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1
Fernandes, Teresa. "Geochemical behaviour of uranium and thorium in the waste of a uranium conversion facility." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/460838.
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Los residuos contenidos en las balsas de decantación de la planta de conversión de
uranio de Comurhex - Malvési, Francia, han sido caracterizados con el objectivo de
investigar el comportamiento de uranio y torio en este entorno específico. El residuo es
una sucesión de estratos heterogénea que comprende una mezcla de los efluentes del
proceso con el suelo (que han tenido su origen en la re-construcción de los diques de
las balsas, el efluente de lodo, y los antiguos desechos de las minas de azufre y de
flotación de residuos sobre las que las balsas han sido localizadas. El efluente de lodo
original tiene una composición química heterogénea que varía espacialmente y con la
profundidad en las balsas debido a la evolución del proceso de conversión con el tiempo
y debido a la materia prima recibida de diferentes minas del mundo.
En esta tesis, se combinó un examen detallado de los desechos y del agua intersticial,
experimentos de batch y en columna, y el modelado geoquímico para caracterizar la
composición del material y determinar la especiación geoquímica del uranio y el torio.
Los datos presentados en esta tesis han elucidado los mecanismos geoquímicos que
controlan la migración de estos elementos y cómo esta migración puede verse afectada
en el largo plazo.
El uranio en el estrato de los lodos está presente en más de una especiación: como una
fase de silicato, como una fase de óxido de uranilo, adsorbido en oxihidróxidos de hierro
y asociados a los principales minerales, tales como yeso y calcita. Uranio en los otros
estratos de residuos está presente en concentraciones más bajas que las cuantificables
mediante técnicas espectroscópicas. La liberación de U (VI) y su transporte dentro de
los estratos oxidantes de los lodos está dominado por disolución limitada cinéticamente
- y transformación de uranofana, o una fase similar de uranilo - silicato. Las
concentraciones de uranio acuoso bajo condiciones experimentales son controladas por
una fase mineral. La fase mineral limitante de solubilidad más común en condiciones
experimentales ha sido la schoepita (deshidratada). Sin embargo, a escala de campo, y
debido a la naturaleza heterogénea de los residuos en las balsas, es posible que, a nivel
local, otras fases de uranio pueden ser los principales minerales de solubilidad control.
El torio se distribuye homogéneamente en los resíduos, y se encuentra, ocasionalmente
correlacionado con el uranio como óxido de U-Th. Las concentraciones de torio en
solución son controladas por ThO2. Este trabajo ha puesto en evidencia la importancia
de un enfoque que comprenda técnicas complementarias en la caracterización de la
especiación sólida de uranio y torio en un material heterogéneo.The waste contained in the decantation basins of the uranium conversion plant of Comurhex-Malvési, France, was characterised to investigate the behaviour of uranium and thorium in this specific environment. The waste is a succession of heterogeneous strata comprising a mixture of the process effluent with soil (arising from the reconstruction of the basins’ dykes), the sludge effluent, and the former sulphur mine tailings and flotation waste over which the basins have been sited. The original sludge effluent has a heterogeneous chemical composition that varies spatially and with depth in the basins due to the evolution of the conversion process over time and due to the different raw material received from mines around the world. In this thesis, a detailed examination of waste cores and pore waters, static batch and kinetic column test work, and geochemical modelling was combined to characterise the composition of the material and the geochemical speciation of uranium and thorium. The data reported in this thesis have elucidated the geochemical mechanisms that control the migration of these elements and how this migration can be affected in the long term. Uranium in the stratum of sludge is present under more than one speciation: as a silicate phase, as a uranyl-oxide phase, adsorbed to iron oxy-hydroxides and associated with major minerals, such as gypsum and calcite. Uranium in the other strata of waste is present at concentrations that were not quantifiable by spectroscopic techniques. The release of U(VI) and its transport within the oxidising strata of sludge is dominated by kinetically-limited dissolution and transformation of uranophane, or a similar uranylsilicate phase. Aqueous uranium concentrations under experimental conditions are controlled by a mineral phase. schoepite (dehydrated) was found to be the most common solubility limiting mineral. However, at the field scale, and due to the heterogeneous nature of the waste in the basins, it is possible that, locally, other uranium phases may be the main solubility controlling minerals. Thorium is homogeneously distributed in the sludge, and occasionally correlated with uranium, as a U-Th oxide. Thorium concentrations in solution are controlled by ThO2. This work has put in evidence the importance of an approach comprising complementary techniques in the characterisation of the solid speciation of uranium and thorium in a heterogeneous material. The use of multiple techniques is required to identify different phases and in order to establish multiple lines of evidence for the presence of a certain physical form.
2
Lee, Kathryn. "Uranium and Thorium: Radioactive Refugees or Simply Irresistible?" Miami University Honors Theses / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=muhonors1111149868.
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Ahmed, Hayam Mohamed Mahmoud. "Lability and solubility of uranium and thorium in soil." Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/14492/.
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The approach used in this study tested the application of an isotope dilution technique (ID) as a means of measuring the labile U(VI) and Th pools in soils. Uranium and Th lability and solubility were investigated for two sets of soils. The first set (Field soils) consisted of thirty seven soil samples representing five contrasting local ecosystems; the second dataset (BGSc) included 40 soils sub-sampled from the British Geological Survey (BGS) archive. Field soil pore water samples were taken from soil columns held at close to field capacity to measure U and Th solubility and speciation; the effects of time, temperature and reducing conditions on Th and U speciation were investigated. Soils were extracted with foursingle extractants: CH3COONH4, EDTA, 0.43 M HNO3 and TMAH to determine their ability to solubilize labile U and Th. Solubility of Th and U varied with soil characteristics, influenced by pH, DOC, DIC and phosphate concentrations. The Kd values for Th and U varied by 4 and 3 orders of magnitude respectively over the range of soils studied. The formation of soluble uranyl carbonate complexes give rise to a strong positive correlation between U and DIC concentrations in soil solutions. This was particularly clear under anaerobic conditions and also at high temperatures which encouraged microbial activity and high CO2partial pressures. Isotopically exchangeable 238U(VI) (the ‘E-value’, UE) in the soils studied varied from 2.7 to 39.1% of the total soil U content. On average, over all groups of soils, CH3COONH4, EDTA and TMAH underestimated E-value by factors of 13.7, 9.5 and 1.6, respectively, while extraction with 0.43M HNO3 overestimated E-value by only a factor of 1.04. Thus, on average across a range of soils, dilute nitric acid gave the best estimate of E-value compared to other extractants. Generally, E-values for U(VI) did not correspond consistently with any single chemical extraction procedure although the degree of correspondence was soil-dependent. Using UEand ThTMAH as input parameters in the geochemical speciation model WHAM-VII improved the prediction of U and Th solubility compared to using the total metal content orthe pools extractable by (other) single extraction methods. Finally, preliminary experiments confirmed the validity of ID for measuring labile soil Th without disturbance of soil-solution equilibrium.
4
Unsworth, Emily Rachel. "Measurement and modelling of uranium and thorium in natural waters." Thesis, University of Plymouth, 2001. http://hdl.handle.net/10026.1/1145.
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Uranium and thorium are the only elements in the actinide series which naturally occur in the environment in sufficient amounts for practical extraction. They are both radiotoxic and chemotoxic to humans due to the effects of the ionising radiation produced by their radioactive decay, the decay of their daughter products, and due to the chemical toxicity resulting from absorption into the body. Thus it is important to be able to quantitatively determine the levels of uranium and thorium in the environment. Measurement of low levels of uramum and thorium in the presence of high levels of inorganic and organic matrix components has been achieved by coupling on-line solid phase extraction (SPE) with inductively coupled plasma mass spectrometry (ICP-MS) detection. This allowed direct analysis of water samples without any sample pre-treatment offering detection Umits of 0.01 ng ml uranium and 0.006 ng ml thorium. However, in many studies not only do the total levels of uranium and thorium need to be determined, but also their speciation, since this can effect their toxicity and mobility in the environment. An on-line uranium speciation method has successfiilly been developed using a chelating resin micro-column attached to an ICP-MS. This method has been applied to the analysis.pf natural water samples (from Dartmoor, Devon, UK) and the results obtained indicate that the uranium-organic species such as those formed with humic substances are the major species present. A comparison of the pH and level of organic carbon (in a range of natural and synthetic water samples), with the level of uraniumorganic species indicates that the organic carbon concentration is a controlling factor in determining the level of uranium-organic species formed. The kinetics of dissociation of uranium and thorium-humic substance species was also studied. The slow rate of dissociation, observed indicates that once the uranium-humic species have formed these species could remain in the environment for some time. These studies also indicate that even if a change in environmental conditions affected the speciation,it would take time before the uranium and thorium-humic species dissociated and the system equilibrated to a new speciation profile. Two computer programs (WHAM and PHREEQCI) were used to model uranium and thorium speciation in aquatic systems. The Nuclear Energy Agency Thermocheraical Database Project (NEA-TDB) values were incorporated into both programs, as differences in the thermodynamic data provided with the two programs were found to have a major effect on the predicted speciation profiles produced by the two programs. Using the NEATDB values, both programs produced similar inorganic speciation profiles for a given aqueous system but when an organic carbon component was added to the system the two programs produced different predictions for the level of uranium-organic species. This reflected the different organic speciation components utilised within the two programs. WHAM uses a discreet site electrostatic humic substance model and PHREEQCI uses an analogy type model based on a 'model fulvic acid' dataset. A comparison of model predictions with experimental data for the same water sample, indicates that the WHAM program produces closer predictions to the experimental results than the PHREEQCI program. A fiirther study of the WHAM program, using synthetic water solutions with a range of pH, organic carbon and uranium concentrations, indicates that the program has a bias towards low predictions at high pH and low organic carbon concentrations (pH>7, organic carbon < 0.5 ug ml), but wil function satisfactorily within the range of conditions found in the natural (Dartmoor) water samples. The results of these studies should aid environmental investigation based on uranium and thorium where model predictions are to be used.
5
Lucas, Frank W. A. A. "The distribution of uranium and thorium in the Cornubian batholith." Thesis, University of Exeter, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386120.
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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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Van, Wyk Yazeed. "Transport mechanisms of uranium and thorium in fractured rock aquifers." Diss., University of Pretoria, 2010. http://hdl.handle.net/2263/25799.
