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Dissertations / Theses on the topic 'Radionuclides'

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Published: 4 June 2021
Last updated: 15 June 2025

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1

Brookshaw, Diana Roumenova. "Mineralisation and biomineralisation of radionuclides." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/mineralisation-and-biomineralisation-of-radionuclides(6c4c0f0e-96f6-4960-a1aa-9c0aa6eaa126).html.

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Management of contamination from industrial activities and wastes from nuclear power generation and weapons development are arguably amongst the greatest challenges facing humanity currently and into the future. Understanding the mobility of toxic radioactive elements is essential for successful remediation strategies and safe management of our nuclear waste legacy (DEFRA, 2008). Interactions between minerals and radionuclides, such as sorption and precipitation, govern the mobility of the contaminants through the subsurface environment. Microbial metabolic processes (redox cycling or release of metabolites) have the potential to affect drastically these abiotic interactions. Microbially-driven mineralisation processes could provide long-term solid-phase-capture solutions to radionuclide contamination problems and support safety cases for geological disposal of radioactive waste. The recent advancements at the intersection between mineralogy, microbiology and radiochemistry were reviewed with the aid of a cluster analysis (Self-Organising Map). This is a relatively novel method of creating a map of the ‘research landscape’ which provides a visual summary of the reviewed literature and can help to identify areas of promising and active research as well as less researched interdisciplinary areas. It is the first time this tool has been applied to research literature on this interdisciplinary topic, and it highlighted the need to gain further understanding of ternary systems including bacteria, minerals and radionuclides. The analysis showed that phyllosilicates are of interest, but few studies have explored the properties of the Fe(II)/Fe(III)-containing micas biotite and chlorite. The ability of model Fe(III)-reducing microorganisms to reduce Fe(III) in biotite and chlorite was demonstrated in batch model systems. In chlorite, approximately 20% and in biotite ~40% of the bulk Fe(III) was transformed to Fe(II) by this reduction. To our knowledge, this is the first study to show the availability of Fe(III) in biotite for such reduction and the ability of the model organism Shewanella oneidensis MR-1 to conserve energy for growth using Fe(III) in biotite as the sole electron acceptor. The microbial Fe(III) reduction led to a decrease in the sorption of Cs and Sr by chlorite, but had very little effect on sorption to biotite. The data indicate that remediation strategies based on microbial Fe(III) reduction may exacerbate the movement of Cs and Sr through strata where sorption is dominated by phyllosilicates, particularly chlorite. While microbial Fe(III) reduction had only a slight effect on the sorption properties of biotite and chlorite, it drastically altered their redox properties. Previously bioreduced biotite and chlorite readily removed Cr(VI), Tc(VII) and Np(V) by surface-mediated reduction. The minerals were also able to reduce U(VI), but solution chemistry affected this reaction, reflecting the complexity of the biogeochemistry of this actinide. Overall, this work highlights the importance of decoupling microbial and geochemical processes in developing a holistic understanding of radionuclide behaviour in the environment. This body of work forms the thesis is entitled ‘Mineralisation and Biomineralisation of radionuclides’, and was prepared by Diana Roumenova Brookshaw for submission in August 2013 for the degree of Doctor of Philosophy to the University of Manchester.
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Kleinot, Jacqueline. "Interactions of radionuclides with estuarine sediments." Thesis, Imperial College London, 1994. http://hdl.handle.net/10044/1/8485.

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3

de, Sousa Fernando Nuno. "Movement of radionuclides through unsaturated soils." Diss., Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/17875.

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4

James, Patrick R. "Natural #alpha#-radionuclides in children's teeth." Thesis, University of Bristol, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299336.

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5

Borgna, Francesca. "Pharmaceutical development of the ISOL technique for the production of radionuclides and their applications in targeted radionuclide therapy." Doctoral thesis, Università degli studi di Padova, 2017. http://hdl.handle.net/11577/3427169.

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Radiopharmaceuticals are the fundamental tool for nuclear medicine procedures, enabling imaging and therapy of cancer after administration of a radioligand. Imaging or therapy are performed with radionuclides that are bound to a ligand, which selectively accumulates into cancer tissues. The discovery of new radionuclides on one side and the optimization of ligands on the other are fundamental parts of the research in the radiopharmaceutical field. In the first part of this thesis work we aimed at the development of a new technique for the production of pure radionuclides. The study was born from the collaboration between the Department of Pharmaceutical and Pharmacological Sciences (DSF) of the University of Padua (UniPD) and the Legnaro National Laboratories (LNL) of the National Institute for Nuclear Physics (INFN), where the Selective Production of Exotic Species (SPES) project is under development. This project aims at the production of Radioactive Ion Beams (RIBs) by means of the Isotope Separation On-Line technique (ISOL), which can be exploited for radionuclides production. Thanks to mass separation, a feature of the ISOL technique, radionuclides can be produced at high purity because isotopic contaminants can be cleared away easily. Suitable secondary targets (chapter 2) were developed to allow ion beams collection, depending on the accelerated ions. To verify the suitability of the method for radionuclides production, tests with accelerated stable ion beams were carried out and are described in chapter 3. The SPES test bench was used for the elements ionization and acceleration. The beams were collected on the produced secondary targets and quantified. The tests were carried out for yttrium, iodine and copper, elements interesting for the production of 90Y, 125/127/131I and 64/67Cu. The ISOL method guarantees the purification of the radionuclides from the isotopic contaminants, but isobaric and pseudo-isobaric contaminants can be present in the beam and thus in the final solution. For this reason chemical purification methods have to be developed for radionuclides purification. In chapter 4 the synthesis of an inorganic material (sodium nonatitanate) and its use for strontium and yttrium purification is described. The second part of this thesis, chapters 5 and 6, was developed in collaboration with the group of PD Dr. Cristina Müller at the Center for Radiopharmaceutical Sciences (CRS) of Paul Scherrer Institute (PSI). Targeted radionuclide therapy (TRT) represents one of the most promising therapeutic strategies for cancer therapy ; it is based on the use of energetic particles (alpha, beta- or Auger electrons) selectively delivered in proximity of tumors thanks to specific biologic features. Small molecules are an attractive strategy for active targeted delivery because they are amenable for chemical synthesis and have some advantages if compared with high molecular weight vehicles, such as antibodies. A potential challenge of small molecular radiotherapeutics is their fast elimination from the body preventing sufficient accumulation of radioactivity in the malignancies due to glomerular filtration and fast renal clearance; high accumulation of radioactivity in the kidneys increases at the same time the risk of nephrotoxicity. For this reason, new strategies to allow a higher translation from preclinical to clinical phase of small molecule-based radiopharmaceuticals should be developed. In this thesis project two strategies to improve TRT with small molecules were developed. The first relies on the development of radioligands with a serum protein-binding domain. This strategy is based on the consideration that serum proteins have high molecular weight, and for this reason do not undergo glomerular filtration (filtration cut-off 30-50 kDa). In particular, three serum proteins-binding compounds were radiolabeled and characterized in vitro and in vivo (chapter 5). Another strategy to improve TRT efficacy while decreasing side effects is the use of combined-modality regimens. This approach is very popular in cancer therapy since targeting the cancer cell on diverse molecular path mechanisms makes the cell less prone to developing resistance to the therapy. At the same time, the use of multimodality therapies allows to decrease the dosage of single therapies, thus reducing side-effects. In the last chapter of this thesis (chapter 6) a preliminary study combining radionuclide therapy (177Lu-cm10) with two tyrosine kinases inhibitors is described, based on the assumptions of a possible synergistic effect of the two agents.<br>I radiofarmaci rappresentano uno strumento fondamentale per la medicina nucleare, rendendo possibile, grazie alla somministrazione di un radioligando, procedure diagnostiche e terapeutiche in ambito oncologico. I radiofarmaci sono costituiti da un radionuclide e da un ligando; quest’ultimo permette la localizzazione della radioattività solamente nei tessuti bersaglio. La ricerca in ambito radiofarmaceutico è dedicata sia alla scoperta di nuovi radionuclidi, sia all’ottimizzazione dei ligandi. Scopo della prima parte di questo lavoro di tesi è stato lo studio e lo sviluppo di una tecnica innovativa per la produzione di radionuclidi ad alta purezza per la medicina nucleare. Lo studio è nato dalla collaborazione presente tra il Dipartimento di Scienze del Farmaco (DSF) dell’Università di Padova (UniPD) e i Laboratori Nazionali di Legnaro (LNL) dell’Istituto Nazionale di Fisica Nucleare (INFN). Presso questi ultimi, infatti, è in fase di costruzione il progetto Selective Production of Exotic Species (SPES), che prevede la produzione di fasci di ioni radioattivi (RIBs), prodotti tramite la tecnologia Isotope Separation On Line (ISOL). La separazione in massa prevista dalla tecnica ISOL, la rende un’ottima via di produzione di radionuclidi, perché permette di eliminare tutti i contaminanti isotopici del radionuclide d’interesse. Per la deposizione dei fasci sono stati sviluppati e costruiti dei bersagli secondari; questi oggetti, posizionati alla fine della linea di fascio, sono utilizzati per depositare e recuperare gli ioni accelerati. La progettazione e realizzazione di tali bersagli è descritta nel capitolo 2. In seguito, con lo scopo di verificare la possibilità di utilizzare l’apparato sperimentale di SPES per la produzione di radionuclidi per la medicina nucleare, sono stati condotti dei test utilizzando fasci di ioni stabili degli elementi di interesse, in particolare sono stati studiati fasci di ittrio, iodio e rame, ai fini della produzione futura di 90Y, 125/127/131I e 64/67Cu. Il metodo ISOL consente grazie alla separazione in massa di purificare i radionuclidi dai contaminanti isotopici, ma contaminanti isobarici e pseudo-isobarici devono essere rimossi tramite altri metodi, in particolare tramite metodi chimici. Per questo motivo nel capitolo 4 vengono descritti la sintesi e l’uso di una resina inorganica a scambio ionico per la purificazione di ittrio e stronzio. La seconda parte di questa tesi è stata sviluppata in collaborazione con il Center for Radiopharmaceutcal Sciences (CRS) presso il Paul Scherrer Institute (PSI), Villigen (CH), in particolare nel gruppo della Dott.ssa PD Cristina Müller. La targeted radionuclide therapy (TRT) è un strategia terapeutica molto promettente in campo oncologico e si basa sull’uso radionuclidi che emottono particelle ad energia medio-alta (alfa, beta- o elettroni di Auger) che vengono selettivamente direzionati nel tessuto canceroso in seguito al riconoscimento di una particolare caratteristica della cellula tumorale. L’utilizzo di piccole molecole per il direzionamento dei radionuclidi rappresenta una strategia vantaggiosa rispetto all’uso di veicoli ad alto peso molecolare (come gli anticorpi monoclonali) ed inoltre possono essere prodotte tramite sintesi chimica. Tuttavia, nonostante il successo di alcune small molecules in clinica, molte volte questa tipologia di radiofarmaci va incontro ad una veloce eliminazione ematica a causa della loro filtrazione glomerulare. In questo modo l’acccumulo della radioattivià nel tumore è diminuito, mentre può esserci un accumulo indesiderato nei reni con aumentato rischio di nefrotossicità. In questa tesi vengono descritte due strategie per il miglioramento della TRT basata sull’uso di piccole molecole. La prima prevede la modifica della struttura chimica dei ligandi con un dominio di legame alle proteine plasmatiche. Questa strategia permette, infatti, di evitare la filtrazione glomerulare del radioligando. Questo, se dopo la somministrazione si lega in modo reversibile ad una proteina plasmatica, viene ad assumere un peso molecolare >30 kDa, valore del cut-off della filtrazione nel glomerulo ed aumenta per questo motivo la sua emivita plasmatica. Nel capitolo 5 vengono descritte la radiomarcatura e la caratterizzazione in vitro ed in vivo di tre radioligandi con affinità per le proteine plasmatiche. La seconda strategia è quella dello sviluppo di terapie combinate con altri agenti chemioterapeutici. Questo approccio è molto popolare in quanto permette da una parte di ridurre le dosi dei singoli agenti e ridurre così gli effetti collaterali, dall’altra di ridurre la resistenza alla terapia. Nel capitolo 6 della tesi, è descritto lo studio preliminare dell’associazione di un radioligando per la terapia (177Lu-cm10) con due inibitori tirosin chinasici.
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6

