Physical Sciences and Mathematics Commons^™

Genetic Algorithm Optimization Of Experiment Design For Targeted Uncertainty Reduction, Alexander Amedeo Depillis

Masters Theses

Nuclear cross sections are a set of parameters that capture probability information about various nuclear reactions. Nuclear cross section data must be experimentally measured, and this results in simulations with nuclear data-induced uncertainties on simulation outputs. This nuclear data-induced uncertainty on most parameters of interest can be reduced by adjusting the nuclear data based on the results from an experiment. Integral nuclear experiments are experiments where the results are related to many different cross sections. Nuclear data may be adjusted to have less uncertainty by adjusting them to match the results obtained from integral experiments. Different integral experiments will adjust …

Multi-Objective Radiological Analysis In Real Environments, David Raji

Doctoral Dissertations

Designing systems to solve problems arising in real-world radiological scenarios is a highly challenging task due to the contextual complexities that arise. Among these are emergency response, environmental exploration, and radiological threat detection. An approach to handling problems for these applications with explicitly multi-objective formulations is advanced. This is brought into focus with investigation of a number of case studies in both natural and urban environments. These include node placement in and path planning through radioactivity-contaminated areas, radiation detection sensor network measurement update sensitivity, control schemes for multi-robot radioactive exploration in unknown environments, and adversarial analysis for an urban nuclear …

Understanding The Impact Of Divertor And Main Chamber Ion Fluxes On Divertor Closure In The Diii-D Tokamak, Kirtan M. Davda

Doctoral Dissertations

The diverted tokamak redirects extreme heat and particles to targets, a plasma-facing component designed for such loads. Here, the local fluxes produce strong particle recycling and sputtering. Recycled neutrals can “leak” into the region between the core and wall, the scrape-off-layer (SOL), impacting plasma performance. Increasing divertor closure can reduce leakage by containing neutrals within the divertor. However, there exists a need to quantify divertor baffle restrictions and understand closure directly from empirical data as opposed to indirectly through modeling.

Our study introduces the Geometric Restriction Parameter (GRP) based on simplifying neutral transport to ballistic pathways. Specifically, it considers the …

Radiation Exposure Calibration Of The Al2o3:C With Radium-226 And Cesium-137 Using The Osl Method, Selma Tepeli Aydin

All Theses

Optically stimulated luminescence (OSL) dosimetry was utilized to calibrate Al₂O₃:C powder dosimeters, available commercially as the nanoDot® from Landauer Inc., and compare the dosimeter response to radium-226 (²²⁶Ra) and cesium-137 (¹³⁷Cs). The signal from the OSL was quantified using a microSTARii^® OSL reader also produced by Landauer Inc. Dose-response curves were developed for ²²⁶Ra and ¹³⁷Cs experiments (5 dosimeters each) at thirteen absorbed doses. Individual dosimeter response was tracked by serial number. Linear regression analysis was performed to determine if there were significant differences between the intercepts of the …

Direct Measurement Of The 114cd(N, Gamma)115cd Cross Section In The 1 Ev To 300 Kev Energy Range, Kofi Tutu Addo Assumin-Gyimah

Theses and Dissertations

The large thermal cross section of cadmium makes it ideal for many practical applications where screening of thermal neutrons is desired. For example, in non-destructive assay techniques, or for astrophysical studies of the s-process. All such applications require precise knowledge of the neutron-capture cross section on cadmium. Although there are some data on neutron-capture cross sections particularly at thermal energies and at energies relevant for astrophysics, there is very little data at most other energies. Further, the evaluated cross sections from the ENDF and JENDL databases disagree at high energies. Therefore, there is a critical need for precise knowledge of …

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 …

Fabrication, Measurements, And Modeling Of Semiconductor Radiation Detectors For Imaging And Detector Response Functions, Corey David Ahl