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The Karoo has been receiving considerable attention since the early 1970’s when uranium mining was at its peak, with numerous research studies being instigated to look at all aspects of uranium mining. It has recently been observed that there seems to be resurgence in uranium exploration in and around the town of Beaufort West. A study on the transport mechanisms of uranium and thorium in fractured-rock aquifers, initiated in the hope of understanding the actual processes controlling radionuclide mobilisation, is reported here. Hydrochemical investigations of the various boreholes were sampled for water quality in June, 2009. The hydrochemical description is typical of shallow fresh groundwater, changing composition to a more sulphate hydrochemical facies along the flow path. While the geochemistry of groundwater in the study area seems to have minimal effects on uranium concentrations, the low levels of uranium in boreholes sampled suggest the importance of hydrological and lithological variability on the measured concentrations. Nevertheless, the uranium concentration is within the recommended levels as specified in the US-EPA, WHO and SA water quality guidelines and thus poses no immediate threat to the general public. Analysis of pumping and tracer tests, reveals that the fractured-rock aquifer can be highly transmissive and that transport can take place via multiple flow paths having different hydraulic properties. Tracer diffusing into stagnant water zones within fracture asperities and the rock matrix are seen as an important retardation mechanism, that has implications for remediation should the aquifer be contaminated by radionuclides. In terms of conceptualising flow at a local scale, aperture sizes ranging from (563-828ìm) along with high flow velocities (1.90E-03m/s), points to the importance of bedding-plane fractures as conduits of groundwater flow. The groundwater flow has been influenced by dolerite dykes creating compartments isolated from each other, suggesting a highly complex aquifer system. Based on the conceptual model, it is shown that these structures can create unique, site specific flow conditions. The integration of all available data into the conceptual model provides an effective research tool that can be built upon as a basis for further research.Dissertation (MSc)--University of Pretoria, 2011.
Geology
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Rowe, P. J. "Uranium series dating of cave sites in the English Midlands." Thesis, University of East Anglia, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376083.
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MARTINS, ELAINE A. J. "Reaproveitamento de valores nos efluentes liquidos das unidades-piloto de uranio e torio." reponame:Repositório Institucional do IPEN, 1990. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10253.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Sullens, Tyler Andrew Albrecht-Schmitt Thomas E. "Hydrothermal synthesis and characterization of novel thorium, uranium, and neptunium solids." Auburn, Ala, 2005. http://repo.lib.auburn.edu/2005%20Summer/doctoral/SULLENS_TYLER_59.pdf.
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Larch, Christopher Paul. "Multidentate amide and cyclopentadienyl uranium and thorium complexes and related studies." Thesis, University of Sussex, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436239.
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Ernoult, Marc. "Gestion avancée du Plutonium en REP Complémentarité des cycles thorium et uranium." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112333/document.
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Dans le but d'étudier les possibilités de gestion avancée du plutonium dans les réacteurs actuels, 8 stratégies de multi-recyclage du plutonium dans des REP sont étudiées. Suite à des études à l'équilibre, il a été montré que, en utilisant des assemblages homogènes, l'utilisation du thorium ne permet pas de réduire les inventaires de plutonium en cycle à l'équilibre ni la production d'américium. En répartissant les différents types de combustibles au sein d'un même assemblage, certaines stratégies thoriées permettent cependant d'obtenir des inventaires et des productions d'américium inférieur aux meilleures stratégies utilisant uniquement le cycle uranium. Cependant dans tous les cas, le faible taux de conversion des combustibles thoriés en REP conduit à l'impossibilité de faire baisser la consommation de ressources de plus de quelques pour-cent par rapport aux stratégies sans thorium. Afin d'étudier la transition, une participation active au développement du code de scénario CLASS a eu lieu. Elle a aboutie à la simulation de deux scénarios parmi ceux étudiés à l'équilibre avec CLASS. Ces simulations ont montrées des écarts avec les scénarios simulés précédemment. Les causes majeures de ces écarts ont été identifiées et quantifiéesIn order to study the possibility of advanced management of plutonium in existing reactors, 8 strategies for plutonium multi-recycling in PWRs are studied. Following equilibrium studies, it was shown that, by using homogeneous assemblies, the use of thorium cannot reduce the plutonium inventory of equilibrium cycle or production of americium. By distributing the different fuel types within the same assembly, some thoriated strategies allow however lower inventories and lower production americium best strategies using only the uranium cycle. However, in all cases, low fuel conversion theories in PWRs makes it impossible to lower resource consumption more than a few percent compared to strategies without thorium. To study the transition, active participation in development of the scenario code CLASS has been taken. It led to the two simulation scenarios among those studied in equilibrium with CLASS. These simulations have shown discrepancies with previously simulated scenarios. The major causes of these differences were identified and quantified
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Heisbourg, Guillaume. "Synthèse, caractérisation et études cinétiques et thermodynamique de la dissolution de ThO2 et des solutions solides Th1-xMxO2 (M=U, Pu)." Paris 11, 2003. https://tel.archives-ouvertes.fr/tel-00005511.
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L'objectif de ce travail est d'étudier la résistance à la corrosion aqueuse des céramiques ThO2 et Th(1-x)MxO2 (M = U, Pu), dans le cadre du stockage direct de combustibles nucléaires potentiels en site géologique profond. Ces solides ont été synthétisés par précipitation en milieu oxalique, calcinés à haute température puis caractérisés par diverses techniques d'analyse: DRX, MEB, MET, XPS, SAX, PIXE, MASE. La caractérisation structurale des solides a montré que tous les oxydes mixtes synthétisés forment des solutions solides homogènes. Les conditions de frittage ThO2 et des solutions solides Th(1-x)UxO2 ont été optimisées afin d'obtenir des échantillons frittés de densité mesurée très proche des densités théoriques. Enfin, l'étude de la dissolution de ces composés a été entreprise dans plusieurs milieux aqueux (HNO3, HCl, H2SO4, eaux naturelles) en fonction de plusieurs paramètres chimiques variant indépendamment afin de déterminer leurs lois cinétiques de dissolution. De manière générale, les solutions solides Th(1-x)UxO2 possèdent des vitesses de lixiviation supérieures à celle de ThO2 principalement du fait des réactions d'oxydation de l'uranium d'autant plus importantes que le taux de substitution est élevé. Les concentrations en actinides dissous sont d'abord contrôlées cinétiquement puis par la solubilité de la phase néoformée (ThO2, nH2O) dès lors que la saturation en thorium du lixiviat est atteinte. Afin de comparer la résistance de ces solides vis-à-vis de la dissolution à celles d'autres matériaux, les vitesses de lixiviation normalisées ont été extrapolées à pH = 5,5 et à 90ʿC. Les taux de lixiviation normalisés obtenus sont environ 10^(-8) g. M^(-2). J^(-1) pour ThO2 et Th(0,87)PU(0,13)O2 et 10^(-6) g. M^(-2). J^(-1) pour Th(0,76)U(0,24)O2. Ces vitesses de dissolution sont faibles par rapport à celles des matériaux actuellement étudiés dans le cadre des matrices de conditionnement spécifiquesThe goal of this work is to study the aqueous corrosion resistance of ThO2 and Th(1-x)MxO2 (M = U, Pu) ceramics, within the framework of direct storage of potential nuclear fuels in deep geological site. These solids were synthesized by precipitation in oxalic medium, calcined at high temperature then characterized by various analytical techniques: XRD, SEM, TEM, XPS, XAS, PIXE, MASE. The structural characterization of the solids showed that ail the synthesized mixed oxides are homogeneous solid solutions. The optimization of sintering conditions of ThO2 and Th(1-x)UxO2 solid solutions was studied in order to obtain sintered pellets with the highest experimental density. At last, the dissolution study of these ceramics was undertaken in several aqueous media (HNO3, HCl, H2SO4, natural waters) versus several chemical parameters, varying independently in order to determine the kinetics law of dissolution. In a general way, the leaching rate of Th(l-x)UxO2 solid solutions increases ail the more than the molar fraction U/Th+U is increasing. Dissolution process is governed by the relative importance of the process described by the dissolution rate of the solid and the oxidation rate of uranium. The concentration of dissolved actinides is controlled at first by dissolution kinetics then by the solubility of secondary phase (ThO2, nH2O) when the saturation of the leachate is reached. In order to compare the resistance of these solids with respect to the dissolution with those of other materials, normalized leaching rates were extrapolated with pH = 5. 5 and 90ʿC. The normalized dissolution rates obtained are approximately 10^(-8) g. M^(-2). J^(-1) for ThO2 and Th(0,87)Pu(0. 13)O2 and 10^(-6) g. M^(-2). J^(-1) for Th(0,76)U(0,24)O2. These normalized dissolution rates are low compared to those of ceramics currently studied within the framework of the specific conditioning matrices
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Wells, Jordann Ashley Logan Slovenne Denis. "Bimetallic actinide complexes for small molecule activation." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31167.
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The work described in this thesis concerns the synthesis of actinide complexes and their reactivity towards small unsaturated molecules. Complexes bearing tetraphenoxide, borohydride and boroxide ligands have been evaluated. Additionally, work towards the synthesis of heterobimetallic uranium transition metal complexes and their applications in catalysis is discussed. Chapter one reviews important organoactinide complexes reported in the literature which effect chemical transformations on small unsaturated substrates. Actinide complexes supported by aryloxide or borohydride ligands are reviewed, along with actinide complexes in which metal p-arene interactions are present. Chapter two reports the synthesis and characterisation of a set of tetraphenol ligands, in addition to a number of attempted synthetic routes to tetraphenol ligands with alternate substitution. The chemistry of those tetradentate aryloxide ligands is introduced with bimetallic uranium(IV) and thorium(IV) complexes using different An(IV) and U(III) precursors. Chapter three reports the synthesis and characterisation of monometallic uranium and thorium complexes using a tetraphenol ligand. The varying chemistry between the two similar An(IV) ions, where the uranium complexes exist as a mixture of oligomers and the thorium complexes remain as well defined mononuclear complexes, is discussed within. A range of base adducts of mononuclear actinide complexes are reported, including a thorium trimethylsilylazide complex, a rare example of a metal organoazide. Chapter four describes the synthesis of homoleptic boroxide and heteroleptic borohydride complexes of uranium(III). The reactivities of these complexes with small unsaturated molecules are assessed, including the reaction of a low coordinate uranium(III) boroxide complex towards CO2 to provide a dinuclear uranium carbonate bridged complex. Chapter five introduces work towards heterobimetallic uranium transition metal complexes carried out in the Arnold group. The application of these complexes towards ring opening polymerisation chemistry is discussed in addition to investigations into the incorporation of transition metals into uranium(IV) complexes. Chapter Six presents the detailed experimental methods used to carry out this research.
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Njiki, Noufele Christelle [Verfasser]. "Uranium and Thorium Complexes with Aroylbis(N,N-dialkylthioureas) / Christelle Njiki Noufele." Berlin : Freie Universität Berlin, 2018. http://d-nb.info/1154766632/34.
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Al-Daher, A. G. M. "Complexes of Thorium(IV) and Uranium(IV) compounds with oxygen donor ligands." Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374555.
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Bailey, Elizabeth Helen. "The solubility of uranium and thorium in hydrothermal fluids and subduction zones." Thesis, University of Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385739.
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Elbouadili, Abdelaziz. "Complexes organométalliques des actinides : réactivité de la liaison sigma - uranium (thorium) - carbone." Dijon, 1985. http://www.theses.fr/1985DIJOS022.
