Uranium (U) contamination can be introduced to the environment as a result of mining and manufacturing activities related to nuclear power, detonation of U-containing munitions (DoD), or nuclear weapons production/processing (DOE facilities). In oxidizing environments such as surface soils, U predominantly exists as U(VI), which is highly water soluble and very mobile in soils. U(VI) compounds typically contain the UO22+ group (uranyl compounds). The uniquely structured and long-lived green luminescence (fluorescence) of the uranyl ion (under UV radiation) has been studied and remained a strong topic of interest for two centuries. The presented research is distinct in its objective of improving capabilities for remotely sensing U contamination by understanding what environmental conditions are ideal for detection and need to be taken into consideration. Specific focuses include: 1) the accumulation and fluorescence enhancement of uranyl compounds at soil surfaces using distributed silica gel, and 2) environmental factors capable of influencing the luminescence response, directly or indirectly. In a complex environmental system, matrix effects co-exist from key soil parameters including moisture content (affected by evaporation, temperature and humidity), soil texture, pH, CEC, organic matter and iron content. Chapter 1 is a review of pertinent background information and provides justification for the selected key environmental parameters. Chapter 2 presents empirical investigations related to the fluorescence detection and characterization of uranyl compounds in soil and aqueous samples. An integrative experimental design was employed, testing different soils, generating steady-state fluorescence spectra, and building a comprehensive dataset which was then utilized to simultaneously test three hypotheses: The fluorescence detection of uranyl compounds is dependent upon 1) the key soil parameters, 2) the concentration of U contamination, and 3) time of analysis, specifically following the application of silica gel enhancing material. A variety of statistical approaches were employed, including the development of multiple regression models for predicting both intensity and band structure responses. These statistical models validated the first two listed hypotheses, while the third hypothesis was not supported by this dataset. The combination of inadequate moisture levels and reaction times (≤ 24 hrs) greatly limited the detection of varying levels of U, depending on the soil.

Les relations entre composés organiques et uranium montrent que ces interactions vont depuis la complexation et le transport de l’uranium dans des fluides organiques jusqu'à sa réduction par celles-ci conduisant à la précipitation de minéraux uranifères. Une étude expérimentale à 200°C et 500 bar des réactions entre des composés modèles (composés organiques purs) tels que les n-alcanes (n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-décane, n-dodécane, n-tétradécane et n-hexadécane), un n-alcène (n-déc-1-ène), des cycles (butyl-cyclohexane et cyclo-hexane) et des aromatiques (butyl-benzène et naphtalène) et des oxydes d’uranium hexavalents a été entreprise. La détermination du degré d’oxydation des oxydes d’uranium après expérience a permis de déterminer qu’en milieu aqueux les composés modèles aliphatiques sont des réducteurs plus puissants que les composés aromatiques. Ces expériences ont permis de démontrer une oxydation progressive des n-alcanes à partir des composés C6. La taille croissante des chaînes aliphatiques et l’augmentation du temps de mise en interaction sont des facteurs majeurs de l’augmentation du pouvoir réducteur du milieu, dont de la réduction de l’uranium hexavalent et par voie de conséquence de l’intensité de l’oxydation du composé organique. Une matière organique d’origine lacustre ou marine possédant généralement une fraction aliphatique plus importante que la matière organique d’origine continentale sera donc plus susceptible de réduire l’uranium. Un exemple naturel, les gisements d’uranium de type tectonolithologique localisés dans les grès de la région d’Arlit, ont été choisis afin d’appliquer les résultats obtenus dans la partie expérimentale. Les auteurs précédents ont considéré que seule cette matière organique de type III était responsable de la réduction de U(VI) en U(IV). Les travaux que nous avons entrepris montrent que des huiles