Physical Sciences and Mathematics Commons^™

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 …

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 …

Preparation And Evaluation Of Uranium Alloys Based On Burnup, Andrew Jonathan Swift

UNLV Theses, Dissertations, Professional Papers, and Capstones

Next generation fast reactor designs utilizing metallic fuel are being developed as an alternative fuel cycle option in an effort to reduce carbon emissions. Historically, oxide fuels have been the industry standard, but interest in metallic fuel systems has grown considerably due to their thermal conductivity, fissile atom density, inherent safety, and ability to reach progressively higher burnups. Chemical complexity of metallic fuel systems increase as a function of burnup from fission product ingrowth and associated fuel cladding chemical interactions (FCCI) brought on by elemental redistribution and phase formation. To date, the most extensive operational study for metallic fuel was …

Development Of Chemical Separation Methods Using Transition Metals For Nuclear Forensic And Medicinal Applications, Lucas Peter Boron-Brenner

UNLV Theses, Dissertations, Professional Papers, and Capstones

Insufficient data exists on the effects of prompt fast neutron activation on metals found commonly in nuclear devices and the urban environment. Different metals such as Ti, Au, Fe, and Cu were activated using the Flattop Criticality Benchmark at the Device Assembly Facility on the Nevada Test Site using a known neutron spectrum and flux to determine a baseline cross section value. Cross section information gathered from these neutron activation measurements could provide information that helps government and law enforcement agencies to correctly trace the origin of a nuclear device’s fuel or component features.

Based on activation products produced in …

Rapid Methods For Actinide And Strontium-89,90 Determination In Urban Matrices, Sherrod Maxwell

UNLV Theses, Dissertations, Professional Papers, and Capstones

Rapid radiochemical methods are needed to provide fast, reliable analytical measurements on a variety of different sample matrices in the case of a radiological event to protect the public, mitigate dose and protect the environment. If a radiological dispersive device (RDD), an Improvised Nuclear Device (IND) or a nuclear accident occurs, there will be an urgent need for quick analyses of urban matrices materials to support decision-making, dose mitigation and environmental clean-up. Since an incident involving a RDD or IND will likely occur in an urban or metropolitan area, it is very important to employ swift, robust analytical methods that …

Use Of Sodium Bismuthate Chromatography For Separation Of Americium From Curium And Other Elements In Spent Nuclear Fuel, Jason Michael Richards

UNLV Theses, Dissertations, Professional Papers, and Capstones

A novel method for partitioning americium from curium has been developed using sodium bismuthate as both an oxidant and a separation medium. The presence of americium and curium in nuclear waste increases the heat load in geological repositories and leads to larger waste volumes. These elements are also the source of most of the long-term radiotoxicity of the waste. However, the heat load and long-term radiotoxicity contribution from americium is much greater than that from curium. The contribution of curium to the heat load and radiotoxicity of the waste is significant on the same time scale as longer-lived fission products …

Separation Of Neighboring Trivalent Lanthanides For Neutron Capture Cross Section Measurements, Balazs Jozsef Bene

UNLV Theses, Dissertations, Professional Papers, and Capstones

The determination of the low-energy neutron capture cross-section of 171Tm with greater accuracy is important for both astrophysics and Stockpile Stewardship. Thulium-171 is a branching point in the s-process of stellar nucleosynthesis. Branching point nuclei, with half-lives in the order of 1 – 100 years are places where neutron capture and beta decay competes. This isotope is also the second order (n, γ) reaction product of 169Tm, which was used as a radiochemical detector in nuclear weapon experiments. It was placed at strategic locations in nuclear devices. Following the test, samples were analyzed in the collected samples for products of …

Synthesis, Characterization And Biological Studies Of Technetium-99m And Rhenium-188 Peptides, Vanessa Anne Sanders

UNLV Theses, Dissertations, Professional Papers, and Capstones

Radiopharmaceuticals are very powerful diagnostic tools for evaluation of a host of medical conditions. These drugs are labeled with radioactive isotopes, which are utilized to create pictures of areas of interest through absorption of the drug. They are currently in high demand due to their ability to image areas that traditional imaging devices cannot. The radioisotope 99mTc, with a half-life of 6.01 hours and a 140 keV gamma emission, is central to many radiopharmaceutical compounds. This isotope is easily obtained from a 99Mo-99mTc generator, through beta decay and column chromatography separations. Very little technetium, less than 6 ng, is needed …

Interference Effects Of Urban Rubble On The Radioanalytical Analysis Of Strontium, Derek Roger Mclain

UNLV Theses, Dissertations, Professional Papers, and Capstones

Most current radioanalytical protocols have been developed for the analysis of air, water, soil and bioassay samples. While these protocols build the foundation of operational environmental monitoring, they are not necessarily suitable for the analysis of samples that will be encountered in the aftermath of a nuclear incident. In such a situation, it will be important to characterize the isotopes of interest present in the affected area to obtain signatures for nuclear forensics and ensure the appropriate response. Specifically, this research is aimed at the determination of strontium-90 and its separation from zirconium-90 in a post-detonation situation.