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Contribution à l'étude de la chimie organométallique des actinides : insertion d'isonitriles dans les liaisons t-actinide-carbone des complexes tris et biscyclopentadienyle uranium, réactivité de la liaison t-actinidine-carbone de métallocycles de l'uranium et du thorium vis a vis de molécules polaires et de composés à hydrogène acide, synthèse et applications en chimie organométallique d'un nouveau liganol peralkyle optiquement actif
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Pointer, Christopher M. "Remobilisation of uranium and thorium by ore-forming fluids : a mineralogical study." Thesis, Aston University, 1987. http://publications.aston.ac.uk/14359/.
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Mineralogical investigations have determined the sites of u and Th associated with two radioelement-enriched granites from different geological settings. In the Ririwai ring complex, Nigeria, the u- and Th-bearing accessories have been greatly affected by post-magmatic alteration of the biotite granite. Primary thorite, zircon and monazite were altered to Zr(±Y)-rich thorite, partially metamict zircon (enriched in Th, U, Y, P, Fe, Mn, Ca) and an unidentified LREE-phase respectively, by pervasive fluids which later precipitated Zr-rich coffinite. More intense, localised alteration and albitisation completely remobilised primary accessories and gave rise to a distinctive generation of haematite- and uranothorite-enriched zircon with clear, Hi-enriched rims and xenotime overgrowths. In the Ririwai lode, microclinisation and later greisenisation locally remobilised or altered zircon and deposited Y-ricl1 coffinite and Y(±Zr)-rich thorite which was overgrown by traces of xenotime and LREE-phase(s) of complex and variable composition. Compositions indicating extensive solid-solution among thorite, coffinite, xenotime and altered zircon are probably metastable and formed at low temperatures. The widespread occurrence of REE-rich fluorite suggests that F-complexing aided the mobility of REE, Y, U, Th and Zr during late-magmatic to post-magmatic alteration, while uranyl-carbonate complexing may have occurred during albitisation. The Caledonian, Helmsdale granite in northern Scotland has undergone pervasive and localised hydrothermal alteration associated with U enrichment. Zircon xenocrysts, primary sphene and apatite contain a small.proportion of this U which is largely adsorbed on to secondary iron-oxide, TiOand phyllosilicates. Additional sites for U in the overlying, Lower Devonian Ousdale arkose include coffinite, secondary uranyl phosphates, hydrocarbon and traces of xenotime and unidentified LREE-phases. U may have been leached from the granite and deposited in the arkose, along channelways associated with the Helmsdale fault, by convecting, hydrothermal fluids.
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Blake, P. C. "Some organo-thorium and -uranium chemistry in oxidation states (III) and (IV)." Thesis, University of Sussex, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374454.
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Carter, Helen. "Uranium separations using extraction chromatography." Thesis, Loughborough University, 2000. https://dspace.lboro.ac.uk/2134/11261.
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In the analysis of environmental samples for uranium and thorium pollutants and at natural levels for the dating of geological samples there was felt a need to develop better uranium and thorium separation procedures to replace the established anion exchange method used at AEA Technology plc. This was the first aim of the PhD research. Separation of uranium from thorium prior to measurement of the isotopes by alpha spectrometry was necessary due to the similar alpha energies of234U and 230Th. TRU and UTEVA extraction chromatography resins (EIChroM Industries) were investigated as potential replacements to the anion exchange separation method. The resins are claimed by EIChroM to offer the advantage of providing an actinide specific separation while reducing the separation time from 2 to 0.5 days; the volume of acidic waste produced by a factor of 3, therefore, the cost of analysis was reduced. A uranium and thorium separation procedure using the UTEVA extraction chromatography resin was developed. The uranium and thorium were sorbed by the UTEVA resin from 2M nitric acid. The thorium was then eluted from the resin with 5M hydrochloric acid and the uranium with 0.02M hydrochloric acid. The separation procedure was then evaluated using uraninite ore, coral, granite and lake sediment reference materials. The uranium and thorium concentrations and the 234U/238U and 23oTh/234U activity ratio values determined for the reference material were in good agreement with certified values. The presence of plutonium was found to interfere with the measurement of uranium and thorium by alpha spectrometry. This was due to the similar alpha energies of uranium, thorium and plutonium. The co-elution of plutonium with uranium and thorium from the UTEVA resin was prevented by the inclusion of a reduction step using iron (Il) sulphamate. The resulting plutonium (Ill) was not retained by the UTEVA column. The chemical recoveries for the procedure were similar to those for anion-exchange, but the extraction chromatography procedure provided a more rapid separation using less reagents.
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Zimmer, Patrick. "Étude expérimentale, à haute température et haute pression, du système ternaire UO-ThO-SiO en présence d'une phase fluide : comparaison avec les systèmes ZrO-ThO-SiO et UO-ZrO-SiO : implications géologiques /." Vandœuvre-les-Nancy : Centre de recherche sur la géologie de l'uranium, 1986. http://catalogue.bnf.fr/ark:/12148/cb34870209d.
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Meyers, Lisa A. "Investigations of Nuclear Forensic Signatures in Uranium Bearing Materials." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1380556939.
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Wang, Dean 1971. "Optimization of a seed and blanket thorium-uranium fuel cycle for pressurized water reactors." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29956.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2003.Includes bibliographical references (p. 189-194).
A heterogeneous LWR core design, which employs a thorium/uranium once through fuel cycle, is optimized for good economics, wide safety margins, minimal waste burden and high proliferation resistance. The focus is on the Whole Assembly Seed and Blanket (WASB) concept, in which the individual seed and blanket regions each occupy one full-size PWR assembly in a checkerboard core configuration. A Westinghouse 4-loop 1150 MWe PWR was selected as the reference plant design. The optimized heterogeneous core, after several iterations, employs 84 seed assemblies and 109 blanket assemblies. Each assembly has the characteristic 17x17 rod array. The seed fuel is composed of 20 w/o enriched annular UO2 pellets. Erbium is used in the fresh seed to help regulate local power peaking and reduce soluble boron concentrations. Erbium was evenly distributed into all pin central holes except for the peripheral pins and four corner pins of each assembly where more erbium was used due to their higher power level. The blanket fuel is a mixture of 87% ThO2 - 13% UO2 by volume, where the uranium is enriched to 10 w/o. The blanket fuel pin diameter is larger than the seed fuel pin diameter. There are two separate fuel management flows: a standard three-batch scheme is adopted for the seed (18 month cycle length) and a single-batch for the blanket, which is to stay in the core for up to 9 seed cycles. The WASB core design was analyzed by well known tools in the nuclear industry. The neutronic analysis was performed using the Studsvik Core Management System (CMS), which consists of three codes: CASMO-4, TABLES-3 and SIMULATE-3. Thermal-hydraulic analysis was performed using EPRI's VIPRE-01.
(cont.) Fuel performance was analyzed using FRAPCON. The radioactivity and decay heat from the spent seed and blanket fuel were studied using MIT's MCODE (which couples MCNP and ORIGEN) to do depletion calculations, and ORIGEN to analyze the spent fuel characteristics after discharge. The analyses show that the WASB core can satisfy the requirements of fuel cycle length and safety margins of conventional PWRs. The coefficients of reactivity are comparable to currently operating PWRs. However, the reduction in effective delayed neutron fraction (eff) requires careful review of the control systems because of its importance to short term power transients. Whole core analyses show that the total control rod worth of the WASB core is about 1/3 less than those of a typical PWR for a standard arrangement of Ag-In-Cd control rods in the core. The use of enriched boron in the control rods can effectively improve the control rod worth. The control rods have higher worth in the seed than in the blanket. Therefore, a new loading pattern has been designed so that almost all the control rods will be located in seed assemblies. However, the new pattern requires a redesign of the vessel head of the reactor, which is an added cost in case of retrofitting in existing PWRs. Though the WASB core has high power peaking factors, acceptable MDNBR in the core can be achieved under conservative assumptions by using grids with large local pressure loss coefficient in the blanket. However, the core pressure drop will increase by 70% ...
by Dean Wang.
Ph.D.
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Channer, Michael. "(Uranium-Thorium)/Helium Thermochronologic Constraints on Secondary Iron-Oxide Mineralization in Southwestern New Mexico." DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/5887.
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Southwestern New Mexico experienced protracted volcanism from ~60 Ma to 500 ka and associated epithermal mineralization. We apply hematite (U-Th)/He (hematite He) thermochronology to fracture-hosted hematite in the Lordsburg Mining District to resolve the timing of mineralization related to hydrothermal fluid circulation. We interpret hematite He dates with integrated field and structural observations, scanning electron microscopy to characterize hematite texture and grain size distribution, and zircon U-Pb and zircon (U-Th)/He (zircon He) chronology to constrain the timing of host rock formation and the ambient low-temperature thermal history, respectively. Undeformed hematite fills fractures cut a brecciated rhyolite and preserve open voids. Scanning electron microscopy reveals botryoidal hematite comprises stacked sublayers of ultra-fine grained crystals, corresponding to low He retentivity hematite. Forty-nine hematite aliquots from 12 samples, across seven fracture coatings yield reproducible mean hematite He dates from 3.4 to 0.8 Ma. U-Pb zircon geochronology dates range from ~90 to ~54 Ma, excluding ~1.3–1.0 Ga zircon components. These data overlap previously published dates (~56–52 Ma) from the host rhyolite overlap with new zircon He dates of ~51 Ma from two rhyolite host rock samples. The mean of the youngest U-Pb zircon dates is 54 ± 1.3 Ma and is inferred to represent the rhyolite eruption age. We suggest the rhyolite has remained in the near surface since emplacement and that hematite He dates record ~3.5–1 Ma epithermal mineralization. Younger dates likely reflect partial diffusive He loss from the fine-grained and thus low He retentivity hematite. Our data suggests the hematite fracture-fills are unaffiliated with Paleocene-Eocene economic mineralization.
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Negrel, Justine. "Etude couplée des fractionnements isotopiques du LI, B et U dans des profils d'altération : exemple du bassin versant du Strengbach (Vosges, France)." Thesis, Strasbourg, 2019. http://www.theses.fr/2019STRAH001/document.
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Comparer de manière approfondie la réponse des différents outils isotopiques choisis (Li, B et U) durant l’altération chimique dans un profil déjà connu (e.g. le profil du Sommet sur le Bassin versant du Strengbach ; Ackerer, 2017) afin de dégager les mécanismes moteurs des fractionnements isotopiques de chacun de ces éléments pour faire le lien entre la réponse de ces outils lors de l’altération chimique et remonter ainsi au régime d’altération des roches. Développer les observations réalisées sur le profil du Sommet et les appliquer sur cinq autres profils d’altération répartis sur l’ensemble du bassin versant en se concentrant sur la fraction <2µm. Cela permettra de voir si les observations faites dans le premier profil se retrouvent dans les autres profils et si nous sommes capables de remonter au régime d’altération. Étudier de manière préliminaire comment évolue le signal isotopique de l’altération chimique acquis dans les profils d’altération au cours du transport sédimentaire et s’il est possible de déterminer le régime d’altération d’un bassin versant à partir des sédiments de ce même bassinIn-depth comparison of the response of various selected isotopic tools (Li, B and U) during chemical weathering in an already known profile (eg the Summit profile in the Strengbach watershed, Ackerer, 2017) to identify the driving mechanisms of isotopic fractionations of these elements to link the response of these tools compared to the chemical alteration to go back to the alteration regime. Develop the observations made on the Summit profile and apply them to five other weathering profiles distributed over the entire watershed focusing on the <2μm fraction. This will make it possible to see if the observations made in the first profile are found in the other profiles and if we are able to go back to the alteration regime. Preliminarily investigate how the isotopic signal of chemical alteration acquired in alteration profiles evolves during the sediment transportation and if it is possible to determine the alteration regime of a watershed from it sediments
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Braun, Jean-Jacques. "Comportement géochimique et minéralogique des terres rares, du thorium et de l'uranium dans le profil latéritique d'Akongo (sud-ouest Cameroun)." Nancy 1, 1991. http://docnum.univ-lorraine.fr/public/SCD_T_1991_0261_BRAUN.pdf.
