Deaerated acidic, neutral, and basic aqueous N₂0 solutions were irradiated with Co-60 γ -rays in order to: 1) determine the primary yields, and 2) resolve anomalies in relative rate constant ratios of the type k(e⁻aq +S)/k(e⁻aq +N₂0). The yields of the gaseous products N₂, 0₂, and H₂ were determined as a function of both pH and [N₂0]. About 10⁻² M N₂0 is commonly used to evaluate relative rate constant ratios, but this [N₂0] scavenges not only hydrated electrons (e⁻aq ) but also another species, X, (where G(X) = 0.65±0.1), resulting in erroneous rate constant ratios. Yields of primary species found were: Ge⁻aq = 2.4±0.1, G H₂O* ̴ 1.6, and G,H₂⁺, = 0.35±0.05. Kinetic competition studies of the reaction of N₂0 and H⁺ with e⁻aq were undertaken in the concentration ranges 3 x 10⁻⁵ to 2 x 10⁻⁴ M H⁺ and 10⁻⁴ to 10⁻³ M N₂O. The results cannot be explained by: 1) simple competition; 2) charge transfer, or 3) two species being scavenged. They may be explained by assuming a conversion of N₂O to another species in acid solution. This acid species, suggested to be H₂N₂O₂, is apparently five times less reactive toward e⁻aq than is N₂0 in neutral solution. Deaerated neutal N₂0 solutions were irradiated at extremely high intensity with very short pulses of 0.52 Mev electrons. The yields of the gaseous products N₂, O₂, and H₂ were studied in order to examine an expected decrease in solute products, and to determine primary yields at high dose rates. As predicted, significant scavenging occurs for high dose rates only at N₂0 concentrations an order of magnitude larger than those at low dose rates. Also the scavenging, which is complete at ~ 10⁻² M N₂O for low intensity irradiations, is not complete at 2.6 x 10⁻² M N₂0 for high intensity irradiations. These results indicate that the radiation yield of scavengable hydrated electrons is significantly larger at the high intensity used. The yield of hydrogen in pure water (G(H₂) = 1.15±0.2) can be explained on the basis of inter-spur reactions of e⁻aq, H, and OH. / Science, Faculty of / Chemistry, Department of / Graduate

