The environmental mobility of Technetium-99 is inextricably tied to its oxidation state. Under oxidizing conditions Tc-99 predominates as the Tc(VII)O4- anion. This anion has a high solubility and is precluded from sorption on most soil or mineral surfaces, giving it a high environmental mobility. Under reducing conditions, Tc-99 predominates as Tc(IV)O2 or Tc(IV)2S7. Tc(IV) species tend to be insoluble and are therefore immobile. Due to this redox dichotomy, there has been significant interest in developing reductive immobilization strategies for Tc-99, particularly in anoxic environments where Tc(IV) is conventionally assumed to be stable. However, O2 is not the only common environmental oxidant. Many high valent manganese species are environmentally prolific and well known to exist in anoxic and overall reducing environments. These powerful oxidants can create localized oxidizing conditions in otherwise reducing environments. Limited research on the oxidation of Tc(IV) species has left a knowledge gap in the true recalcitrance of such immobilization forms in environmental settings. Our work aims to bridge this knowledge gap by studying the oxidation of Tc(IV) by various, environmentally common, high valent manganese species. Mn(III)-ligand complexes in particular have been overlooked. Up until recently, aqueous Mn(III) was assumed to be absent from the environment due to its disproportionation in aqueous systems without suitable complexing ligands. More recently, Mn(III)-ligand complexes have been shown to be prolific in a variety of natural waters. We have shown that various manganese oxides and Mn(III)-ligand complexes are capable of rapidly oxidizing Tc(IV) to Tc(VII), even in the absence of oxygen, resulting in dissolution of Tc-99 and release to the aqueous phase. This thesis presents novel information on the redox interface chemistry of Tc-99, which is crucial to developing effective remediation methods.

In this thesis, the effect of fluorinating reagents on a selection of transition metal-mediated organic transformations was investigated. The first four chapters are focused on gold-catalysed nucleophilic addition processes performed in the presence of “F⁺” sources. Chapter 1 provides a general introduction to homogeneous gold catalysis and summarises the aims and objectives of the project. The effect of the electrophilic fluorinating reagent Selectfluor (82) on the gold-catalysed rearrangement of propargyl acetates 85 is discussed in Chapter 2. α-Fluoroenones 92 resulting from fluorodeacetylation of an allenyl acetate intermediate were delivered as the major products of these reactions (Scheme i). [Scheme i Gold-Catalysed Rearrangement-Fluorodeacetylation of Propargyl Acetates 85.] By contrast, performing the gold(I)-catalysed cyclisation of allenoates 102 in the presence of Selectfluor (82) led to products of oxidative coupling. The “F⁺” source in these processes most likely acts as an external oxidant in an Au<sup>I</sup</Au^III redox cycle. In Chapter 3, the cascade cyclisation-intramolecular arylation of benzyl-substituted substrates is discussed whilst the extension of the methodology towards intermolecular homocoupling and intermolecular alkynylation is presented in Chapter 4 (Scheme ii). [Scheme ii Gold-Catalysed Cyclisation-Oxidative Coupling of tert-Butyl Allenoates 102.] In Chapter 5, the feasibility of palladium-catalysed allylic [¹⁸F]radiofluorination was investigated using high-specific-activity [¹⁸F]fluoride. This study led to the development of the first transition metal-mediated C-¹⁸F bond-forming process of relevance for the preparation of radiotracers for PET imaging (Scheme iii). [Scheme iii Palladium-Catalysed Allylic [18F]Radiofluorination of Allylic Methyl Carbonate 227b.] Chapter 6 gives full experimental procedures and characterisation data for all compounds.

Elements when bombarded with neutrons emit a gamma ray that is characteristic of the isotope that underwent a neutron induced nuclear reaction; this is known as neutron activation. The characteristic gamma energy of an isotope can then be detected and recorded. One can then analyze the gamma energies captured and determine the elemental makeup of the sample. This form of analysis can be used in an underwater environment making it potentially a valuable tool for agencies tasked with maritime security of ports and waterways, or clean-up operations. This thesis will focus on the feasibility of neutron interrogation using pulsed fast/thermal neutrons in an underwater environment for detecting various chemical substances in metal containers. A hermetically sealed, submersible container was used to test a d-T neutron generator’s and semiconductor detector’s functionality underwater in regards to detecting such chemicals as sulfur, nitrogen and chlorine rich materials.