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La géochimie et la minéralogie du thorium, de l'uranium et des terres rares ont été étudiées dans un profil latéritique développé aux dépens d'une syénite (akongo, sud-ouest Cameroun). Le thorium a été utilisé en tant qu'élément invariant dans les calculs de bilans iso élémentaires. La mobilité de l'uranium, dans ce profil est comparable à celle du sodium, du calcium et du magnésium. Dans les différentes zones du profil latéritique, les terres rares ont un comportement contraste. La majeure partie des terres rares est évacuée des horizons supérieurs riches en fer. Dans la zone de battement de la nappe phréatique (saprolite et plinthite), les terres rares peuvent être accumulées de façon absolue dans deux types d'environnements. Le premier correspond aux zones argileuses ou les solutions du sol ont un temps de résidence plus long lors de la vidange de la nappe. Le second correspond à la syénite pourrie et aux veines blanches très poreuses de la base du saprolite. Dans la syénite, l'allanite, l'épidote, le sphene et l'apatite contrôlent la majeure partie du stock de terres rares. Ces phases sont détruites des les premiers stades de l'altération. Les terres rares légères sont immobilisées sous forme de florencite. Les fortes accumulations en cérium rencontrées dans ce profil sont dues à la présence de cerianite.
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Karam, Habib. "Mise au point de la mesure de sections efficaces de réactions (n,XN) par spectroscopie γ prompte sur des cibles très radioactives." Strasbourg, 2009. http://www.theses.fr/2009STRA6014.
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La loi « Bataille » fait obligation au CNRS de développer des recherches sur le retraitement des déchets nucléaires. C’est dans ce cadre que notre équipe GRACE (Groupe de Recherche sur l’Aval du Cycle Electronucléaire) de l’IPHC a entrepris des mesures nécessaires à la mise au point des réacteurs hybrides. Le champ de recherche s’est élargi puisqu’il inclut maintenant des études visant à développer le cycle de Thorium. GRACE s’est plus précisément attaché à mesurer des sections efficaces de réactions (n,xng) mal connues jusqu’à présent ou pour lesquelles aucune mesure n’existe. Les mesures ont été effectuées auprès du faisceau « blanc » de Gelina (IRMM Geel, Euratom). La technique de temps de vol a été appliquée. La spectroscopie g en ligne, utilisée pour étudier les réactions (n,xng), requiert avant tout de mesurer l’énergie des rayons g avec une bonne résolution. A cause de l’existence d’un flash g créé en même temps que le faisceau, il faut aussi un temps mort très faible, de façon à pouvoir détecter les neutrons de haute énergie. GRACE a réussi à concilier ces deux impératifs en mettant au point une nouvelle méthode basée sur la digitalisation et le traitement numérique du signal. Des mesures de section efficaces (n,xng) sur le 206,207,208Pb ont été réalisées ainsi avec succès à Geel, à l’aide des détecteurs coaxiaux de gros volume et à une distance de vol de 200 m. Le travail présenté dans ce mémoire a consisté à adapter la méthode pour rendre possible la spectroscopie g en ligne sur des cibles radioactives. Pour cela, la nouvelle mesure s’est déroulée sur une piste de vol de 30 m, et des détecteurs germanium planaires ont été utilisés. Dans un premier temps, et afin de s’assurer du bon fonctionnement du nouveau dispositif expérimental, des mesures de sections efficaces (n,n’g) sur une cible de plomb naturel ont été effectuées et les résultats sont comparés à ceux de la mesure à 200 m et aux calculs du code TALYS. Ensuite, les sections efficaces inélastiques partielles sur le 182,186W ont été mesurées entre le seuil de la réaction et 8 MeV. Enfin, une cible de 235U enrichie à 93 ,2 % a été bombardée et trois transitions dues à la réaction 235U(n,2ng)234U ont été analysées avec succès dont celle de l’état 8+ vers l’état 6+ jamais mesurée avant. Ce travail est une étape essentielle pour utiliser cette nouvelle méthode afin de mesurer des réactions (n,2ng) sur l’233UThe “Bataille” law obliged the CNRS to develop researches on the reprocessing of the nuclear waste. It is in this frame that our group GRACE (Groupe de Recherche sur l’Aval du Cycle Electronucléaire) of the IPHC began researches that contribute to the development of the hybrid reactors. However, the field of research widened because it now includes studies to develop the Thorium cycle. GRACE has undertaken measurements of (n,xng) reactions cross sections badly known or for which no measurement exists yet. The experiments were performed at the “white” neutron beam generated by GELINA facility in Geel, Belgium. The time of flight technique was applied. The g spectroscopy used for these measurements requires the detection of g rays with a good energy resolution. Because of the existence of a g flash created at the same time as the neutron beam, a short dead time is also required, to be able to detect the high energy neutrons. GRACE managed to conciliate these two imperatives by finalizing a new method based on the digital treatment of the signal. Using large HPGe coaxial detectors, (n,xng) cross sections measurements on the 206,207,208Pb nuclei were successfully realized at a 200 m flight path. The work presented in this thesis consists in adapting the method to highly radioactive targets. For that reason, the new measurement took place on a 30 m flight path and planar germanium detectors were used. In order to check the correct functioning of the new experimental method, (n,n’g) cross section measurements on a natural lead target were done and the results found were compared with the experiments at 200 m and with the theoretical calculations of the TALYS code. After that, the partial inelastic scattering cross sections on the 182,186W were performed from the threshold up to 8 Mev. Finally, a 93,2% enriched 235U target was bombarded and three transitions due to the 235U(n,2ng)234U reaction were successfully analysed including the one from the 8+ to the 6+ state, never measured before. This work is an essential step for using this new method in order to measure the (n,2ng) reaction cross sections on the highly radioactive 233U isotope
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Roberts, Helen Marie. "Post-depositional migration of uranium- and thorium-series radionuclides : the potential impact of luminescence ages." Thesis, University of Liverpool, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338456.
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Sukjai, Yanin. "Silicon carbide performance as cladding for advanced uranium and thorium fuels for light water reactors." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/87496.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 285-288).
There has been an ongoing interest in replacing the fuel cladding zirconium-based alloys by other materials to reduce if not eliminate the autocatalytic and exothermic chemical reaction with water and steam at above 1,200 °C. The search for an accident tolerant cladding intensified after the Fukushima events of 2011. Silicon carbide (SiC) possesses several desirable characteristics as fuel cladding in light water reactors (LWRs). Compared to zirconium, SiC has higher melting point, higher strength at elevated temperature, and better dimensional stability when exposed to radiation, as well as lower thermal expansion, creep rate, and neutron absorption cross-section. However, under irradiation, the thermal conductivity of SiC is degraded considerably. Furthermore, lack of creep down towards the fuel causes the fuel-cladding gap and gap thermal resistance to stay relatively large during in-core service. This leads to higher fuel temperature during irradiation. In order to reduce the high fuel temperature during operation, the following fuel design options were investigated in this study: using beryllium oxide (BeO) additive to enhance fuel thermal conductivity, changing the gap bond material from helium to lead-bismuth eutectic (LBE) and adding a central void in the fuel pellet. In addition, the consequences of using thorium oxide (ThO₂) as host matrix for plutonium oxide (PuO₂) were covered. The effects of cladding thickness on fuel performance were also analyzed. A steady-state fuel performance modeling code, FRAPCON 3.4, was used as a primary tool in this study. Since the official version of the code does not include the options mentioned above, modifications of the source code were necessary. All of these options have been modeled and integrated into a single version of the code called FRAPCON 3.4-MIT. Moreover, material properties including thermal conductivity, swelling rate, and helium production/release rate of BeO have been updated. Material properties of ThO₂ have been added to study performance of ThO₂-PuO₂ . This modified code was used to study the thermo-mechanical behavior of the most limiting fuel rod with SiC cladding, and explore the possibility to improve the fuel performance with various design options. The fuel rod designs and operating conditions of a 4-loop Westinghouse pressurized water reactors (PWR) and Babcock and Wilcox (B&W) mPower small modular reactors (SMR) were reactors (PWR) and Babcock and Wilcox (B&W) mPower small modular reactors (SMR) were chosen as representatives of conventional PWRs and upcoming SMRs, respectively. Sensitivity analyses on initial helium gap pressure, linear heat generation rate (LHGR) history, and peak rod assumptions have been performed. The results suggest that, because of its lower thermal conductivity, SiC is more sensitive to changes in these parameters than zirconium alloys. For a low-conducting material like SiC, an increase in cladding thickness plays a significant role in fuel performance. With a thicker cladding (from 0.57 to 0.89 mm), the temperature drop across the cladding increases, which makes the fuel temperature higher than that with the thin cladding. Reduction of fuel volume to accommodate the thicker cladding also causes negative impact on fuel performance. However, if the extra volume of the cladding replaces some coolant, the reduced coolant fraction design (RCF) has superior performance to the decreased fuel volume fraction design. In general, the most effective fuel temperature improvement option appears to be the option of mixing beryllium oxide into the fuel. This method outperforms others because it improves the overall thermal conductivity and reduces the overall temperature of the fuel. With lower fuel temperature, fission gas release and eventually plenum pressure -- one of the most life-limiting factor for SiC -- can be lowered.
by Yanin Sukjai.
S.M.
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Hsieh, Yu-Te. "Using uranium- and thorium-series isotopes as tracers for trace-metal inputs to the oceans." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:9574b34a-3932-4a16-a823-17028ef889f2.
