Littérature scientifique sur le sujet « Radiochimica »

Cette étude, réalisée par l’IRSN (Institut de Radioprotection et de Sûreté Nucléaire) dans le cadre d’une demande de l’ASN (Autorité de Sûreté Nucléaire), concerne la caractérisation des formes physico-chimiques des composés radioactifs rejetés par les installations françaises de fabrication de radiopharmaceutiques au moyen d’un cyclotron. Elle vise à disposer d’une meilleure connaissance sur les effluents gazeux radioactifs rejetés par ces installations. Cette étude porte sur les deux principaux radionucléides produits par irradiation d’une cible à des fins de fabrication de radiopharmaceutiques : le fluor 18 (18F) et le carbone 11 (11C). L’azote 13 (13N), principal radionucléide parasite produit dans la cible et relâché essentiellement lors du transfert du contenu de cette dernière vers le laboratoire de radiochimie, a également été étudié.

La transition écologique contemporaine impose de se pencher sur les conséquences sanitaires et environnementales du passé industriel des territoires. Le projet de recherche « Traces, Transfert, Patrimoine », dont il est question ici, s’inscrit précisément dans cette réflexion, en s’intéressant au devenir des anciennes mines d’uranium françaises. La notion de radioactivité naturelle renforcée consécutive à la post-exploitation de l’uranium rend nécessaire une compréhension de la dynamique des territoires et des contaminants, afin de contribuer à une gestion des risques plus intégrée et plus anticipatrice. Le projet s’appuie sur une démarche conduite pour appréhender le risque environnemental dans sa dimension physique et sociale. Issu d’un programme de recherche conduit entre la sociologie et la radiochimie, il vise à caractériser l’empreinte de l’uranium au travers des traces, des processus de transfert et de la qualification du patrimoine.

Abstract On the occasion of the diamond jubilee of Radiochimica Acta (RCA), this article briefly describes the progress made by the journal during the last 10 years; a detailed account of the developments during the first 50 years having been given earlier ( Radiochimica Acta 2012, 100, 483–492). Publishing responsibility for the journal was taken over in 2014 by Walter De Gruyter, a traditional German publishing company founded in 1749. This allowed RCA also to maintain its established traditional standard of publishing. Being broad-based, the journal encompasses all chemical aspects of nuclear science and technology. It has kept pace with the changing trends in radiochemical research. Today, besides fundamental nuclear chemistry, applied topics, such as chemical behaviour and mobility of actinides and fission products, accelerator-based radiochemistry, development of novel radiochemical techniques, study of radiation chemical effects, etc., are well represented. The journal is supported by a group of international Editors and Advisors who are distinguished radiochemists themselves. It follows a strict peer-review system and is assisted by a network of about 500 referees. About 200 manuscripts are received per year, out of which 40–45% are rejected. The impact factor (IF) of RCA is comparable to those of other radiochemistry-related journals, but the cited half-life (CHL) of RCA is by far the highest of all related journals. A list of top highly cited 100 articles has been provided alongside this article. In the past, most of the articles originated from Europe and North America, but in recent years the number of contributions from China and several developing countries has been increasing. All articles are published in English, and the journal is presently available to read both online and in a printed format.