Heath, Charlotte Rebecca. "Interactions of radionuclides with cellulose degradation products." Thesis, Loughborough University, 2008. https://dspace.lboro.ac.uk/2134/11676.

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The aim of this work was to determine the solubility of radionuclides in solutions of cellulose degradation products (CDP) and isosaccharinic acid (ISA) the main product of cellulose degradation. Thorium was the main radionuclide investigated as the solubility of tetravalent actinides in the near field of a nuclear waste repository at high pH and low Eh has been shown to increase in the presence of such ligands. The measurement of thorium solubility was achieved by using different methods e.g. liquid scintillation counting, gamma spectrometry, ICP-MS and ICP-OES. ICP-OES was shown to be the most accurate method for this analysis. Various methods have been used to obtain solubility values e.g. undersaturation and oversaturation, and these have been investigated to determine whether the values obtained from these methods differ. Solubility studies were carried out at different pHs (6, 8 and 12). The kinetics of the complexation of thorium with ISA and with CDP were investigated at these pHs. The concentration of ISA in a solution of synthesised 10% CDP was approximately 0.01 mol dm⁻³ . In high pH solutions, the solubility of thorium was found to be 31 times greater in a solution of CDP compared to a solution of ISA at the same ISA concentration. No significant differences in thorium solubilities were found in similar solutions at pH 6 and 8. The solubilities of cobalt, nickel and cadmium were measured in the presence of 10% CDP and an equivalent concentration of ISA. The solubilities of all the metals studied in a CDP solution increased when compared to solubilities in ISA. These findings suggest that there are other complexing ligands present in the CDP other than ISA. The CDP mixture was investigated by LC-ICP-MS to determine what other complexing agents were increasing the metal's solubility.
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7

Qaim, S. M. "Development of Cyclotron Radionuclides for Medical Applications." Helmholtz-Zentrum Dresden - Rossendorf, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-162101.

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Soon after the discovery of radioactivity it was shown that radionuclides can be used both for diagnostic and therapeutic studies, depending on the characteristic radiations emitted by them. By 1960’s the radionuclide production technology using nuclear reactors was well established. In early 1970’s a renaissance of the cyclotrons occurred because many of the neutron deficient radionuclides could only be produced using irradiations with charged particles, like protons, deuterons, α-particles, etc. Initially, interest was directed towards radioactive gases for inhalation studies and other radionuclides for scintigraphy. Later, with the advent of emission tomography, i.e. Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET), the emphasis shifted to 123I and positron emitters [cf. 1–3], and tremendous progress ensued. In order to keep abreast of the fast developments, a Symposium was organized at the Brookhaven National Laboratory (BNL), USA, in 1976, with the title “Radiopharmaceutical Chemistry”. This became a biennial event, with alternate meetings in North America and Europe. It included all aspects of radionuclide and radiopharmaceutical research. About a decade later, however, it was realized that for discussion of technical aspects, a separate forum would be more appropriate. A group of experts therefore convened the first Targetry Workshop in Heidelberg in 1985. Thereafter it was established as a recurring Workshop, with its scope enlargened to include also nuclear and radiochemical problems. Today, the major conference on Radiopharmaceutical Sciences and the specialist International Workshop on Target-ry and Target Chemistry are held in alternate years. The present Workshop is No. 15 in the series and it is being jointly held by the research groups in Dresden and Prague, both of which have a long tradition of cyclotron production of radionuclides. In this talk, some personal reminiscences and impressions of the historical de-velopments in the field over the last 40 years will be briefly described.
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8

Walker, Michael Ian. "The sea to air transfer of radionuclides." Thesis, University of East Anglia, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328257.

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9

Nzuruba, Alexander Chukwudumaga Nnawuihe. "Evaluations of radionuclide data." Thesis, Imperial College London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271266.

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10

Price, Rachel Mary. "Interactions of groundwater-borne radionuclides with geological sediments." Thesis, Northumbria University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359522.

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11

Chow, John Kam Keung. "Sorption of radionuclides onto clay minerals and soils." Thesis, University of Salford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241543.

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12

Mikhieiev, O. M., O. V. Lapan, L. H. Ovsiannikova, and S. M. Madzhd. "WATER BODIES TREATMENT FROM RADIONUCLIDES AND CHEMICAL POLLUTION." Thesis, ПАЛИВОДА А.В, 2017. http://er.nau.edu.ua/handle/NAU/30497.

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13

Maietta, Maddalena. "Radioprotection aspects associated to radionuclides for medical applications." Thesis, Nantes, 2018. http://www.theses.fr/2018NANT4101/document.

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La protection des travailleurs et du public est de primordiale importance dans toutes les phases de la chaîne de production des radionucléides, de la collecte . l’expédition, en passant par la gestion et l’élimination des déchets. Ce travail de thèse explore différents aspects de ces étapes. Les phases de la collecte dans l’installation CERN-Medicis ont été étudiées et la première idée de la chambre de collecte a été décrite. Dans le secteur des transports, l’Agence internationale de l’énergie atomique (AIEA) établit des règles strictes en matière de respect de la conception de nouveaux emballages. De plus, lorsque les activités produites d.passent certaines limites imposées par la réglementation, des emballages spécifiques doivent être utilisés pour le transport. Ils doivent assurer une protection optimale dans des conditions de transport normales et accidentelles et sont appel.s type B. Le coeur de cette étude est la conception d’un nouveau conteneur pour d.placer les échantillons irradiés du site de production aux radiopharmacies. La conception utilise la technique des calculs de Monte Carlo pour l’analyse de la radioprotection et la technique par éléments finis pour prévoir les performances de l’emballage dans les conditions d’essai. Un prototype a été réalisé et la procédure d’homologation a commencé. Pour certains radionucléides, les limites de transport ne sont pas tabulées et des valeurs générales sont utilisées. Une méthode utilisant des calculs de Monte Carlo a été mise en place pour recalculer ces quantités en fonction de leur risque réel. La méthode montre la possibilité d’augmenter la limite de transport pour une liste d’isotopes utilisés dans le domaine de la médecine nucléaire. Le processus de collecte des radionucléides a comme principale conséquence la production de matériaux hautement activés à traiter et à éliminer en tant que déchets. Un outil permettant de d.finir correctement le niveau de dangerosité récemment développé au CERN a été adapté aux scénarios d’irradiation typiques du cyclotron Arronax<br>The protection of the workers and the public is of primary importance in all the phases of the radionuclides production chain, from the collection to the shipment, but also in the management and the disposal of the waste. This thesis works explore some aspects of those steps. The phases of the collection in the CERN-Medicis facility have been studied and the first idea of the collection chamber has been outlined. In the transport sector The International Atomic Energy Agency (IAEA) establish strict rules to respect for the design of new packages. Moreover when the activities produced exceed some limits imposed by the regulation per each radionuclides, specific containers shall be used for the transport. They must insure optimal protection in normal and accidental conditions of transport and are called type B. The core of this PhD study is the design of a new transport container to move the irradiated samples from the place of production to the radiopharmacies. The design makes use of several techniques, as Monte Carlo calculations for radiosafety analysis and finite element techniques to foresee the performance of the package under the testing conditions. A prototype has been realized and the homologation procedure started. For some radionuclides the transportation limits are not tabulated and general values are used to limit the activity to transport. A method making use of Monte Carlo calculations has been put in place to recalculate those quantities depending on their real hazard. The method shows the possibility to increase the transport limit for a list of isotopes used in the field of nuclear medicine. The process of radionuclidesÕ collection has as main consequence the production of highly activated materials to be treated and disposed as waste. A tool for a proper definition of the level of hazard recently developed at CERN has been customized for irradiation scenarios typical of the Arronax cyclotron
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14

MOU, LILIANA. "Cyclotron production of theranostic radionuclides: 67Cu and 47Sc." Doctoral thesis, Università degli studi di Ferrara, 2020. http://hdl.handle.net/11392/2488256.

