Nuclear Engineering Commons^™

Au@Tio2 Nanocomposites Synthesized By X-Ray Radiolysis As Potential Radiosensitizers, Maria C. Molina Higgins

Theses and Dissertations

Radiosensitization is a novel targeted therapy strategy where chemical compounds are being explored to enhance the sensitivity of the tissue to the effects of ionizing radiation. Among the different radiosensitizers alternatives, nanomaterials have shown promising results by enhancing tumor injury through the production of free radicals and reactive oxygen species (ROS). In this work, Gold-supported titania (Au@TiO₂) nanocomposites were synthesized through an innovative strategy using X-ray irradiation, and their potential as radiosensitizers was investigated. Radiosensitization of Au@TiO₂ nanocomposites was assessed by monitoring the decomposition of Methylene Blue (MB) under X-ray irradiation in the presence of the nanomaterial. …

Neutron Spectroscopy Using Rubberized Eu:Licaf Wafers, Michael A. Ford

Theses and Dissertations

With the increasing cost and decreasing availability of ³He, there have been many efforts to find alternative neutron detection materials. Lithium calcium aluminum fluoride (LiCAF) enriched to 95% ⁶Li doped with europium was evaluated here as a replacement material for ³He, based on the absorption of thermalized neutrons by the ⁶Li and subsequent energy release of the ⁶Li(n,t)⁴He reaction. Wafers 0.5 cm thick, consisting of LiCAF crystals in a rubberized matrix, were embedded with wavelength shifting fibers (WSF) and mated to silicon photo-multipliers (SiPMs) to measure the photon response in a flux of …

Innovative Fuel Design To Improve Proliferation Management, Taylor C. Britt

Theses and Dissertations

This research uses an existing innovative fuel design (IFD) that has intrinsic safety features and enhanced economics over the current uranium dioxide (UO₂) light water fuel design and evaluates promising methods to improve the waste management and proliferation resistance of the IFD by doping the fresh fuel with select actinides.The most robust approach for proliferation resistance is to denature these materials by adding a uranium or plutonium isotope that hampers the usability of the materials in weapons. The proposed modifications to the IFD use this approach through elevated fractions of ²³⁸Pu. ²³⁸Pu generates large quantities of …

Lanthanide-Based Core-Shell Nanoparticles As Multifunctional Platforms For Targeted Radionuclide Therapy And Multimodal Molecular Imaging, Miguel Toro-Gonzalez

Theses and Dissertations

Lanthanide phosphate (LnPO₄) and lanthanide vanadate (LnVO₄) nanoparticles (NPs) are promising platforms for theranostic applications because of their chemical stability, low solubility, low toxicity, and unique luminescence and magnetic properties. Motivated by the high radiation resistance and ability to host actinides of naturally occurring lanthanide-based compounds, LnPO₄ and LnVO₄ NPs were studied as radionuclide carriers for targeted radionuclide therapy using in vivoα-generators, ²²³Ra, ²²⁵Ac, and ²²⁷Th. The implementation of these radionuclides has shown potential for the treatment of micrometastases and solid tumors as well as challenges in the retention of …

Experimental Evaluation Of Uranyl Transport Into Mesoporous Silica Gel Using Fluorescence, Brandon M. Dodd

Theses and Dissertations

This research investigated parameters that can affect the use of nanoporous silica gel as a media for accumulating a detectable amount of uranium. The unique fluorescence of the Uranyl (UO₂²⁺) ion was used to evaluate the transport kinetics and accumulation within silica gel in a static fluid and under pressure driven flow. The addition of fluid flow decreased the time constant from on the order of an hour to approximately 2s with a very low fluid velocity of 0.36cm/s. The 0.36cm/s fluid velocity was found to be the critical velocity above which there was no gain in …

Neutronics Studies On The Nist Reactor Using The Ga Leu Fuel, Kyle A. Britton

Theses and Dissertations

The National Bureau of Standards Reactor (NBSR) located on the National Institute of Standards and Technology (NIST) Gaithersburg campus, is currently underway of fuel conversion from high enriched uranium (HEU) fuel to low enriched uranium (LEU) fuel. One particular challenging part of the conversion of the NBSR is the high average flux level (2.5×10¹⁴ n/cm²-s) required to maintain experimental testing capabilities of the reactor, without significant changes to the external structures of the reactor. Recently the General Atomics (GA) Training Research Isotopes General Atomics (TRIGA) fuel has shown some promising features as a LEU candidate for the …