M.Sc. (Chemistry) / Please refer to full text to view abstract

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Os isótopos de índio, 111In, 113In and 115In são amplamente utilizados como radiotraçadores na indústria e no meio ambiente. Geradores de 113mIn são produzidos e podem ser encontrados no mercado internacional. No entanto, eles são fabricados por poucas empresas em todo o mundo, são avaliados a preços bastante elevados e nem sempre estão disponíveis para venda. É de grande interesse construir o equipamento no país em que vai ser utilizado, desde que o radionuclídeo pai possa ser produzido. No Brasil, a situação ideal seria produzir um gerador 115Cd/115mIn, cujo alvo precursor seria o 114Cd. Inicialmente, testes preliminares utilizando CdO não enriquecido e inativo foram realizados. A separação dos nuclídeos pai e filho foi feita através da interação das espécies químicas Cd(II) e In(III) com as resinas de troca iônica Ag11A8, Chelex100 e Dowex 1x8. As soluções 0,1 M, 1 M e 2 M de HCl e 2M HCl + 0,1 M NH4Cl foram testadas como eluentes. A quantidade de Cd(II) e In(III) nas soluções eluídas foram determinadas por ICP-AES. As condições de irradiação do alvo 114CdO foram definidas de acordo com o fluxo de nêutrons do reator TRIGA MARK-I IPR-R do CDTN e as propriedades nucleares do alvo. Posteriormente aos testes preliminares, experimentos com o par 115Cd/115mIn foram desenvolvidos. Análises por espectrometria gama foram realizadas para determinar a presença dos nuclídeos 115Cd e 115m In nas frações eluídas. Os testes utilizando a resina AG 11A8 e solução eluente de HCl 1 M resultaram em 100% de adsorção do Cd(II) e aproximadamente 50% de eluição do In(III), correspondendo às melhores condições de eluição. Ao serem expostas à radiação as resinas podem sofrer danos, como a diminuição da capacidade de troca iônica e alteração no volume dos grãos poliméricos. Dessa forma, colunas empacotadas com a resina escolhida foram expostas a doses de radiação entre 15 e 200 Gy e foram eluídas com o eluente mais eficaz. Os resultados mostraram que a radiação não alterou a capacidade de adsorção de Cd(II) pelas resinas, além disso não houveram alterações significativas na quantidade de In(III) eluído. Um gerador de 113Sn/113mIn doado ao CDTN pela IAEA (International Atomic Energy Agency) foi desmontado para ser utlizado como um gerador 115Cd/115mIn. Verificou-se que a montagem pode ser reutilizada para construir um gerador 115Cd/115mIn com as concepções desenvolvidas neste estudo, evitando a etapa de projetar e construir o kit gerador. / Indium isotopes, 111In, 113In and 115In are widely used as radiotracers in industrial and environmental applications. 113mIn generators can be found in the international market. However they are manufactured by only a few companies worldwide, are rated at rather high prices and not always are available for sale (they are frequently manufactured only upon request). Hence it is of interest to produce the equipment in the country in which it will be used, especially if the parent nuclide can be also produced there. In Brazil, the ideal situation would be to produce a 115Cd/115mIn generator, whose target precursor is the 114Cd. Preliminary tests using non-enriched and inactive CdO were developed. The parent and daugther nuclides were separated flowing the eluate containing the chemical species Cd (II) and In (III) through ion exchange resins, Ag11A8, Chelex100 and Dowex 1x8. 0.1M, 1M and 2M HCl and 2M HCl + 0.1 M NH4Cl solutions were tested as the eluant. The amount of Cd (II) and In (III) eluted were determined by ICP-AES. The irradiation conditions of the target 114CdO were defined according to the neutron flux provided TRIGA MARK-I-R IPR reactor and the nuclear properties the of target. After to preliminary tests with the 115Cd/115mIn pair, column experiments were developed. Analyses were accomplished by gamma spectrometry to determine the presence of the 115Cd and 115mIn nuclides in the fractions eluted. Tests using the resin AG 11A8 and HCl 1 M eluent solution resulted in 100% adsorption of the Cd (II) and nearly 50% elution of In (III), corresponding to the best conditions for elution. Exposure to radiation can damage the resins, as the decrease in ion exchange capacity and change in volume of the polymer grains. Thus, columns packed with the chosen resin were exposed to radiation doses from 15 to 200 Gy, and eluted with the most effective eluent. The results showed that radiation does not change the adsorption capacity of Cd (II) by the resins and, in addition, there were no significant changes in the amount of eluted In (III). An exhausted 113Sn/113mIn generator provided to CDTN by IAEA was disassembled to be converted to 15Cd/115mIn generator. It was found that the assembly can be reused to build a 115Cd/115mIn generator with the concepts developed in this study.

The main electrophilic source used in radiolabelling is [18F]F2, which is highly reactive, toxic and requires specialist equipment for safe handling. The Gouverneur group has initiated a research programme focused on the preparation of new stable and easy-to-handle N-18F reagents. In the development of [18F]radiolabelling reactions it would be extremely valuable to develop a library of selective N-18F reagents possessing reactivity tailored to the desired chemical transformation. The aim of this thesis is to further assess the scope of electrophilic N- 18F reagents in new transformations for the construction of C-18F bonds.