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Il lavoro descritto in questa tesi di dottorato è stato sviluppato nell’ambito del progetto LARAMED (LAboratory of RAdioisotopes for MEDicine), una branca del progetto SPES (Selective Production of Exotic Species), presso i Laboratori Nazionali di Legnaro dell’Istituto Nazionale di Fisica Nucleare (INFN-LNL). Il progetto LARAMED si propone di studiare la produzione di radionuclidi per la realizzazione di nuovi radiofarmaci, utilizzando il fascio di protoni generato dal ciclotrone SPES. Questo lavoro riporta i principali risultati ottenuti con i progetti COME (COpper MEasurement) e PASTA (Production with Accelerator of Sc-47 for Theranostic Applications) nei quali ho lavorato durante i tre anni di dottorato. Poiché la conoscenza accurata delle sezioni d’urto è il primo step nell’ottimizzazione della produzione di radioisotopi, entrambi i progetti erano focalizzati su queste misure, rispettivamente per il 67Cu e lo 47Sc, usando fasci di protoni di energia fino a 70 MeV. Il 67Cu e lo 47Sc sono radionuclidi teranostici (entrambi emettitori γ- e β- che possono anche essere accoppiati con isotopi β+), permettendo la selezione dei pazienti che hanno una buona probabilità di rispondere positivamente allo specifico radiofarmaco con imaging SPECT (o PET) prima della terapia. Un reale problema da risolvere è la mancanza di disponibilità di 67Cu e 47Sc, come sottolineato dal CRP IAEA (No. F22053) focalizzato sulla produzione dei radionuclidi teranostici 67Cu, 186Re e 47Sc. Nel progetto COME sono state realizzate le prime misure delle sezioni d’urto 70Zn(p,x)67Cu, 64Cu, 67Ga, 66Ga, 65Zn and 69mZn nel range energetico 45-70 MeV. Questi risultati, confrontati con la ben nota reazione nucleare 68Zn(p,x)67,64Cu, mi ha permesso di trovare un range di energia ottimale per massimizzare la produzione di 67Cu e nello stesso tempo minimizzare la produzione dell’isotopo contaminante 64Cu; questo risultato è descritto nel Patent Internazionale n° WO 2019/220224 A1 (Novembre 2019). Nel progetto PASTA sono state investigate le reazioni nucleari indotte da protoni su bersagli di 48Ti e natV. I risultati delle sezioni d’urto delle reazioni nucleari 48Ti(p,x) 47Sc, 46Sc, 44Sc, 44mSc mostrano un trend regolare in accordo con i dati di letteratura. Sono anche stati ottenuti i risultati delle sezioni d’urto natV(p,x)47Sc, 46Sc, 44Sc, 44mSc, 43Sc, 48Sc, 48Cr, 49Cr, 51Cr, 48V, 42K, 43K che sono state confrontate con i dati di letteratura e con alcune stime teoriche. Sono anche stati realizzati dei calcoli di produzione su bersagli spessi, sia nel caso del 67Cu che dello 47Sc per studiare la fattibilità di una reale produzione sfruttando le reazioni nucleari studiate ed il ciclotrone presente presso i LNL. Nel caso dello 47Sc, sono stati effettuati anche calcoli dosimetrici, considerando il radiofarmaco DOTA-folate conjugate cm10 ([47Sc]-cm10). L’incremento della dose efficace dovuta alla presenza di una piccola contaminazione dovuta alla co-produzione di 46Sc è inferiore al 10%, limite richiesto per uso clinico del radiofarmaco, per Ep<35 MeV.<br>The work described in this Ph.D. thesis was carried out in the framework of the LARAMED (LAboratory of RAdioisotopes for MEDicine) project at the Legnaro National Laboratories of the National Institute of Nuclear Physics (INFN-LNL). The LARAMED project is a branch of SPES (Selective Production of Exotic Species) with the purpose to evaluate the cyclotron-based production of emerging radionuclides to produce innovative radiopharmaceuticals. This work reports the main results obtained in the COME (COpper MEasurement) and PASTA (Production with Accelerator of Sc-47 for Theranostic Applications) projects in which I was involved in the three years of my Ph.D.. Since the accurate knowledge of the reaction cross section is the first step in the optimization of radioisotope production, both projects were focused on these measurements, for 67Cu and 47Sc respectively, by using proton beams up to 70 MeV. 67Cu and 47Sc are theranostic radionuclides as they can decay simultaneously by γ- and β- emission. This property allows visualization of a specific biological target by γ imaging that, in turn, can be used for applying selectively targeted β- therapy. Worldwide a real problem to be solved is the lack of 67Cu and 47Sc availability, as underlined by the IAEA CRP (No. F22053) focused on the production of the theranostic radionuclides 67Cu, 186Re and 47Sc. In the COME project the first measurements of the 70Zn(p,x)67Cu, 64Cu, 67Ga, 66Ga, 65Zn, and 69mZn cross sections in the 45-70 MeV energy range were obtained. These results, compared with the well-known 68Zn(p,x)67,64Cu nuclear reaction, allowed us to find an optimal energy range to maximize the 67Cu production and, in the same time, minimize the co-produced 64Cu; this result is described in the International Patent n° WO 2019/220224 A1 (November 2019). In the PASTA project the proton-induced reactions on 48Ti and natV targets were investigated. The cross sections values obtained for the 48Ti(p,x)47Sc, 46Sc, 44Sc, 44mSc nuclear reactions show a regular trend, in agreement with the previous experimental data. The results of the natV(p,x)47Sc, 46Sc, 44Sc, 44mSc, 43Sc, 48Sc, 48Cr, 49Cr, 51Cr, 48V, 42K, 43K cross sections were also obtained and compared with literature data and theoretical calculations. Calculations of the Thick Target Yield were also performed for both 67Cu and 47Sc to study the feasibility of their real production by exploiting the nuclear reactions investigated and the 70 MeV proton cyclotron installed at INFN-LNL. For the 47Sc case, dosimetric calculations were performed considering the DOTA-folate conjugate cm10 ([47Sc]-cm10) radiopharmaceutical; the effective Dose Increase (DI) due to the presence of a small amount of the co-produced contaminant 46Sc for Ep<35 MeV was maintained within the 10%, limit required for the radiopharmaceutical clinical use.
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15

Rangel, Elizabeth Vega. "Analysis of caesium and strontium in biological and environmental materials." Thesis, University of Surrey, 1994. http://epubs.surrey.ac.uk/843384/.

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Atmospheric testing of nuclear weapons and nuclear reactor accidents has resulted in widespread distribution of radioactive fission products into the environment. Determination of these radionuclides in biological and environmental samples presents serious difficulties because of interferences (90Sr with a continuous beta spectrum needs separation from other radionuclides, such as 90Y) and the poor limits of detection established by currently available counting equipment. In this project an ion exchange chromatography procedure for the separation of Cs, Sr and Y was developed. Since these radionuclides are hazardous, the method was developed using stable isotopes and inductively coupled plasma mass spectrometry (ICP-MS) as an elemental detector. In the first instance, the optimum operating conditions of the instrument for the analysis of Cs, Sr and Y were determined. These values were found to be 1.1 kW incident power and 1 1 min-1 nebuliser flow rate. The accuracy of the ICP-MS measurments was then assessed through the use of international reference materials NIST:SRM 1572 Citrus Leaves and NIST:SRM 1573 Tomato Leaves. In general a good agreement was observed for most of the elements between certified values and the results obtained in this study. The developed separation technique consisted of three stages. In the first stage ammonium molybdophosphate (AMP) and BioRad AG 50W-X8 resins were used. Caesium was separated from the other two isotopes using 2 M NH4OH. In the second stage Sr and Y were eluted from the above mentioned column using 4 M HNO3. The solution was then loaded onto a Sr-SpecRTM column where Sr is retained. In the third stage Sr was eluted from the column using deionised water. This setup provided excellent recoveries for the three stages namely: 85 % for Cs, 93 % for Y and 95 % for Sr. The analysis of Cs, Sr, and Y in foodstuffs, namely beans and milk was carried out after using the aforementioned separation procedure. Different growth media (commercial white silica sand, Lightwater garden soil, commercial garden soil, Rose Batch compost, and commercial compost) were used to assess the effect of organic content on the uptake of Cs and Sr by bean plants. These experiments involved the addition of different doses of added elemental concentration (100 to 1000 ?g ml-1) to the substrate and also various solution pH's (4 to 9). It was observed that the higher uptake of Cs and Sr by bean plants was at solution pH 7 and also for growth media with high organic content, i.e. Rose Batch compost and commercial compost. The distribution of Cs and Sr into the bean plant tissue resulting through absorption from commercial compost, showed that Cs is absorbed mostly in the stem (95 %) and with minimal levels in root and leaves (5 %). On the other hand, Sr was readily absorbed to the aboveground parts of the bean plants (36 % stem, 63 % in leaves) in contrast to other parts; 0.3 % root and 0.05 % beans. A study was undertaken to assess the uptake of Cs and Sr by bean plants in the presence of K and Ca at various solution pH's. It was found that in general, for all solution pH's, potassium inhibits the uptake of Cs. On the other hand, there appears to be a competition between Sr and Ca at high pH (7 to 9) which resulted in a rapid reduction of the Sr uptake. The addition of Ca to the substrate decreased the uptake of Sr by stems/leaves and increased the uptake of Sr by beans. As an application, solutions with different pH and radionuclide 137Cs and 90Sr) levels were added to mature bean plants. The developed ion exchange chromatography procedure was then adopted to separate 137Cs and 90Sr from these plants. In this study a Ge(Li) gamma ray spectrometer (ND 66) was used as a detector for 137Cs whilst a liquid scintillation counter was used for measuring 90Sr. Prior to the 137Cs measurements, the detection limits, resolution, absolute full energy peak and calibration of the instrument were evaluated. In general the values obtained in this work were in good agreement with the certified values.
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Al-Othmany, Dheya Shuja'a. "Tritium enrichment by gas chromatography." Thesis, University of Aberdeen, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240675.

