[en] In a first part, this research thesis presents the general context of nuclear waste processing (nature of wastes to be processed, characteristics of the used method and products), and proposes an overview of results obtained during previous campaigns which were based on the use of the technique of supported liquid membranes, but with other types of extracting components. The second part focuses on the tracking of complexing and extractive properties of all functionalized calixarenes which had been synthesised by different research teams. Several experiments have been performed to determine the extraction efficiency and selectivity of these organic compounds with respect to the studied radio-elements. The third part reports the detailed study of a specific family of functionalized calixarenes for which two thermodynamic models of membrane transport described in the literature have been applied. Validity limits are discussed with respect to operation conditions. Some results are finally given on the caesium and actinide (neptunium, plutonium) decontamination of synthetic concentrates which simulate actual radioactive wastes

[en] In order to better understand the extraction mechanisms of An(III) and Ln(III) by bis-triazinyl-pyridines (Btp), as well as the affinity of the latter towards An(III), the extraction of ¹⁵²Eu and ²⁴¹Am by 2,6-bis(5,6-iso-butyl-1,2,4-triazin-3-yl)-pyridine (iBu-Btp) was deeply studied. The distribution ratios (D_M) of both radiotracers were determined by γ spectrometry. The analyses of the slopes of ''log-log'' plots of experimental D_M values vs the concentration of iBu-Btp or that of nitrate anions at equilibrium, allowed the stoichiometry of the extracted complexes to be estimated. The extraction constants of Eu(III) and Am(III) were thereafter calculated at different temperatures and thermodynamic data, such as ΔH_ex and ΔS_ex, were deduced from the Van't Hoff's law. (author)

[en] Bis-triazinyl-pyridines have been developed at CEA-Marcoule to separate actinides(III) from lanthanides(III). Although high separation performances were observed in the counter-current hot test carried out in 1999 on a highly active effluent, the extraction and back-extraction yields of actinides(III) were lower than expected from calculation. A strong sensitivity of the extractant towards air oxidation and acidic hydrolysis was actually pointed out. Therefore, the hydrolysis of bis-triazinyl-pyridines has been deeply investigated (qualitative determination of the degradation products) in different experimental conditions. It appeared that the branching of the alkyl groups on the α position of the triazine rings hindered the hydrolysis of the extractant. The formulation of the solvent was thus optimized and tested again in 2001 on a genuine DIAMEX back-extraction solution in the ATALANTE facility. (author)

[en] Actinide recycling by separation and transmutation is considered world wide and particularly in several European countries as one of the most promising strategies to reduce the inventory of radioactive waste, thus contributing to making nuclear energy sustainable. By joining together European universities, nuclear research bodies and major industrial players in a multi-disciplinary consortium, the FP7 EURATOM Fission Project ACSEPT provides the sound basis and fundamental improvements for future demonstrations of fuel treatment in strong connection with fuel fabrication techniques. In accordance with the Strategic Research Agenda of the Sustainable Nuclear Energy Technology Platform (SNE-TP), the timelines of this four-year R and D project (2008-2012) should allow the offering of technical solutions in terms of separation process that may be reviewed by governments, European utilities as well as technology providers at that time horizon. By showing a technically feasible recycling of actinides strategy, ACSEPT will certainly produce positive arguments in the sense that European decision makers, and more globally public opinion, could be convinced that technical solutions for a better management of nuclear wastes are now technologically feasible. ACSEPT is thus an essential contribution to the demonstration, in the long term, of the potential benefits of actinide recycling to minimise the burden on geological repositories. To succeed, ACSEPT is organised in three technical domains: i) Considering technically mature aqueous separation processes, ACSEPT will optimise and select the most promising ones dedicated either to actinide partitioning or to group actinide separation. These developments are appropriately balanced with an exploratory research focused on the design of new molecules. ii) Concerning pyrochemical separation processes, ACSEPT first focuses on the enhancement of the two reference cores of process selected within EUROPART. R and D efforts shall also be brought to key scientific and technical points compulsory for building a whole separation process. iii) All experimental results will be integrated by carrying out engineering and systems studies on hydro- and pyro-processes to prepare for future demonstration at a pilot level. In parallel, with a view to consolidate future actinide recycling strategies, ACSEPT is in charge of the design of the minor-actinide-containing pins, prior to their fabrication in the future FAIRFUELS FP7 project. A training and education programme is also being implemented to share the knowledge within the partitioning community and present and future generations of researchers. Specific attention will be given to the funding of multi-partite post-doctorate fellowships. (authors)