Comparative Studies Of Diffusion Models And Artificial Neural Intelligence On Electrochemical Process Of U And Zr Dissolutions In Licl-Kcl Eutectic Salts, Samaneh Rakhshan Pouri

Theses and Dissertations

The electrorefiner (ER) is the heart of pyroprocessing technology operating at a high-temperature (723 K – 773 K) to separate uranium from Experimental Breeder Reactor-II (EBR-II) used metallic fuel. One of the most common electroanalytical methods for determining the thermodynamic and electrochemical behavior of elemental species in the eutectic molten salt LiCl-KCl inside ER is cyclic voltammetry (CV). Information from CV can possibly be used to estimate diffusion coefficients, apparent standard potentials, transfer coefficients, and numbers of electron transferred. Therefore, predicting the trace of each species from the CV method in an absence of experimental data is important for safeguarding …

Mechanical Characterization And Non-Destructive Evaluation Of Sicf-Sicm Composite Tubing With The Impulse Excitation Technique, Nathaniel Truesdale

Theses and Dissertations

With growing interest on ceramic fiber reinforced ceramic matrix composites (CMC) for accident tolerant fuel, the need for mechanical characterization of ceramic composite arises. It has been of particular interest to non-destructively evaluate the mechanical performance of these composites. Impulse excitation (IE) is a well-established method for non-destructive mechanical characterization of homogeneous isotropic material of well-defined shapes. In this thesis, impulse excitation technique was applied for non-destructive characterization of composite tube for the first time as far as we know. CMC, when stressed beyond its damage threshold, will experience various forms of structural damage, such as matrix micro-cracking, fiber-matrix debonding, …

Neutron Versus Gamma Radiation Effects On Ytterbium-Doped Optical Fibers, Olivia M. Borman

Theses and Dissertations

Multimode ytterbium-doped optical fibers (YDFs) are increasingly utilized in military applications involving fiber lasers and amplifiers. YDFs were irradiated with three different radiation sources (neutron, gamma, and mixed gamma/neutron) in order to determine the independent effects that gamma and neutron radiation have on the fibers. The transmission spectra of the fibers were measured during each irradiation and the spectral shapes and attenuation were compared at similar doses. Comparisons of the spectra showed that gamma radiation results in increased attenuation over the 550-975 nm wavelengths. Fast neutrons were found to contribute to increased attenuation near 500 nm. Neutron radiation also caused …

Radiation Response From A Novel Uo2 Crystal, Stephan A. Varga

Theses and Dissertations

The radiation response of a novel, single-crystalline UO2 sample was analyzed using several types of radiation. The crystal was exposed to alpha, gamma, and neutron radiation under various environmental conditions and the electronic response of the crystal was measured using a pulse shape discrimination algorithm. The distributions of pulse amplitude (Vmax) and pulse decay times (τ) were used to compare the output. This research revealed that the crystal radiation response is exceptionally sensitive to surface conditions, specifically humidity, which tends to alter the time dependent currents resulting from the radiation interactions. The pulse τ can be made to …

Evaluation Of The Visible Infrared Imaging Radiometer Suite (Viirs) Cloud Base Height (Cbh) Pixel-Level Retrieval Algorithm For Single-Layer Water Clouds, Kyle E. Fitch

Theses and Dissertations

Evaluation of the Visible Infrared Imaging Radiometer Suite (VIIRS) Cloud Base Height (CBH) product was accomplished. CBH is an important factor for aviation, but a lack of coverage for ground-based retrieval is a significant limitation. Space-based retrieval is essential; therefore, the VIIRS CBH pixel-level retrieval algorithm was assessed for single-layer water clouds. Accurate (truth) measurements were needed not only for the CBH product, but also for VIIRS cloud optical thickness (COT), effective particle size (EPS), and cloud top height (CTH). Data from Atmospheric Radiation Measurement (ARM) sites were used, with VIIRS-ARM matchups created from June 2013 through October 2015 for …