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This thesis explores the use of U-Th series isotopes as tracers to study ocean mixing and chemical inputs to the open ocean from atmospheric dust, rivers, continental shelves and ocean sediments. The use of Th isotopes as an improved tracer of dust input has been tested by measuring 232Th and 230Th concentrations of upper-ocean seawater at six stations along a meridional Atlantic section that spans the Saharan dust plume. The results of 232Th-derived dust fluxes show good agreements with dust model depositions, and suggest that thorium may be a more accurate tracer of dust input than Aluminium, which is frequently used for this purpose. A new technique has been developed for the precise measurement of 228Ra/226Ra ratios and 228Ra and 226Ra concentrations in seawater by multi-collector ICP mass spectrometry (MC-ICP-MS). This methods offers improved analytical precision and detection limits relative to previous decay-counting approaches, though is more labour intensive. The accuracy of this method has been proved in the GEOTRACES Ra intercalibration, and shows consistent results with decay counting measurements from other labs. This technique has been applied to water samples in Loch Etive, a Scottish fjord, and in the Cape Basin during the UK-GEOTRACES cruise (GA10E) to investigate ocean mixing and trace-metal fluxes in the oceans. In Loch Etive, Ra data provide an estimation of sedimentary 228Ra flux of 5.5 ± 0.3 (× 109 atoms m-2 yr-1) in the inner loch deep basin. Short-lived Ra isotope (223Raex) has also been used to estimate surface water transport rate, which is ~ 2.4 ±0.2 cm s-1 from the mouth to the head of the loch. In the Cape Basin, seawater 228Ra and 226Ra activities have been used to estimate vertical and horizontal mixing in the surface ocean. The horizontal mixing (Kx) from the continental shelf to the open ocean is 3.8 ± 0.8 (× 107 cm² s-1) and the vertical mixing (Kz) in the upper 400 m layer is 0.9 – 2.1 cm² s-1. These mixing rates enable the calculation of nutrient flux in the surface ocean. The calculated vertical nitrate fluxes in the Cape Basin are 0.4 – 0.5 mmol N m-2 d-1. This finding shed light on the nutrient inputs to the South Atlantic Subtropical Gyre.
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Belkalem, Mohamed dit Boussad. "Synthèse et étude physicochimique de porphyrines et de phtalocyanines de thorium et d'uranium." Dijon, 1986. http://www.theses.fr/1986DIJOS017.
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Ce mémoire apporte une contribution à l'étude des complexes porphyriniques des actinides : uranium et thorium. Les principaux points sont : la synthèse et les propriétés spectroscopiques des porphyrines dichlorées et bisacétylacétonates de ces métaux ; la préparation des dihydroxyatinoporphyrines qui cristallisent en édifices trinucléaires ; la caractérisation des bisacétylacétonatoactinophtalocyanines, une nouvelle classe de phtalocyanines en série des actinides.
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Lidman, Fredrik. "Radionuclide transport in the boreal landscape : Uranium, thorium and other metals in forests, wetlands and streams." Doctoral thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-80485.
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The boreal landscape is complex mosaic of vast forests, lakes and wetlands. Through the landscape flows a fine network of streams and rivers, carrying dissolved and suspended material from atmospheric deposition and weathering of soils and bedrock to downstream recipients. This thesis investigates the transport of U, Th and other metals in the boreal landscape by comparing a set of catchments with contrasting characteristics, ranging from 0.12-68 km2 in area. Using uranium (234U/238U) and oxygen isotopes (δ18O) it was demonstrated that catchment size has a strong impact on the hydrological pathways and on the mobilisation of uranium. Both tracers also displayed a consistent shift towards more superficial sources and more superficial flow pathways when going from winter baseflow conditions to the spring flood. Large spatiotemporal variability was observed with U fluxes ranging from 1.7 -30 g km-2 a-1. Using a wide set of hydrochemical parameters and landscape characteristics it was demonstrated that wetlands play a decisive role for the biogeochemical cycling of many metals. Comparing normalised fluxes of 13 different elements (Al, Ba, Ca, Cr, Cu, La, Mg, Na, Ni, Si, Sr, U and Y) 73% of the spatial variance could be explained based on the wetland coverage and the affinity for organic matter, the latter of which was quantified using thermodynamic modelling. Hence, it was possible to link the large-scale transport patterns of a wide range of metals to fundamental biogeochemical properties. When restraining the analysis to the smaller streams (<10 km2), the explanatory power increased to 88%. For elements such as Na and Si with low affinity for organic matter the decrease in wetland-dominated catchments corresponded closely to the area of mineral soils that had been replaced by peat, indicating that reduced weathering was the main cause of the decrease. For organophilic metals the decrease in wetland-dominated catchments was even greater, suggesting that there also was an accumulation of these metals in the peat. This was confirmed by investigating the distribution of radionuclides in local mire, which revealed considerable accumulation of uranium and thorium along the edges of the mire. Based on the inventories of uranium and thorium and their distribution in the peat it was concluded that the mire historically had been a sink for these metals and that it most likely will continue to be so for a long time to come. All and all, wetlands were estimated to decrease the fluxes of metals from the boreal forests to downstream lakes and oceans by 20-40%, depending on how strongly they bind to organic matter.
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Ricard, Estelle. "Datation par ICP-MS des hydrocarbures accumulés dans un réservoir par la méthode uranium/thorium/plomb." Pau, 2010. http://www.theses.fr/2010PAUU3009.
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La quantification des métaux traces dans les matrices organiques représente un challenge dans le domaine de la géochimie pétrolière afin d’étudier les corrélations huile-huile, huile source, et d’obtenir des informations concernant les migrations des hydrocarbures. Entre autre, l’estimation de l’âge d’expulsion des huiles brutes depuis la roche mère aura une implication importante pour la modélisation des systèmes pétroliers. Une nouvelle approche analytique a été développée, basée sur l’utilisation d’un laser IR-femtoseconde à haute cadence de tir couplé à une détection ICP-MS, afin de déterminer les teneurs en métaux traces dans les huiles brutes avec très peu de préparation d’échantillons préalable. Les limites de détection obtenues sont de l’ordre de la ppb. L’étude de l’uranium, du thorium et des rapports isotopiques du plomb dans les matrices pétrolières permet d’obtenir les informations suivantes : − Les huiles brutes sont très pauvres en uranium et en thorium (concentration < 1 ppb) comparé au plomb (10 ppb – 10 ppm), ce qui implique des rapports U/Pb and Th/Pb très faible (< 0,05). Ainsi, la détermination de l’âge d’expulsion à partir les huiles brutes est difficilement réalisable avec les isochrones U/Th/Pb classiquement utilisées, et nécessite donc de comparer les informations comprises dans les huiles brutes avec les kérogènes associés. − Les rapports isotopiques du plomb mesurés par ICP-MS multicollecteur, a permis de montrer le potentiel du système uranium/thorium/plomb pour l’estimation de l’âge d’accumulation des hydrocarburesTrace metal quantification in organic matrices represents a challenge for organic geochemistry to study oil-to-oil correlation, oil-to-source correlation, or to obtain information on oil migration. Estimation of crude oil expulsion timing from the rock source will have an important implication for petroleum systems modelling. A new analytical approach using a high repetition rate IR-femtosecond laser coupled to an ICP-MS detection was developed, for the direct determination of trace elements in crude oil with limited sample preparation. Limits of detection in the range of the level were typically obtained. The study of uranium, thorium and lead isotopes in petroleum matrices gives the following information: − Crude oils are very low concentrated in uranium and thorium (concentration < 1 ppb) compared to lead (10 ppb – 10 ppm) i. E. Very low U/Pb and Th/Pb ratios (< 0,05). So the determination of crude oil expulsion time is hardly realizable with classical U/Th/Pb isochrones, and needs to be confronted to lead isotopes ratios obtained from source rocks and crude oils. − Lead isotopes ratios in crude oils and source rocks measured by multi-detection ICP-MS, shows the potential of the uranium/thorium/lead system for dating hydrocarbon accumulation
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Carrier, Frédéric. "Utilisation de la spectrométrie gamma aéroportée (uranium, thorium, potassium) pour quantifier les processus d'érosion et d'altération." Paris, Institut de physique du globe, 2005. http://www.theses.fr/2005GLOB0021.
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La campagne de spectrométrie gamma aéroportée sur le Massif armoricain fourni les teneurs en U, Th et K en ppm des sols. Leurs variations et celles du 137Cs ont permis de quantifier et de cartographier les processus d'érosion chimique et mécanique au sein d'une unité géologique homogène. Notre nouvelle approche, basée sur une analyse multivariée (classification ascendante hiérarchique), intègre les données de spectrométrie gamma aéroportée à large distribution spatiale et les données ponctuelles (éléments majeurs, traces et isotopes) issues de l'étude des sols et des produits d'érosion actuellement véhiculés par une rivière pérenne. L'exportation totale de potassium a été estimée en tout point d'un bassin versant (résolution 50 m) jusque 17+2 t/km2/a pour un profil d'altération épais de 50m. L'étude intégrante des processus d'érosion par les rivières présente un biais, car actuellement la signature géochimique des vallées est davantage représentée que les plateauxThe airborne gamma-ray spectrometry survey carried out on the Armorican Massif provided soil contents in U, Th and K in ppm. Chemical and mechanical erosion processes within a homogeneous geological unit have been estimated using their variations and those of the 137Cs. Our new approach, based on a multivariate analysis (hierarchic ascending classification), integrates the airborne gamma-ray spectrometry data, with their broad spatial distribution, together with precisely located station data (major elements, traces and isotopic geochemistry) resulting from a soil and river water erosion products survey. The total export of potassium was estimated in any point of an area catchment (50-m resolution) until 17+2 t/km2/a for a 50-m thick weathering profile. Erosion study by river sampling provide important biases, for the perennial river does not integrate the whole range of erosion products : the geochemical signature of the valleys is currently more represented than plateau areas
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Gréaux, Steeve. "Étude de la localisation dans le manteau terrestre de l'uranium et du thorium : principales sources de chaleur de la Terre." Université de Marne-la-Vallée, 2006. http://www.theses.fr/2006MARN0357.
