Physical Sciences and Mathematics Commons^™

Electrochemical Approaches To Life-Support Resources In Space Missions And Nuclear Technologies: Hydrogen Peroxide And Uranium Films, Armando Manuel Pena-Duarte

Open Access Theses & Dissertations

Space race has developed several technological advances that have achieved and continue to achieve the success of space missions in the aerospace timeline. Currently, the number of space technical and scientific innovations is still growing––demanding new materials and developments for extreme performing applications of fuel cells, batteries, supercapacitors, and systems of nuclear energy. Space missions require life-support solutions, auto-sustainable closed-loop living environments, cleaning and sanitizing solutions against pathogens, and safe nuclear-based resources of energy––with fissile materials with well-controlled dimensions within the core fuel elements. Likewise, to guarantee safety conditions, reduce costs, and facilitate operational logistics, space missions must reduce their …

Dissolution And Electrochemical Recovery Of Uo2, Uo3, And U3o8 In Ionic Liquids, Katherine Iolani Thornock Luebke

UNLV Theses, Dissertations, Professional Papers, and Capstones

This research explores a novel method of increasing the solubility of uranium oxides and other actinide oxides in room temperature ionic liquids (IL) using direct dissolution. The goal is to further expand our knowledge of actinide dissolution and possible nuclear fuel cycle material applications using ionic liquids. The novelty of the methods is focused on the use of oxidizing gas generated using air passed through an ozone generator. While examples of dissolution exist in IL using acidic functionalized ionic liquids, the solubility of all possible oxide species was not demonstrated. Also, the addition of aqueous acid to IL containing actinide …

Revisiting The Chemistry Of Uranium And Rhenium Fluorides: Implication To Fuel Cycle And Nuclear Forensics Science, James Amos-Aimé Louis-Jean

UNLV Theses, Dissertations, Professional Papers, and Capstones

Fluorine plays a major role in the nuclear industry where F2(g) and HF(g) are critical to the preparation of UF6 and UF4. These materials are prepared for uranium enrichment to increase the isotopic concentration of 235U. During separation efforts, the isotope 99Tc (a high yield fission product, 6.1% from 235U) is extracted along with uranium and can be converted to binary technetium fluorides (i.e., TcF4, TcF6) during re-enrichment of used uranium material. This provides a route for 99Tc to reenter the reactor environment and affect the nuclear properties of fuel pellets made with reprocessed uranium. The objective of this work …

Molten Salt Technologies For Advanced Nuclear Fuel Cycles And Molten Salt Reactors, Dimitris Killinger

Theses and Dissertations

This dissertation provides five topics—an assessment of different monitoring and analytical techniques often cited in the literature for molten salt systems and designs for nuclear engineering applications. First, we explored commonly used materials for quasi-reference electrodes in molten chloride salts. Second, the limitations of the electrochemical analysis known as cyclic voltammetry due to the concentration of uranium(III) present were being investigated. Third, we provided an experimental assessment on the development of a spectroelectrochemical cell for interrogating various spectroelectrochemical techniques, namely chronoabsorptometry and chronofluorometry, and their limitations due to the presence of uranium(III) ions. Fourth, a study on the corrosion resistance …

Exploratory Molten Flux Crystal Growth Of Complex Uranium Oxides, Christian A. Juillerat

Theses and Dissertations

While the use of nuclear technology has proven useful for energy generation and for military use, the proper disposal and storage of the resulting nuclear waste requires serious attention to ensure radioactive species are indefinitely sequestered to protect the biosphere. There are several classifications of nuclear waste such as spent nuclear fuel (from industrial power plants), low level waste (slightly contaminated trash), and high level waste (HLW) which is in the form of a sludge, precipitated salt, or liquid. Each of these requires a different approach to processing and storage. Of these, HLW requires the most attention because it is …

Synthesis And Characterization Of Synthetic Urban Melt Glass, Rebecca Kristien Lowe

UNLV Theses, Dissertations, Professional Papers, and Capstones

Melt glass formed from the explosion of a nuclear device is a unique post-detonation material that can aid in the ensuing forensics investigation. Trapped in the melt glass are chemical and isotopic signatures that can provide diagnostic and source information about the weapon by comparison with documentation of previous detonations. A nuclear terrorist attack would likely take place in an urban environment and as such, the melt glass formed would consist of a complex matrix including urban materials like cement and glass, activation products from the large neutron flux that will be seen, and fission products from the detonation. The …

The Retrospective Analysis Of Radionuclides In Banded Coral From The Bikini Atoll, Athena Marie Gallardo

