A route for polonium 210 production from alpha-particle irradiated bismuth-209 target

A method is proposed for production of polonium-210 via the 209Bi(α, 3n)210At nuclear reaction. Bombardment of a bismuth-209 target was performed with a 37 MeV alpha-particle beam that leads to the production of astatine-210 (T1/2 = 8.1 h), which decays to polonium-210. It is purified from the bismuth target matrix by employing liquid-liquid extraction using tributyl phosphate (TBP) in para-xylene from 7 M hydrochloric acid. Back extraction of polonium-210 was performed by 9 M nitric acid. This method allows to purify a tracer amount of Po-210 (2.6 * 10-13 mol) from macroscopic amount of Bi (2.8 * 10-2 mol)

Sorption de lanthanides et actinides en présence de complexants organiques simples. Approche thermodynamique et spectroscopique

Ce travail s'inscrit dans le cadre du stockage géologique des déchets nucléaires. L'étude des réactions de sorption de radionucléides sur des phases minérales est fondamentale pour la compréhension de leur migration. Ce travail concerne l'influence des complexants, tels que les acides acétique, oxalique et carbonique, sur la rétention des lanthanides et actinides sur alumine. Deux approches complémentaires ont été menées : thermodynamique (mesure des constantes d'équilibres, identification des stoechiométries des espèces) et spectroscopique (études SLRT et XPS des complexes sorbés). La première approche conduit ainsi à une base de données thermodynamiques complète et cohérente concernant les équilibres de rétention des systèmes cation/ligand/alumine. Nous avons exploité cette base afin d'optimiser les conditions nécessaires à l'observation spectroscopique des espèces adsorbées. Les propriétés spectroscopiques de chacune des espèces adsorbées ont ainsi été acquises en SLRT et en XPS.This work comes within studies of nuclear waste disposal. The sorption of radionuclide onto mineral is very important to understand their migration. So this work deals with the influence of ligands like oxalic, acetic and carbonic acids on lanthanides and actinides sorption onto alumina. Two complementary approaches were carried out: thermodynamic (determination of chemical reactions and associated constants). So we obtain a thermodynamic database for the ternary systems metal/ligand/alumina which we use to define the experimental conditions to observe by spectroscopy sorbed species. Then the identification of surface complexes was carried out using two spectroscopies, XPS and TRLIFS.EVRY-BU (912282101) / SudocSudocFranceF

Recent progress in ruthenium chemistry for establishing a 103Ru/103mRh generator for Auger therapy

International audienceThe most challenging task for establishing a Ru-103/Rh-103m generator for Auger therapy, is to reach an effective separation between the two radionuclides because of the highly unpredictable, very complicated and poorly understood chemistry. In HCl, this work was able to evidence the formation of Ru colloids. It has been evidenced that the starting material of Ru, time and temperature have a strong influence on Ru speciation, but no polynuclear species of ruthenium-chloride was observed. This work has showed that it is fully possible to control the speciation of ruthenium, especially Ru(IV), within a mononuclear species; that is a huge step forward compared to literature

Is Polonium-210 a Good Indicator for Anthropogenic Radioactivity?

International audienceAnthropogenic radioactivity generated by nuclear or chemical events results in the liberation of quadrillions of Becquerel and tons of materials to the environment. These events include nuclear accidents, nuclear weapon experiments, and high levels of generated radioactive and chemical waste. Po-210 is a high-energy alpha emitter that presents in the environment at extremely low concentration. It is considered as one of the highly toxic elements and is estimated to contribute about 7% of the total effective dose equivalent to humans from ingested natural internal radiation. The assessment of Po-210 activity/concentration in the environment could be used as an indicator of the level of anthropogenic radioactivity. The Po-210 concentration present in the most frequently sold cigarette produced in Lebanon was assayed using alpha spectrometry after a radiochemical separation and spontaneous deposition of Po on a copper disk. Although the geographical nature of Lebanese land is an extension of Syrian territory, the polonium activity concentration obtained is 8.8 times higher and attributable to the excessive use of phosphate fertilizers in agriculture. The individual committed effective dose was estimated to be equal to 219 +/- 17 mu Sv/year of cigarette smoking

