O Oceano Austral é o maior repositório dos oceanos, com concentrações elevadas de nutrientes e baixas de clorofila. A região tem papel fundamental para regular a transferência líquida de dióxido de carbono entre o oceano e a atmosfera, em parte devido à assimilação anual de CO2 pelo fitoplâncton, que resulta na exportação do carbono orgânico particulado (POC) para o oceano profundo. O elemento tório apresenta múltiplos isótopos que tem emergido como traçadores poderosos dos processos associados à transferência de material particulado nos oceanos. De todos os isótopos de Th, o 234Th (meia-vida de 24,1 d) tem sido foco de destaque e aplicação nos últimos anos. A produção do 234Th a partir do 238U, além do comportamento conservativo solúvel do 238U na água do mar, tornam fácil a caracterização das fontes de 234Th neste cenário. Além disso, a meiavida do 234Th é suficientemente curta para torná-lo sensível a mudanças a curto prazo (sazonais) que ocorrem na coluna dágua superficial dos oceanos, ou nas colunas dágua e de sedimentos nas regiões costeiras. Devido ao seu comportamento partículo-reativo, o 234Th é removido da água de duas formas, por decaimento ou pelo fluxo de material particulado. Desta forma, um modelo de balanço uni-dimensional no estado estacionário pode ser utilizado para estimar seu fluxo. Os isótopos naturais de Ra também tem sido amplamente empregados em estudos marinhos para traçar massas dágua e quantificar processos de mistura. Este trabalho apresenta os resultados de um projeto de pesquisa multidisciplinar que investigou a distribuição dos fluxos de carbono orgânico no Estreito de Bransfield com a finalidade de avaliar sua influência na remoção de CO2 da atmosfera local. As distribuições de macro-nutrientes, micro-nutrientes e clorofila-a foram utilizadas para examinar possíveis fontes e vias de transferência. Os isótopos de Ra foram aplicados como traçadores de massas dágua, enquanto o 234Th foi utilizado como traçador do fluxo particulado no oceano, uma vez que o afundamento deste material é o principal mecanismo de seqüestro de carbono no Oceano Austral. As amostras foram coletadas no período de 9 a 14 de Dezembro de 2007, a bordo do Navio de Apoio Oceanográfico Ary Rongel, da Marinha do Brasil. / The Southern Ocean is the largest of several high-nutrient, low-chlorophyll (HNLC) regions in the worlds oceans. This region plays a major role in regulating the global net transfer of carbon dioxide between the ocean and the atmosphere, in part because the annual photosynthetic uptake of CO2 by phytoplankton and resulting export of particulate organic carbon (POC) to the deep ocean. The element thorium has multiple radioisotopes that have emerged collectively as a powerful set of tracers for particle associated processes in the oceans. Of all the Th isotopes, 234Th (half-life 24.1 d) has been the focus of increasing attention and application in the past years. The production of 234Th from 238U, coupled with the conservative behavior of 238U in seawater, makes the source of 234Th easy to characterize. Moreover, the half-life of 234Th is sufficiently short to make it sensitive to the short-term (e.g. seasonal) changes that occur in the upper water column of the open ocean or in sediments or water column in coastal areas. Because of its very particle reactive behavior, 234Th is removed from a parcel of water in only two ways, through decay and through particle flux. Therefore, a steady-state 1D activity balance can be used to calculate its flux. Natural Ra isotopes have been also widely used in marine studies to trace water masses and to quantify mixing processes. This work presents results of a collaborative research on organic carbon fluxes distribution in the Bransfield Strait in order to evaluate its influence in the CO2 drawdown. Macro-nutrients, micro-nutrients and chlorophyll-a distributions were used to examine the pathway sources. Natural radium isotopes were applied as tracers to study the movement of shelf water, while 234Th was used as a tracer of particle flux in the upper ocean, since POC export via sinking particles is the primary mechanism of carbon sequestration in the Southern Ocean. Sea water samples for total 234Th and natural Ra isotopes were collected from 9 to 14 December 2007 on the RV Ary Rongel (Brazilian Navy). Analyses of total 234Th activities were performed by gross beta counting using a gas-flow low background proportional counter. The longlived Ra isotopes were determined by low-background high efficiency gamma spectrometry.