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La Terre est une planète vivante dont l’intense activité interne se traduit par les tremblements de Terre, les éruptions volcaniques, la dérive des continents, etc … Ces manifestations sont liées énergétiquement au flux de chaleur mesuré à la surface de la Terre (44 TW). On estime que la moitié de l’énergie requise par cette activité est générée par la désintégration radioactive de l’uranium, du thorium et du potassium, dont 80% de cette énergie vient de U et Th. La localisation des sources de chaleur du globe dans le manteau terrestre est essentielle à la compréhension de la géodynamique et du comportement thermique de notre planète. Dans cette étude, nous montrons que l’uranium et le thorium du manteau inférieur sont principalement concentrés dans la perovskite calcique alumineuse Al-CaSiO3, qui est la 3ème phase en abondance du manteau inférieur. Nous avons réalisé des expériences à HP-HT dans le système (U,Th)-Ca-Al-Si-O, en presse multi-enclumes jusqu’à 26 GPa et en cellule à enclumes de diamant jusqu’à 54 GPa. L’analyse des échantillonssynthétisés à HP-HT par microsonde électronique et diffraction des rayons X, a permis de mettre en évidence une structure tétragonale pour la pérovskite (U,Th)-Al-CaSiO3 (groupe d’espace P4/mmm). La spectroscopie d’absorption des rayons X a permis de connaître l’état d’oxydoréduction de U et nous a donné des pistes sur la spéciation de U et Th dans cette pérovskite. Des calculs ab initio par simulation de densité fonctionnelle avec l’approximation de gradient généralisé (GGA) et les ondes de projection augmentées (PWA), ont été réalisés afin de valider nos expériences et déterminer le scénario le plus favorable énergétiquement à l’incorporation de U dans la Ca-pv. Les résultats obtenus dans un système simple ont été par la suite confirmés dans un système plus complexe, de composition pyrolitique, représentatif de la composition du manteau terrestre. Cette étude propose de concentrer U et Th dans une Ca-pv, qui se retrouverait au sein d’une couche de matière primitive et radiogénique, récemment proposée dans des modèles géochimiques et sismologiques, à partir de 1600 km de profondeur, et jusqu’à la base du manteau inférieurThe internal activity of the Earth is evidenced through earthquakes, volcanic eruptions, continental drift etc. . . These events are energetically related to the heat flux at the Earth surface (44 TW). About half of the energy required for this activity is generated by the radioactive decay of uranium, thorium and potassium, with roughly 80 % accounting for uranium and thorium. The location of these heat sources in the mantle is essential for a better understanding of the geodynamics and thermal behaviour of the Earth. In this study, we show that most of the U and Th in the Earth’s mantle are mainly concentrated in the Al-bearing CaSiO3 perovskite, which is the third phase in abundance within the lower mantle. We performed experiments at high pressure and high temperature in the (U,Th)-Ca-Al-Si-O system with both multi-anvil apparatus to 26 GPa and diamond anvil cell up to 54 GPa. The occurrence of a tetragonally distorted perovskite structure for the (U,Th)-bearing Al-CaSiO3 phase (space group: P4/mmm) is evidenced by analyzing HP-HT samples with electronic probe and x-ray diffraction methods. X-ray absorption spectroscopy confirmed that the incorporation of U and Th is made through the coupled substitution of CaSi by (U,Th)Al2 in the CaSiO3 perovskite. We performed ab initio calculations by density functional simulations within the generalized gradient approximation (GGA) and projector-augmented wave (PAW) method, to calculate the most favourable scenario of incorporation of U in the Ca-pv. In addition, results obtained in simple systems are confirmed by preliminary HP-HT experiments performed with U and Th in the pyrolitic system. This study propose that U and Th are concentrated in a Ca-pv that can be part of a primitive radiogenic deep layer recently proposed in geochemical and seismological models, from 1600 km depth to the lowermost part of the lower mantle
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Podor, Renaud. "Synthèse et caractérisation des monazites uranifères et thorifères." Nancy 1, 1994. http://docnum.univ-lorraine.fr/public/SCD_T_1994_0404_PODOR.pdf.
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Les composés (La1-2x[U,Th]xCax)PO4 ont été synthétisés par voie hydrothermale à 780°C et 200MPa, en milieu [H3PO4]=30m, pour des fractions molaires x comprises entre 0 et 0,5. Le principal mécanisme d'insertion des radioéléments dans la monazite est : LaPO4 + x[U,Th]4+ + xCa2+ = (La1-2x[U,Th]xCax)PO4 + xLa2O3. La stabilité des composés (La1-2xUxCax)PO4 diminue lorsque la température décroît de 780 à 300°C, alors que les composés (La1-2xThxCax)PO4 restent stables dans un domaine de température compris entre 500 et 780°C, 200MPa et [H3PO4]=30m. Les composés obtenus cristallisent dans le système monoclinique et forment deux solutions solides complètes entre LaPO4-(Ca0,5U0,5)PO4 et LaPO4-(Ca0,5Th0,5)P04. Leurs paramètres cristallins diminuent linéairement lorsque le taux d'insertion des radioéléments augmente. Le composé (Ca0,5U0,5)PO4, synthétisé à 500°C, 200MPa et [H3PO4]=30m, cristallise dans le système orthorhombique, groupe d'espace Pnma et les paramètres cristallins sont a=13,926(4)Â, b=6,958(3)Â et c=6,136(2)Â. L'étude par microspectroscopie Raman des monazites synthétiques U et Th montre que la distribution des atomes dans le site cationique est aléatoire. Le déplacement des bandes de vibration est directement lié à l'augmentation du taux d'insertion des radioéléments dans la monazite. L'étude des monazites naturelles par spectroscopie Raman permet de caractériser semi-quantitativement certaines propriétés physico-chimiques de ces minéraux, telles que la zonation ou la métamictisation. A l'issue de ce travail, une nouvelle approche des mécanismes de fractionnement des terres rares par les monazites naturelles basée sur la valeur moyenne du rayon ionique des terres rares dans le site cationique est proposée. Les paramètres contrôlant et limitant l'insertion des radioéléments dans la monazite cristallisant dans un magma sont la solubilité et la diffusion des terres rares, Ca, Th et U dans les liquides silicatés.
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Phinney, Lucas C. "Thorium and Uranium M-shell X-ray Production Cross Sections for 0.4 – 4.0 MeV Protons, 0.4 - 6.0 MeV Helium Ions, 4.5 – 11.3 MeV Carbon Ions, and 4.5 – 13.5 MeV Oxygen Ions." Thesis, University of North Texas, 2011. https://digital.library.unt.edu/ark:/67531/metadc68032/.
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The M-shell x-ray production cross section for thorium and uranium have been determined for protons of energy 0.4 - 4.0 MeV, helium ions of energy 0.4 - 6.0 MeV, carbon ions of energy 4.5 - 11.3 MeV and oxygen ions of energy 4.5 - 13.5 MeV. The total cross sections and the cross sections for individual x-ray peaks in the spectrum, consisting of the following transitions Mz (M4-N2, M5-N3, M4-N3), Ma (M5-N6,7), Mb (M4-N6, M5-O3, M4- O2), and Mg (M4-O3, M5-P3, M3-N4, M3-N5), were compared to the theoretical values determined from the PWBA + OBKN and ECUSAR. The theoretical values for the carbon and oxygen ions were also modified to take into account the effects of multiple ionizations of the target atom by the heavier ions. It is shown that the results of the ECUSAR theory tend to provide better agreement with the experimental data.
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Tamain, Claire. "Etude des effets d'irradiation sur le phosphate diphosphate de thorium (béta-PDT) : conséquences sur la durabilité chimique." Paris 11, 2005. https://tel.archives-ouvertes.fr/tel-00011749.
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Le Phosphate Diphosphate de Thorium (béta-PDT) est considéré comme une matrice céramique potentielle en vue de l'immobilisation des actinides en formation géologique profonde. Il s'est avéré donc impératif d'étudier les effets de l'irradiation sur la structure de cette céramique et les conséquences sur sa durabilité chimique. Des échantillons de PDT et les solutions solides de PDTU ont été irradiés puis altérés en solution aqueuse. Selon la valeur du TEL électronique, le PDT peut s'amorphiser totalement ou partiellement. La capacité de recristallisation du matériau amorphe par recuit thermique a également été démontrée. Les tests de lixiviation menés sur ces échantillons irradiés ont montré une influence significative de la fraction amorphe sur la vitesse de dissolution normalisée qui augmente d'environ un facteur 10 entre le matériau non irradié et le matériau amorphe. Corrélativement, la fraction amorphe modifie le temps requis pour atteindre les conditions de saturation associées aux équilibres thermodynamiques. En revanche, elle ne présente aucune influence ni sur d'autres paramètres cinétiques, tels que l'énergie d'activation du processus de dissolution ou l'ordre partiel par rapport aux protons, ni sur la nature de la phase néoformée identifiée comme le Phosphate HydrogénoPhosphate de Thorium Hydraté (PHPTH). Des échantillons de PDTU ont aussi été irradiés sous rayonnement gamma et alpha pendant les tests de lixiviation afin d'étudier les effets de la radiolyse du milieu lixiviant sur la vitesse de dissolution du matériau. Les espèces radiolytiques intervenant dans le mécanisme de dissolution sont peu stables, disparaissant rapidement dès la fin de l'irradiationSince Thorium Phosphate Diphosphate (beta-TPD) can be considered as a potential host matrix for long-term storage in underground repository, it is necessary to study the irradiation effects on the structure of this ceramics and the consequences on its chemical durability. Sintered samples of beta-TPD and of associated solid solutions of beta-TUPD were irradiated under ion beams and then altered in aqueous solutions. Depending on the electronic LET value, beta-TPD can be completely or partly amorphized. Furthermore, the ability of recristallization of the amorphous material by thermal annealing was also demonstrated. Some leaching tests, realized on these irradiated samples, have shown a significant effect of the amorphous fraction on the normalized dissolution rate which was increased by a factor of 10 from the crystallised to the fully amorphized material. Correlatively, the amorphous fraction also modified the delay to reach the saturation conditions associated to the thermodynamic equilibria involved. On the other hand, it exhibited no influence neither on other kinetic parameters, such as activation energy of the dissolution process or partial order related to the proton concentration, nor on the nature of the neoformed phase formed at the saturation of the leachate and identified as Thorium Phosphate HydrogenoPhosphate Hydrate (TPHPH). Beta-TUPD samples were also irradiated by gamma and alpha rays during leaching tests to study the effects of radiolysis in the leaching medium on the normalized leaching rate. It appeared that the radiolytical species occurring in the dissolution mechanism were unstable, disappearing quickly when stopping the irradiation
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Brizi, Julie. "Cycles uranium et thorium en réacteurs à neutrons rapides refroidis au sodium : Aspects neutroniques et déchets associés." Phd thesis, Université Paris Sud - Paris XI, 2010. http://tel.archives-ouvertes.fr/tel-00545616.
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Les réacteurs `a neutrons rapides refroidis au sodium `a cycle uranium 238/plutonium 239, dont la faisabilité technique a déj`a ´et´e ´eprouv´ee, permettent de s'affranchir du prob- lème des ressources d'uranium naturel en r´ealisant la r´eg´en´eration de l'´elément fissile du combustible. En outre, une gestion des déchets visant `a réduire la production et la ra- diotoxicité des actinides mineurs produits par le réacteur peut ˆetre mise en oeuvre en transmutant les AM en coeur (transmutation homog`ene). Une autre alternative pour min- imiser les d´echets est l'utilisation d'un autre couple fertile-fissile : le thorium 232 et l'ura- nium 233 (Th/U). La comparaison des deux cycles est men´ee sur les aspects neutroniques et la sˆuret´e et sur la production de d´echets, en utilisant un Monte Carlo ´evoluant. Con- cernant la radiotoxicit´e des d´echets, mˆeme si on ne d´egage pas v´eritablement d'avantages clairs pour un cycle ou l'autre, le cycle Th/U r´eduit la radiotoxicit´e durant les p´eriodes o`u elle est la plus ´elev´ee. La transmutation homog`ene r´eduit significativement, pour les deux cycles, la radiotoxicit´e des d´echets, de facteurs variables selon la p´eriode de temps consid- ´er´e. Toutefois, elle se fait au d´etriment d'une augmentation importante de l'inventaire des AM dans le coeur. Si l'on consid`ere la fin de jeu, l'inventaire du coeur du r´eacteur devient alors un d´echet. Le gain apport´e par la transmutation, en prenant en compte `a la fois la radiotoxicit´e du coeur et des d´echets cumul´es, sera quantifi´e, et montre que la transmuta- tion n'offre pas de gain consid´erable si l'incin´eration des ´el´ements fissiles principaux (Pu ou U selon le cycle) n'est pas mise en oeuvre lors de l'arrˆet de la fili`ere.