Complexation of europium( iii ) with exopolysaccharides from a marine bacterium envisaged as luminescent probe in a theranostic approach

International audienceExopolysaccharide (EPS) derivatives, produced by Alteromonas infernus bacterium, showed anti-metastatic properties in osteosarcoma (bone tumor). These EPSs could be employed as new drug deliverysystems for therapeutic uses. They may represent a new class of ligands to be combined in a theranosticapproach with fluorescent metals, such as Eu(III), to serve as imaging probe. The goal of this work was toinvestigate the feasibility of such coupling by time-resolved laser-induced fluorescence spectroscopy(TRLFS). Since these EPSs are polyelectrolytes their conformation could affect the complexation properties.Thus, viscosimetric measurements were performed as a function of their concentration as well asthe background electrolyte concentration. Polysaccharides conformation exhibited a lower hydrodynamicvolume for the highest ionic strengths. The resulting random-coiled conformation could affect the complexationwith metal for high concentration but no change was evidenced when increasing europiumconcentration. Two sites of complexation of Eu(III) were evidenced by TRLFS in heparin, whereas only onesite was evidenced in two modified EPSs produced from Alteromonas infernus

Radiolabeling Chemistry with Heavy Halogens Iodine and Astatine

International audienceIodine and astatine radioisotopes are particularly attractive in nuclear medicine since their available isotopes cover all imaging and therapeutic modalities, from SPECT and PET imaging to beta, alpha and Auger electron therapy. Furthermore, their radiolabeling chemistry is highly versatile, being mainly based on covalent chemistry, unlike most other radionuclides that are metals. This makes them easily adaptable for the radiolabeling of a broad range of carrier compounds, from small molecules to large proteins. Iodine and astatine being both neighboring halogens, their radiolabeling chemistry is very similar. Knowledge on At is however limited given its low availability over the past decades and the facts that it exists only as short-lived isotopes, which has long hampered the study of its chemical properties. Nonetheless, recent research has highlighted features that distinguish it from its lighter halogen homologues and late developments open new perspectives with astatine radioisotopes to produce radiopharmaceuticals.In this chapter, the basics of iodine and astatine labeling chemistry are covered in parallel, starting with general principles and then detailing more specific applications and issue. In a first part the main production methods for the most relevant radionuclides, and the corresponding chemicals forms available for radiolabeling chemistry are presented. Radiolabeling reactions, which can be classified as electrophilic or nucleophilic, are introduced and their advantages and drawbacks are discussed. The second part introduces issues encountered in the specific case of proteins radiolabeling and the main strategies available. Finally, a third part discusses the stability issues encountered with iodine and especially At-labeled radiopharmaceuticals and the main approaches under investigation to improve it. The perspectives sections discuss the potential of iodine and astatine radioisotopes in the context of the development of the radiotheranostic modality

Flow Field-Flow fractionation for an accurate characterization of polysaccharides

As size exclusion chromatography (SEC), Flow Field Flow Fractionation is a separation technique that assesses the size distribution of the molecules via theoretical equations or representative standards. In FFF technique, high-resolution separation is achieved within a very thin flow against which a perpendicular force field is applied. It takes place in an asymmetrical flat channel (A4F) or in a hollow fiber (HF5). Separation depends on the Brownian diffusion coefficient of the molecule / particle, and thus on its size. Multi Angle Light Scattering detector (MALS) is used for the determination of the absolute molar mass and size determination of macromolecules / nanoparticles. In FFF separation, no stationary phase is required that avoids interferences with the samples. Consequently, for very high molar weight polymers, shearing forces do not apply. The entire separation is smooth, fast, and non-destructive without a stationary phase that may interact, degrade, or alter the sample.   Field-Flow Fractionation-based techniques are powerful tools for characterizing polysaccharides and for monitoring the potential polydispersity and/or polymodality. They are powerful tools especially in the case of drug delivery. In a Pharmacopeia approach, these techniques must be coupled to complementary techniques for a full characterization of products. Viscosity measurements have been conducted together with A4F-UV-MALS and to study the size and size distribution of exopolysaccharides.

A new route of production of Polonium-210

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A new route for polonium-210 production from a bismuth-209 target

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Use of electrodeposition for the production of Tb-149

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