[en] After a presentation of the evolution of the membership of the IPNO's Scientific Council, slide presentations and articles address and propose: a presentation of the activities of the Radiochemistry group (actinides in biological environments, metallic wastes in cement matrices and the Cigeo project, fabrication of actinide thin targets), containment matrices for nuclear wastes (corrosion of metals in storage conditions), the behaviour of radionuclides in non aqueous environments (molten salts, ionic liquids, organic solvents), molecular modelling (modelling of carbon diffusion in zirconium and in monoclinic zirconia, effects of point defects on carbon diffusion in Zr and ZRO₂), a general presentation of the PACS group (Physical of the upstream part of the cycle and of Spallation) and of its activities, the chemistry of protactinium and of other actinides, and simulation of reactors and study of nuclear scenarios

[en] This review highlights recent data on the complexation of Pa(V) with inorganic (fluoride and sulphate) and organic (oxalate, nitrilotriacetate, diethylenetriaminepentaacetate) ligands in solution. New thermodynamic parameters relative to the complexation of Pa(V) with sulphate are presented. The review also includes gas phase and theoretical studies focused on the interaction of Pa(V) in the dioxo and oxo forms with water.

[en] Because of the strong tendency of Pa(V) towards hydrolysis and polymerization, speciation studies have been conducted with the element at ultra-trace scale (CP_a < 10^-10 M). A systematic study using liquid-liquid extraction with a β-diketone as extractant has been performed at constant ionic strength and temperature. Under these experimental conditions, the variations of the distribution coefficient of ²³³Pa(V) as a function of nitrilotriacetic acid (NTA) and proton concentrations provides information on the stoichiometry of the complexes Pa-NTA in aqueous phase and also on their mean charge (slope method). Results indicate the formation of two successive complexes that are likely to be PaO(NTA) and PaO(NTA)₂^3-. The formation of complexes (1:1) and (1:2) are observed with actinides at oxidation states +3 and +4. In contrast, only (1:1) complexes are formed with actinides +5 and +6. In addition, capillary electrophoresis inductively coupled plasma mass spectrometry experiments have been performed with several actinides (²³⁹Pu(IV), ²⁴³Am(III), ²³¹Pa(V)) at tracer scale. Pu(IV) and Am(III) namely are known to form complexes of charge -2 ( Pu^IV(NTA)₂^2- and -3 (Am^III(NTA)₂^3-. Comparison of electrophoretic mobility for the complexes Am(III), Pu(IV) and Pa(V) with NTA, confirms the charge -3 for the maximum stoichiometry complex. The formation constants of PaO(NTA) and PaO(NTA) ₂^3- have been deduced from solvent extraction experiments. The value obtained for the (1:1) complex is similar to those relative to actinides + 6 whereas the formation constant of the (1:2) complex is close to the ones observed for the actinides at the oxidation state +3. Thus, these results emphasize the distinctive feature of protactinium chemistry as compared to the other actinides. To complete the results already obtained, a structural study by X-ray absorption spectroscopy (XAS) and density functional theory (DFT) calculations is currently being processed to determine the coordination geometry and the interatomic distances of the formed complexes. Preliminary results on the structural study performed with the maximum stoichiometry complex will be also presented

[en] The nature of the Tc species produced after the alpha-irradiation of Tc(VII) in concentrated triflic acid has been investigated by X-ray absorption fine structure (XAFS) spectroscopy and first principles calculations. Experimental and theoretical results are consistent with the formation of Tc"("V")O(F_3CSO_3)_2(H_2O)_2"+.

[en] The specific molecular interactions responsible for uranium toxicity are not yet understood. The uranyl binding sites in high-affinity target proteins have not been identified yet and the involvement of phosphoamino acids is still an important question. Short cyclic peptide sequences, with three glutamic acids and one phosphoamino acid, are used as simple models to mimic metal binding sites in phosphoproteins and to help understand the mechanisms involved in uranium toxicity. A combination of peptide design and synthesis, analytical chemistry, extended X-ray absorption fine structure (EXAFS) spectroscopy, and DFT calculations demonstrates the involvement of the phosphate group in the uranyl coordination sphere together with the three carboxylates of the glutamate moieties. The affinity constants measured with a reliable analytical competitive approach at physiological pH are significantly enhanced owing to the presence of the phosphorous moiety. These findings corroborate the importance of phosphoamino acids in uranyl binding in proteins and the relevance of considering phosphoproteins as potential uranyl targets in vivo. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