migrées d'origine marine probable ont fortement contribué à la genèse de la minéralisation en uranium. Les analyses pétrographiques prouvent que (i) des bitumes solides, issus de la polymérisation des huiles migrées, sont présents en abondance dans la porosité des grès et dans des fractures au niveau des chenaux des formations gréseuses du Tarat (Tamou, Takriza, Taza Sud en carrières) ainsi que du Guézouman (mine secteur d’Akouta), et (ii) la minéralisation en uranium est principalement associée à cette matière organique migrée exprimée actuellement sous forme de bitumes solides. Dans ceux-ci, l’uranium est lié à une échelle infra-micrométrique dans les bitumes solides. Des huiles mises en évidence dans les inclusions fluides dans les surcroissances des grains détritiques de quartz des grès minéralisés des gisements des formations du Guézouman et du Tarat confirment la migration d’huile dans les chenaux et de ces formations. Ainsi le rôle prépondérant de la matière organique d'origine marine dans la genèse des minéralisations uranifères de type tectono-lithologique est mise en évidence de manière conjointe par l’approche expérimentale des interactions matière organique/uranium et par l’étude de la caractérisation de cette matière dans les gisements d’uranium de la région d'Arlit. / Formers studies on the relations between organic matter and uranium have shown that these interactions go since the complexation and the transport of uranium in organics fluids until its reduction by the organic matter leading to the uranium-bearing mineral precipitation. An experimental study of these reactions to 200°C and 500 bars between experimental compounds (pure organic compounds) such as the n-alkanes (n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-dodecane, n-tétradécane and n-hexadecane), an n-alcene hydrocarbon (n-dec-1-ene), cycles (butyl-cyclohexane and cyclo-hexane) and the aromatic ones (butyl-benzene and naphthalene), and hexavalent uranium oxides was undertaken. These experiments allowed to show a progressive oxidation of n-alkanes starting from made up C6. The increasing size of the aliphatic chains and the increase in the time of setting in interaction are major factors of the increase in the environment oxidizing capacity in interaction with uranium on the organic compound. The determination of the oxidation step of uranium oxides after experiment made it possible to determine that in aqueous environment the aliphatic model compounds are reducers more powerful than the aromatic compounds. An organic matter from lake or marine origin generally has an aliphatic fraction larger than the organic matter of continental origin and thus will be more likely to reduce uranium. A natural example, the uranium deposits in the sandstones from Arlit, the tectonolithologic type, was selected in order to apply the results obtained in the experimental part. They are located in fluviatil sandstones rich in organic matter of continental origin (type III) deposited in the paleochannels. Former authors considered that only this organic matter of type III was responsible for the reduction of U (VI) in U (IV). Work which was undertaken in the present study shows that migrated oils of probable marine origin strongly contributed to the genesis of uranium mineralisation. The petrographic analyses proved that (i) solid bitumens, resulting from the polymerization of migrated oils, are present in abundance in the porosity of the sandstones and fractures at the level of the channels of the Tarat formation (Tamou, Takriza, Southern Taza in careers) and Guézouman (mine sector of Akouta), and (ii) uranium mineralization is mainly associated with this migrated organic matter currently expressed in the form of solid bitumens. In those, uranium is related which are present at an infra-micrometric scale in the solid bitumens. The oils highlighted in fluid inclusions in the overgrowths of the detrital quartz grains in the sandstones of the Guézouman and Tarat formations confirm that channels of these two formations are the source of the oil migration. Thus, the dominating role of the organic matter of marine origin in the genesis of uranium-bearing mineralization of tectono-lithological type is highlighted in a joint way by the experimental approach of the interactions organic matter/uranium and by the characterization of this matter from the uraniferous layers in the Arlit area.