Strontium-90’s relatively long …

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. …

Laser Ablation Icp-Ms Of Actinide Oxides As Simulated Used Nuclear Fuels, Keri Campbell

UNLV Theses, Dissertations, Professional Papers, and Capstones

The ability to examine elemental and isotopic ratios of fuels, waste forms, and other solids by direct analysis using laser ablation techniques can greatly reduce analysis costs and time. This is particularly true for actinide elements, as they contain useful information of the fuel cycle and nuclear forensics. Current methods to evaluate the composition of used fuel include a lengthy process of digestion, separations and often require multiple techniques and sample preparations to determine the elemental and isotopic composition. Furthermore all spatial information is lost during the digestion process, eliminating potentially useful data for detailed analysis. The goal of this …

Simultaneous Determination Of Multiple Actinide Elements In A Variety Of Soils Utilizing A Standardized Sequential Extraction Protocol, Sherry Alina Faye

UNLV Theses, Dissertations, Professional Papers, and Capstones

To obtain a better understanding of the mobility of actinide element contaminants in the environment, the association of the contaminants with specific host phases of soils and sediments must be investigated. This investigation is most commonly conducted using sequential extraction techniques that employ the selective dissolution of soil phases with increasingly aggressive chemical treatment. Though several sequential extraction studies exist in literature, conclusions cannot be made by direct comparison of data due to the lack of uniformity in the protocols used. This work aims to continue development of a standard sequential extraction protocol and expanding its capabilities to include the …

Technetium Sulfide: Fundamental Chemistry For Waste Storage Form's Application, Maryline Ghislaine Ferrier

UNLV Theses, Dissertations, Professional Papers, and Capstones

Technetium is the lightest radioelement. The isotope ⁹⁹Tc has around a 6% yield from ²³⁵U with a half-life of 2.13 x 10⁵ years. The high mobility of TcO₄^-, the common chemical form of technetium in the environment makes ⁹⁹Tc an isotope of concern in nuclear waste management. Despite its important role in radiopharmaceuticals and in the nuclear fuel cycle, the fundamental chemistry of technetium is not as well developed as that of the neighboring transition metals; one of the most striking examples being its sulfide chemistry.

Only two technetium binary sulfide compounds had …

Speciation Behavior Of Americium Higher Oxidation States For The Separation Of Americium From Curium, Catherine Lynn Riddle

UNLV Theses, Dissertations, Professional Papers, and Capstones

Several countries are currently expanding the use of nuclear energy as a method for the safe generation of carbon free energy and a number are evaluating starting up a nuclear power program. Closed fuel cycle technologies may be key to waste reduction and a sustainable nuclear energy future and to support the development of more efficient fuel cycles, the investigation of the chemical properties of key actinides is at the forefront of separations research. In this work the characterization of higher oxidation states of americium (Am) has been performed using spectroscopic methods. Americium in the formal oxidation state of Am(V) …

Binary Technetium Halides, Erik Vaughan Johnstone

UNLV Theses, Dissertations, Professional Papers, and Capstones

In this work, the synthetic and coordination chemistry as well as the physico-chemical properties of binary technetium (Tc) chlorides, bromides, and iodides were investigated. Resulting from these studies was the discovery of five new binary Tc halide phases: α/β-TcCl₃, α/β-TcCl₂, and TcI₃, and the reinvestigation of the chemistries of TcBr₃ and TcX₄ (X = Cl, Br). Prior to 2009, the chemistry of binary Tc halides was poorly studied and defined by only three compounds, i.e., TcF₆, TcF₅, and TcCl₄. Today, ten phases are known (i.e., TcF …

Characterization And Optimization Of Extraction Chromatography Resins For Rapid Separations For Safeguard And Nuclear Forensics Purposes, Audrey Roman

UNLV Theses, Dissertations, Professional Papers, and Capstones

In this work, extraction chromatography resins, DGA and UTEVA, were characterized under various conditions in order to identify novel rapid separations for safeguards and nuclear forensic purposes. For safeguards purposes, mixed matrices containing some of the largest components found in used fuel and either Am, Pu, or U were characterized on DGA and UTEVA resins in order to determine any effects from the addition of these constituents. Results indicated that 5 M HNO₃ would be an optimal loading condition due to the consistent actinide adsorption in the presence of the additional used fuel components. Investigations of varying the anion …