[en] In the framework of nuclear waste reprocessing, separation processes of minor actinides from fission products are developed by Cea. In order to understand the mechanisms involved in the extraction processes, the 'ligand/metallic cation' complexes, formed in the organic phases are characterized by electro-spray-mass-spectrometry (ESI-MS). This paper deals with the extraction of lanthanides (III) and americium (III) cations by an organic phase composed of a malonamide or / and a dialkyl phosphoric acid, diluted in an aliphatic diluent. For the dialkyl phosphoric acid, Ln(DEHP)₃(HDEHP)₃ complexes are observed and in the presence of a large excess of Ln(NO₃)₃, dinuclear species are also observed. For the malonamide extractant, it appears that the complexes formed in the organic phase are of the Nd(NO₃)₃D_x type, with 2 ≤ x ≤ 4: their distributions depend on the ratio [Ln]/[DMDOHEMA]. When the two extractants are present in the organic phase, mixed 'Ln-malonamide-dialkyl phosphoric acid' species are observed. The influence of several parameters, such as extractant concentration, solute concentration, aqueous acidity and the nature of the cations (lanthanides or americium) are studied. (authors)

[en] One of the hydrometallurgical options studied by CEA to separate trivalent minor actinides (An(III)) from highly active PUREX raffinates, consisted first in co-extracting An(III) and Ln(III) by a malonamide and, second, in separating An(III) from Ln(III) by a bis-triazinyl-pyridine (BTP). If malonamides have been successfully applied to the treatment of genuine spent fuel dissolution liquors, the various tetra-alkyl substituted BTP molecules studied until 2001 have shown that they were too sensitive to acidic hydrolysis and alpha radiolysis to envisage the development of an An(III)/Ln(III) separation process. That is why, in the framework of FP5 and FP6 European Integrated Projects (PARTNEW and EUROPART), new structures of Nitrogen polydentate extractants have been synthesized at Reading University (UK) and tested at CEA Marcoule, both on the view point of their extraction properties and on their radiolysis stability. These new ligands are (1) BTPs bearing 'annulating' groups on their triazinyl rings (BTPs), (2) bis-triazinyl-bis-pyridines (BTBPs) and (3) annulated BTBPs (BATBPs). This paper presents the basic research carried out at CEA Marcoule for the past three years to strengthen the BTP stability vs radiolysis and to improve their extraction properties and kinetics (both in extraction and stripping steps of An(III)). (author)

[en] Actinide recycling by separation and transmutation is considered worldwide and particularly in several European countries as one of the most promising strategies to reduce the inventory of radioactive waste, thus contributing to the sustainability of nuclear energy. Consistently with potentially viable recycling strategies, the Collaborative Project ACSEPT will provide a structured research and development framework to develop chemical separation processes compatible with fuel fabrication techniques, with a view to their future demonstration at the pilot level. Two strategies are proposed for the recycling of the actinides issuing from various forms of future nuclear fuels: -) their homogeneous recycling in mixed fuels via a prior group separation of the actinides and -) their heterogeneous recycling in targets or core blankets via their selective separation from fission products. Two major technologies are considered to meet these challenges: hydrometallurgical processes and pyrochemical processes. A training and education programme will also be implemented to share the knowledge among communities and generations so as to maintain the nuclear expertise at the fore-front of Europe. The challenging objectives of ACSEPT will be addressed by a multi-disciplinary consortium composed of European universities, nuclear research bodies and major industrial players. This consortium will generate fundamental improvements for the future design of a potential Advanced Processing Pilot Unit