L'esperimento JUNO è stato proposto con l'obiettivo principale di risolvere il problema relativo all'ordinamento di massa dei neutrini attraverso misure accurate del flusso di antineutrini prodotto da reattori nucleari. A causa della sezione estremamente ridotta dei neutrini, il numero di eventi segnale previsti è molto piccolo, circa 60 eventi IBD al giorno, ed è quindi essenziale tenere sotto controllo il tasso di eventi di fondo. Ciò può essere ottenuto minimizzando tutte le sorgenti che contribuiscono alla produzione di eventi spuri e in primo luogo quelle generate dal fondo radioattivo. Per ogni capostipite delle catene naturali (U238 e Th232), per il 40K, e per alcuni nuclidi chiave, come 60Co e 210Pb, è necessario imporre forti limiti alla concentrazione che può essere presente all'interno dei materiali del rivelatore. Data la struttura del rivelatore JUNO, il materiale più critico è il liquido scintillante per il quale sono richieste concentrazioni di uranio e torio inferiori a 1E-15 g/g e potassio inferiori a 1E-16 g/g. In questa tesi, presento il lavoro che ho svolto in questo contesto con due scopi principali. Il primo è la validazione del software Monte Carlo dell'esperimento JUNO applicato alle simulazioni di fondo con l'obiettivo di verificare i limiti di radiopurezza imposti per i materiali e determinare il background-budget dell'esperimento. La seconda è l'implementazione di una tecnica di misura che permette di raggiungere le sensibilità richieste per la misura del contenuto di uranio, torio e potassio nel liquido scintillante. La validazione del software Monte Carlo dell'esperimento JUNO (SNiPER) è stata effettuata confrontandone i risultati con quelli di altri due codici di simulazione, in particolare con il software Arby, sviluppato presso l'Università degli studi di Milano-Bicocca. Ho potuto studiare diversi aspetti e molte criticità della simulazione del fondo e dei risultati riportati dallo strumento ufficiale, come l'applicazione del quenching factor e la forma degli spettri beta. Gli spettri dell'energia depositata prodotta dalle contaminazioni nei componenti principali del rivelatore JUNO sono stati calcolati con i codici Monte Carlo. Il tasso di eventi indotti nel rivelatore è stato valutato in base ai limiti di radiopurezza imposti, ottenendo il rate totale di eventi di fondo previsto. Il valore ottenuto è inferiore al limite imposto per garantire la sensibilità finale dell'esperimento. Ciò ha consentito di correggere e validare la risposta del software ufficiale dell'esperimento JUNO e di verificare l'attualità dei limiti di radiopurezza inizialmente definiti per i componenti del rivelatore. Durante il mio dottorato di ricerca ho completato lo sviluppo del nuovo sistema di misura, chiamato GeSparK che sfrutta la coincidenza tra uno scintillatore liquido e un rivelatore HPGe per ridurre il fondo del rivelatore HPGe singolo. È stata anche sviluppata una nuova tecnica di coincidenza ritardata che sfrutta la struttura nucleare del 239Np, il prodotto di attivazione del 238U, al fine di ottenere un marcatore estremamente forte di questo particolare decadimento e aumentare significativamente la sensibilità di misura rispetto all'approccio tradizionale. La sensibilità ottenuta era ancora insufficiente rispetto alle richieste di JUNO e per questo si decise di attuare una serie di trattamenti radiochimici. Diversi trattamenti sono stati proposti, testati e implementati con i due obiettivi di aumentare la massa del campione misurabile e ridurre la concentrazione di nuclidi interferenti. La tecnica sviluppata per uranio e torio prevede una fase di estrazione liquido-liquido e di estrazione cromatografia con resine UTEVA e TEVA rispettivamente prima e dopo l’irraggiamento. Due misurazioni condotte su campioni "bianchi" con la procedura finale hanno permesso di ottenere una sensibilità compatibile con i limiti imposti da JUNO per lo scintillatore liquido a livello del ppq.
The JUNO experiment was proposed with the main aim of solving the problem related to the neutrino mass ordering through accurate measurements of the antineutrinos flow produced by nuclear reactors. Due to the extremely small cross-section of neutrinos, the number of expected signal events is very small, about 60 IBD events per day, and it is therefore essential to keep under control the rate of background events. This can be achieved by minimizing all the sources that contribute to the generation of spurious events and in the first place those generated by the radioactive background. For each progenitor of the natural chains (U238 and Th232), for the 40K, and for some key nuclides, such as 60Co and 210Pb, it is necessary to impose strong limits on the concentration that may be present within the materials of the detector. Given the structure of the JUNO detector, the most critical material is the liquid scintillator for which uranium and thorium concentrations below 1E-15 g/g and potassium below 1E-16 g/g are required. In this thesis, I present the work I did in this context with two main purposes. The first one is the validation of the Monte Carlo software of the JUNO experiment applied to the background simulations with the aim of verifying the radiopurity limits imposed for the materials and determining the background budget of the experiment. The second one is the implementation of a measurement technique that allows reaching the sensitivities required for the measurement of the content of uranium, thorium, and potassium in the liquid scintillator. The validation of the Monte Carlo software of the JUNO experiment (SNiPER) was performed by comparing its results with those of two other simulation codes, in particular with the software Arby, developed at the University of Milano-Bicocca. I was able to study different aspects and many critical issues of the simulation of the background and the results reported by the official tool, such as the application of the quenching factor and the shape of the radioactive β-decay spectra. The spectra of the deposited energy produced by the contaminations in the main components of the JUNO detector were computed with the Monte Carlo codes. The rate of events induced in the detector was assessed based on the imposed radiopurity limits, obtaining the expected total background event rate. The value obtained is lower than the limit set to ensure the final sensitivity of the experiment. This allowed correcting and validating the answer of the official software of the JUNO experiment and verifying the actuality of the radiopurity limits initially defined for the components of the detector. During my Ph.D. I completed the development of the new measurement system, called GeSparK that exploits the coincidence between a liquid scintillator and an HPGe detector to reduce the background of the single HPGe detector. I also worked on the development of a new delayed coincidence technique that exploits the nuclear structure of 239Np, the activation product of 238U, in order to obtain an extremely strong marker of this particular decay and significantly increase the measurement sensitivity compared to the traditional approach. The sensitivity obtained was still insufficient compared to the requests of JUNO and for this reason, it was decided to implement a series of radiochemical treatments. Different treatments have been proposed, tested, and implemented with the two aims of increasing the mass of the measurable sample and reducing the concentration of interfering nuclides. The technique developed for uranium and thorium involves a liquid-liquid extraction phase and the extraction chromatography with UTEVA and TEVA resins respectively before and after irradiation. Two measurements conducted on "blank samples” with the final procedure allowed us to achieve a sensitivity that is compatible with the limits imposed by JUNO for the liquid scintillator at the ppq level.