Doctoral Dissertations

In the first part of this dissertation, we cover the development of a diamond semiconductor alpha-tagging sensor for associated particle imaging to solve challenges with currently employed scintillators. The alpha-tagging sensor is a double-sided strip detector made from polycrystalline CVD diamond. The performance goals of the alpha-tagging sensor are 700-picosecond timing resolution and 0.5 mm spatial resolution. A literature review summarizes the methodology, goals, and challenges in associated particle imaging. The history and current state of alpha-tagging sensors, followed by the properties of diamond semiconductors are discussed to close the literature review. The materials and methods used to calibrate the …

Total Absorption Spectroscopy Of Mo-106 And Tc-106, Michael Cooper

Doctoral Dissertations

Total absorption spectroscopy is a method of gamma-ray spectroscopy that has gained prominence in the past several decades, as nuclear data revisions are performed on older nuclear data, which is often incomplete. A strong understanding of underlying nuclear data, particularly fission and beta decay data, is essential for nuclear reactors and nuclear fuel decay heat. This PhD work involves the analysis of fission fragments 106Mo [Mo-106] and 106Tc [Tc-106]. These neutron rich isotopes contribute upwards of 6% of the cumulative fission yield of 241Pu [Pu-241] fission, and 4% of 239Pu [Pu-239] fission. Prior data for these two fission fragments only …

Pulsed Power Neutron Production With Deuterated Polymer Accelerator Targets, Anthony O. Hagey

Theses and Dissertations

This document presents an investigation of the effect of deuterated polyethylene accelerator targets on the neutron fluence from a local mass injection dense plasma focus driven by the United States Naval Research Laboratory’s Hawk pulsed-power generator. After successful production of thin targets, the acquisition of thicker targets, and testing inside Hawk, it was found that the presence of a deuterated polyethylene target increased the neutron fluence. Results suggested that fluence can significantly increase with the presence of a deuterated target vs a nondeuterated target. Additive manufacturing printing was used as a production method in order to determine if deuterated accelerator …

A Method For Monte Carlo Neutral Particle Radiation Transport In A Variable Density Atmosphere, Aiden B. Edens

Theses and Dissertations

This study focuses on accurately simulating the transport of radiation in the atmosphere to better understand the effects of nuclear weapons. The variable nature of the atmosphere poses a challenge in accurately simulating the prompt radiation following a nuclear explosion. To address this challenge, the Mass Integral Scaling technique is integrated with the Monte Carlo method to perform calculations in a variable density atmosphere. In addition to previous free-field estimates, this work also enables the simulation of transport calculations with other media, such as clouds. Results of neutron and photon fluence have been verified against the standard version of MCNP …

Simulation Of Neutron Generation From Laser-Driven Fusion In A Liquid D2o Sheet Using Novel Warpx Module, Colton R. Stoner

Theses and Dissertations

Using WarpX’s new nuclear fusion module, this work attempts to model an experimental system at the ELL at the AFIT with WarpX and draw conclusions about fusion products from resulting simulations. Recently, a table-top, high repetition rate, mixed radiation source was demonstrated at the ELL employing a HIL to fuse the deuterium nuclei present in a unique liquid target of heavy water. Analysis of the simulations predicted an isotropic output of neutrons from deuterium-deuterium fusion. These simulated neutrons were created in tens of femtoseconds from dense bodies of deuterons that were perturbed by the laser. However, it was found that …

Automated Additive Layering Of Vat Polymerized Plastic Organic Scintillators, Chandler J. Moore

Theses and Dissertations

The current technology for fast neutron detection imaging is limited in achieving the required high spatial resolution, strong neutron discrimination, and practical time of manufacturing. Traditional fabrication methods require days of thermal polymerization and hundreds of man-hours to produce average resolution pixelated scintillator arrays. The present work helps to eliminate this limitation by developing an additive manufacturing technique to construct such detectors for use in in dual particle imaging applications. In this work, fast-, light-curing resins are used in a prototype automated assembly machine, capable of layering of individual light-cured resin layers and optical segmentation with a self-bonded specular reflector, …