Differential (P, P′) And (P, D) Cross Sections Of 89Y And 92Zr, Molly A. Wakeling

Theses and Dissertations

Differential cross sections for the (p, p′) and (p, d) reactions on ⁸⁹Y and ⁹²Zr were measured using a 28.25-MeV proton beam at the 88-inch cyclotron at Lawrence Berkeley National Laboratory. Angular distributions were obtained for the ground state and several excited states of each isotope using silicon detector telescopes over angles 10° to 140° in the reaction plane. These data were obtained by fitting a Gaussian function to each peak in the energy spectra and integrating the number of counts under each peak. These cross sections will be included in nuclear structure models …

Analysis Of Neutron Effects For Asteroid Disruption, Aaron J. Ferguson

Theses and Dissertations

The use of nuclear weapons is one possible method for disrupting or deflecting an asteroid on a trajectory to impact the earth. A largely unexplored component of weapon yield in a disruption scenario is the impact of the neutron output. The results of MCNP-6 simulations are presented demonstrating the effect that incident neutron energy has on the total energy deposited in an asteroid, including that the efficiency of energy deposition in a material is inversely proportional to the incident neutron energy due to negative Q-value reactions. The effects of material composition on the total energy deposited as well as the …

Nuclear Forensics Applications Of Principal Component Analysis On Micro X-Ray Fluorescence Images, Sarah T. Castro

Theses and Dissertations

A method is developed for rapid detection and analysis of actinides and correlated materials in nuclear fallout debris using principal component analysis on quantified micro x-ray fluorescence intensity values. This method is then applied to address goals of nuclear forensics. The first implementation is a collaborative effort with the National Institute of Standards and Technology and the Federal Bureau of Investigation Laboratory to produce a standard reference material that is a surrogate for glassy nuclear fallout debris in a modern urban environment. This reference material will enable researchers in the development and validation of nuclear forensics methods. A method for …

Applications Of Correlated 2d-Acar And Cdbar Using A Low-Energy Positron Beam, Angelo M. Bonavita

Theses and Dissertations

The three-dimensional positron annihilation spectroscopy system (3D-PASS) at the Air Force Institute of Technology (AFIT) correlates coincidence Doppler broadening of annihilation radiation with two-dimensional angular correlation of annihilation radiation measurements using two position-sensitive, high-purity germanium (HPGe) detectors. The low photoelectric cross section of germanium, combined with the limited output of the radioisotope-based positron beam, produced sparse data necessitating careful data extraction. Processing techniques employed to increase 3D-PASS spectra quality include an improved algorithm for determining radiation-interaction position on HPGe double-sided strip detectors, a momentum sampling function based correction scheme and spectra folding informed by crystal symmetries. The 3D nature of …

Neutron Radiation Effects On Ge And Gesn Semiconductors, Christopher T. O'Daniel

Theses and Dissertations

Two different semiconductor materials received neutron radiation for assessment of radiation damage. The two materials are undoped bulk Ge and epitaxial Ge_0.991Sn_0.009, which is doped heavily with phosphorous. At room temperature, the Ge sample has direct and indirect bandgaps at 0.78 eV and 0.66 eV, respectively. The Ge_0.991Sn_0.009 sample has direct and indirect bandgaps at 0.72 eV and 0.63 eV, respectively. Two samples of each material were exposed to research reactor neutrons, delivering a 1 MeV equivalent neutron fluence of 2.52 × 10¹⁵ n/cm². In order to assess the radiation …

Using Mavt To Incorporate Public Perception When Choosing A Nuclear Fuel Cycle, Stephen Clement

Theses and Dissertations

Nuclear energy is a source of carbon free power. With many countries striving to make deep carbon cuts in their energy sectors, nuclear energy could be a large part of the solution. One of the main obstacles standing in the way of the use of nuclear energy is the issue of used nuclear fuel disposal. According to the NEI, the U.S. creates about 2000 metric tons of used nuclear fuel per year and has generated around 76,000 metric tons of used nuclear fuel over the last 4 decades. While there are technical problems that need to be solved, it is …

Magnetic Materials Characterization And Modeling For The Enhanced Design Of Magnetic Shielding Of Cryomodules In Particle Accelerators., Sanjay K. Sah