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.

La simulation neutronique des réacteurs nucléaires suppose la connaissance de l'interaction neutron noyau (sections efficaces, nombres et spectres des neutrons de fission) pour les quelques dizaines de noyaux présents dans le réacteur sur une douzaine d'ordres de grandeur d'énergie des neutrons. Le développement d'un nucléaire durable impose de nouvelles contraintes aux réacteurs du futur : l'optimisation de l'utilisation de la matière première nécessite la régénération des noyaux fissiles et la gestion des déchets suppose leur transmutation. Les réacteurs proposés permettant d'atteindre ces objectifs (génération IV et ADS) sont chargés de combustibles nouveaux (thorium et actinides lourds) et fonctionnent avec des spectres neutroniques pour lesquels les données nucléaires ne bénéficient pas des 50 années de l'expérience industrielle. Après leur validation sur un réacteur expérimental dans le cadre d'un exercice international, nous appliquons des outils classiques de physique de réacteurs en combinaison avec les incertitudes sur les données de base disponibles pour calculer l'incertitude sur la criticité et le coefficient de température d'un réacteur à sel fondu au thorium. De plus, une réflexion sur les taux de réactions importants pour le cycle a l'équilibre donne une estimation de l'efficacité des différentes stratégies de retraitement en ligne du combustible et les contributions de ces taux de réactions à l'incertitude sur la régénération et donc l'impact de ces incertitudes sur le dimensionnement de l'usine de retraitement. Nous pouvons alors lister les données à améliorer prioritairement pour améliorer la précision des calculs.

Dans le cadre du programme GenIV, les propriétés physico-chimiques d'intérêts des combustibles envisagés, telles que la durabilité chimique, doivent être évaluées. Ainsi, une étude préliminaire a été entreprise sur les composés modèles MIV1-xLnIIIxO2 (M=Ce,Th) preparés à partir de précurseurs oxalate. La structure fluorine caractéristique des oxydes CeO2 et ThO2 demeure stable jusqu'à x ≈ 0,4, la substitution d'ions MIV par LnIII étant accompagnée par la formation de lacunes en oxygène. Pour des valeurs de x plus importantes, une surstructure cubique est formée suite à l'ordonnancement des lacunes en oxygène. Par la suite, les tests de dissolution réalisés en milieu acide ont montré que la vitesse de dissolution normalisée dépend très fortement de la fraction en élément lanthanide incorporé. A l'opposé, la nature des éléments MIV et LnIII constitutifs du solide ne semble que peu modifier la vitesse de dissolution normalisée. Par ailleurs, les effets de paramètres plus " conventionnels " tels que la température ou la concentration en acide ont également été évalués, et ont permis de conclure à une dissolution contrôlée par des réactions de surface. Parallèlement à cette étude, l'évolution microstructurale de composés pulvérulents et frittés a montré d'importantes modifications de la surface réactive durant la dissolution. A partir des observations par MEBE, les joints de grains et les défauts cristallins sont apparus comme des zones préférentielles de dissolution. Par ailleurs, la formation de phases gélatineuses à la surface des solides, agissant comme une barrière de diffusion et ralentissant ainsi la dissolution du matériau a été démontrée.