The Effect Of Ionization Density In Applications Of Radiation Detection, Dosimetry, And Therapy, Daniel Mulrow

Arts & Sciences Electronic Theses and Dissertations

This dissertation covers a wide range of topics but is linked by the common theme of radiation interacting with materials and studying the result of those interactions. The introduction describes the fundamentals of how radiation interacts with material and how we are able to detect that radiation and the application of how we use those interactions in radiation oncology. The thesis starts with a chapter detailing the temperature dependence of the photophysics in two organic scintillators. This chapter is the foundation for a future study that will look the degree to which these scintillators can distinguish between gammas and neutrons …

Near-Ir Laser Ablation Of Simulated Radiologically Contaminated Oxides On Carbon Steel Feeder Pipes, Thao Viet Do

Electronic Thesis and Dissertation Repository

As nuclear power plants age and retire from service, many countries face significant challenges concerning the safe long-term storage and disposal of large volumes of low and intermediate level radioactive wastes (L&ILW). The volumes of metallic waste are of particular concern, as when metal corrodes it produces hydrogen that could lead to pressure build-up in interim storage and disposal. In Canada, a significant fraction of the metallic wastes for Canada Deuterium Uranium (CANDU) nuclear reactors are out-of-core reactor components, such as carbon steel (CS) feeder pipes. The radioactive contamination is expected to be largely confined to the surface oxide layers …

Enabling Rapid Chemical Analysis Of Plutonium Alloys Via Machine Learning-Enhanced Atomic Spectroscopy Techniques, Ashwin P. Rao

Theses and Dissertations

Analytical atomic spectroscopy methods have the potential to provide solutions for rapid, high fidelity chemical analysis of plutonium alloys. Implementing these methods with advanced analytical techniques can help reduce the chemical analysis time needed for plutonium pit production, directly enabling the 80 pit-per-year by 2030 manufacturing goal outlined in the 2018 Nuclear Posture Review. Two commercial, handheld elemental analyzers were validated for potential in situ analysis of Pu. A handheld XRF device was able to detect gallium in a Pu surrogate matrix with a detection limit of 0.002 wt% and a mean error of 8%. A handheld LIBS device was …

Tokamak 3d Heat Load Investigations Using An Integrated Simulation Framework, Thomas Looby

Doctoral Dissertations

Reactor class nuclear fusion tokamaks will be inherently complex. Thousands of interconnected systems that span orders of magnitude in physical scale must operate cohesively for the machine to function. Because these reactor class tokamaks are all in an early design stage, it is difficult to quantify exactly how each subsystem will act within the context of the greater systems. Therefore, to predict the engineering parameters necessary to design the machine, simulation frameworks that can model individual systems as well as the interfaced systems are necessary. This dissertation outlines a novel framework developed to couple otherwise disparate computational domains together into …

Wetland Uranium Transport Via Iron-Organic Matter Flocs And Hyporheic Exchange, Connor J. Parker

All Dissertations

Uranium (U) released from the M-Area at the Department of Energy Savannah River Site into Tims Branch, a seasonal wetland and braided stream system, is estimated to be 43,500 kg between 1965 and 1984. The motivation for this work is the uranium’s persistence in the wetland for decades, where it is estimated that 80% of the U currently remains in the Tims Branch wetland. U has begun to incorporate into wetland iron (Fe) and carbon cycles, associating with local Fe mineralogy and deposits of rich wetland organic matter (OM). The objective of this work is to characterize the chemical phases …

Enigma - Ongoing Development Towards Novel Beta-Decay Spectroscopy Station At Isolde, Philipp Wagenknecht

Masters Theses

Beta decay and collinear laser spectroscopy are proven efficient tools to study nuclear structure far from stability. Two areas of significance are investigations into nuclear deformation and shape coexistence, as well as delayed neutron emissions used in nuclear energy applications. This contribution presents the ongoing development towards a novel beta-decay spectroscopy station for the VITO experiment at CERN’s radioactive ion beam facility ISOLDE. The setup will utilize both collinear laser spectroscopy and beta-decay spectroscopy to measure the energy and spin-parities of the ground and excited states of radioactive beams. Initial designs of the support structure, magnetic field, and detector array …