Theses and Dissertations

Particle accelerators produce beams of high-energy particles, which are used for both fundamental and applied scientific research and are critical to the development of accelerator driven sub-critical reactor systems. An effective magnetic shield is very important to achieve higher quality factor (Qo) of the cryomodule of a particle accelerator. The allowed value of field inside the cavity due to all external fields (particularly the Earth’s magnetic field) is ~15 mG or less. The goal of this PhD dissertation is to comprehensively study the magnetic properties of commonly used magnetic shielding materials at both cryogenic and room temperatures. This knowledge can …

Analysis Of Pellet Cladding Interaction And Creep Of U3si2 Fuel For Use In Light Water Reactors, Kathryn E. Metzger

Theses and Dissertations

Following the accident at the Fukushima plant, enhancing the accident tolerance of the light water reactor (LWR) fleet became a topic of serious discussion. Under the direction of congress, the DOE office of Nuclear Energy added accident tolerant fuel development as a primary component to the existing Advanced Fuels Program. The DOE defines accident tolerant fuels as fuels that “in comparison with the standard UO2- Zircaloy system currently used by the nuclear industry, can tolerate loss of active cooling in the reactor core for a considerably longer time period (depending on the LWR system and accident scenario) while maintaining or …

Dosimetry, Activation, And Robotic Instrumentation Damage Modeling Of The Holtec Hi-Storm 100 Spent Nuclear Fuel System, C. Ryan Priest

Theses and Dissertations

The Holtec HI-STORM 100 spent fuel storage system is an intermediate storage mechanism for SNF assemblies. Long term licensing and storage requires consideration of material degradation of the stainless steel multi-purpose canister holding the spent fuel. This material degradation is predicted to take the form of environmentally assisted cracking on weld interfaces of the stainless steel cylinder. Several of these spent fuel storage arrays are located in coastal environments. These sites include both the Hope Creek and Diablo Canyon nuclear power stations. A multi-sensory robotic package is being designed for non-destructive assay of the cask annular environment. It will be …

Deformation Induced Martensitic Transformation In 304 Stainless Steels, Junliang Liu

Theses and Dissertations

304 stainless steel is an austenitic steel widely used for various applications due to a good combination of strength and ductility and relative low cost. It is known to be metastable as the austenite phase can transform into martensite under stress. In this work, a new method (in-situ tensile TEM) and the traditional method (ex-situ tensile tests and TEM, XRD characterization) were used to investigate the mechanisms of deformation-induced martensitic transformation in 304SS samples at different temperatures.

The ex-situ tensile tests were conducted under a strain rate of 10-3 s-1 until rupture. After the tensile tests, the fractured area was …

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 …

Electrochemical Studies Of Cerium And Uranium In Licl-Kcl Eutectic For Fundamentals Of Pyroprocessing Technology, Dalsung Yoon

Theses and Dissertations

Understanding the characteristics of special nuclear materials in LiCl-KCl eutectic salt is extremely important in terms of effective system operation and material accountability for safeguarding pyroprocessing technology. By considering that uranium (U) is the most abundant and important element in the used nuclear fuel, measurements and analyses of U properties were performed in LiCl-KCl eutectic salt. Therefore, the electrochemical techniques such as cyclic voltammetry (CV), open circuit potential (OCP), Tafel, linear polarization (LP), and electrochemical impedance spectroscopy (EIS) were conducted under different experimental conditions to explore the electrochemical, thermodynamic, and kinetic properties of U in LiCl-KCl eutectic. The ultimate goal …

Intercode Advanced Fuels And Cladding Comparison Using Bison, Frapcon, And Femaxi Fuel Performance Codes, Aaren Rice

Theses and Dissertations

The high density uranium-based fuels are regaining popularity as the current fleet of LWR’s are showing interest in uprating plants to increase accident tolerance and performance. Fuels such as U3Si2, UN, and UC all contain a higher uranium loading and thermal conductivity than that of UO2 making them attractive in combination with an advanced cladding type such as the ceramic SiC cladding. In addition to adding more mass uranium to the core without surpassing current enrichment limits, these advanced fuels and claddings are designed with increased accident tolerance performance in a LOCA type scenario in mind. One of the possible …