The advanced fuels investigated in this thesis comprise fuels non− conventional in their design/form (TRISO), their composition (high content of plutonium and minor actinides) or their use in a reactor type, in which they have not been used before (e.g. nitride fuel in BWR). These fuels come with a promise of improved characteristics such as safe, high temperature operation, spent fuel transmutation or fuel cycle extension, for which reasons their potentialis worth assessment and investigation. Their possible use also brings about various challenges, out of which some were addressed in this thesis. TRISO particle fuels with their superior retention abilities enable safe, high−temperature operation. Their combination with molten salt in the Advanced High Temperature Reactor (AHTR) concept moreover promises high operating temperature at low pressure, but it requires a careful selection of the cooling salt and the TRISO dimensions to achieve adequate safety characteristic, incl. a negative feedback to voiding. We show that an AHTR cooled with FLiBe may safely operate with both Pu oxide and enriched U oxide fuels. Pu and Minor Actinides (MA) bearing fuels may be used in BWR for transmutation through multirecycling; however, the allowable amounts of Pu and MA are limited due to the degraded feedback to voiding or low reactivity.We showed that the main positive contribution to the void effect in the fuelswith Pu and MA content of around 11 to 15% consist of the decreased thermalcapture probability in Pu-240, Pu-239 and Am-241 and increased fast and resonance fission probability of U-238, Pu239 and Pu-240. The total void worthmoreover increases during multirecycling, limiting the allowable amount ofMA to 2.45% in uranium−based fuels. An alternative, thorium−based fuel allows for 3.45% MA without entering the positive voiding regime at any point of the multirecycling. The increased alpha−heating associated with the use of transmutation fuels, is at level 24−31 W/kgFUEL in the uranium based fuels and 32−37 W/kgFUEL in the thorium−based configurations. The maximum value of the neutron emission, reached in the last cycle, is 1.7·106 n/s/g and 2·106 n/s/g for uranium and for thorium−based fuels, respectively. Replacing the standard UO2 fuel with higher−uranium density UN orUNZrO2 fuels in BWR shows potential for an increase of the in-core fuelresidence time by about 1.4 year. This implies 1.4% higher availability of the plant. With the nitride fuels, the total void worth increases and the efficiency of the control rods and burnable poison deteriorates, but no major neutronics issue has been identified. The use of nitride fuels in the BWR environment is conditioned by their stability in hot steam. Possible methods for stabilizing nitride fuels in water and steam at 300◦ C were suggested in a recent patentapplication. / <p>QC 20121004</p>

The ACME collaboration has completed a measurement setting a new upper limit on the size of the electron's permanent electric dipole moment (EDM). The existence of the EDM is well motivated by theories extending the standard model of particle physics, with predicted sizes very close to the current experimental limit. The new limit was set by measuring spin precession within the metastable H state of the polar molecule thorium monoxide (ThO). A particular focus here is on the automated data acquisition system developed to search for a precession phase odd under internal and external reversal of the electric field. Automated switching of many different experimental controls allowed a rapid diagnosis of major systematics, including the dominant systematic caused by non-reversing electric fields and laser polarization gradients. Polarimetry measurements made it possible to quantify and minimize the polarization gradients in our state preparation and probe lasers. Three separate measurements were used to determine the electric field that did not reverse when we tried to switch the field direction. The new bound of |de|< 8.7 &times; 10^-29 e cm is over an order of magnitude smaller than previous limits, and strongly limits T-violating physics at TeV energy scales. / Physics

Les ligands β-diiminates sont des plateformes intéressantes utilisées en chimie de coordination en particulier pour la catalyse homogène, leurs paramètres électroniques et géométriques facilement ajustables les rendant particulièrement attractifs. Toutefois, ces modifications sont limitées à l'introduction de bases de Lewis neutres (éthers, amines tertiaires) sur les substituants portés par les atomes d'azote du squelette β-diiminate. L'objectif principal de ce travail de thèse porte sur le dépassement de telles limitations avec la synthèse de nouveaux ligands β-diiminates fonctionnalisés par un ou deux groupements phénolates anioniques et l'étude de leur chimie de coordination avec des ions lanthanides et actinides. Un intérêt particulier a été apporté à l'élucidation du mécanisme de formation de ces ligands, qui a mis en lumière la sensibilité des fonctions imines vis-à-vis des fonctions phénols, à l'origine des limitations décrites ci-dessus. Deux nouveaux ligands N-aryloxy-β-diiminates ont été synthétisés à l'échelle de plusieurs grammes avec de très bons rendements. Ces ligands diffèrent par leur encombrement stérique, qui influe sur leur coordination aux ions lanthanides et actinides. La réactivité de trois des complexes N-aryloxy-β-diiminate a été explorée. Un complexe du Ce(III) possède des propriétés de réduction intéressantes, sa sphère de coordination permettant un abaissement significatif du potentiel d'oxydation du couple Ce(III)/Ce(IV). La présence d'une lacune de coordination dans un complexe du Th(IV) a été mise àprofit pour stabiliser différents adduits de bases de Lewis. Deux types de réarrangement du complexe de thorium ont été mis à jour, qui sont contrôlés par la minimisation de répulsions inter-ligands. La réactivité rédox d'un complexe N-aryloxy-β-diiminate de l'U(IV) a été exploitée pour préparer un exemple rare de complexe monooxo terminal d'uranium. Cette espèce possède une chimie rédox riche et sa réduction a permis la synthèse des analogues de l'U(V) et de l'U(IV), formant ainsi la première série de complexes monooxo terminaux d'uranium stables à trois degrés d'oxydation successifs. Cette série représente une opportunité unique d'étudier l'influence des électrons f sur le phénomène d'influence trans inverse (ITI) observés dans les complexes oxo de l'uranium. Des calculs DFT préliminaires ont été réalisés pour rationaliser les comportements expérimentaux.