Meta-Heuristic Optimization Techniques For The Production Of Medical Isotopes Through Special Target Design, Cameron Ian Salyer

Masters Theses

Medical isotopes are used for a variety of different diagnostic and therapeutic purposes Ruth (2008). Due to recent newly discovered applications, their production has become rapidly more scarce than ever before Charlton (2019). Therefore, more efficient and less time consuming methods are of interest for not only the industry’s demand, but for the individuals who require radio-isotope procedures. Currently, the primary source of most medical isotopes used today are provided by reactor and cyclotron irradiation techniques, followed by supplemental radio-chemical separations Ruth (2008). Up until this point, target designs have been optimized by experience, back of the envelope calculations, and …

A High Rate Pixelated Neutron Detector For Neutron Reflectometry At The Spallation Neutron Source, Su-Ann Chong

Doctoral Dissertations

This work presents the development of a high-rate 6Li-based pixelated neutron detector for neutron reflectometry instruments at the Spallation Neutron Source (SNS), Oak Ridge National Laboratory. The current detector technology falls short on the instrument requirements, particularly on the counting rate capability. This detector was designed specifically to overcome the limitation in counting rate by having a fully pixelated design from neutron conversion layer to photodetector and readout system. For the neutron converting layer, a 6Li-based neutron scintillator was used. Each scintillator element was coupled to a photodetector, in this case, a silicon photomultiplier (SiPM). The output of each SiPM …

Viability Of Energy And Fuel Sources For Interstellar Travel; Design And Feasibility Of The Construction Of Manned Interstellar Space Shuttles, Lukas Mittelman

UNLV Theses, Dissertations, Professional Papers, and Capstones

The importance of proving the viability of interstellar transport and addressing its potential hazards and pitfalls is immense. If we do not look toward the future and examine what could be waiting for us, we are doing our children, our children’s children, and so on, a disservice. Here we must attempt to lay the groundwork for our future scientists, engineers, and adventurers. Asking and answering questions like, which propulsion and energy systems must we incorporate to send us through the cosmos? Will we utilize technologies known today, such as fossil fuel rockets, fission or fusion rockets, and antimatter drives (pion …

Feasibility Of Fireball Trail Detection Using Ground-Based Gps Receivers, Ian R. Moffett

Theses and Dissertations

The feasibility of using GPS data to detect fireballs is analyzed by first modeling the fireball’s trail diffusion and plasma chemistry to get a resulting ion density profile of the trail over time. The signal perturbation caused by the fireball trail is simulated for a ground receiver using an analytic solution for diffraction from a Gaussian lens. Five cases were modeled with varying initial peak ion densities and altitudes taken from fireball and reentry vehicle data. This paper shows that it is feasible to detect a fireball trail using GPS if the fireball has a sufficiently high initial ion density, …

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 …

Effects Of Vacancies And Electron Temperature On The Electron Phonon Coupling In Cubic Silicon Carbide And Their Connection To The Inelastic Thermal Spike, Salah Al-Smairat

Doctoral Dissertations

“The electron-phonon interaction is an important interaction in many solids as it influences transport phenomena and related quantities such as the electrical and thermal conductivities, especially in nuclear and space applications. The importance of the electron-phonon interaction in primary damage production in 3C-SiC is the subject of this research.

The electron-phonon coupling factor was calculated using a hybrid Density Functional Perturbation Theory - Classical Electron Gas model. The coupling factor was calculated as a function of electron temperature in pristine and defective 3C-SiC, and relaxed defective cells. The electron-phonon coupling is found to depend strongly on the electronic temperature and …

Particle Swarm Optimization For Critical Experiment Design, Cole Michael Kostelac

Masters Theses

“Critical experiments are used by nuclear data evaluators and criticality safety engineers to validate nuclear data and computational methods. Many of these experiments are designed to maximize the sensitivity to a certain nuclide-reaction pair in an energy range of interest. Traditionally, a parameter sweep is conducted over a set of experimental variables to find a configuration that is critical and maximally sensitive. As additional variables are added, the total number of configurations increases exponentially and quickly becomes prohibitively computationally expensive to calculate, especially using Monte Carlo methods.