Thesis advisor: Jeremy D. Shakun / The Arctic is one of the fastest warming regions on the planet. Currently, much of the Arctic is covered by permafrost, which contains approximately 1,700 gigatons of organic carbon. Permafrost thaw could release a substantial amount of this carbon as greenhouse gases into the atmosphere through microbial decomposition, potentially dramatically amplifying anthropogenic warming. However, the risk of permafrost thaw is uncertain, with models exhibiting a wide range of possibilities. Assessing the stability of permafrost during past interglacial periods enables evaluation of the sensitivity of permafrost to warming. Cave mineral deposits (speleothems) in areas currently covered with permafrost can act as a proxy for past permafrost thaw, as liquid water is one criterion for speleothem growth and thus speleothem deposition implies thawed ground conditions. Previous uranium-thorium (U-Th) dating of speleothems (n=73) from a wide range of latitudes and permafrost zones across the southern Canadian Rockies, Northwest Territories, and northern Yukon indicate that most of these formations exceed the U-Th dating limit of 500 ka. In this study, I apply uranium-lead (U-Pb) geochronology to several of these speleothems to extend the record of speleothem growth further back in time. Results include a U-Pb age of 412.8 ± 1.3 ka that replicates a previous U-Th age of 415.0 ± 11.5 ka, demonstrating the reliability of the U-Pb methodology. Additionally, U-Pb ages on six other speleothems are determined to be 876 ± 9 ka, 1501 ± 31 ka, 1570 ± 66 ka, 2046 ± 106 ka, 7636 ± 184 ka, and 7697 ± 185 ka. Further application of this technique could result in long records of past permafrost thaw and Arctic terrestrial climate extending back millions of years. / Thesis (MS) — Boston College, 2018. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

David Lai. / Thesis -- Chinese University of Hong Kong. / Bibliography: l. 103-104. / Acknowledgement --- p.v / Abstract --- p.vi / Format of the Thesis --- p.viii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter Chapter 2 --- Experimental Techniques / Chapter 2.1 --- Introduction --- p.10 / Chapter 2.2 --- Arrangement for Fluorescence Spectrum Measurements --- p.10 / Chapter 2.3 --- Fluorescence Spectrum Measurements by Photographic Method --- p.11 / Chapter 2.4 --- Arrangement for Fluorescence Decay Rate Measurements --- p.11 / Chapter Chapter 3 --- Soda-lime Glass Matrix / Chapter 3.1 --- Introduction --- p.17 / Chapter 3.2 --- Theory --- p.19 / Chapter 3.3 --- Samples --- p.23 / Chapter 3.4 --- Experiments and Results --- p.26 / Chapter 3.5 --- Discussion / Chapter 3.5.1 --- Fluorescence Spectra --- p.35 / Chapter 3.5.2 --- Decay Rate Measurements --- p.39 / Table (3-1) --- p.43 / Table (3-3) --- p.43 / Table (3-2) --- p.44 / Chapter Chapter 4 --- Lithium Phosphate Glass / Chapter 4.1 --- Introduction --- p.45 / Chapter 4.2 --- Samples --- p.46 / Chapter 4.3 --- Experiments and Results --- p.47 / Chapter 4.4 --- Discussion --- p.54 / Table (4-1) --- p.64 / Table (4-2) --- p.65 / Table (4-3) --- p.66 / Table (4-4) --- p.66 / Chapter Chapter 5 --- Hydrogen Oxide (H20) and Deuterium Oxide (D20) / Chapter 5.1 --- Introduction --- p.67 / Chapter 5.2 --- Theory --- p.69 / Chapter 5.3 --- Experiments and Results --- p.71 / Chapter 5.4 --- Discussion --- p.71 / Table (5-1) --- p.78 / Table (5-2) --- p.79 / Chapter Chapter 6 --- Conclusion --- p.80 / Appendix I --- p.82 / Appendix II --- p.83 / Appendix III --- p.84 / Appendix IV --- p.85 / Appendix V --- p.86 / Appendix VI --- p.90 / Appendix VII --- p.91 / Appendix VIII --- p.95 / Appendix IX --- p.96 / Appendix X --- p.102 / References --- p.103

Thesis (Ph.D.)--Boston University / Due to the necessity of recovering uranium from reactor fuels, a number of separation methods have been investigated in recent years. Of these, the method of solvent extraction has proved to be a practical one. Long chain symmetrical phosphine oxides have been shown to extract uranium and a number of other metals under different conditions. It was the object of the present investigation to establish the nature of the species resulting from uranyl nitrate-R3Po (R =alkyl group) interaction. The two phosphine oxides selected for the study were: (i) Tri-n-octylphosphine oxide (TOPO) and (ii) Tris(2-ethylhexyl)phosphine oxide (TEHPO). An attempt was made to obtain pure TEHPO. Though the attempt has not met with complete success, yet significant conclusions concerning the stoichiometry and relative stability of the uranyl nitrate-TEHPO complex could be drawn. [TRUNCATED]