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Avivar, Cerezo Jessica. "Automated flow systems for total and isotopic analysis of thorium and uranium in samples of environmental interest." Doctoral thesis, Universitat de les Illes Balears, 2012. http://hdl.handle.net/10803/80088.
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Tenint en compte, les característiques i la presència d’urani i tori al medi ambient, així com la evolució de les directives que estipulen els nivells màxims de materials radioactius al medi ambient, en aquesta tesis es presenten dues revisions exhaustives i quatre mètodes analítics per a la determinació total e isotòpica de tori i urani, com alternatives a les separacions radioquímiques clàssiques, que es caracteritzen per ser laborioses i de llarga duració. Aquestes metodologies varen ser automatitzades mitjançant l’ús de tècniques d’anàlisis en flux multiconmutades, les quals proporcionen un important estalvi de reactius, amb la conseqüent reducció de cost per anàlisis i de generació de residus permetent una major freqüència d’anàlisis, i una mínima manipulació de les mostres. La espectrofotometria de llarg pas òptic i la espectrometria de masses de plasma acoblat inductivament (ICP-MS) varen ser les tècniques de detecció emprades en els mètodes desenvolupats com alternatives a detectors radiomètrics.Taking into account the occurrence, the characteristics of uranium and thorium in the environment as well as the evolution of the directives which stipulate the limit values of radioactive materials in water samples, in this thesis two comprehensive reviews and four automated analytical systems for total and isotopic thorium and uranium determination are presented as alternatives to classical radiochemical separations which are laborious and time consuming. These methodologies have been automated exploiting multicommutated flow techniques, which provide minimal sample handling, low reagent consumption and waste generation and a high frequency of analysis. Long path length spectrophotometry and ICP-MS have been implemented in the developed methods as detection techniques instead of radiometric detectors in order to obtain fully automated, low cost and fast thorium and uranium analyzers. All the developed methods proposed in this thesis have been satisfactorily applied to environmental samples and have been validated with reference materials
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Gintner, Stephan Konrad. "Thorium–based fuel cycles : saving uranium in a 200 MWth pebble bed high temperature reactor / S.K. Gintner." Thesis, North-West University, 2010. http://hdl.handle.net/10394/4581.
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The predominant nuclear fuel used globally at present is uranium which is a finite resource. Thorium has been identified as an alternative nuclear fuel source that can be utilized in almost all existing uranium–based reactors and can significantly help in conserving limited uranium reserves. Furthermore, the elimination of proliferation risks associated with thorium–based fuel cycles is a key reason for re–evaluating the possible utilization of thorium in high temperature reactors. In addition to the many advantages that thorium–based fuel has over uranium–based fuel, there are vast thorium resources in the earth's crust that up until the present have not been exploited optimally.
This study focuses on determining the amount of uranium ore that can be saved using thorium as a nuclear fuel in HTR's. Four identical 200 MWth high temperature reactors are considered which make use of different fuel cycles. These fuel cycles range from the conventional uranium fuel cycle to a thorium–based fuel cycle in which no U–238 is present and have been simulated using the VSOP–A system of computer codes. This study also considers the effect that protactinium, an isotope that occurs in thorium–based fuel cycles, will have on the decay heat production in the case of a depressurized loss of coolant (DLOFC) accident.Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2011.
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Amaral, Janúbia Cristina Bragança da Silva. "Recuperação de tório e urânio a partir do licor gerado no processamento da monazita pela INB/Caldas, MG." CNEN - Centro de Desenvolvimento da Tecnologia Nuclear, Belo Horizonte, 2006. http://www.bdtd.cdtn.br//tde_busca/arquivo.php?codArquivo=37.
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Este trabalho apresenta o desenvolvimento de um processo para extração simultânea de tório e urânio, pela técnica de extração por solventes, a partir do licor sulfúrico proveniente da lixiviação do minério de monazita realizado pela Industrias Nucleares do Brasil INB, unidade de Caldas MG. Na primeira etapa do estudo, investigou-se as variáveis de processo através de ensaios descontínuos para estabelecimento das melhores condições de operação. Na segunda etapa foram realizados experimentos contínuos de extração do tório e urânio com base nos resultados dos testes descontínuos, objetivando otimizar os parâmetros do sistema. As variáveis de processo investigadas foram: tipo e concentração do agente extratante, tempo de contato entre as fases, tipo e concentração do agente reextratante, relação volumétrica das fases (aquoso/orgânico) nas etapas de extração e reextração. Os extratantes investigados foram: Primene JMT, Primene 81R, Alamine 336 e Aliquat 336. Os melhores resultados foram obtidos com a mistura Primene JM-T/Alamine 336. No processo desenvolvido o tório e o urânio são extraídos simultaneamente, pela mistura Primene JM-T e Alamine 336, diluídos em Exxsol D-100. A reextração foi realizada utilizando-se solução de ácido clorídrico (HCl) 2,0mol/L. O estudo foi conduzido à temperatura ambiente. Depois de selecionadas as melhores condições de processo, foram realizados dois experimentos contínuos contemplando as etapas de extração e reextração. No primeiro experimento utilizou-se a mistura Primene JM-T e Alamine 336 nas concentrações 0,15mol/L e 0,05mol/L, respectivamente. No segundo experimento, a concentração de Alamine 336 foi de 0,15mol/L, enquanto a concentração de Primene JM-T foi mantida a mesma. Em ambos experimentos foram utilizados quatro estágios de extração e cinco estágios de reextração. No primeiro experimento obteve-se um reextrato com 34.3g/L ThO2 e 1,49g/L U3O8. A concentração dos metais no rafinado foi de 0,1g/L ThO2 e 0,05g/L U3O8. No segundo experimento as concentrações dos óxidos de tório e urânio no reextrato foram 29,3g/L e 0,94g/L, respectivamente. No rafinado estes teores foram menores que 0,001g/L, obtidos a partir de uma alimentação com 3,6g/L ThO2 e 0,17g/L U3O8. A recuperação do tório foi superior a 99,9% enquanto a recuperação do urânio foi de 99,4%.This work describes the study of thorium and uranium recovery from sulfuric liquor generated in chemical monazite treatment by solvent extraction technique. The sulfuric liquor was produced by Industries Nuclear of Brazil INB, Caldas Minas Gerais State. The study was carried out in two steps: in the first the process variable were investigated through discontinuous experiments; in the second, the parameters were optimized by continuous solvent extraction experiments. The influence of the following process variables was investigated: type and concentration of extracting agents, contact time between phases and aqueous/organic volumetric ratio. Extractants used in this study included: Primene JM-T, Primene 81-R, Alamine 336 and Aliquat 336. Thorium and uranium were simultaneously extracted by a mixture of Primene JM-T and Alamine 336, into Exxsol D-100. The stripping was carried out by hydrochloric acid (HCl) 2.0mol/L. The study was carried out at room temperature. After selected the best process conditions, two continuous experiments of extraction and stripping were carried out. In the first experiment a mixture of 0.15mol/L Primene JM-T and 0.05mol/L Alamine 336 were used. The second experiment was carried out using 0.15mol/L Primene JM-T and 0.15mol/L Alamine 336. Four extraction stages and five stripping stages were used in both experiments. The first experiment showed a ThO2 and U3O8 content in loaded strip solution of 34.3g/L and 1.49g/L respectively and 0.10g/L ThO2 and 0.05g/L U3O8 in the raffinate. In the second experiment a loaded strip solution with 29.3g/L ThO2 and 0.94g/L U3O8 was obtained. In this experiment, the metals content in raffinate was less than 0.001g/L, indicating a thorium recovery over 99.9% and uranium recovery of 99.4%.
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Argo, Lisa. "Experimental determination of the dry oxidation behavior of a compositional range of uranium-thorium mixed-oxide pellet fragments." [Gainesville, Fla.] : University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0001521.
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Tolich, Kazumi. "Measurement of neutrino oscillation parameters and investigation of uranium and thorium abundances in the earth using anti-neutrinos /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Glendinning, John Edward. "Factors influencing the mobility of uranium, thorium and rare earth elements at the Steenkampskraal monazite, North Western Cape." Master's thesis, University of Cape Town, 1997. http://hdl.handle.net/11427/21332.
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It is well known that the release of long-lived radionuclides to the water path is probably the most relevant radiological risk originating from an underground repository. Transuranic elements (ie. all elements with an atomic number greater than 92 (U)) do not have any non-radioactive isotopes and are very rare in natural materials. The long term geochemical behaviour of these elements must thus be derived from chemical analogues such as the rare earth elements (REE), Th and U. Steenkampskraal monazite mine, situated 350 km north of Cape Town, has been found to be an excellent locality for the study of these elements, due to the high concentration of these elements in the ore as well as the ideal geology, which consists of low permeability rocks with groundwater flow governed by fractures. The ore body consists of a monazite [(REE, Th, U)P04], apatite [Ca₃P0₄)₂], chalcopyrite [CuFeS] and magnetite [FeP₄] veindeposit. Water was sampled from six boreholes in the vicinity of the mine and five wi.ndpumps on the surrounding farm Nabeep and Brandewynskraal. Surface water samples were taken from the slimes dam, an ephemeral stream on the western side of the mine, as well as from the surface of a road shortly after rain, below the tailings. Four water samples were taken from within the underground mine workings (Mainshaft, Main shaft extension, Sump on level 3 and Inclined shaft). Colloids were sampled from three of the boreholes and a precipitate was taken from the surface of the main shaft water. Soils were sampled along two transects away from the mine on the eastern and western side of the ore body. Due to the topography of the area, surface contamination could only occur on these two sides. Stable isotopes of oxygen (8 180) and hydrogen ((8 180) indicated the presence of two distinct groups of waters within the vicinity of the mine. One group is composed of unevaporated waters and includes all borehole sand the water sampled in the inclined shaft. The water moving through the inclined shaft is in contact with the ground water. A second group of highly evaporated waters was present in the slin1es dam samples as well as the underground water samples not directly in contact with groundwater. Groundwater contamination by REE-bearing phosphate minerals has resulted in measurable concentrations of U, Th and REE in all mine waters and boreholes in the near vicinity of the mine. The chondritenormalized REE patterns of the water samples are sin1ilar to those displayed by monazite, with a distinctive Eu depletion and an obvious enrichment in LREE with respect to HREE. Monazite-normalized REE patterns for the selected borehole waters show a marked fractionation between LREE and HREE, with the HREE strongly enriched in the aqueous phase. Heavy REE have been shown to have a greater tendency for complexatioi1 and a greater affinity for mineral surfaces. In the present study, the three boreholes in which colloids were found had high concentrations of U, Th and REE. It is likely that colloidal transport of these elements is the dominant mechanism of transport.
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Milicic, Anita. "Étude des temps de vie des niveaux fluorescents de l'uranium tétravalent dans la phase incommensurable du tétrabromure et du tétrachlorure de thorium." Paris 11, 1989. http://www.theses.fr/1989PA112028.