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In the studies related to trace analysis in meteorology, hydrology, medical and clinical research, the measurement and monitoring of tritium released from nuclear facilities and its health physics aspects on human and the environment are of growing importance. The techniques employed currently for the enrichment of tritium are carried out using large samples and require long periods of operation (7 days or more) to obtain the enriched tritium sample. In the present investigation, a laboratory scale chromatography based system was designed, constructed and commissioned successfully to collect enriched tritiated water samples which were then counted to determine the levels of activity. The total time taken to conduct the complete enrichment procedure and counting of the collected samples was less than one working day. This system also showed the capability of enriching quantities of water samples as small as 20 ml. This was about ten times less than required in the conventional enrichment techniques. Extensive efforts were made to attain optimum operational, reproducible and efficient measurements of tritium enrichment for quantitative analysis. The developed experimental technique involved injecting a known volume of water into a preheated furnace to react with magnesium turnings, in the presence of a carrier gas, to produce the hydrogen isotopes. These isotopes were separated using the principles of chromatography. Liquid scintillation counting method was employed to determine the activity of the collected samples. Two gases, nitrogen and helium, were utilized as the carrier gases during this investigation. Best values of enrichment were obtained with the use of nitrogen as a carrier gas, but the samples collected were difficult to count due to the formation of ammonia with consequent chemical complications.
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17

Bailey, Dale L. "Quantification in 3D positron emission tomography." Thesis, University of Surrey, 1996. http://epubs.surrey.ac.uk/770395/.

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Acquisition and reconstruction of data in three-dimensional positron emission tomography (3D PET) was introduced in 1990 almost 20 years after the first PET scanners were developed. 3D PET offers a significant sensitivity improvement over conventional, sliceoriented 2D PET, but at the cost of a three-fold increase in acceptance of scattered events. In addition, processing time is increased and new methods for applying corrections such as for photon attenuation, calibration, and detector/geometry normalisation are required. 3D PET raised concerns that the high quantitative accuracy that was possible with 2D PET (with its moderate sensitivity) would not be matched in 3D, primarily because of the greatly increased scattered photon component in the measured data. The aim of this thesis was to develop methods that enable quantitatively accurate measurements with 3D PET. A technique to correct for scattered photons prior to reconstruction has been developed, implemented and assessed. A device for normalising the data for detector efficiency and the geometry of the cylindrical detector system has been developed, and the factors affecting reconstruction investigated. A new approach to calibration of the reconstructed data to produce images of activity concentration which is independent of scatter has been implemented. Finally, the techniques have been applied to data from brain scans of human subjects. Evaluation of images reconstructed from 3D PET demonstrates that the methodology developed in this work produces data accurate to within 10% of the true activity concentration in an object with reasonably homogeneous density. 3D PET is shown to be as accurate as 2D PET, but with a sensitivity advantage that improves signal-to-noise by approximately a factor of three in the human brain and slightly less in other regions of the body.
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18

McDonald, Paul. "The uptake and distribution of radionuclides in marine organisms." Thesis, University of Glasgow, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261793.

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19

Hosseini, Seyed Abbas. "Mechanisms controlling the migration of radionuclides in the environment." Thesis, University of Aberdeen, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265441.

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The mechanisms controlling radiocaesium migration through the peat soil were investigated by considering physico-chemical & biological factors affecting radionuclide adsorption/desorption in the peat soil using the Batch & Column Methods as well as a "Direct Fumigation Extraction Method". The biological factors were investigated under different conditions by variation of the micro-organisms content in the peat soil, the soil solution and leaching conditions. Samples of peat soil were reacted with solutions containing caesium ions, and the effect on caesium-K<sub>d</sub> determined. The caesium adsorption/desorption was found to be influenced by concentration of caesium and other cations (NH<sub>4</sub><sup>+</sup>, K<sup>+</sup> and Ca<sup>++</sup>) and by the pH of the solution. Below pH 3, in presence of calcium and potassium, desorption could occur as the exchangeable sites on microparticles were replaced by other cations. At pH>1, in presence of ammonium, adsorption could occur. The distribution coefficient, K<sub>d</sub> value was strongly reduced following the addition of NH<sub>4</sub><sup>+</sup>, K<sup>+</sup> and Ca<sup>++</sup> at a fixed pH. NH<sub>4</sub><sup>+</sup> was found to be more effective in the caesium desorption than the other cations. By increasing the concentration of radiocaesium (>0.2 MBq/100μl) the effect became much less leading eventually to an increase in caesium-K<sub>d</sub> values. A decrease in the caesium-K<sub>d</sub> was also observed at pH<3 in peat samples. It was found that the caesium adsorption approached to an equilibrium state at pH>3 depending upon caesium concentration in peat solution. Caesium adsorption took 180 days to reach equilibrium state. For the measurement of the release/uptake of radionuclides in the peat soils by the microbial biomass, homogenised wet peat samples were fumigated by chloroform. The influence of the microbial population present in the peat on the environmental mobility of caesium was clearly demonstrated.
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20

Orcutt, Kelly Davis. "Protein engineering for targeted delivery of radionuclides to tumors." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/58268.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, February 2010.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 117-121).<br>Traditional cancer treatment strategies include systemic chemotherapy, external beam radiation, and surgical excision. Chemotherapy is nonspecific, and targets all rapidly dividing cells. External beam radiation and surgery only target known cancer sites. However, targeted therapeutics, such as antibodies, will bind to all cancer cells that express the targeted antigen, including small metastases that are invisible by current imaging technology. In the past decade, nine antibodies have been approved for the treatment of cancer and are demonstrating moderate success in the clinic. Some of these antibodies have intrinsic toxic effects and block the interaction of growth factors or induce cell death. Other antibodies are conjugated to drugs, toxins, or radioactive isotopes. Unfortunately, antibodies exhibit slow clearance from the body and exposure of healthy tissues to toxins or radiation can result in undesirable side effects that limit the doses that can be safety administered to the patient. We have used rational engineering design and mathematical modeling to develop a novel pretargeted radioimmunotherapy (PRIT) approach for the treatment of cancer. In PRIT, a bifunctional antibody is administered and allowed to bind to a cancer antigen. After sufficient tumor uptake of the antibody, a small molecule carrying a radionuclide is administered and captured by the pretargeted antibody while unbound molecules clear rapidly from the body. PRIT combines the high binding specificity of antibodies with the rapid clearance properties of small molecules. We have identified a small molecule metal chelate, DOTA, which exhibits rapid whole-body clearance and that has demonstrated safety in humans.<br>(cont.) We engineered a high-affinity antibody fragment specific to DOTA and subsequently engineered a novel bispecific antibody (bsAb) construct with specificity for both DOTA and carcinoembryonic antigen (CEA). The bsAb exhibits retention of parental affinities, in vivo stability, and tumor targeting. The engineered PRIT approach was tested in a mouse tumor model and demonstrates excellent DOTA capture at the site of the tumor with the best 48 hour tumor to blood and tumor to kidney ratios reported to date for CEA targeting. The PRIT approach developed here can be easily applied to other disease targets and has the potential to impact clinical cancer radioimmunotherapy.<br>by Kelly Davis Orcutt.<br>Ph.D.
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21

Ishidera, Takamitsu. "Study on diffusion behavior of radionuclides in compacted bentonite." 京都大学 (Kyoto University), 2008. http://hdl.handle.net/2433/57264.

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22

Fukui, Masami. "DISTRIBUTIONS AND BEHAVIOR OF SOME RADIONUCLIDES IN THE ENVIRONMENT." Kyoto University, 1992. http://hdl.handle.net/2433/78256.

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23

Choudhary, Mohammad Sabir. "Determination of spatial distribution of radionuclides in absorbing media." Thesis, University of Surrey, 1987. http://epubs.surrey.ac.uk/843768/.