This work presents the development of a particle swarm optimization algorithm to design …

Impurity Production And Transport In The Prototype Material Plasma Exposure Experiment, Clyde J. Beers

Doctoral Dissertations

The Prototype Material Plasma Exposure eXperiment (Proto-MPEX) is a linear pulse plasma device at Oak Ridge National Laboratory with the purpose of doing the research and development for the heating concepts on the planned full MPEX device. The goal of MPEX is to perform material studies at fusion relevant conditions. To understand the conditions at the material target for performing plasma-material interaction studies the ion temperature and density, the electron temperature and density, and the particle flux and fluence must be known. Impurities within Proto-MPEX can alter the desired conditions at the material target and need to be understood for …

Production Of Protactinium-229 Via Deuteron Irradiation Of Thorium-232, Naser Burahmah

Doctoral Dissertations

²²⁵Ac [Actinium-225] is a promising radionuclide for targeted alpha therapy of cancer. ²²⁹Pa can lead to the production of ²²⁹Th [Thorium-229] and ²²⁵Ac [Actinium-225]. Deuteron bombardment on natural thorium targets has been investigated to measure cross sections of protactinium isotopes. In this work, ²²⁹Pa [Protactinium-229] excitation function was measured via deuteron energies up to 50 MeV [Mega electron volt] of thin thorium foils. The irradiation took place at Lawrence Berkeley National Laboratory’s (LBNL) 88-Inch Cyclotron. The target processing and analysis were performed at Oak Ridge National Laboratory (ORNL). The target consisted of 4 thin foils …

Neutron Energy Tuning Assemblies For Nuclear Weapon Environment Applications At The National Ignition Facility, Nicholas J. Quartemont

Theses and Dissertations

An energy tuning assembly was developed to spectrally shape the National Ignition Facility deuterium-tritium fusion neutron source to a notional thermonuclear and prompt fission neutron spectrum to fulfill neutron source capability gaps. The experimental neutron environment was characterized with activation dosimetry, neutronics and covariance models, and unfolded to determine the as-fielded neutron spectrum. The first energy tuning assembly was demonstrated to create synthetic spectrally accurate post-detonation fission products, enhancing U.S. technical nuclear forensics capabilities. ATHENA, a second-generation energy tuning assembly, was also optimized to meet similar objectives, but the new platform neutron fluence efficiency was increased by a factor of …

Fabrication Of Specialized Scintillators For Nuclear Security Applications, Cordell James Delzer

Doctoral Dissertations

Radiation detectors are important for a variety of fields including medical imaging, oil drilling, and nuclear security. Within nuclear security, they can serve a multitude of purposes whether that be imaging, localization, isotopic identification, or even just activity measurement. Even without directly seeing a nuclear material it is often able to notice their existence without a detector. Scintillators make up an important part of these detectors due to their large intrinsic efficiency, low cost, large volume, and relatively low upkeep. Due to the importance of the large number of purposes these scintillators may be used for, it can often be …

Collector Probe Measurements Of Sol Impurity Accumulation And The Implications Of Sol Flows On The Accumulation Amount, Shawn Zamperini

Doctoral Dissertations

A collector probe in its simplest form is a rod inserted into a plasma so that impurities are deposited onto it. These probes are then removed and analyzed to determine the deposition profile both along the length of probe and across the width of it. This dissertation covers a series of collector probes experiments and accompanying interpretive modelling all with the main goal of providing evidence for long-hypothesized near scrape-off layer (SOL) accumulation of impurities that can lead to efficient core contamination. The structure of this dissertation is as follows. A brief outline of fusion energy and why we need …