The geological province of the Mount Painter in the North Flinders Ranges (South Australia) is well-known for its uranium mineralisation, and uraniferous granites. The presence in the nearby Cenozoic sediments of the Lake Frome basin of uranium mineralisations (Beverley deposit) and the recent discovery of the Four Mile deposit has triggered the interest of explorers. Based on extensive laser-ablation inductively-coupled-plasma-mass-spectrometry (LA-ICPMS) U-Pb geochronological data and mineralogy of U-Th-bearing minerals, rock geochemistry and petrography, we present a global study on the mobility of U, Th and REE in the Mount Painter Domain, including a detailed reconstitution of the Beverley deposit genesis. Seven significant stages of U-Th-REE mobility are recognised: 1. The possible presence U-enriched ~1600 Ma lower crust under the MPD 2. Intrusion of two A-type Mesoproterozoic granites suites (~1575, and ~1560 Ma respectively) with high HFSE contents and crustal origin; the porphyritic biotite K-rich highly-enriched Yerila granite belongs to the youngest suite and hosts magmatic allanite-(Ce), potassic-hastingsite, ilmenite, fergusonite-(Y), chevkinite, molybdenite, zircon, uranothorite, uraninite and titanite and fluorite 3. Late-magmatic or post-magmatic metasomatism in the same granites; evidenced by F-rich annite, zircon, Y-bearing Al-F-titanite (< 6 kbar, >400°C), Y-rich fluorapatite, synchysite-(Ce) and fluorite. Early ilmenite, molybdenite, allanite-(Ce) and oligoclase reacted with an alkaline oxidising F-rich melt or fluid. The latemagmatic to post-magmatic metasomatism is also recorded at the intrusion contact in regional rocks, forming allanite-, magnetite-, uranothorite-, zircon- (1501 ± 6 Ma), and uraninite-bearing calcsilicate skarns. The spreading of zircon ages in the Yerila granite (~1565 to ~1521) relates to the mixing of magmatic and metasomatic crystals. 4. the MPD was subject to the Delamerian orogeny and related metamorphism (amphibolite facies); most Mesoproterozoic granitic assemblages present signs of recrystallisation or stress; recrystallisation of monazite-(Ce) and xenotime-(Y) during Paleozoic (Cambrian) (490-495 Ma). U-Th-rich minerals also bear Delamerian ages (polycrase-(Y), euxenite-(Y), davidite-(La) and uraninite). 5. Anatexis of local basement during Ordovician and generation of peraluminous granite (British Empire granite) with low Th/U. The granite is enriched in U and Y. We provide the first robust ages on it: 456 ± 9 and 459 ± 9 Ma on zircon, 453.3 ± 4.6 on xenotime-(Y). 6. Very active hydrothermal/pegmatitic uranium remobilisation along active faults; brannerite-quartz veins formation (367 ± 13 Ma), further signs of remobilisation or hydrothermal event during Permian (284 ± 25 Ma in thorite) and around the Mt Gee (~290 Ma radiogenic gain in davidite) which agrees with the previous data (paleomagnetic ages of 250-300 Ma). 7. Cenozoic supergene uranium remobilisation in MPD and migration of U-rich oxidised groundwaters into the Lake Frome. The uranium is precipitated in the sandy formation of the lake and in the top layer of the underlying organic-matter-rich clays and silts. The micro-environment of reduction efficiently trap U but also REE, fingerprinting the REE-rich MPD granite source. Coffinite and carnotite give concordant Pliocene ages (6.7 to 3.4 Ma). Provenance studies on the sands hosting the Beverley mineralisations suggest a reworking of Early Cretaceous glacial or glacio-lacustrine sediments originally sourced in Eastern Australia (Lachlan Fold Belt). The youngest recorded zircon (130 Ma) doesn’t constrain the sediment age but refines the provenance region (New England Orogen). / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1370301 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2009