UNLV Theses, Dissertations, Professional Papers, and Capstones

Nuclear weapons testing conducted within the Bikini Atoll in the Marshall Islands resulted in local fallout contamination, including long lived isotopes of plutonium (Pu) and uranium (U), within the surrounding environment. The Bikini lagoon provides a continuous source of Pu (239+240Pu) and U (236U) to the Pacific Basin. The rate at which these isotopes are flushed from the lagoon to the ocean is balanced by inputs from remobilization of lagoon sediments. This research will provide a basis for predicting future change in the solubility and export potential of Pu and U in lagoon sediments. This is important to better understand …

Synthesis Of Actinide Materials For The Study Of Basic Actinide Science And Rapid Separation Of Fission Products, Jacquelyn M. Dorhout

UNLV Theses, Dissertations, Professional Papers, and Capstones

This dissertation covers several distinct projects relating to the fields of nuclear forensics and basic actinide science. Post-detonation nuclear forensics, in particular, the study of fission products resulting from a nuclear device to determine device attributes and information, often depends on the comparison of fission products to a library of known ratios. The expansion of this library is imperative as technology advances. Rapid separation of fission products from a target material, without the need to dissolve the target, is an important technique to develop to improve the library and provide a means to develop samples and standards for testing separations. …

Surface Modification Of Pillar Array Systems For Chromatography And Fluorescence Enhancement, Danielle Ruth Lincoln

Doctoral Dissertations

Thin-layer chromatography offers many advantages in the world of chemical separations due to its ease of use, high sensitivity, range of applicability, and multiplex capability. However, this technique is succeptible to band broadening effects that limit its efficiency. Attempting to resolve these effects by decreasing particle size causes a decrease in mobile phase velocity which creates its own band broadening via longitudinal diffusion. However, pillar array systems on the micro- and nanoscale have been shown as useful analogues to thin-layer chromatography which mitigate the efficiency concerns associated with the method.

The work within this dissertation is concerned with the modification …

Spectroscopic Signatures Of Uranium Speciation For Forensics, Nicholas Wozniak

UNLV Theses, Dissertations, Professional Papers, and Capstones

Chemical speciation offers opportunities for development of signatures that arise from the production, conversion, and aging processes of nuclear materials. This information has been useful for environmental science and remediation and the ability to measure chemical signatures, from processed materials may be of great use to nuclear forensics. Many nuclear forensics analyses deal with radiochronometry and isotopic analysis, but because processing is chemical in nature, there are opportunities for chemical signatures from the bulk products, reagents, or reaction intermediates to be measured.

Many spectroscopic techniques can be utilized in a remote setting outside of the laboratory, with minimal or no …

Redox-Active Ligand Uranium Complexes For Approaches To Multi-Electron Chemistry, John J. Kiernicki

Open Access Dissertations

While transition metal complexes are known to participate in multi-electron redox chemistry to facilitate important organometallic transformations, actinides, due to their low redox potentials, have a propensity to perform single electron chemistry. Because of its highly reducing nature, the ability to control the electronics of low-valent uranium is highly sought after as this may lead to unprecedented reactivity. Our lab has specifically been interested in mediating multi-electron transformations at uranium by employing redox-active ligands. Redox-active ligands can be used to facilitate multi-electron processes such as oxidative addition and reductive elimination at single metal centers. Using primarily 2,6-((Mes)N=CMe)2C5H3N) ( MesPDIMe) as …

Direct Dissolution And Electrochemical Investigation Of Cerium And Uranium In Ionic Liquid, Janelle Droessler

UNLV Theses, Dissertations, Professional Papers, and Capstones

The solubility, coordination and speciation of f-elements in ionic liquids (ILs) has been the focus of numerous studies because the purely ionic systems have unique physical properties that can be exploited in comparison to aqueous, organic, or molten salt systems. Ionic liquids are thermally stable, have negligible vapor pressure, and are electrochemically stable at negative potentials that encompass the reduction potential of actinide species. Literature has suggested that the properties of ILs could potentially be utilized in the nuclear fuel cycle for separations and reprocessing. However, the solubility of f-elements in ILs has been significantly lower compared to traditional solvents. …

Controlling Electronics For The Formation Of High Valent Uranium Imido Complexes, Nickolas H. Anderson

Open Access Dissertations

Known primarily for its single electron chemistry, controlling the electronics at uranium to facilitate multi-electron processes remains a fundamental challenge in the actinide sciences. Our group has implemented the use of redox-active ligands to assist in the stabilization of low-valent uranium analogues, capable of performing multi-electron chemistry at a single uranium center. Of particular interest to our group are high-valent imido complexes, which are ubiquitous in organometallic and coordination chemistry due to their unique bonding properties and their ability to mediate bond-forming reactions. Uranium imido complexes, in particular, are the subject of much research to determine the degree of f- …

Measurement Of Rare Earth And Uranium Elements Using Laser-Induced Breakdown Spectroscopy (Libs) In An Aerosol System For Nuclear Safeguards Applications, Ammon N. Williams