The Institute of Radiochemistry (IRC) is one of the seven institutes of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The research activities are fully integrated into the “Nuclear Safety Research Program” of the Helmholtz Association and focused on the topic “Safety of Nuclear Waste Disposal”. The research objectives are to generate better process understanding and data for the long-term safety analysis of a nuclear waste disposal in the deep geological underground. A better knowledge about the dominating processes essential for radionuclide (actinide) mobilization and immobilization on the molecular level is needed for the assessment of the macroscopic processes which determine the transport and distribution of radioactivity in the environment. Special emphasis is put on the biological mediated transport of long-lived radionuclides in the geosphere and their interaction with different biosystems like biota and human organism for a better calculation of environmental and health risks. Advanced knowledge is needed for description of the processes dominating at the interfaces between geo- and bio-systems related to the distribution of long-lived radionuclides in various bio-systems along the food chain.

No description available.

Bi-annual report on the activities at the ROssendorf BeamLine (ROBL) at the ESRF in Grenoble. The report contains selected contributions on actual research topics, a list of all scheduled experiments, and short experimental reports.

The paper describes the Rossendorf Beamline (ROBL) built by the Forschungszentrum Rossendorf at the ESRF. ROBL comprises two different and independently operating experimental stations: a radiochemistry laboratory for X-ray absorption spectroscopy of non-sealed radioactive samples and a general purpose materials research station for X-ray diffraction and reflectometry mainly of thin films and interfaces modified by ion beam techniques. The radiochemistry set-up is worldwide an unique installation at a modern synchrotron radiation source.

L'étude des mécanismes de sorption de l'ion uranyle sur le substrat SrTiO$_3$ en fonction de la température a fait l'objet de cette étude. Tout d'abord, une caractérisation physico¬chimique a été réalisée à l'aide de plusieurs techniques structurales (DRX, FTIR) et morphologique (MEB). La spectroscopie XPS a permis d'identifier deux sites de surface (Ti¬OH et Sr-OH). En utilisant les titrages potentiométriques de SrTiO$_3$ à différentes températures, les caractéristiques acido-basiques ont été déterminées. Ensuite, la simulation des titrages potentiométriques, entre 25 et 90°C, a été réalisée à l'aide du code FITEQL, les constantes d'équilibre ainsi obtenues montrent une nette variation avec la température: la protonation du site $\equiv Sr – OH$ suit un processus endothermique tandis que la déprotonation du site $\equiv Ti – OH$ implique un processus exothermique. A partir de ces constantes d'équilibre, les grandeurs thermodynamiques, enthalpie et entropie de protonation/déprotonation ont été calculées en utilisant la relation de van't Hoff. Les études de sorption de l'ion uranyle sur le substrat SrTiO$_3$ ont été réalisées dans un intervalle de pH de 0.5 à 5. Les sauts de sorption ainsi obtenus montrent une nette augmentation du pourcentage de sorption avec l'augmentation de la température, traduisant un phénomène globalement endothermique. Deux sites de sorption différents ont été identifiés à la surface du solide par SLRTIF. Ils sont associés aux temps de vie de fluorescence de l'uranyle sorbé de 12 $\pm$ 2 et 60 $\pm$ 5 $\mu$s. Les sauts de sorption ont été modélisés à l'aide du code FITEQL en utilisant le modèle à capacitance constante. Cette simulation des sauts de sorption a été réalisée en tenant compte des résultats de l'étude structurale (deux sites de surface $\equiv Sr - OH$ et $\equiv Ti – OH$ et formation de complexe surfacique de sphère interne bidendate, mononucléaire) et des données obtenues dans la modélisation des titrages potentiométriques. Les équilibres de sorption modélisés ont confirmé la formation de deux complexes de surface de caractère bidendate : [($\equiv SrOH)($\equivTiOH)UO_2]^{2+}$ et [($\equiv TiOH)($\equivTiO)UO_2]^{2+}$. Suite à l'obtention des constantes thermodynamiques obtenues par cette simulation, la relation van't Hoff a été appliquée pour déterminer les variations d'enthalpie et d'entropie associés au processus de sorption. Finalement, une étude sur les transferts d'énergie a été présentée entre deux ions sorbés sur le solide SrTiO$_3$. Ainsi, le transfert d'énergie non-radiatif des ions Tb$^{3+}$ vers les ions EU$^{3+}$ a été étudié. L'application du modèle de Inokuti-Hirayama et Dexter a conduit à l'évaluation du rayon de la sphère d'interaction (2,7-3,4 Å) entre les deux ions (Tb$^{3+}$ et EU$^{3+}$)