The geological province of the Mount Painter in the North Flinders Ranges (South Australia) is well-known for its uranium mineralisation, and uraniferous granites. The presence in the nearby Cenozoic sediments of the Lake Frome basin of uranium mineralisations (Beverley deposit) and the recent discovery of the Four Mile deposit has triggered the interest of explorers. Based on extensive laser-ablation inductively-coupled-plasma-mass-spectrometry (LA-ICPMS) U-Pb geochronological data and mineralogy of U-Th-bearing minerals, rock geochemistry and petrography, we present a global study on the mobility of U, Th and REE in the Mount Painter Domain, including a detailed reconstitution of the Beverley deposit genesis. Seven significant stages of U-Th-REE mobility are recognised: 1. The possible presence U-enriched ~1600 Ma lower crust under the MPD 2. Intrusion of two A-type Mesoproterozoic granites suites (~1575, and ~1560 Ma respectively) with high HFSE contents and crustal origin; the porphyritic biotite K-rich highly-enriched Yerila granite belongs to the youngest suite and hosts magmatic allanite-(Ce), potassic-hastingsite, ilmenite, fergusonite-(Y), chevkinite, molybdenite, zircon, uranothorite, uraninite and titanite and fluorite 3. Late-magmatic or post-magmatic metasomatism in the same granites; evidenced by F-rich annite, zircon, Y-bearing Al-F-titanite (< 6 kbar, >400°C), Y-rich fluorapatite, synchysite-(Ce) and fluorite. Early ilmenite, molybdenite, allanite-(Ce) and oligoclase reacted with an alkaline oxidising F-rich melt or fluid. The latemagmatic to post-magmatic metasomatism is also recorded at the intrusion contact in regional rocks, forming allanite-, magnetite-, uranothorite-, zircon- (1501 ± 6 Ma), and uraninite-bearing calcsilicate skarns. The spreading of zircon ages in the Yerila granite (~1565 to ~1521) relates to the mixing of magmatic and metasomatic crystals. 4. the MPD was subject to the Delamerian orogeny and related metamorphism (amphibolite facies); most Mesoproterozoic granitic assemblages present signs of recrystallisation or stress; recrystallisation of monazite-(Ce) and xenotime-(Y) during Paleozoic (Cambrian) (490-495 Ma). U-Th-rich minerals also bear Delamerian ages (polycrase-(Y), euxenite-(Y), davidite-(La) and uraninite). 5. Anatexis of local basement during Ordovician and generation of peraluminous granite (British Empire granite) with low Th/U. The granite is enriched in U and Y. We provide the first robust ages on it: 456 ± 9 and 459 ± 9 Ma on zircon, 453.3 ± 4.6 on xenotime-(Y). 6. Very active hydrothermal/pegmatitic uranium remobilisation along active faults; brannerite-quartz veins formation (367 ± 13 Ma), further signs of remobilisation or hydrothermal event during Permian (284 ± 25 Ma in thorite) and around the Mt Gee (~290 Ma radiogenic gain in davidite) which agrees with the previous data (paleomagnetic ages of 250-300 Ma). 7. Cenozoic supergene uranium remobilisation in MPD and migration of U-rich oxidised groundwaters into the Lake Frome. The uranium is precipitated in the sandy formation of the lake and in the top layer of the underlying organic-matter-rich clays and silts. The micro-environment of reduction efficiently trap U but also REE, fingerprinting the REE-rich MPD granite source. Coffinite and carnotite give concordant Pliocene ages (6.7 to 3.4 Ma). Provenance studies on the sands hosting the Beverley mineralisations suggest a reworking of Early Cretaceous glacial or glacio-lacustrine sediments originally sourced in Eastern Australia (Lachlan Fold Belt). The youngest recorded zircon (130 Ma) doesn’t constrain the sediment age but refines the provenance region (New England Orogen). / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1370301 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2009

Thesis (Ph. D.)--Auburn University, 2005. / Abstract. Vita. Includes bibliographical references.