[en] Since the 1940's, great amounts of Plutonium (Pu) have been produced for both military and civil purposes. Until now, the standard therapy for decorporation following inhalation has been the intravenous injection of diethylenetriaminepentaacetic acid ligand (Ca-DTPA form). This method offers a strong complexing constant for Pu(IV) but has poor chemical specificity, therefore its efficacy is limited to actinides present in the blood. Consequently, there is no decorporation treatment currently available which efficiently removes the intracellular Pu(IV) trapped in the pulmonary macrophages. Our research shows that a nanoparticle approach could be of particular interest due to large contact area and ability to target the retention compartments of the lungs. In this study, we have focused on the inhalation process involving forms of Pu(IV) with poor solubility. We explored the design of biocompatible nanoparticles able to target the macrophages in the lung alveoli and to chelate the forms of Pu(IV) with poor solubility. Nanoparticle formation was achieved through an ionic cross-linking concept using a polycationic polymer and an anionic chelate linker. We chose N-trimethyl chitosan, for its biocompatibility, as the polycationic polymer base of the nanoparticle and the phosphonic analogue of DTPA, diethylenetriamine-penta-methylenephosphonic acid (DTPMP) as the anionic chelating linker in forming NPs TMC-DTPMP. The synthesis and physico-chemical characterization of these NPs are presented. Secondly, the complexation mechanisms of TMC-DTPMP NPs with Thorium (Th(IV)) are discussed in terms of efficiency and structure. The Extended X-Ray Absorption Fine Structure (EXAFS) of the TMC-DTPMP complex with Th(IV) as well as Pu(IV) are defined and completed with DFT calculations to further delineate the plutonium coordination sphere after complexation. Finally, preliminary cytotoxicity tests onto macrophages were assayed. (authors)

[en] Molecular radiochemistry is being developed for various fields of application, such as fundamental chemistry, the environment, nuclear safety and health. Electronic structure or molecular dynamics calculations allow a detailed understanding of the underlying physico-chemical phenomena and are often added to experimental data. This article presents recent examples from the French scientific community, in order to show the challenges and difficulties of theoretical studies, as well as the main obstacles to be overcome in the coming years

[en] The behavior of the UO₂²⁺ uranyl ion at the water/NiO(100) interface was investigated for the first time using Born-Oppenheimer molecular dynamic simulations with the spin polarized DFT +U extension. A water/NiO(100) interface model was first optimized on a defect-free five layers slab thickness, proposed as a reliable surface model, with an explicit treatment of the solvent. Water molecules are adsorbed with a well-defined structure in a thickness of about 4 Å above the surface. The first layer, adsorbed on nickel atoms, remains mainly in molecular form but can partly dissociate at 293 K. Considering low acidic conditions, a bidentate uranyl ion complex was characterized on two surface oxygen species (arising from water molecules adsorption on nickel atoms) with d_{U−Oadsorption}=2.39 Å. This complex is stable at 293 K due to iono-covalent bonds with an estimated charge transfer of 0.58 electron from the surface to the uranyl ion.

[en] The complex formation of protactinium(V) with DTPA was studied at different temperatures (25-50 C) and ionic strengths (0.1-1 M) with the element at tracer scale. Irrespective of the temperature and ionic strength studied, only one neutral complex with (1:1) stoichiometry was identified from solvent extraction and capillary electrophoresis coupled to ICP-MS (CEICP-MS) experiments. Density Functional Theory (DFT) calculations revealed that two complexes can be considered: Pa(DTPA) and PaO(H₂DTPA). The associated formation constants were determined from solvent extraction data at different ionic strengths and temperatures and then extrapolated to zero ionic strength by SIT methodology. These constants are valid, regardless of complex form, Pa(DTPA) or PaO(H₂DTPA). The standard thermodynamic data determined with these extrapolated constants revealed a very stable complex formed energetically by an endothermic contribution which is counter balanced by a strong entropic contribution. Both, the positive enthalpy and entropy energy terms suggest the formation of an inner sphere complex. (authors)

[en] Uranium is widespread in the environment, resulting both from natural occurrences and anthropogenic activities. Its toxicity is mainly chemical rather than radiological. In the blood it is transported as uranyl UO₂²⁺ cation and forms complexes with small ligands like carbonates and with some proteins. From there it reaches the skeleton, its main target organ for accumulation. Fetuin is a serum protein involved in biomineralization processes, and it was demonstrated to be the main UO₂²⁺-binder in vitro. Fetuin's life cycle ends in bone. It is thus suspected to be a key protagonist of U accumulation in this organ. Up to now, there has been no effective treatment for the removal of U from the body and studies devoted to the interactions involving chelating agents with both UO₂²⁺ and its protein targets are lacking. The present work aims at studying the potential role of 3,4,3-LI(1,2-HOPO) as a promising chelating agent in competition with fetuin. The apparent affinity constant of 3,4,3-LI(1,2-HOPO) was first determined, giving evidence for its very high affinity similar to that of fetuin. Chromatography experiments, aimed at identifying the complexes formed and quantifying their UO₂²⁺ content, and spectroscopic structural investigations (XAS) were carried out, demonstrating that 3,4,3-LI(1,2-HOPO) inhibits/limits the formation of fetuin-uranyl complexes under stoichiometric conditions. But surprisingly, possible ternary complexes stable enough to remain present after the chromatographic process were identified under sub-stoichiometric conditions of HOPO versus fetuin. These results contribute to the understanding of the mechanisms accounting for U residual accumulation despite chelation therapy after internal contamination. (authors)