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Les temps de vie des niveaux fluorescents de l'ion uranium tétravalent introduit comme dopant dans la phase incommensurable, basse température, des tétrahalogénures de thorium ont été mesurés en fonction des différents paramètres importants en luminescence: symétrie du site, température et concentration. La phase incommensurable des tétrabromure et tétrachlorure de thorium, est caractérisée par une distribution continue des symétries du site due à un déplacement continu et de faible amplitude des ions halogénures entourant l'ion thorium (uranium). A basse température, 4. 2 K, la variation des temps de vie en fonction de la classe de site excitée est à la fois gouvernée par les probabilités de désexcitation radiative et les transferts d'énergie entre ions uranium situés dans les différents sites. Pour des températures plus élevées, un modèle fondé sur l'établissement d'un équilibre de Boltzmann entre niveaux proches en énergie rend compte parfaitement de la variation des temps de vie mesurés pour une classe de site déterminée. Quant aux variations en fonction de la concentration, dans le cas de U4+ : ThBr4, il y a compétition entre le phénomène de transfert d'énergie et du peuplement thermique. L'un ou l'autre de ces deux processus prédomine selon la nature du niveau étudié. L'ensemble de ces résultats a permis de clarifier le problème de la relaxation en énergie d'un ion actinide optiquement actif (U4+) dans un type de structure particulière de la matrice d'accueil : structure modulée incommensurableThe lifetimes of radiative levels of tetravalent uranium in the incommensurate phase of thorium tetrahalides have been measured as a function of different parameters: site symmetry, temperature and concentration. The incommensurate phase of thorium tetrabromide and tetrachloride is characterized by a continuous distribution of site symmetries induced by a continuous and weak displacement of the halides around the thorium (uranium) ions. At low temperature, 4. 2 K, the lifetime variation as a function of excited classes of symmetry is governed by the radiative process probability as well as the energy transfer between uranium ions in different sites. At higher temperature, a model based on a Boltzmann equilibrium between closed energy levels is able to reproduce the experimental lifetime variation as a function of the temperature, for a given class of symmetry. For the variation of lifetime as a function of uranium ions concentrations, at high dilution and in the case of U4+ : ThBr4, there is a competition between the energy transfer and thermal population of excited states
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Vlachoudis, Vassilis. "Taux de capture et de fission du ²³²Th, ²³⁸U, ²³⁷Np et ²³⁹Pu par des neutrons de spallation dans un grand massif de plomb." Bordeaux 1, 2000. http://www.theses.fr/2000BOR10505.
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Les études sont centrées sur la recherche de la possibilité d'incinération des déchets nucléaires par l'association d'un accélérateur de particules avec un milieu multiplicateur de neutrons, le projet « Amplificateur d'énergie » de C. RUBBIA. Elles consistent en la détermination expérimentale de certains concepts fondamentaux du projet, qui sont les taux de capture et de fission de certains éléments (²³²Th, ²³⁸U, ²³⁷Np et ²³⁹Pu) soumis à un flux de neutrons rapides de spallation. Ces neutrons sont produits par l'interaction de protons de haute énergie (de l'ordre du GeV) fournis par l'accélérateur PS du CERN avec un grand massif de plomb. Les techniques de mesure sont basées sur l'activation et la spectroscopie gamma des noyaux formés pour la capture, et par détection des traces pour la fission. Le développement en parallèle d'un code Monte Carlo permettra d'une part de mieux comprendre les processus mis en jeu et d'autre part de valider le code, par comparaison avec les mesures, pour la conception et la démonstration d'un système d'incinérationThe study is centered on the research of the incineration possibility of nuclear waste, by the association of a particle accelerator with a multiplying medium of neutrons, in the project “Energy Amplifier” of C. RUBBIA. It consists of the experimental determination of the rates of capture and fission of certain elements (²³²Th, ²³⁸U, ²³⁷Np and ²³⁹Pu) subjected to a fluence of fast spallation neutrons. These neutrons are produced by the interaction of high kinetic energy protons (several GeV) provided by the CERN-PS accelerator, on a large lead solid volume. The measurement techniques used in this work, are based on the activation of elements in the lead volume and the subsequent gamma spectroscopy of the activated elements, and also by the detection of fission fragment traces. The development, of a Monte Carlo code makes it possible, on one hand, to better understand the relevant processes, and on the other hand, to validate the code, by comparison with measurements, for the design and the construction of an incineration system
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Beckett, Kirsty A. "Multispectral analysis of high spatial resolution 256-channel radiometrics for soil and regolith mapping." Curtin University of Technology, Dept. of Exploration Geophysics, 2007. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=17703.
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Over the past decade studies into the application of radiometrics for soil and regolith mapping have met with mixed response. While the use of radiometric data for regolith mapping has been generally well received, radiometric methods have not commonly been adopted to assist and improve soil mapping. This thesis contributes to the development of radiometric techniques as soil and regolith mapping tools by examining soil characteristics and radiometric response using non-standard radiometric methods. This is accomplished through the development of new data processing methodologies, which extracts additional information from standard radiometric data that is unattainable using standard processing methods, and development of a new interpretation approach to soil and regolith mapping employing the multispectral processed radiometric data. The new multispectral processing methodology resolves seven gamma ray peaks from standard 256-channel NaI radiometric data to produce new radiometric uranium ternary, thorium ternary and uranium ratio imagery. Changes in the gamma ray relationships, identified through the new imagery, identify changes in soil and/or environmental conditions that are absent or difficult to identify in the standard radiometric imagery. With the isolation of non-standard thorium channels 228 [superscript] Ac (900 keV) and 228 [superscript] Ac (1600 keV), case studies in this thesis demonstrate how the difference of 1.9 years (half-life) between thorium 228 [superscript] Ac and 232 [superscript] Th decay daughter products can be mapped through the interpretation of thorium energy using ternary imagery [red: 208 [superscript] Tl (1764 keV), green: 228 [superscript] Ac (900 keV), blue: 228 [superscript] Ac (1600 keV)]. Energy peak differences may be be linked to local variations in soil chemistry, soil movement, and water movement.Additionally, through the isolation of non-standard uranium channels 214 [superscript] Bi (1120 keV) and 214 [superscript] Bi (1253 keV), preferential attenuation of lower energy gamma-rays from 214 [superscript] Bi decay events are exploited to map variations in soil density and/or porosity. These variations are illustrated through the interpretation of uranium energy using ternary imagery [red: 214 [superscript] Bi (1764 keV), green: 214 [superscript] Bi (1120 keV), blue: 214 [superscript] Bi (1253 keV)] and uranium peak energy ratio [214 [superscript] Bi 1120 keV / 214 [superscript] Bi 1764 keV] pseudo colour imagery. Case studies examined in this thesis explore the characteristics of 256-channel radiometric spectrum from different resolution datasets from different Western Australian soil types, provide recommendations for acquiring radiometric data for soil mapping in different agricultural environments, demonstrate how high resolution 256-channel radiometric data can be used to model soil properties in three-dimensions, and illustrate how three-dimension soil models can be used to separate surface waterlogging influences from rising groundwater induced waterlogging.
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Brunel, Benoît. "Détermination des interactions microscopiques entre les actinides and les substances humiques." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112024/document.
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Détermination des interactions microscopiques entre les actinides et les substances humiques présentes dans l’environnementUne quantité pondérable de plutonium a été introduite dans l’environnement lors d’essais nucléaires ou d’accidents civils. Les zones contaminées, nécessitant une surveillance particulière, sont devenues des lieux d’études très intéressants pour comprendre le comportement du plutonium dans l’environnement. Jusqu’à peu de temps encore, il était admis que le plutonium introduit dans les sols était relativement immobile en raison de sa propension à se sorber fortement sur les roches et de sa faible solubilité dans l’eau. Cependant, des études menées sur des zones contaminées montrent que les substances humiques, omniprésentes dans l’environnement, peuvent influencer la spéciation d’un métal et donc sa migration. C’est pourquoi, il est indispensable de connaître l’influence des substances humiques sur la spéciation du plutonium pour comprendre le transport de celui-ci dans un milieu naturel. Toutefois, en raison de la nature complexe et hétérogène de la matière organique naturelle, il est difficile de décrire de façon microscopique les interactions entre substances humiques et le plutonium. En effet, les substances humiques forment un mélange hétérogène de supra-molécules polydispersées produites par des réactions chimiques ou biochimiques durant la transformation naturelle de matière organique animale, végétale ou microbienne.Le but de ces travaux est d’évaluer à l’échelle de moléculaire les phénomènes de complexation des actinides par la matière organique naturelle. Ces recherches s’organisent autour de deux axes : la caractérisation de dizaines de milliers de molécules dans chaque échantillon de substances humiques naturelles et la détermination des molécules responsables de la vectorisation des actinides dans l’environnement.La mise au point d'une méthodologie a permis de mettre en évidence, pour la première fois, quelques molécules responsables de la complexation des actinides dans des échantillons de matière organique naturelle. Les résultats obtenus montrent l’influence de l’origine du prélèvement de la matière organique sur le type de molécules complexantes. Cette étude montre, également, que la vectorisation des actinides par la matière organique résulte d’une interaction avec un ensemble de molécules présentant des affinités plus ou moins forte pour le métal. Ces résultats semblent être en accord avec les modélisations macroscopiques NICA-DONNAN (approches continue) utilisés actuellementLarge amount of plutonium has been introduced into the environment as a result of nuclear weapons testing, and nuclear power-plant accidents. Contaminated areas, which need a particular survey, have become a very interesting place to study and understand the plutonium behaviour in the environment. Until few years ago, it was admitted that plutonium introduced into subsurface environment is relatively immobile, owing to its low solubility in ground water and strong sorption onto rocks. However, studies of contaminated areas show that humic substances, which are ubiquitous in environment, can alter the speciation of metal ion, e.g. plutonium, and thus their migration. These humic substances are major components of the natural organic matter in soil and water as well as in geological organic deposits such as lake sediments, peats and brown coals. They are complex heterogeneous mixtures of polydispersed supra-molecules formed by biochemical and chemical reactions during the decay and transformation of plant and microbial remains. The knowledge of the impact of humic substances on the plutonium migration is required to assess their transport in natural systems. However, due to the complex and heterogeneous nature of humic substances, there are a lot of difficulties in the description of microscopic interactions. The aim of this PhD thesis is to evaluate as precisely as possible interactions between actinides and humic substances. This work is divided in two parts: on the one hand humic substances will be separated to identify each component, on the other hand the speciation of actinides with characterized humic substances will be studied. In the first part of this study, new methods are developed to study the speciation of actinides with humic substances using two kinds of mass spectrometers: an ICP-MS and a high resolution mass spectrometer using various ionization devices (ESI, APCI, DART, APPI) in order to determine all active molecules for the complexation.In the second part, a new way of humic substances separation had been developed using an electrophoresis capillary apparatus. This efficient separation technique allows to simplify the characterisation of the complex heterogeneous mixtures without changing speciation of the chemical system.This study will lead to point out some molecules responsible for complexation of actinides by the humic substances