archives@tulane.edu / Groundwater contamination due to the presence of uranium is a subject of concern since chronic exposure to uranium can lead to health problems such as renal failure and cancer. Current standard methods for detection and quantification of uranium in groundwater require expensive instrumentation, laborious sample preparation processes and highly skilled labor to perform. Simple, portable immunosensors can reduce analysis times and costs. Immunosensors take advantage the ability of antibodies to recognize specific molecules. The antibody-antigen binding event can then be read using a quantifiable signal such as color. The success of immunosensors largely depends on the quality of the antibody. In this report, a single chain variable fragment antibody (scFv) was generated from the monoclonal antibody, 12F6 to be used for further studies and re-engineering. The 12F6 antibody binds hexavalent uranium complexed to the chelator, 2,9-dicarboxyl-1,10-phenanthroline (DCP). This scFv was re-engineered in attempt to improve stability as well as adjust it for possible application in a lateral flow device. The full length 12F6 was used to develop a paper-based lateral flow immunoassay device for the detection of uranium in groundwater. Gold nanoparticles were conjugated to the 12F6 antibody to be used as a label. Gold nanoparticles were chosen as a label for this immunoassay due to their biocompatibility and intense plasmonic effect. These immunosensors can be used for rapid testing of groundwater at sites of contamination. This assay could quantify uranium at concentrations below the maximum contaminant level (MCL) for drinking water, 30ppb, or 126nM, as stipulated by the U.S. Environmental Protection Agency (EPA) and the World Health Organization (WHO). / 1 / Grace A. Jairo

The objective of the work described in this thesis was to improve the scientific basis for modelling the migration of U in the sub-surface environment. The project involved: ?? studying the sorption of U on model minerals (Georgia kaolinite and ferrihydrite) in laboratory experiments ?? carrying out experimental studies of U sorption on complex natural substrates ?? studying the mechanisms influencing U retardation in the natural environment, including transformation processes of iron oxides ?? identifying chemical factors which control U sorption on model and natural substrates ?? developing a mechanistic model for U sorption on ferrihydrite and kaolinite using the surface complexation adsorption model , and ?? assessing and modelling the effect of complexing ligands on uranyl adsorption. Uranium (VI) sorption on geological materials is influenced by a large number of factors including: pH, ionic strength, partial pressure of CO2, adsorbent loading, total amount of U present, and the presence of inorganic and organic ligands. The sorption of UO22+ typically increases with increasing pH (the 'low pH sorption edge') up to about pH 7. In systems equilibrated with air, there is a sharp decrease in sorption above this pH value (the 'high pH edge'), due to strong complexation between uranyl and carbonate. The adsorption model being used for ferrihydrite is a surface complexation model with a diffuse double layer, and both strong and weak sites for U sorption. Based on the analysis of EXAFS data, the U surface complexes were modelled as mononuclear bidentate surface complexes of the form (&gtFeO2)UO20. Ternary surface complexes involving carbonate with the form (&gtFeO2)UO2CO32- were also required for the best simulation of U sorption data. There was a slight decrease in U sorption on ferrihydrite in systems that contained sulfate. It was necessary to consider competition between UO22+ and SO42- for surface sites, as well as complexation between UO22+ and SO42- to model the data. The presence of citrate considerably reduced U sorption and caused dissolution of ferrihydrite. Complexation of citrate with both uranyl and ferric ions was taken into account in modelling this system. The model required the optimisation of the formation constant for a postulated mixed metal (U/Fe/citrate) aqueous complex. Humic acid increased U uptake at pH values below 7, with little effect at higher pH values. In terms of the amount of U sorbed per gram of adsorbent, U uptake on kaolinites KGa-1 and KGa-1B was much weaker than U uptake on ferrihydrite under similar experimental conditions. Electron microscope examination showed that titanium-rich impurity phases played a major role in the sorption of U by these standard kaolinites. A relatively simple model for uranyl sorption on the model kaolinites was able to account for U sorption under a wide range of experimental conditions. The model involved only three surface reactions on two sites (&gtTiOH and &gtAlOH), with a non-electrostatic surface complexation model. The relative amounts of the sites were estimated from AEM results. Precipitation was taken into account in modelling the experimental data obtained with high U concentrations. The effects of sulfate and citrate on U sorption by kaolinite were also assessed and modelled. Sulfate had a small effect on U sorption, which may be explained by aqueous complexation. Citrate had a greater effect, and this was not wholly explained by the formation of aqueous U-citrate complexes. The most likely explanation would also involve competition for surface sites between U and citrate. Uranyl uptake on ferrihydrite was greatly increased by the presence of phosphate. This was not due to precipitation, and was attributed to the formation of a ternary surface complex with a proposed structure of (&gtFeO2)UO2PO43-. The log K value for the formation of this complex was optimised using FITEQL. Phosphate also increased uptake of uranyl on kaolinite, and this was also attributed to the formation of ternary uranyl phosphate surface species. Uranium sorption on weathered schist samples from the vicinity of the Koongarra U deposit in northern Australia was generally similar to the model minerals (in terms of the effects of pH, ionic strength, total U, etc). Many experiments with the natural materials were spiked with an artificial U isotope (236U), which allowed adsorption (of 236U) and desorption (of 238U) to be distinguished, and provided a means of estimating the 'labile' or 'accessible' portion of the natural U content. A significant advantage of this method is that (unlike chemical extractions) it does not rely on the assumptions about the phases extracted by 'selective' reagents. Uranium sorption experiments were also carried out with Koongarra samples which had been treated with citrate / dithionite / bicarbonate (CDB) reagent to remove iron oxides. Uranium sorption was greatly decreased by the CDB extraction, which reduced the surface area of the samples by about 30-40%. To further elucidate the impact of iron minerals on U mobility in the natural environment, the transformation of synthetic ferrihydrite containing adsorbed natural uranium was studied. In these experiments, the ferrihydrite was partially converted to crystalline forms such as hematite and goethite. The uptake of an artificial uranium isotope (236U) and the leaching of 238U from the samples were then studied in adsorption / desorption experiments. The transformation of ferrihydrite to crystalline minerals substantially reduced the ability of the samples to adsorb 236U from solution. Some of the previously adsorbed 238U was irreversibly incorporated within the mineral structure during the transformation process. Therefore, transformation of iron minerals from amorphous to crystalline forms provides a possible mechanism for uranium immobilisation in the groundwater environment. In considering the overall effect on U migration, this must be balanced against the reduced ability of the transformed iron oxide to adsorb U. The experiments with the model and natural substrates demonstrated that trace impurities (such as Ti-oxides) and mineral coatings (such as ferrihydrite) can play a dominant role in U adsorption in both environmental and model systems. Although the various substrates had different affinities for adsorbing U, the effects of chemical factors, including pH, ionic strength, and carbonate complexation were similar for the different materials. This suggests that a mechanistic model for U sorption on model minerals may eventually be incorporated in geochemical transport models, and used to describe U sorption in the natural environment.