[en] Minor actinide recycling by separation and transmutation is worldwide considered as one of the most promising strategies to reduce the inventory of radioactive waste, thus contributing to make nuclear energy more sustainable. One of the different options investigated at the CEA Marcoule and within the ACSEPT project (a European collaborative project partly funded by the 7. EURATOM Framework Program) to separate trivalent minor actinide (Am(III)-Cf(III)) from the fission and activation products contained in PUREX raffinates is the TODGA process, which consists in: 1. Co-extracting trivalent 4f and 5f elements from highly acidic PUREX raffinates by a mixture of TODGA (tetraoctyl-diglycolamide) and TBP (tributyl-phosphate), dissolved in HTP (hydrogenated tetra-propene). 2. Selectively stripping the trivalent minor actinides by a hydrophilic poly-aminocarboxylic acid used as a complexing agent in a buffered aqueous solution, while the trivalent lanthanides are kept in the organic solvent thanks to a sodium nitrate salting-out effect. 3. Stripping the lanthanides in a diluted nitric acid solution. The major difficulty of this TODGA separation process is to tune the pH in a very narrow range of operating conditions in the second step, because of the high sensitivity of the performances of the flow-sheet vs pH. This difficulty was however overcome. This paper describes the development of the TODGA process from experimental studies to hot test implementation in shielded cells of the ATALANTE facility, including (i) the optimization of the extraction system (both the formulation of the organic solvent and those of the aqueous scrubbing and stripping solutions), (ii) the implementation of a cold test in small scale mixer-settlers in the G1 facility (MARCEL loop), using a surrogate feed composed of major fission products, (iii) the validation of some steps of the process, using a surrogate feed, spiked with Am-241 and Eu-152, and similar laboratory contactors (medium activity test performed in the glove boxes of the ATALANTE facility), (iv) and finally the validation of the whole optimized flowsheet on a genuine PUREX raffinate in the shielded cells of the ATALANTE facility. (authors)

[en] The separation of trivalent minor actinides from trivalent lanthanides is a difficult task. The present paper describes the application of a Bis-Triazinyl-Pyridine in order to separate americium(III) and curium(III) from various lanthanides(III) present in a synthetic aqueous feed solution simulating a stripping solution issued from the DIAMEX process. The performances observed during the counter-current alpha hot test, carried out at CEA Marcoule using two batteries of eight mixer-settlers, are very promising. They remain, up to now, the best An(III)/Ln(III) separation results ever obtained at such a high acidity ([HNO₃]_initial = 1 mol/L)

[en] Actinide recycling by separation and transmutation is considered worldwide and particularly in several European countries as one of the most promising strategies to reduce the inventory of radioactive waste and to optimize the use of natural resources, thus contributing to making nuclear energy sustainable. In accordance with the Strategic Research Agenda (SRA) of the Sustainable Nuclear Energy Technology Platform (SNE-TP), the timelines of the FP7-EURATOM project ACSEPT (2008-2012) should allow the offering of technical solutions in terms of advanced closed fuel cycle technologies including the recycling of actinides and that may be reviewed by Governments, European utilities as well as Technology Providers at the time horizon 2012. By joining in its consortium 34 partners from 12 European countries plus Australia and Japan, ACSEPT is thus an essential contribution to the demonstration, in the long term, of the potential benefits of actinide recycling. To succeed, ACSEPT is organized into three technical domains: (i) Considering technically mature aqueous separation processes, ACSEPT works to optimize and select the most promising ones dedicated either to actinide partitioning or to grouped actinide separation. A substantial review was undertaken either to be sure that the right molecule families are being studied, or, on the contrary, to identify new candidates. After 18 months, results of the first hot tests should allow the validation of some process options. In addition, the first results on dissolution studies will be available as well as the progress in conversion techniques. (ii) Concerning pyrochemical separation processes, ACSEPT is focused on the enhancement of the two reference cores of process selected within EUROPART with specific attention to the exhaustive electrolysis in molten chloride (quantitative recovery of the actinides with the lowest amount of fission products) and to actinide back-extraction from an An-Al alloy. R and D efforts are also brought to key scientific and technical issues compulsory for building a complete separation process (head-end steps, salt treatment for recycling and waste management). (iii) By integrating all the experimental results within engineering and systems studies, both in hydro and pyro domains, ACSEPT will therefore deliver relevant flowsheets and recommendations to prepare for future demonstration at a pilot level, in relation with strategies developed through the SNE-TP. In addition, a training and education programme is implemented to share the knowledge among the partitioning community, and present and future generations of researchers. Specific attention is given to the funding of post-doctorate fellowships, the first one having been appointed at the end of 2008. (authors)