Dans le but d’élaborer un radiopharmaceutique pour l’étude des phénomènes d’addiction par imagerie par Tomographie par Emission de Positons (TEP) des récepteurs aux opiacés de sous-type kappa (KOP-R), nous nous sommes intéressés à la synthèse et radiosynthèse de dérivés pipéridiniques fluorés par référence avec le JDTic, un antagoniste puissant et sélectif des KOP-R. Nous avons mis au point la synthèse de quatre ligands originaux des KOP-R, qui ont été évalués in vitro comme affins et sélectifs. Nous avons réalisé le marquage au fluor-18 (émetteur +, t1/2 = 110 min) du ligand le plus actif, et développé sa radiosynthèse automatisée sur module de production. En parallèle nous avons étudié la synthèse diastéréosélective de (3R*,4R*)- et (3R*,4S*)-4-aryl-4-alkyl-3-méthylpipéridines, ainsi que le radiomarquage au fluor-18 de 4-fluorométhylpipéridines. Enfin, en travauxDans le but d’élaborer un radiopharmaceutique pour l’étude des phénomènes d’addiction par imagerie par Tomographie par Emission de Positons (TEP) des récepteurs aux opiacés de sous-type kappa (KOP-R), nous nous sommes intéressés à la synthèse et radiosynthèse de dérivés pipéridiniques fluorés par référence avec le JDTic, un antagoniste puissant et sélectif des KOP-R. Nous avons mis au point la synthèse de quatre ligands originaux des KOP-R, qui ont été évalués in vitro comme affins et sélectifs. Nous avons réalisé le marquage au fluor-18 (émetteur +, t1/2 = 110 min) du ligand le plus actif, et développé sa radiosynthèse automatisée sur module de production. En parallèle nous avons étudié la synthèse diastéréosélective de (3R*,4R*)- et (3R*,4S*)-4-aryl-4-alkyl-3-méthylpipéridines, ainsi que le radiomarquage au fluor-18 de 4-fluorométhylpipéridines. Enfin, en travaux annexes, nous avons étudié une méthodologie originale de fluoration et radiofluoration de sultones fonctionnalisées pour le marquage au fluor-18 de macromolécules
With the aim of developing a radiopharmaceutical for Positron Emission Tomography (PET) imaging of kappa opioid receptor (KOP-R), we investigated the synthesis and the radiosynthesis of fluorinated piperidines derived from JDTic, a potent and selective KOP-R antagonist. We developed the synthesis of four original KOP-R ligands that have been found to display affinity and selectivity in vitro. We performed the radiolabelling with fluorine-18 (+ emitter, t1/2 = 110 min) of the more potent ligand and developed its automated radiosynthesis. In addition, we studied the diastereoselective synthesis of (3R*,4R*)- and (3R*,4S*)-4-aryl-4-alkyl-3-methylpiperidines, and the radiolabelling with fluorine-18 of 4-fluoromethylpiperidines. Finally, in ancillary works, we developed an original methodology of fluorination and radiofluorination of functionalized sultones for labeling with fluorine-18 of macromolecules