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Determination of the spatial distribution and quantification of concentration of pure beta- and photon-emitting radionuclides in absorbing media by external measurements is the subject of this study. Measurements of radiation and the operation of radiation detectors are based on the radiation interactions with matter and the theory governing these interactions has been discussed. Various techniques for localising pure beta- and photon-emitting radionuclides situated inside attenuating media have been suggested on a theoretical basis, and have been experimentally shown to work successfully. Most of the work is on single photon emission computed tomography (SPECT). The theory of mathematical reconstruction of a two dimensional distribution from its projections is discussed and reconstruction techniques and their relative merits and demerits have been reviewed. SPECT seeks the determination of absolute regional radionuclide concentrations as a function of time. A SPECT system has been developed by modifying an existing transmission CT scanner and the reconstruction algorithms. The performance of the SPECT system has been tested for a number of point sources and various extended sources in gas, liquid and solid forms. The SPECT scanner in its present design is capable of performing in both the transmission and emission modes. The characteristics of the SPECT scanner, including the detector efficiency, spatial resolution and the effect of collimator size, have been studied experimentally. The major problems faced by SPECT include the solid angle effect, which influences the collection efficiency, in scattered radiation, and attenuation of photons inside the surrounding medium. These problems together with their various possible solutions have been discussed in detail. Methods for compensation for solid angle variation, in scattered radiation and photon attenuation have been devised and used successfully to compensate the projection data.
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24

Siddeeg, Saif Eldin Mohammed Babiker. "Geochemistry of natural radionuclides in uranium-enriched river catchments." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/geochemistry-of-natural-radionuclides-in-uraniumenriched-river-catchments(c32e80c3-413a-4513-a0a6-fd3a705abd99).html.

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Radionuclides from natural U-series in sediments from two river catchments in the UK have been studied. The aim was to gain insight into the behaviour of 238U, 234U, 230Th and 226Ra in real natural systems enriched in uranium. A radiochemical method for radium separation followed by alpha spectrometric measurement has been developed. The method allowed use of 225Ra, in equilibrium with the parent 229Th, as a yield determinant, and has been applied in 226Ra concentrations measurements in the selected areas of study.U-series progeny, 238U, 234U, 230Th and 226Ra, in totally dissolved sediments from the valley of the River Noe and the fraction leached by aqua regia, have been measured. Total sediment contents ranged from 9 ± 2 to 184 ± 8 Bq.kg-1 for uranium, 9 ± 3 to 200 ± 13 Bq.kg-1 for thorium and 18 ± 1 to 179 ± 8 Bq.kg-1 for radium. The activity concentrations in the leached fractions, compared with the total, were 46% for uranium, 54% for thorium and 56% for radium, on average. The radionuclides showed extensive disequilibrium and this suggested a complex leaching/accumulation of uranium as well as an impact of organic matter and secondary minerals.Uranium and radium have been geochemically characterised in sediments from near the South Terras abandoned uranium mine, Cornwall. Background activity concentration levels of uranium in sediments ranged from 13 ± 3 to 290 ± 14 Bq.kg-1, with radium from 42 ± 4 to 424 ± 23 Bq.kg-1. Elevated concentrations of uranium and radium were measured in two samples, S3 with 1820 ± 36 Bq.kg-1 for uranium and 940 ± 53 Bq.kg-1 for radium; and S7 with 4350 ± 53 Bq.kg-1 for uranium and 1765 ± 48 Bq.kg-1 for radium. Sequential chemical extraction for the two samples revealed that both uranium and radium were associated with organic and carbonate fractions, with 25 % of the uranium in the resistant phase of S7. 234U/238U activity ratios of the sequential extraction fractions showed different trends in the sediments, and this was linked to the impact of organic matter and/or exchange between water and sediment. Uranium-bearing minerals in association with potassium, calcium, iron, manganese and arsenic have been identified in these sediments.
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25

Диченко, Тетяна Василівна, Татьяна Васильевна Дыченко, Tetiana Vasylivna Dychenko та А. В. Огренич. "Последствия Чернобыльской аварии в республике Беларусь". Thesis, Издательство СумГУ, 2011. http://essuir.sumdu.edu.ua/handle/123456789/7418.

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26

Molera, Marimon Mireia. "On the sorption and diffusion of radionuclides in bentonite clay." Doctoral thesis, KTH, Chemistry, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3390.

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27

Fletcher, Kelly Elizabeth. "New insights into reductive detoxification of chlorinated solvents and radionuclides." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37244.

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Naturally occurring bacterial populations are capable of detoxifying chlorinated compounds and immobilizing the radionuclide uranium via reductive processes. This study addressed the following three knowledge gaps in the fields of chlorinated solvent and uranium bioremediation, 1) the risks and benefits of coupling bioremediation with thermal treatment for clean-up of chlorinated ethene-contaminated sites, 2) the accuracy of available techniques for the monitoring of chlorinated solvent bioremediation, and 3) the role of gram positive Desulfitobacterium spp. in uranium immobilization. Experiments demonstrated that thermal treatment increases electron donor availability, but the increased electron donor was not used to fuel reductive dechlorination and was actually consumed for methanogenesis. Two approaches for monitoring chlorinated solvent bioremediation were investigated, molecular techniques and compound-specific isotope analysis (CSIA). Results demonstrated that while Dehalococcoides (Dhc) gene expression was up-regulated under conditions inhibitory to dechlorination, the isotope effects associated with dechlorination reactions catalayzed by Dhc populations in consortia and in pure cultures were similar. U(VI) reduction by multiple Desulfitobacterium isolates was demonstrated. Interestingly, while almost all U(VI)-reducing populations have been reported to produce uraninite (UO2), the product of U(VI) reduction by Desulfitobacterium isolates was a unique form of insoluble mononuclear U(IV).
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28

Prause, Christopher Alvin. "External detection and measurement of inhaled radionuclides using thermoluminescent dosimeters." Texas A&M University, 2006. http://hdl.handle.net/1969.1/5021.

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Many radiation detection programs use bio-assays, whole-body counters, or air sampling to estimate internal doses. This study examines the possibility of using a common external thermoluminescent dosimeter (TLD) badge as a device for detecting inhaled radionuclides through radiation those radionuclides emit which escape the body. The three common radionuclides chosen for modeling due to their varying decay modes and use or production in the nuclear industry were Cs-137, U-238, and Sr-90. These three radionuclides were modeled for biological and radiological removal in the dynamic systems modeling program of STELLA II and modeled for TLD dose per organ in the geometry and radiation simulation program of MCNP. The results show that none of the nuclides in the study can be detected at air concentrations below regulatory limits for acute inhalation exposures. To achieve a detectable dose from an 8-hour work exposure, with a 90-day wait until the TLD is read, the airborne concentrations for the inhalation classes that produced the most dose per Bq would be 37.9 kBq/m3, 146 MBq/m3, and 1.67 MBq/m3 for Cs-137, U-238, and Sr-90, respectively.
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29

Rouleau, Gary. "A tandem Paul-Penning trap mass measurement system for radionuclides." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=39365.

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A new high-precision atomic mass measurement technique based on a tandem Penning trap system is described. Data from the mass measurements of rubidium and strontium are analyzed to reveal what information desirable for nuclear physics can be extracted and to indicate the limitations in the presently employed set up at the ISOLDE facility at CERN. The possibility of substantially improving the Penning trap collection efficiency through the use of a Paul (radio-frequency quadrupole) ion trap as a collection device for preparing the radionuclides before the measurement system is then presented. Results from engineering tests on the performance of the Paul trap at the ISOLDE facility are discussed. The work concludes with suggestions for the design of feasible system to capture 100% of weak ISOLDE beams. This new system is to be incorporated into the Penning trap set up at the newly constructed ISOLDE-BOOSTER facility.
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30

Sandalls, John. "The sources and fate of radionuclides emitted to the atmosphere." Thesis, Oxford Brookes University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367389.

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31

Brown, Justin. "The behaviour of radionuclides in the Ribble Estuary, NW England." Thesis, University of Reading, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394515.

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The main aim of this project was to consider the geochemical behaviour of a suite of radionuclides (137Cs, 241 Am, isotopes of Pu, Th and U and 234mpa)in the Ribble estuarine environment. Controls on the vertical distribution of radionuclides in sediment deposits were considered and the fluxes of sediment and radionuclides at sites close to the river channel were investigated. Vertical activity distributions were studied by taking cores from various intertidal sediment deposits. Sediment/activity fluxes were studied by installing sediment traps. All samples were analysed by gamma spectrometry. Selected samples were analysed for total organic carbon, mineralogy (XRD), major and trace-metals (XRF), grainsize distribution (laser granulometry) and alpha-emitting radionuclides (alpha spectrometry). The geochemical phase associations of radionuclides were investigated using sequential extraction experiments. Sellafield-derived radionuclides exhibited distinct subsurface maxima (up to 4 785 ± 42 Bq kg" 137Cs, 618 ± 14 Bq kg" 239,240pUand 868 ± Bq kg" 241Am) in mature saltmarsh sediment deposits. Thorium-230 exhibited more complex depth profiles (maximum = 2383 ± 36 Bq kg"). Variations in grain-size were low and therefore not important in controlling the specific activity variation with depth at these sites. The effects of early diagenesis on the specific activity profiles of 137Cs, 241 Am, 239,240pU and 230Th were small. The vertical distribution of Sellafield-derived radionuclides reflected the cumulative discharge pattern from Sellafield implicating a sediment transport mechanism that has involved the integration of contamination from previous discharge events. The vertical distribution of 230Th reflected the annual discharge pattern from BNFL Springfields implicating a transport pathway that involves little mixing of sediment. Levels of Springfields-derived 234mpaand 234Th were highly variable in time and space «0.5 - 495 kBq kg' recorded at Penwortham over the course of the study). The antecedent river discharge regime appears to be the dominant influence on the specific activity of these radionuclides at upstream sites.
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32

Livens, F. R. "Geochemistry of plutonium and other artificial radionuclides in Cumbrian soils." Thesis, University of Glasgow, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375452.