Multidimensional Analysis Of Nuclear Detonations, Robert C. Slaughter

Theses and Dissertations

The focus of this research is to develop the methods for 3-dimensional reconstructions and temperature distributions of early time nuclear fireballs. Initial developments have resulted in the first 2-dimensional temperature distribution of a nuclear fireball using digitized film. This same process was then extended to perform the first limb darkening calculations of nuclear fireballs. Limb darkening coefficients were then used to derive a temperature profile of the nuclear fireball as a function of optical path length. A 3-dimensional reconstruction was performed using a variation of a structure from illuminance technique in combination with limb darkening coefficients to produce structure using …

Coupling Nuclear Induced Phonon Propagation With Conversion Electron Mössbauer Spectroscopy, Michael J. Parker

Theses and Dissertations

Mössbauer spectroscopy is a very sensitive measurement technique (10^-8 eV) which prompted motivation for the experiment described in this thesis. Namely, can a sensitive detection system be developed to detect nuclear recoils on the order of 10 to 100 of eVs? The hypothesis that this thesis tests is: Nuclear induced phonon bursts caused by Rutherford scattered alphas, decayed from ²⁴¹Am, in a type-310 stainless steel material can couple with 7.3 keV conversion electron Mössbauer events at the other end of the material which will have a statistically significant effect on a Mössbauer spectrum. The phonon bursts produced by …

Surface Geometry And Chemistry Of Hydrothermally Synthesized Single Crystal Thorium Dioxide, Scott W. Key

Theses and Dissertations

The surface chemistry and geometry of hydrothermally grown, single crystal ThO2 was studied using X-ray Photoemission Spectroscopy (XPS) and Atomic Force Microscopy (AFM). The crystal was studied before and after sputter etching with Ar⁺, heating up to 675 K, and dehydration with dry nitrogen. The hydrothermal growth technique incorporated Cs and F into the near surface bulk. Heating to 675 K drove off the F, but did not the Cs. Sputtering with Ar⁺ at 75° cleaned the crystal and created a more uniform surface geometry. The Th 4f peak resolution, as measured by XPS improved by …

The Effect Of Anisotropic Scatter On Atmospheric Neutron Transport, Nicholas J. Mcintee

Theses and Dissertations

Anisotropy is present in the angular distributions of neutrons departing from a nuclear scattering event. This anisotropy cannot be defined in a closed-form solution, and it is dependent on the incident neutron energy, elastic or inelastic scatter, along with the inelastic level, and the species struck. The underlying question is, if anisotropic behavior is worth the computational cost to be included in certain simulations, and if so, what level of precision is effected by the inclusion of anisotropic scatter. A Watt spectrum of U²³⁵ fission neutrons was examined as it collided with species in a nitrogen-oxygen atmosphere. In a …

Ionizing And Non-Ionizing Radiation Effects In Thin Layer Hexagonal Boron Nitride, Brian L. Barnett

Theses and Dissertations

The radiation response of 14nm h-BN/Si metal insulator semiconductor (MIS) devices was investigated using current-voltage and capacitance-voltage measurements indicating Frenkel Poole (FP) and Fowler-Nordheim tunneling (FNT) are the primary current mechanisms before and after irradiation. The data were fit to a composite model of FP and FNT currents. Irradiations to 33.1, 99.3, and 331 krad(Si) from a cobalt-60 source causes a negative voltage shift to the current-voltage measurements of -0.14, -0.45, and -0.46 V respectively. The negative shift indicates radiation induced production of positive space charge at the h-BN/Si interface. No device characteristic changes were observed following gamma irradiation. Fitting …

Incorporating Public Perceptions Into The Selection Of A Nuclear Fuel Cycle, John M. Swanson

Theses and Dissertations

The final disposal location for used nuclear fuel in the U.S. remains unresolved. A major complication in resolving this issue has historically been the lack of public acceptance. This motivates the creation of a decision making model for selecting a nuclear fuel cycle in the U.S. that incorporates the preferences of the public. A model based on the Analytic Hierarchy Process (AHP) was created, tested, and shown to be problematic in incorporating public opinion into decision objectives. A new model based on Multi-Attribute Utility Theory (MAUT) has been created. This model contains the fundamental objectives for both technical and non-technical …