This thesis examines the shift in governance structures, bargains, and processes in the Saskatchewan uranium industry between the 1970s and 2000s. Using a framework based on international political economy, the thesis analyzes the security, production, financial and knowledge structures that shaped the environment of the provinces uranium industry. In addition, an analysis of bargains created between and among structures helps provide further insight into the industry. Through this type of analysis, the thesis draws comparisons between the Allan Blakeney New Democratic Party and the Brad Wall Saskatchewan Party governments attempts to expand the uranium cycle in Saskatchewan. Due to conditions both internal and external to their administrations, the Blakeney and Wall governments engaged in two different processes, one closed and one open.<p> Looking at these two events through content analysis, studying official statements, public documents, government positions and media reports, this thesis explores the circumstances that engendered two different processes and the outcomes each process produced. The 1970s and 80s refinery debate relied on a state-centric process that limited relationships with the industrial sector and the societal sector. These factors contributed to the failure of the provincial government to win the refinery contract. Given different governance structures during this era, the outcome reached for the refinery may have been different. Two decades later, the nuclear energy debate in the 2000s benefitted from evolved governance structures. The state engaged in a stronger working relationship with industry and a more open discourse with the public. However, the increased governing versatility remained unable to counteract economic forces at the global level. Both cases exemplify the difficulty expanding an industry as complex and contentious as uranium despite substantial change in governance models.

This thesis examines the shift in governance structures, bargains, and processes in the Saskatchewan uranium industry between the 1970s and 2000s. Using a framework based on international political economy, the thesis analyzes the security, production, financial and knowledge structures that shaped the environment of the provinces uranium industry. In addition, an analysis of bargains created between and among structures helps provide further insight into the industry. Through this type of analysis, the thesis draws comparisons between the Allan Blakeney New Democratic Party and the Brad Wall Saskatchewan Party governments attempts to expand the uranium cycle in Saskatchewan. Due to conditions both internal and external to their administrations, the Blakeney and Wall governments engaged in two different processes, one closed and one open.<p> Looking at these two events through content analysis, studying official statements, public documents, government positions and media reports, this thesis explores the circumstances that engendered two different processes and the outcomes each process produced. The 1970s and 80s refinery debate relied on a state-centric process that limited relationships with the industrial sector and the societal sector. These factors contributed to the failure of the provincial government to win the refinery contract. Given different governance structures during this era, the outcome reached for the refinery may have been different. Two decades later, the nuclear energy debate in the 2000s benefitted from evolved governance structures. The state engaged in a stronger working relationship with industry and a more open discourse with the public. However, the increased governing versatility remained unable to counteract economic forces at the global level. Both cases exemplify the difficulty expanding an industry as complex and contentious as uranium despite substantial change in governance models.

The development of fast reactor systems capable of burning recycled transuranic (TRU) isotopes has been underway for decades at various levels of activity. These systems could significantly alleviate nuclear waste storage liabilities by consuming the long-lived isotopes of plutonium (Pu), neptunium (Np), americium (Am), and curium (Cm). The fabrication of metal fuel alloys by melt casting pins containing the volatile elements Am and Np has been a major challenge due to their low vapor pressures; initial trials demonstrated significant losses during the casting process. A low temperature hot extrusion process was explored as a potential method to fabricate uranium-zirconium fuel alloys containing the TRU isotopes. The advantage of extrusion is that metal powders may be mixed and enclosed in process canisters to produce the desired composition and contain volatile components. Uranium powder was produced for the extrusion process by utilizing a hydride-dehydride process that was developed in conjunction with uranium alloy sintering studies. The extrusions occurred at 600 degrees C and utilized a hydraulic press capable of 450,000 N (50 tons) of force. Magnesium (Mg) metal was used as a surrogate metal for Pu and Am because of its low melting point (648 degrees C) and relatively high vapor pressure (0.2 atm at 725 degrees C). Samples containing U, Zr, and Mg powder were prepared in an inert atmosphere glovebox using copper canisters and extruded at 600 degrees C. The successful products of the extrusion method were characterized using thermal analysis with a differential scanning calorimeter as well as image and x-ray analysis utilizing an electron microprobe. The analysis showed that upon fabrication the matrix of the extruded metal alloy is completely heterogeneous with no mixing of the metal particle constituents. Further heat treating upon this alloy allows these different materials to interdiffuse and form mixed uraniumz-irconium phases with varying types of microstructures. Image and x-ray analysis showed that the magnesium surrogate present in a sample was retained with little evidence of losses due to vaporization.