La coprécipitation des radionucléides avec des phases secondaires est un phénomène actuellement négligé dans les études de sûreté d’un stockage des déchets nucléaires en formation géologique profonde. La coprécipitation peut, pourtant, jouer un rôle important dans la rétention des radionucléides en limitant leur concentration en solution. Le but de ce travail est d’étudier la coprécipitation du technétium-99 avec la sidérite comme phase d’accueil. Le coprécipitation a été étudiée en fonction des rapports initiaux Tc/Fe. Dans cet objectif, une méthode de coprécipitation a été mise au point en maintenant des conditions réductrices anaérobies. L’étude des phases pures montre la formation de cristallites de sidérite de 450 A dont la taille diminue avec la vitesse de précipitation. Les complexes carbonates de technétium (IV) ont pour stoechiométrie TcCO3(OH)3 et sont solubles dans nos conditions de travail. L’analyse de la solution (scintillation liquide) couplée avec la caractérisation de la phase solide (DRX, MET, spectroscopie infrarouge et Mössbauer) montrent la formation de deux phases dans le cas de solides ayant une faible teneur en technétium (de 1 à 2 %). La première phase est une rouille verbe carbonatée, la seconde est composée de sidérite dans laquelle le technétium est incorporé. Dans le cas de solide ayant une forte teneur, le technétium coprécipite avec une phase assimilée à une rouille verte
Coprécipitation of radionuclides with secondary phase is currently neglected in safety assessments for radioactive waste repository, although this process thought to be important in limiting radionuclide solution concentrations. The aim of this work is to study the coprecipitation of technetium-99 with siderite as host phase. The coprecipitaion has been studied as function of Tc/Fe initial concentration radio. A method of coprecipitation has been developed under reducing and anoxic conditions. The study of pure phases shows the formation of crystalline siderite phase whose crystallites size decrease with the precipitation rate. Concerning the pure carbonate of technetium (IV), the soluble complexes stoechiometry is TcCO3(OH)3. Solution analyses (liquid scintillation counting) combined with solid phase characterization (XRD, TEM, IR, spectroscopy and Mössbauer spectroscopy) show the existence of two phases in the case of a low technetium concentration into the solid (from 1 to 2 %). The first one is a carbonate green rust and the second is composed of technetium incorporated within the siderite structure. In the case of high technetium concentration into the solid, it coprecipitates with a phase assimilated to a green rust

La coprécipitation peut jouer un rôle important dans la rétention des radionucléides (RN) au cours de la dissolution/reprécipitation du combustible nucléaire en stockage géologique en profondeur. Le but de ce travail est d'étudier la coprécipitation de Th, Eu, La et Ac avec UO2(s) comme phase d'accueil en milieu réducteur ( conditions anaérobies N2 et Eh <-100mV/E. N. H. ). La coprécipitation est étudiée en fonction du pH, des rapports de concentrations initiales [RN]/[RN+U] et des propriétés intrinsèques des RN (solubilité, état d'oxydation, rayon ionique et structure cristalline de l'oxyde de RN). Dans cet objectif, deux méthodes de coprécipitation sont mises au point pour deux domaines de pH, en milieu "acide" (2,5