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33

Cooke, Andrew Iain. "The availability of soil-associated radionuclides after ingestion by ruminants." Thesis, University of Newcastle Upon Tyne, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283017.

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34

Rudge, Stephen Alan. "The biological transport of radionuclides in grassland and freshwater ecosystems." Thesis, University of Liverpool, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292164.

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35

Van, der Meulen N. P. (Nicolas Philip). "The cyclotron production of selected radionuclides using medium energy protons." Thesis, Stellenbosch : Stellenbosch University, 2008. http://hdl.handle.net/10019.1/21914.

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Thesis (PhD)--Stellenbosch University, 2008.<br>ENGLISH ABSTRACT: Radiochemical research involving ion exchange chromatography is of paramount importance to the future of radionuclide production at the Radionuclide Production Group (RPG) of iThemba LABS. It is required for the production of high-activity yields of radionuclides to effectively remove impurities and for the safety of the operators performing such productions. The radiochemical separations of some new products from their target material, as well as experiments to determine whether production is viable, are described. 67Ga is currently being produced at the RPG and makes use of zinc targets. With the production of ultra-pure 67Ga, it was necessary to remove any Fe(III) impurities from the final product, such that it may be possible to label peptides with this product. The use of Amberchrom CG161M for this purpose was found to be satisfactory. Interest was shown in 88Y by an overseas company for the manufacture of sources. While a method involving extraction of the radionuclide and the ion exchange thereof using Chelex 100 chelating resin had been published, problems with the production persisted. Three methods, using ion exchange chromatography, were devised to produce the radionuclide, with two of them being adopted for production purposes. Thick-target nuclear data have also recently been accumulated in collaboration with colleagues from ATOMKI, Debrecen, Hungary. There is a large demand for 82Sr for the manufacture of 82Sr/82Rb generators for medical use. A method was developed to manufacture this radionuclide with thicker (32 g) target material, bombarded in the Vertical Beam Target Station (VBTS), and to separate 82Sr from its target material with the use of Purolite S950 chelating resin. 68Ge/68Ga generators are becoming increasingly important in the world of radiopharmaceuticals. A project to develop a local generator was funded by the Innovation Fund and research was performed to produce 68Ge, such that the generator could be manufactured. This involved bombarding thicker Ga targets in the VBTS and performing the chemical separation using AG MP-1 anion exchange resin. The final product was loaded onto generators, although tests performed on different materials to the ones being marketed are also reported in this work. A project was initiated to study the cluster radioactive decay of 223Ac via 14C and 15N emission. To produce 223Ac for these observations, a Th target was bombarded. The 227Pa was separated from the target material using AG MP-1 macroporous anion exchange resin and used as a source, which decayed to 223Ac. The chemical separation and the drying of the final product onto a source plate were completed within approximately 70 minutes from the end of bombardment. The work was performed in collaboration with JINR, Russia, and University of Milan and INFN, Italy. 133Ba has a half-life of over 10 years and is an expensive radionuclide to produce. It has been used in medical and biological studies and there still appears to be a demand for it. A method was devised, utilizing AG50W-X4 cation exchange resin, to separate 133Ba from its CsCl target material. Agricultural specialists in the past have shown an interest in 28Mg, to determine the uptake of the element in fruit. It has long been regarded by some of the local researchers as an interesting project to investigate. It has been determined that the product can be produced in reasonable quantities using LiCl target material, with ten targets being bombarded in series using a 200 MeV proton beam delivered by the Separated Sector Cyclotron. A method, involving the use of Purolite S950 chelating resin, was devised to separate 28Mg from its target material.<br>AFRIKAANSE OPSOMMING: Radiochemiese navorsing, wat ioonuitruiling chromatografie behels, is van uiterste belang vir die toekoms van die produksie van radionukliede by die Radionukliedproduksiegroep (RPG) van iThemba LABS. Dit is nodig vir die hoë aktiwiteit opbrengs van radionuklied produkte om onsuiwerhede te verwyder en vir die veiligheid van die operateurs wat die produksies moet uitvoer. Die skeiding van nuwe produkte van hulle skyfmateriaal, sowel as eksperimente om vas te stel of ‘n produksie uitvoerbaar is, word in die werk beskryf. 67Ga word tans by RPG vervaardig en maak gebruik van sink as skyfmateriaal. Vir die produksie van “ultra-suiwer” 67Ga was dit belangrik om enige Fe(III) onsuiwerhede uit die finale produk te verwyder om sodoende peptiede merking te kan uitvoer. Die gebruik van Amberchrom CG161M hars was voldoende vir dié eksperiment. ‘n Oorsese maatskappy het belangstelling getoon in 88Y vir die vervaardiging van bronne. Alhoewel ‘n metode wat die ekstraksie van die radionuklied en die ioonuitruiling daarvan met die gebruik van Chelex 100 chelerende hars reeds gepubliseer was, het probleme met die produksie voortgeduur. Drie metodes is opgestel om 88Y te produseer, waarvan twee van die metodes tans gebruik word vir produksie doeleindes. Dik-skyf kerndata is ook versamel in samewerking met kollegas van ATOMKI, Debrecen, Hongarye. Daar is ‘n groot aanvraag vir 82Sr vir die vervaardiging van 82Sr/82Rb generators vir mediese doeleindes. ‘n Metode is ontwikkel om die radionuklied te vervaardig van dikker skyfmateriaal (32 g), in die Vertikale Bundelstasie gebombardeer, en om 82Sr van sy skyfmateriaal te skei met die gebruik van Purolite S950 chelerende hars. 68Ge/68Ga generators is besig om toenemend belangrik te word in die wêreld van radiofarmasie. iThemba LABS kry baie navrae om die produk te vervaardig. Die projek was ook deel van die voorlegging aan die “Innovation Fund” en ‘n manier is ondersoek om 68Ge te vervaardig, wat benodig word om so ‘n generator te laai. Dik Ga skyfmateriaal word in die Vertikale Bundelstasie gebombardeer en ‘n chemiese skeiding is uitgevoer deur gebruik te maak van AG MP-1 anioonuitruiling hars. Die finale produk is op die generators gelaai vir toetsdoeleindes. Toetse is ook op ‘n ander tipe generator uitgevoer en word in die werk beskryf. ‘n Projek is begin om “cluster” radioaktiewe verval van 223Ac, via 14C en 15N emissie, te bestudeer. ‘n Th-skyf is met protone gebombardeer om die 223Ac te produseer vir die eksperiment. 227Pa is vervaardig en geskei van die skyfmateriaal. Dit is gedoen met die gebruik van AG MP-1 makroporeuse anioonuitruiling hars en drooggemaak op ‘n bronplaat, waar dit verval het na 223Ac. Die chemiese skeiding en die droogmaak van die finale produk op ‘n bronplaat is uitgevoer binne 70 minute na Einde van Bombardering (EVB). Die werk is deel van ‘n samewerking met kollegas van JINR, Rusland, en die Universiteit van Milaan, sowel as INFN, Italië. 133Ba het ‘n halveertyd van oor die tien jaar en is ‘n duur produk om te vervaardig. Dit is al gebruik in mediese en biologiese studies en daar is deesdae ‘n redelike aanvraag daarvoor. ‘n Metode is uitgewerk om 133Ba te skei van die CsCl skyfmateriaal met die gebruik van AG50W-X4 katioonuitruiling hars. Spesialiste in landboustudies het in die verlede belangstelling getoon in 28Mg. Dit word gebruik om die absorpsie van dié element in vrugte te ondersoek. Die produk kan vervaardig word met die gebruik van LiCl skyfmateriaal: tot soveel as tien skywe (agter mekaar) word gebombardeer met ‘n 200 MeV protonbundel te iThemba LABS. ‘n Metode, wat Purolite S950 behels, is daargestel om 28Mg van die skyfmateriaal te skei.
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36

Copplestone, David. "The food chain transfer of radionuclides through semi-natural habitats." Thesis, University of Liverpool, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309875.

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37

Jia, Wei. "The production of high specific activity radionuclides for radiotherapy application /." free to MU campus, to others for purchase, 1996. http://wwwlib.umi.com/cr/mo/fullcit?p9720538.

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38

Trivedi, D. P. "The mobility of uranium and thorium series radionuclides in groundwaters." Thesis, University of Bath, 1989. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277360.

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39

Al-Shanawa, Maytham. "Detection of environmental pollution (radionuclides and heavy metals) using microorganisms." Thesis, Sheffield Hallam University, 2015. http://shura.shu.ac.uk/19261/.