Investigation Of Storage-Phosphor Autoradiography For The Rapid Quantitative Screening Of Air Filters For Emergency Response Purposes, Athena Marie Gallardo

UNLV Theses, Dissertations, Professional Papers, and Capstones

Past nuclear accidents, such as Chernobyl, resulted in a large release of radionuclides into the atmosphere. Radiological assessment of the vicinity of the site of the incident is vital to assess the exposure levels and dose received by the population and workers. Therefore, it is critical to thoroughly understand the situation and risks associated with a particular event in a timely manner in order to properly manage the event. Current atmospheric radiological assessments of alpha emitting radioisotopes include acquiring large quantities of air samples, chemical separation of radionuclides, sample mounting, counting through alpha spectrometry, and analysis of the data. The …

Separation Of Tc From U And Development Of Metallic Tc Waste Forms, Edward Mausolf

UNLV Theses, Dissertations, Professional Papers, and Capstones

The isotope Technetium-99 (⁹⁹Tc) is a major fission product of the nuclear industry. In the last decade, approximately 20 tons of 99Tc have been produced by the US nuclear industry. Due to its long half-life (t_1/2 = 214,000 yr), beta radiotoxicity, and high mobility as pertechnetate [TcO₄]^-, Tc represents long-term concern to the biosphere. Various options have been considered to manage ⁹⁹Tc. One of them is its separation from spent fuel, conversion to the metal and incorporation into a metallic waste form for long-term disposal. After dissolution of spent fuel in nitric …

Forensic Signatures Of Chemical Process History In Uranium Oxides, Jonathan Plaue

UNLV Theses, Dissertations, Professional Papers, and Capstones

This dissertation comprehensively explores and develops new tools for nuclear forensic science to facilitate the identification of chemical process history in uranium oxides. Nuclear forensics is an emerging discipline motivated by the need to prevent and combat malevolent acts involving nuclear and radiological materials. This dissertation examined process signatures in uranium oxide powders, precursors, and sintered fuel pellets.

Signatures were investigated on set of powder and pellet exemplars synthesized in the laboratory and a set of real‐world samples with process information obtained from the literature or manufacturer. The examined techniques included morphology as revealed by scanning electron microscopy, near‐infrared reflectance …

Elemental Contributions From Minor And Major Constituents Of Bone On The Separation Of Radiostrontium, Ashlee Rae Dailey

UNLV Theses, Dissertations, Professional Papers, and Capstones

While many methods exist to separate and analyze radionuclides from a variety of environmental matrices, the performance of all of these methods is often limited by other interfering constituents that are consistently found in most of these samples. The presence of such constituents can significantly reduce the recovery of the radioisotopes of interests and lead to incomplete separations.

Strontium has the same oxidation state and a similar atomic radius as calcium and is therefore readily able to substitute for calcium in lattice sites. This similarity in behavior leads to the preferential accumulation of strontium in newly formed bone. The study …

Recycling And Reuse Of Radioactive Materials, Thomas Joseph O'Dou

UNLV Theses, Dissertations, Professional Papers, and Capstones

The Radiochemistry Program at the University of Nevada, Las Vegas (UNLV) has a Radiation Protection Program that was designed to provide students with the ability to safely work with radioactive materials in quantities that are not available in other academic environments. Requirements for continuous training and supervision make this unique program capable of turning out graduates that have an understanding of contamination and dose control techniques that complement their knowledge of the elements that they work with. The Program has also adopted a radionuclide recovery and reuse program that has provided materials from other universities, government agencies, and private companies …

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 …

Evaluating Actinide Sorption To Graphite With Regards To Triso Repository Performance, Corey Christopher Keith

UNLV Theses, Dissertations, Professional Papers, and Capstones

Graphite has the potential for inclusion in nuclear waste for disposal in waste repository settings. Implementation of High Temperature Gas-cooled Reactors contributes to this potential through use of TRISO fuel, if direct disposal of the graphite matrix surrounding the fuel is employed. The inclusion of the large mass and volume in the TRISO fuel waste form differs significantly from used light water reactor fuel waste forms, requiring new performance models to describe the behavior in a repository setting. The purpose of this study is to evaluate the potential for the graphite to improve actinide, specifically uranium and neptunium, retardation from …

Spectroscopic Methods Of Process Monitoring For Safeguards Of Used Nuclear Fuel Separations, Jamie Lee Warburton

UNLV Theses, Dissertations, Professional Papers, and Capstones

To support the demonstration of a more proliferation-resistant nuclear fuel processing plant, techniques and instrumentation to allow the real-time, online determination of special nuclear material concentrations in-process must be developed. An ideal materials accountability technique for proliferation resistance should provide nondestructive, realtime, on-line information of metal and ligand concentrations in separations streams without perturbing the process. UV-Visible spectroscopy can be adapted for this precise purpose in solvent extraction-based separations.

