feed solutions, [A336][NO3] extracts nitric acid (D ≈ 0.5) and partially An(III) as well as Ln(III) (DAm = 0.02 -0.1, DEu and DCm = 0.01 - 0.04). The influence of the acid concentrations and kinetics on extraction and back-extraction of Ln(III) and An(III) by 0.05 M TODGA in [A336][NO3] was investigated using radiotracer-spiked dilute Ln(III) feed solutions. With the solvent composed of 0.05 M TODGA in [A336][NO3], DAn and DLn increased as a function of aqueous feed acidity. In the case of a spiked, simulated highly active raffinate (HAR) feed solution, [A336][NO3] extracted La(III) (DLa = 1.36), Ru (DRu = 1.64) and Pd (DPd = 38), while the distribution ratios of other Ln(III) and An(III) were lower than unity. The solvent composed of 0.05 M TODGA in [A336][NO3] co-extracted from HAR Zr(IV) (DZr > 300), Pd (DPd = 206) and Ln(III) (DLn > 1, except for Nd(III)), but An(III) were retained in the aqueous phase. The interference caused by the co-extraction of several fission (Zr, Pd, Ru, Mo) and corrosion (Zr) products, which are present in the HAR at relatively high concentrations, was suppressed using masking agents (oxalic acid and trans-1,2-diaminocyclohexane-N,N,N’,N’-tetraacetic acid or CDTA). In the case of the actual HAR solution, the kinetics were found to be faster compared to the extraction from dilute Ln(III) feed solutions, possibly due to the different aqueous speciation of the Ln(III) and An(III)

Selective Extraction of Americium from Curium and the Lanthanides by the Lipophilic Ligand CyMe(4)BTPhen Dissolved in Aliquat-336 Nitrate Ionic Liquid

status: publishe

Selective extraction of trivalent actinides using CyMe4BTPhen in the ionic liquid Aliquat-336 nitrate

The extraction of Am(iii), Cm(iii) and Eu(iii) by 2,9-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-1,10-phenanthroline (CyMe4BTPhen) from nitric acid solution was studied using the ionic liquid Aliquat-336 nitrate ([A336][NO3]) as diluent. Results show a high selectivity of the solvent for Am(iii) and Cm(iii) over Eu(iii), but rather slow extraction kinetics. The kinetics of CyMe4BTPhen were largely improved by the addition of 0.005 mol L−1 N,N,N′,N′-tetra-n-octyl-diglycolamide (TODGA) as a phase transfer reagent and by the use of 1-octanol as co-diluent. The addition of the phase transfer catalyst and co-diluent did not compromise the selectivity towards the actinide/lanthanide separation and thus this four-component system can be successfully applied to separate Am(iii) and Cm(iii) from the lanthanides

Application of Aliquat-336 nitrate ionic liquid based extractants for minor actinide separation

Oral presentation by Peter Zsabkastatus: publishe