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Radionuclide and heavy metal pollutants are a major concern for the environment nowadays as thousands of waste sites around the world pose a serious threat to all living organisms and humans in particular. In order to find an effective technique for the detection of these pollutants and their disposal, great efforts have been made. This is one of the most important reasons and motivation for research in this important field. In the present work bacteria cells were used as a sensitive material in biosensor for the detection of gamma radiation and heavy metals (cadmium chloride and nickel chloride) dissolved in water. The main aim of this project is to develop novel sensing technologies for the detection of environmental pollution; the project utilized two types of bacteria samples, E. coli and D. radiodurans, for this task. The biomass (bacteria density or concentration) was firstly characterised by the optical techniques,including fluorescence microscopy, fluorescence spectroscopy, optical density OD600 and UV-visible spectroscopy and was evaluated or estimated according to or attributed to the time of exposure to gamma radiation, which are emitted from CO57 radiation source. From the exponentially decaying response it was shown that the E. coli bacteria (DH5alpha strain, belong gram-negative bacteria) are very sensitive to gamma radiation and the time constant is around 40 hours, that it can be relied upon in determining the low level of radiation. While, D. radiodurans (R1 Anderson strain, which belongs to gram positive bacteria) appeared to be much less affected by gamma radiation and showed even smaller increase in the bacteria counts at low radiation doses followed by rather moderate decay at intermediate and high doses; the time constant is around 240 hours. A series of DC and AC electrical measurements were carried out on the same bacteria samples. As a first step, a correlation between DC and AC electrical conductivity and capacitance with bacteria concentration in solution was established. The study of the effect of gamma-radiation on DC and AC electrical characteristics of bacteria revealed a possibility of pattern recognition of the above inhibition factors. The electrical results showed some match or consistency with the optical results. The optical and electrical techniques were also used to study the effect of heavy metals, mainly NiCb and CdCb on bacteria samples. The relations between the optical and electrical properties with metals concentration were established. The electrical characteristics showed clear sequences according to metals concentration. Pattern recognition seems very interesting and proved to provide a simple method to calculate the environmental contamination levels. The equivalent circuit was investigated and their results were compared with the experimental results; significant match to some extent between the practical and theoretical results was established.
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40

Jansson, Mats. "Diffusion of Radionuclides in Bentonite Clay : Laboratory and in sity Studies." Doctoral thesis, KTH, Kemi, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3443.

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This thesis deals with the diffusion of ions in compactedbentonite clay. Laboratory experiments were performed toexamine in detail different processes that affect thediffusion. To demonstrate that the results obtained from thelaboratory investigations are valid under in situ conditions,two different kinds of in situ experiments were performed. Laboratory experiments were performed to better understandthe impact of ionic strength on the diffusion of Sr2+ and Cs+ions, which sorb to mineral surfaces primarily by ion exchange.Furthermore, surface related diffusion was examined anddemonstrated to take place for Sr2+ and Cs+ but not for Co2+,which sorbs on mineral surfaces by complexation. The diffusion of anions in bentonite clay compacted todifferent dry densities was also investigated. The resultsindicate that anion diffusion in bentonite clay consists of twoprocesses, one fast and another slower. We ascribe the fastdiffusive process to intralayer diffusion and the slow processto diffusion in interparticle water, where anions are to someextent sorbed to edge sites of the montmorillonite. Two different types of in situ experiments were performed,CHEMLAB and LOT. CHEMLAB is a borehole laboratory, where cation(Cs+, Sr2+ and Co2+) and anion (I- and TcO4-) diffusionexperiments were performed using groundwater from a fracture inthe borehole. In the LOT experiments cylindrical bentoniteblocks surrounding a central copper rod were placed in a 4 mdeep vertical borehole. The borehole was then sealed and theblocks are left for 1, 5 or&gt;&gt;5 years. When the bentonitewas water saturated the central copper rod is heated tosimulate the temperature increase due to radioactive decay ofthe spent fuel. Bentonite doped with radioactive Cs and Co wasplaced in one of the lower blocks. Interestingly, the redox-sensitive pertechnetate ion (TcO4-)which thermodynamically should be reduced and precipitate asTcO2·nH2O, travelled unreduced through the bentonite.However, at some spots in the clay, the Tc activity wasconsiderably higher. We ascribe these activity peaks toiron-containing minerals in the bentonite, by which Tc(VII) hasbeen reduced to Tc(IV) and precipitated. The cations Sr2+, Cs+and Co2+, as well as the anion I-, behaved in the CHEMLABexperiments as expected from laboratory studies. Three experiments in the LOT series are completed. The firsttwo diffusion experiments in LOT were less successful, thefirst due to the fact that saturation of the bentonite was notobtained during the experimental period and the radionuclidesdid not move at all. In the second, the uptake of the bentoniteparcel was less successful. Water from the drilling flushedaway large pieces of the top part of the bentonite and thelower part of the test parcel was super-saturated with waterand expanded when released from the rock. The activity distribution in the second experiment wasanalysed. The Co2+ profile looked as we had expected, while Cs+had spread more than our calculations indicated. However, thethird experiment was successful from emplacement, watersaturation and heating to uptake. The activity distribution forboth cations was as expected from laboratory studies. Altogether the three different types of experiments give auniform picture of radionuclide diffusion in bentonite clay forthe ions investigated.<br>QC 20100621
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41

Dinoko, Tshepo Samuel. "Modeling of the dispersion of radionuclides around a nuclear power station." Thesis, University of the Western Cape, 2009. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_3451_1360933219.

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<p>Nuclear reactors release small amounts of radioactivity during their normal operations. The most common method of calculating the dose to the public that results from such releases uses Gaussian Plume models. We are investigating these methods using CAP88-PC, a computer code developed for the Environmental Protection Agency (EPA) in the USA that calculates the concentration of radionuclides released from a stack using Pasquill stability classification. A buoyant or momentum driven part is also included. The uptake of the released radionuclide by plants, animals and humans, directly and indirectly, is then calculated to obtain the doses to the public. This method is well established but is known to suffer from many approximations and does not give answers that are accurate to be better than 50% in many cases. More accurate, though much more computer-intensive methods have been developed to calculate the movement of gases&nbsp<br>using fluid dynamic models. Such a model, using the code FLUENT can model complex terrains and will also be investigated in this work. This work is a preliminary study to compare the results of the traditional Gaussian plume model and a fluid dynamic model for a simplified case. The results indicate that Computational Fluid Dynamics calculations give qualitatively similar results with the possibility of including much more effects than the simple Gaussian plume model.</p>
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42

Reinoso-Maset, Estela. "Aqueous and solid phase interactions of radionuclides with organic complexing agents." Thesis, University of Plymouth, 2010. http://hdl.handle.net/10026.1/300.

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Characterising the geochemistry and speciation of major contaminant radionuclides is crucial in order to understand their behaviour and migration in complex environmental systems. Organic complexing agents used in nuclear decontamination have been found to enhance migration of radionuclides at contaminated sites; however, the mechanisms of the interactions in complex environments are poorly understood. In this work, radionuclide speciation and sorption behaviour were investigated in order to identify interactions between four key radionuclides with different oxidation states (Cs(I) and Sr(II) as important fission products; Th(IV) and U(VI) as representative actinides), three anthropogenic organic complexing agents with different denticities (EDTA, NTA and picolinic acid as common co-contaminants), and natural sand (as simple environmental solid phase). A UV spectrophotometric and an IC method were developed to monitor the behaviour of EDTA, NTA and picolinic acid in the later experiments. The optimised methods were simple, applied widely-available instrumentation and achieved the necessary analytical figures of merit to allow a compound specific determination over variable background levels of DOC and in the presence of natural cations, anions and radionuclides. The effect of the ligands on the solubility of the radionuclides was studied using a natural sand matrix and pure silica for comparison of anions, cations and organic carbon. In the silica system, the presence of EDTA, NTA and, to a lesser extent, picolinic acid, showed a clear net effect of increasing Th and U solubility. Conversely, in the sand system, the sorption of Th and U was kinetically controlled and radionuclide complexation by the ligands enhanced the rate of sorption, by a mechanism identified as metal exchange with matrix metals. Experiments in which excess EDTA, NTA and picolinic acid (40 – 100 fold excess) were pre-equilibrated with Th and U prior to contact with the sand, to allow a greater degree of radionuclide complex formation, resulted in enhanced rates of sorption. This confirmed that the radionuclide complexes interacted with the sand surface more readily than uncomplexed Th or U. Overall this shows that Th and U mobility would be lowered in this natural sand by the presence of organic co-contaminants. In contrast, the complexation of Sr with the complexing agents was rapid and the effect of the ligands was observed as a net increase on Sr solubility (EDTA, picolinic acid) or sorption (NTA). As expected, Cs did not interact with the ligands, and showed rapid sorption kinetics. Finally, ESI-MS was used to study competitive interactions in the aqueous Th-Mn-ligand ternary system. Quantification presented a challenge, however, the careful approach taken to determine the signal correction allowed the competitive interactions between Mn and Th for EDTA to be studied semi-quantitatively. In an EDTA limited system, Th displaced Mn from the EDTA complex, even in the presence of a higher Mn concentration, which was consistent with the higher stability constant of the Th-EDTA complex.
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43

Conroy, David James Robert. "Nanostructured surfaces for sensing heavy metals and radionuclides in aqueous systems." Thesis, University of Leeds, 2012. http://etheses.whiterose.ac.uk/4164/.