Le comportement de certains radionucléides (RN) anthropiques (137Cs, 238,239+240Pu et 241Am) a été étudié dans des échantillons naturels de sol, d’eau et de sédiments prélevés dans le Massif du Boréon. Dans ce milieu non anthropisé, ces RN restent détectables et proviennent des essais nucléaires atmosphériques (238,239+240Pu et 241Am) et de l’accident de la centrale nucléaire de Tchernobyl (137Cs). Les pollutions radioactives restent en surface dans ces sols non perturbés. Dans les sédiments lacustres, l’apport direct des retombées radioactives est détectable en profondeur car sous l’effet de la sédimentation les RN ont quitté la surface. Les transferts entre ces 2 compartiments naturels ont montré l’importance de l’eau comme vecteur de transport et la prédominance du lessivage par rapport à la lixiviation. Le lessivage transporte les RN des pentes du bassin versant, vers la clairière puis vers les sédiments via la phase aqueuse. Dans les échantillons solides, les RN ont une faible mobilité, 241Am est l’isotope le plus mobile et 137Cs l’isotope le moins mobile. Les isotopes 238,239+240Pu ont un comportement intermédiaire. La mobilité est corrélée au contact de l’échantillon solide avec l’eau, ainsi la mobilité des RN est plus importante dans les sédiments que dans le sol. L’évolution temporelle de la radioactivité n’a pu être décrite malgré un essai basé sur les isotopes de Pb en raison de la complexité du milieu naturel. Deux approches (tests de sorption et analyse structurale de l’eau et du sédiment dopés par spectroscopie d’absorption X et spectroscopie laser résolue en temps) au laboratoire ont permis de mieux comprendre le comportement de Am à travers son analogue Eu. Dans l’eau dopée, la présence de 2 complexes, un inorganique Eu(OH)CO3(aq) et un organique avec les acides humiques, a été envisagée. Les sédiments lacustres ont une importante capacité de rétention avec une cinétique de sorption rapide présageant de la faible mobilité de Am dans ce milieu naturel. / The behavior of certain anthropogenic radionuclides (RNs) (137Cs, 238,239+240Pu, 241Am) was studied in samples of soil, water and sediment collected in the Boreon Massif. In this non-anthropized environment, these RNs are still measurable. They come from nuclear weapon tests (238,239+240Pu and 241Am) and from the Chernobyl nuclear power plant accident (137Cs). Radioactive pollutions stay near the surface in these undisturbed soils. In the lake sediments, direct deposits of the radioactive fallouts are detected in depth due to the effect of sedimentation causing RNs to leave the ground surface. The transference between those two natural compartments has shown the importance of water as a transport vehicle and the prevalence of leaching compared to lixiviation. Leaching carries RNs from the drainage basin slopes, to the clearing and then to the sediment through the aqueous phase. In solid samples, RNs have a low mobility, 241Am is the most movable isotope and 137Cs the less movable. 238,239+240Pu isotopes have an intermediate behavior. Mobility rate is correlated with the contact of the solid sample with water. Thus, RN mobility is more important in sediment than in soil. Temporal evolution has not been performed despite a tentative based on Pb isotopes due to the natural environment complexity. Two approaches (sorption tests and structural analysis of spiked water and sediment by X-ray absorption spectroscopy and time-resolved laser induced spectroscopy) in the laboratory have led to a better knowledge of Am behavior using Eu as an analog. In spiked water, the presence of two complexes, one inorganic Eu(OH)CO3(aq) and one organic with humic acids, has been considered. Lake sediment has an important retention capacity with a kinesis of rapid sorption predicting the low mobility of Am in this natural environment.

As unconventional drilling has emerged as a major industry in the US and around the world, many environmental health and pollution risks have surfaced. One emerging concern is the risk of environmental contamination arising from unconventional wastes that are enriched in naturally-occurring radioactive materials (NORM). Although NORM has been a well-documented contaminant of oil and gas wastes for decades, there are new challenges associated with unconventional drilling. This thesis discusses several of these challenges, focusing on NORM from black shale formations. Chapter 1 provides background information on environmental radioactivity and unconventional drilling. Chapter 2 describes the potential for NORM to migrate into groundwater around unconventional drilling operations. Chapters 3 and 4 describe radiochemical methods developed for the analysis of Marcellus Shale unconventional drilling wastes. Chapter 5 describes environmental partitioning of Marcellus Shale unconventional drilling wastes. Collectively, this thesis attempts to broaden the scientific understanding of NORM in unconventional drilling wastes so that potential environmental impacts may be mitigated.

At the beginning of 2011, the former Forschungszentrum Dresden-Rossendorf (FZD) was fully integrated into the Helmholtz Association, as Helmholtz-Zentrum Dresden-Rossendorf (HZDR). Therefore, the present Annual Report 2010 of the Institute of Radiochemistry (IRC) is published as the first HZDR-Report. The Institute of Radiochemistry is one of the six Research Institutes of this centre. IRC contributes to the research program “Nuclear Safety Research” in the “Research Field of Energy” and performs basic and applied research in radiochemistry and radioecology. Motivation and background of our research are environmental processes relevant for the installation of nuclear waste repositories, for remediation of uranium mining and milling sites, and for radioactive contaminations caused by nuclear accidents and fallout. Because of their high radiotoxicity and long half-life the actinides are of special interest.

Thesis (Ph. D.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed Feb. 27, 2008). Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1958. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 136-139).