Theses and Dissertations

The primary objective of this research is to develop an applied technology and provide an assessment for remotely measuring and analyzing the real time or near real time concentrations of used nuclear fuel (UNF) elements in electrorefiners (ER). Here, Laser-Induced Breakdown Spectroscopy (LIBS) in UNF pyroprocessing facilities was investigated. LIBS is an elemental analysis method, which is based on the emission from plasma generated by focusing a laser beam into the medium. This technology has been reported to be applicable in solids, liquids (includes molten metals), and gases for detecting elements of special nuclear materials. The advantages of applying the …

Quantum-Mechanical Calculations Of Actinyl And Europium Sorption To Graphene Oxide, Edward Helvenston

All Theses

Quantum-mechanical calculations were performed to model the interactions of U(VI), Np(V), Pu(VI), and Eu(III) with carboxyl and hydroxyl functional groups of graphene oxide (GO). Models were created for sorption to a single sheet of GO. For U(VI) and Eu(III), models were also created for sorption to two sheets to evaluate the possibility of cation-induced GO aggregation via cation cross-linking of GO sheets. The quantum-mechanical calculations were used to characterize the sorption reactions in terms of energetics and vibrational peak shifts. The calculations performed used Gaussian09 with the B3LYP hybrid functional. Sorption was seen as favorable for all cations considered; the …

Selective Solid Phase Extraction Of Uranium Using An Aminophosphonic Acid Functionalized Composite Material, Ranalda Tsosie

Graduate Student Theses, Dissertations, & Professional Papers

Uranium is an element of interest because it is an abundant source of concentrated energy. In 1948 the US offered money for uranium ore mined in the US, which created a mining boom in the southwest that included the Navajo Reservation. During the late 1960s the demand for uranium decreased and many mining operations shutdown and left behind a legacy of contamination. As a result many Navajo communities have numerous water sources that exceed established maximum contamination levels for uranium and other toxic metals. These contaminations are a direct result of abandoned Cold War uranium mines and mill waste sites …

Electrochemical Reduction Of Aqueous Uranium, Jonathan M. Scaggs

Boise State University Theses and Dissertations

The electrochemical reduction of uranium in acidic aqueous environments with the express purpose of generating U(III) consistently is critically evaluated. Generating U(III) in an aqueous environment is difficult and extremely unstable and has historically been difficult to achieve and isolate for further investigation. The electrochemical cell, electrodes, supporting electrolytes, and pH’s are all reviewed and evaluated for the purpose of optimizing the systemic requirements to electrochemically generate U(III). Several new types of electrochemical cells to include two new spectroelectrochemical for UV-Vis and FT-Raman investigation were designed and tested for the purpose of analyzed the redox species of aqueous uranium generated …

Molecular Forensic Science Analysis Of Nuclear Materials, Dallas Reilly

UNLV Theses, Dissertations, Professional Papers, and Capstones

Concerns over the proliferation and instances of nuclear material in the environment have increased interest in the expansion of nuclear forensics analysis and attribution programs. A new related field, molecular forensic science (MFS) has helped meet this expansion by applying common scientific analyses to nuclear forensics scenarios. In this work, MFS was applied to three scenarios related to nuclear forensics analysis. In the first, uranium dioxide was synthesized and aged at four sets of static environmental conditions and studied for changes in chemical speciation. The second highlighted the importance of bulk versus particle characterizations by analyzing a heterogeneous industrially prepared …

Speciation And Spectroscopy Of The Uranyl And Tetravalent Plutonium Nitrate Systems: Fundamental Studies And Applications To Used Fuel Reprocessing, Nicholas A. Smith

UNLV Theses, Dissertations, Professional Papers, and Capstones

This dissertation explores the use of UV-Visible spectroscopy and Time Resolved Laser Induced Fluorescence spectroscopy as near real time process monitors of uranium and plutonium concentrations in aqueous reprocessing trains. The molar absorptivities and linear ranges of these metals were investigated under total nitrate and acid concentrations similar to those found in current reprocessing systems. Concurrent to this, a new multiple wavelength monitor was derived that is capable of determining the total nitrate concentration spectroscopically. This method uses the uranium absorbance spectrum to calculate the nitrate concentration in solution. When used as part of an Advanced Safeguard suite, this technique …

A New Method For The Quantitative Determination Of Radon-222 In Natural Waters, Charles Whitlow

Honors Theses

Several studies in the past have shown radon to be present in many natural waters including mineral springs, hot springs, rivers, lakes, and rainwater. A compilation of tables of radon concentration in mineral and hot springs all over the world was published by Kuroda in 1953. Most of this radon comes from radium and uranium minerals which the springs flow over. The radon concentration in lakes is from two major souces [sic]. One source is dissolved radium and the other is the inflow of high radon concentration groundwaters [sic].