Nuclei at closed shells tend to be spherical and are well-described by the shell model, while those between closed shells are deformed and better described by collective models. The nuclei which are in transitional regions between spherical and deformed may be studied to gain insight into the nature of this transition. The stable isotopes of zirconium and xenon span such transitional regions and are the subject of this dissertation. Gamma-ray spectroscopy following inelastic neutron scattering has been performed on the stable isotopes of Zr as well as 132,134Xe at the University of Kentucky Accelerator Laboratory. Level lifetimes have been measured using the Doppler-shift attenuation method, which allow the determination of transition probabilities that are of utmost importance in elucidating the structure of these nuclei. The lifetime measurements were the focus of the study of the Zr isotopes. Previously measured level lifetimes in 94Zr by our group were called into question by recent electron scattering experiments. This motivated a re-measurement of these lifetimes and led to a study of the role of the chemical properties of the scattering samples employed in the measurements. Various Zr-containing compounds were characterized with powder X-ray diffraction and scanning electron microscopy and were employed as scattering samples. These studies revealed the impact of using amorphous materials and those composed of small particles as scattering samples on the resulting lifetimes, and has important implications for future lifetime measurements employing the Doppler-shift attenuation method. For the xenon experiments, highly enriched (>99.9%) 132Xe and 134Xe gases were converted to solid 132XeF2 and 134XeF2, and were used as scattering samples. The xenon isotopes have not been particularly well-studied as elemental targets are gases under ambient conditions, which introduces difficulties into the measurements. Much new information was obtained for these nuclei, including the placement of many new transitions and levels, and measurement of many new level lifetimes, allowing the determination of reduced transition probabilities. This additional information provided important insight into the structure of these two transitional nuclei.

La radioimmunothérapie alpha est une thérapie anticancéreuse prometteuse qui consiste à vectoriser des radioisotopes émetteurs de particules a à l'aide d'agents immunospécifiques de certaines tumeurs afin de les détruire. La notion de générateurs in vivo a été introduite en 1989 par Leonard Mausner. Le concept consiste à marquer le vecteur (anticorps, peptides,...) avec un radioisotope, de demi-vie intermédiaire, dont la décroissance permettra de produire in situ, dans l'organisme, le radioisotope d'intérêt. Ce mémoire de thèse porte sur l'étude de deux générateurs in vivo potentiellement intéressants pour la radioimmunothérapie alpha : le générateur Pb-212 / Bi-212 et le générateur U-230 / Th-226. La première partie de ce travail présente le générateur Pb-212 / Bi-212, et les approches utilisées pour permettre sa vectorisation. Une approche par chélation sur une protéine et une approche par encapsulation dans des liposomes ont ainsi été proposées. Celle-ci s'est avérée être l'approche la plus intéressante. Des études de stabilité in vitro ont ainsi été réalisées sur ces marquages. La seconde partie de ce travail porte sur le générateur U-230 / Th-226. Des études ont dans un premier temps été réalisées afin de réaliser un modèle théorique permettant de décrire la spéciation du Th(IV) en milieu sérique. L'efficacité du DTPA, en tant qu'agent chélatant pour la complexation du Th(IV) en milieu sérique, a ainsi pu être estimée.