Physical Sciences and Mathematics Commons^™

Optimization Of Useful Hard X-Ray Photochemistry, David Lewis Goldberger

UNLV Theses, Dissertations, Professional Papers, and Capstones

X-ray induced damage is generally considered a nuisance, but in the field of Useful Hard X-ray Photochemistry we harness the highly ionizing and penetrating properties of hard X-rays (> 7 keV) to initiate novel photochemical decomposition and synthesis at ambient and extreme conditions. Preliminary experiments suggest that the energy of irradiating photons and the sample pressure play roles in determining the nature of X-ray induced damage. Here, we present the X-ray energy dependence of damage induced in strontium oxalate, strontium nitrate, and barium nitrate, as well as the pressure dependence of X-ray induced damage of strontium oxalate. Our results indicate …

Mechanisms For The Incorporation And Distribution Of Radionuclides In Near-Surface Fallout, Marc Alan Fitzgerald

UNLV Theses, Dissertations, Professional Papers, and Capstones

Fallout is the radioactive glass formed from a mixture of vaporized anthropogenic materials with proximate environmental material. These glassy byproducts constitute a compositional record of environmental materials such as soil and vapor precursors that are responsible for chemical heterogeneity in the glasses. The work of this dissertation is to untangle these different sources of compositional heterogeneity, distinguishing low-abundance vaporized anthropogenic-rich material from natural compositions, in order examine soil behavior and chemical evolution during fallout formation. Unfortunately, mixing convolutes the multivariate elemental relationships in these melts due to overlapping element abundances that might distinguish different source materials and chemical behaviors, making …

Crystallographic Exploration Of Fundamental Technetium Species At Nonambient Conditions, Daniel S. Mast

UNLV Theses, Dissertations, Professional Papers, and Capstones

The study of mater under extreme conditions has yielded fascinating insight into the physical and chemical nature of materials that under more modest conditions are considered mundane but have quite unusual properties when under pressure. Examples of this are the lightest of elements found in the first two rows and in the heaviest elements of the lanthanide and actinide series. Pure elements, though the simplest possible chemical systems, have proven to be among the most complex and interesting. Technetium metal is a simple HCP transition metal that, due to its half-filled d-shell, has a rich chemistry and an important place …

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 …

Solvent Extraction And Extraction Chromatography Of Homologs And Pseudohomologs Of Rutherfordium Using Teha And Tehp, Jeffrey Rolfes

UNLV Theses, Dissertations, Professional Papers, and Capstones

Studies of the chemical properties of the heaviest elements have always been difficult due to the short half-lives and low cross sections involved. To solve this problem, atom-at-a-time methods are necessary to determine the properties of these short-lived isotopes. Extremely fast kinetics for the chemical reactions studied (on the same order as the nuclide’s half-life) are required, and the system should have the potential for automation. Solvent extraction, with its selectivity and quick kinetics, has historically been used for these investigations into characteristics of super heavy elements. Another technique, extraction chromatography, offers potentially a way of investigating rutherfordium’s properties, without …

Applications Of Nanoporous Materials In Gas Separation And Storage, Amit Sharma

UNLV Theses, Dissertations, Professional Papers, and Capstones

Past decades in the field of gas separation and storage utilized the concepts of both cryogenic distillation and non-cryogenic methods such as high-pressure cylinders but few concerns – efficiency, energy intensiveness, cost associated, risk of failure always existed. Recent advances in the field focuses on using porous materials especially nanoporous materials. Nanoporous materials, due to their well-defined structure, range of pore diameters, and striking surface chemistry hold over traditional porous materials for gas separation and storage. With pore diameter less than 2 nm and abundance of energetically favorable sites (such as unsaturated metal sites, channels, cages, cavities etc.), these materials …

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 …

Determination Of Anthropogenic Radionuclides In Ocean Water Using Extraction Chromatography, Jaimie Daum

UNLV Theses, Dissertations, Professional Papers, and Capstones

In the aftermath of the reactor accident in Fukushima, it has become obvious that there is a severe lack in methods that would allow for the rapid determination of anthropogenic radionuclides in ocean water. Current radioanalytical techniques for the determination of radionuclides in natural waters have a number of disadvantages including the fact that they are time consuming, generate a substantial amount of waste, and are typically multi-step processes. Additionally, the elevated amount of dissolved ions in ocean water imparts a complex matrix that can interfere with the rapid separation and determination of anthropogenic radionuclides. Therefore, due to the size, …

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 …

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 …

Breaking The Language Barrier: Equitable Assessment In General Chemistry, Eshani Lee

UNLV Theses, Dissertations, Professional Papers, and Capstones

Because language provides the framework through which knowledge is constructed, it is crucial to consider the ways in which students with limited English proficiencies are able to express their understanding. English language learners (ELLs) make up a significant portion of the student body in the education system and represent many ethnic and racial minorities in STEM (Science, Technology, Engineering & Mathematics) fields (Burke & Mattis, 2007). Despite the national push to build a more diversified, STEM-ready workforce, there is little research that considers the way ELLs are assessed in STEM courses at the postsecondary level. Literature reports that science tests …