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An interdisciplinary approach was used to engineer a range of nanostructured surfaces with specificities for a number of radioactive waste contaminants that are typical of low level legacy contamination at sites across the UK. Specifically, analytes 238/234UO22+, 90Sr2+ and 137Cs+. Because traditional mercury based electrochemical methods lacked the specificity to differentiate individual analytes from complex solutions, combining electrochemical impedance spectroscopy with receptor molecules of desired specificity was used to create sensors with specificity and sensitivity to these radionuclides and which could give responses in real time. For UO22+, combining the evolved uranyl sequestering ability of the surface layer protein (SLP) from the bacterial strain Bacillus sphaericus JG-A12 allowed sub nanomolar levels of uranyl to be monitored in real time using the capacitative component of impedance at low frequency, whilst being largely selective against contaminant divalent cations. Whilst this approach, based on two tethering mechanisms for the SLP, has potential for fabrication of bespoke biosensors for other metal analytes, because of the lack of available metal binding proteins with appropriate cation specificity, alternative synthetic hosts were investigated as receptors. A number of macrocycles, including crown ethers and lariat ethers with specificity to either 90Sr2+ or 137Cs+ were obtained commercially and chemically modified, or chemically synthesised, to permit surface tethering to sensor electrodes. Combining these tethered synthetic hosts with real time cyclic voltammetry, electrochemical impedance and microgravimetric interrogation methods revealed some interesting interfacial phenomena and gave insight into host interactions with the electrode surface. However, this approach did not yield devices that could be used to empirically quantify binding 90Sr2+ or 137Cs+. Accordingly, an alternative approach of combining engineered surfaces that had high surface areas and metal ion specificity, with direct quantification of analyte by  or  counting of the captured radionuclide was investigated using  counting for 90Sr2+ and counting for 137Cs+. This allowed differentiation and quantification of 90Sr2+ or 137Cs+ ions from their non-radioactive isotopes which exist naturally and abundantly in the environment. Functionalised silanes allowed metal chelator functionality to be deposited onto bulk silica surfaces, polymeric nanofibres and silica nano – and micro- particles. Whilst the bulk surfaces and nanofibres were able to bind significant amounts of isotopes, at very low level analyte concentrations typical of contaminated ground water, reproducibility between batches was poor. However, the functionalised nanoparticles performed well, binding significant amounts of radionculide and exhibiting high saturation limits. They were also were able to bind low levels of radionculide in complex analyte solutions such as synthetic groundwater. Bifunctional chelators particles were also made which allowed simultaneous deposition of a solid scintillant. This allowed simultaneous binding and quantification of radioisotopes without the need of scintillation fluid for counting of -particles from 90Sr2+.
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44

Zweit, Jamal H. "The production of medium half-life radionuclides for positron emission tomography." Thesis, University of Manchester, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.257443.

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45

Williams, Mark Steven. "Radionuclides as tracers of sediment mixing in natural and enclosed estuaries." Thesis, University of Plymouth, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247510.

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46

Murdock, Robert Neil. "The transport, behaviour and fate of radionuclides in the freshwater environment." Thesis, University of Liverpool, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317144.

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47

Shortkroff, Sonya. "The influence of radionuclides on synovitis and its assessment by MRI." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326039.

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48

Nelis, Patrick M. "The transfer of radionuclides from sea to land in sea spray." Thesis, University of Edinburgh, 1990. http://hdl.handle.net/1842/15496.

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This thesis reports on an investigation into the transport inland in sea spray of radionuclides discharged into the Irish Sea from the nuclear plant at Scllafield in Cumbria. The work was carried out in response to a concern about the increased incidence of childhood leukaemia in the vicinity of Britain's nuclear reprocessing facilities. It is proposed that the sea spray transfer is an important pathway of discharged radioactivity into the human environment. The inland transfer of contaminated sea spray was investigated on the beach at Drigg, between 6 and 10 km south of the BNFL Scllafield marine discharge pipeline, through which significant levels of radionuclides have been flushed since 1952. The radionuclide concentrations of coastal marram grass vegetation and collected on exposed muslin screen passive droplet collectors are reported. The method used to determine the mass of sea-salt collected by the exposed screens is described and the results of these measurements presented. The collection of the natural atmospheric radionuclide 7Bc on the exposed muslin screens was used to extract the effects of the changing wind flow on the collection of the spray droplets at different distances inland. This allowed an elucidation of the true reduction in the radionuclide air concentrations with distance from the sea. The Sellafield-produced radionuclides present on the exposed screens were found to decrease with distance inland at the same rate as the collected sea-salt, implicating the sea spray droplets as the carriers of the radioactivity. A model of the inland transfer of sea spray droplets produced in the turf zone along the shoreline is described. The collection of the contaminated spray in coastal soil, vegetation and muslin screen collectors is simulated. This model gives results which fit the measured reduction in radionuclide air concentrations with distance from the sea. A successful application to datasets of the inland transfer of spray and radioactivity reported elsewhere is also illustrated. The analysis of the changing surface air concentration with distance inland illustrated that the initially rapid reduction measured here and elsewhere is due more to the spray droplets being mixed to higher altitudes than their deposition to the ground. An analysis of a sea spray collection event in which very high radionuclide air concentrations were measured calculates that under certain conditions 1 km of coastline can produce 1.54xl05Bq of 239+240pu and 1.10xl05Bq of 241Am per hour. This material is thought to be efficiently transported inland in sea spray, and 60% of it is calculated to be still airborne 1 km from the coast. It is concluded that the sea spray transport of marine discharged radioactivity transfers significant levels of long-lived radionuclides to the land, much of it in the respirable size range, and that this material can be carried to large distances from the sea. This pathway merits further investigation as the causes of the increased leukaemia incidence in West Cumbria are sought.
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49

Sanders, Heather K. "Interactions between anionic radionuclides (129I, 79Se and 99Tc) and soil geocolloids." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/51460/.

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The aim of this work was to investigate the interactions of anionic radionuclides 129I, 77Se (as a proxy for 79Se) and 99Tc with soil geocolloids under a range of conditions. These anionic fission products are of specific concern to policy makers regarding human and environmental risk assessments. Previous research has demonstrated strong links between soil organic matter (SOM) content and reduced mobility of these radionuclides. Negatively charged humic substances (HS), such as humic acid (HA) and fulvic acid (FA), may constitute 80% of organic matter and the mechanisms that allow anionic radionuclide to interaction with these HSs are not well understood. In the case of all three radionuclides, speciation plays a significant role in controlling their environmental mobility, therefore HPLC and SEC coupled to ICP-MS was used to monitor the speciation changes as the isotopes were progressively incorporated into HA. X-ray absorption spectroscopy was also employed in order to establish the solid phase speciation of Se after reaction with soil geocolloids. Surface charge development of the HA significantly affected reaction with iodate (129IO3-) and iodide (129I-). Iodide added to HA systems demonstrated slow oxidation and formation of organically bound iodine (Org-129I) predominantly at higher pH (pH 6). Conversely IO3-, was rapidly transformed to form both I- and Org-I. As pH decreased, the rate of this reduction reaction increased. Increasing HA concentration also increased the rate of IO3- reduction and formation of Org-I. Previous research has suggested that the most likely mechanism is IO3- reduction to I2 or HOI which then binds with phenolic groups on OM forming Org-I species. However, IO3- was observed to rapidly bind to HA forming Org-I species with no initial evidence of I- formation; I- concentration then increased over time as Org-I decreased. Where Fe2+/Fe3+ was present increased reduction of IO3- to I- was observed, mediated by association with HA, resulting in less Org-I formation overall. Instantaneous reaction of I- with HA was observed in the presence of Fe2+/Fe3+, with bonding via cation bridging. Some I- was subsequently re-released as I- likely due to ongoing Fe hydrolysis. Modelling of the systems alone was successful and will assist the improvement of whole soil assemblage models. Selenite (Se(IV)) reaction with HA was most rapid at low pH, with minimal/no reduction occurring at > pH 6. Reduction of selenate (Se(VI)) also occurred but this was less than for Se(IV), at low pH. No formation of Se(VI) from Se(IV) was observed, suggesting no oxidation took place, however some formation of Se(IV) from Se(VI ) was observed, also the formation of an unknown Se species suspected to be organic in nature. Humic acid concentration had no significant effect on the rate of Se(IV) or Se(VI) reduction, suggesting that HA itself was not responsible for the reduction. X-ray absorption spectroscopy (XAS) demonstrated the potential for significant reduction to Se(0) at pH 4 and bonding through a Se-O-C chain. The role of microbial communities on Se(IV) and Se(VI) reduction in the HA systems was demonstrated through the use of soil inoculum and glucose additions in sterile and non-sterile systems. No reduction of Se(IV) or Se(VI) and bonding to HA was observed in filter and -irradiation systems. Additions of inoculum and glucose increased the rate of reduction. Additions of Fe2+ did not increase reduction of Se(IV) or Se(VI) when compared to non-sterile HA systems, however XAS analysis demonstrated formation of HA-Fe cation bridges. No reaction of pertechnetate (99Tc(VII)) with HA was observed in these aerobic systems. An unknown Tc species was occasionally observed (< 0.005 μ L-1) and it is possible that this is an organic-Tc species. Significant incorporation of Tc into the solid phase was observed in aerobic soils, with most Tc(VII) being retained in soils with high OM contents and low pH. The mechanisms considered here build upon the basic processes considered in current biosphere models for I and Se. Assemblage models must be used in order to reliably model the interactions of elements within soils due to the complexity of the systems. In order to understand the long-term radiological risks associated with geological repositories, the fine-scale mechanisms must be understood geochemically across a range of different soil types and conditions. The effect of I and Se speciation on bioavailability in soils determines both the potential transfer of radioactive isotopes to the food chain from GDF’s and from aerial sources of contamination. Alongside this, the work also has significant implications for advising on cost-effect fertiliser application methods for both I and Se, in order to tackle nutrient deficiencies worldwide.
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50

Liu, Min-Chang. "Short-lived radionuclides and early solar system chronology a hibonite perspective /." Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1692097281&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.

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