The primary goal of this project is to understand fundamental URanium EXtraction (UREX) and Plutonium-URanium EXtraction (PUREX) reprocessing chemistry and corresponding UV-Visible spectroscopy for application in process monitoring for safeguards. By …

Intragroup Separation Of Trivalent Lanthanides And Actinides For Neutron Capture Experiments In Stockpile Stewardship Sciences, Narek Gharibyan

UNLV Theses, Dissertations, Professional Papers, and Capstones

Knowledge of low-energy cross sections for stable and unstable nuclei in neutron-, γ- and ion induced reactions is important in both the simulation and radiochemistry diagnosis of nuclear device performance. This dissertation explores extraction chromatography and ion chromatography methods for the intragroup separation of trivalent actinides and lanthanides in support of cross section measurements for isotopes of interest. For trivalent actinides, americium (Am(III)) and curium (Cm(III)), separation is necessary to assist in experiments related to the measurement of neutron capture cross section for ²⁴¹ Am and the production of ^{242 m} Am/^242g Am isomeric ratio. Extraction chromatography resins …

Synthesis, Extraction, Dissolution, And Voltammetry Of F-Species In A Room Temperature Ionic Liquid Solvent, Wendy Jacqueline Pemberton

UNLV Theses, Dissertations, Professional Papers, and Capstones

Room temperature ionic liquids (RTILs) are salts that are liquids from as low as -96 °C to up to 100 °C. RTILs are of high interest in many fields of study because of their negligible vapor pressure, high electrochemical stability, high conductivity, and wide electrochemical windows. These diverse solvents have recently been used in organic synthesis, as extraction solvents, and as electrochemical solvents. It is as a direct result of the multifunctional capabilities of these RTIL solvents that they are examined in this work. The ability to probe the chemistry of lanthanides and actinides is based on the unique properties …

Equilibrium Speciation Of Select Lanthanides In The Presence Of Acidic Ligands In Homo- And Heterogeneous Solutions, Troy Robinson

UNLV Theses, Dissertations, Professional Papers, and Capstones

This dissertation explores lanthanide speciation in liquid solution systems related to separation schemes involving the acidic ligands: bis(2-ethylhexyl) phosphoric acid (HDEHP), lactate, and 8-hydroxyquinoline. Equilibrium speciation of neodymium (Nd³⁺ ), sodium (Na⁺ ), HDEHP, water, and lactate in the TALSPEAK liquid-liquid extraction system was explored under varied Nd³⁺ loading of HDEHP in the organic phase and through extraction from aqueous HCl and lactate media. System speciation was probed through vapor pressure osmometry, visible and Fourier Transform Infrared (FTIR) spectroscopy, ²² Na and ¹³ C labeled lactate radiotracer distribution measurements, Karl Fischer titrations, and equilibrium pH measurements. Distribution …

Electrochemistry Of Technetium Analogues Rhenium And Molybdenum In Room Temperature Ionic Liquid, Pauline Nancy Serrano

UNLV Theses, Dissertations, Professional Papers, and Capstones

Rhenium was used as an analog for Technetium to study the electrochemical redox properties because the two elements share the same stable oxidation states in aqueous solutions. However, Tc-99 is radioactive and is not readily available for experimentation purposes. Molybdenum is also of interest because when Mo-99 is irradiated, the decay products are Tc-99m and Tc-99. Approximately 30% Tc-99m is eluted from the Mo columns for radiopharmaceutical use with the remaining Mo-99 source decaying to Tc-99 which is discarded as radioactive hospital waste. Currently there are no viable procedures for the reclamation of the radioactive Tc-99 from either fission streams …

Extraction Chromatographic Studies Of Rutherfordium And Dubnium Homologs, Megan E. Bennett

UNLV Theses, Dissertations, Professional Papers, and Capstones

Studying the chemistry of transactinide elements does not only allow for these elements to be properly placed in the Periodic Table, but it also permits for the extrapolation of the electronic structure based upon the position of the element in the Periodic Table. In addition it enable for the assessment of the role that relativistic effects play in the chemical behavior of the heaviest elements. An improved understanding of the role of relativistic effects in chemistry of the heaviest elements allows for a better understanding of the fundamentals principles that govern the Periodic Table. In order to investigate the chemistry …