Nuclear Engineering Commons^™

Development Of An Unmanned Aerial System For Radiation Mapping In Nuclear Facilities, Jackson Ball, Guangying Jiang, Robert Bean

The Summer Undergraduate Research Fellowship (SURF) Symposium

Efficiently planning a decontamination and decommissioning (D&D) operation at a nuclear facility requires detailed information on the conditions present. In the wake of a disaster, or just years of abandonment, a facility’s layout may have dramatically changed, making previous facility drawings unreliable, and radioactive particles may have been spread over the site, contaminating equipment and structures. Rather than tasking workers with mapping and characterizing the contamination, which can take days or weeks and poses a health and safety risk to the workers, mapping the site and locating contamination can be done remotely by an unmanned aerial vehicle (UAV), which would …

Numerical Simulations Of Transcritical Natural Convection, Ruiwen Wei, Carlo Scalo, Mario Tindaro Migliorino, Kukjin Kim, Jean-Pierre Hickey

The Summer Undergraduate Research Fellowship (SURF) Symposium

In modern engineering applications, system overheating is a key issue that needs to be solved with efficient and reliable cooling technologies. Among the possible mechanisms that these are based on, natural convection cooling is one of the most frequently employed, with applications ranging from cooling of computer micro-components to large nuclear reactors. While many studies have been performed on natural convection employing supercritical or subcritical fluids, little attention has been given to fluids in their transcritical regime. The latter has the potential to yield high performances while avoiding detrimental effects of two-phase systems (e.g. cavitation). In the present study, 2D …

Verification Of Tfit Code Numerical Method For Flow Excursion Simulation, Patrick S. Foster, Subash Sharma, Martin L. Bertodano

The Summer Undergraduate Research Fellowship (SURF) Symposium

This research is aimed towards accurately modeling and predicting the onset of the two-phase flow excursion instability using the code TFIT (Two Fluid Interfacial Temperature). In order to do this we first had to show that the numerical diffusion of the code’s finite difference equations could be reduced to an insignificant level by decreasing the mesh size.

Understanding and being able to accurately model flow excursion can help us understand how to prevent the potential negative effects of this instability. We are using a two-fluid model with physics-based closure relations. The results will be validated against the experimental data available …

Comparison Of Pm-Hip To Cast Alloy 625 For Nuclear Applications, Alexander L. Bullens, Keyou Mao, Janelle P. Wharry, Esteban Bautista

The Summer Undergraduate Research Fellowship (SURF) Symposium

PM-HIP, or Powder Metallurgy and Hot Isostatic Pressing, metals have been a low cost alternative to forged and cast structural metals within various industries. The nuclear industry has recently developed interest in PM-HIP alloys, but further research needs to be done to quantify their mechanical properties and characterize the microstructure. Specifically, we must understand the mechanical and microstructural evolution of PM-HIP materials after long-term operation at the elevated temperatures that PM-HIP components will experience in service. We focus on Ni-base alloy Inconel 625, and compare the PM-HIP version to the cast version. Our methodology consists of annealing samples to various …

Electrical Characterization Of Irradiated Semiconducting Amorphous Hydrogenated Boron Carbide, George Glen Peterson

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Semiconducting amorphous partially dehydrogenated boron carbide has been explored as a neutron voltaic for operation in radiation harsh environments, such as on deep space satellites/probes. A neutron voltaic device could also be used as a solid state neutron radiation detector to provide immediate alerts for radiation workers/students, as opposed to the passive dosimetry badges utilized today. Understanding how the irradiation environment effects the electrical properties of semiconducting amorphous partially dehydrogenated boron carbide is important to predicting the stability of these devices in operation. p-n heterojunction diodes were formed from the synthesis of semiconducting amorphous partially dehydrogenated boron carbide on silicon …

Evaluation And Enhancement Of Clean Energy Systems: Analytical, Computational And Experimental Study Of Solar And Nuclear Cycles, Nima Fathi

Mechanical Engineering ETDs

Clean (and specifically renewable) energy is steadily improving its global share. However, finite availability of fossil fuels and the growing effects of climate change make it an urgent priority to convince the industry and governments to incentivize investment in the renewable energy field and to make it more attractive by decreasing the capital cost. Until recently, uncertainties in funding limited renewable energy development, especially in the US. That limitation has been one of the barriers to progress. Another limitation of many renewable energy systems is the variability in their output, which makes them unsuitable for baseline power production. Therefore, fossil …

Time And Energy Characterization Of A Neutron Time Of Flight Detector Using A Novel Coincidence Method For Constraining Neutron Yield, Ion Temperature And Liner Density Measurements From Maglif Experiments, Jedediah Styron

Nuclear Engineering ETDs

The focus of this work is the characterization of a typical neutron time-of-flight (NTOF) detector that is fielded on inertial confinement fusion (ICF) experiments conducted at the Z-experimental facility with emphasis on the Magnetized Liner Fusion (MagLIF) concept. An NTOF detector consisting of EJ-228 scintillator and two independent photomultiplier tubes (PMTs), a Hamamatsu-mod 5 and Photek-PMT240, has been characterized in terms of the absolute time and energy response. The characterization was done by measuring single, neutron-induced events in the scintillator by measuring the alpha particle and neutron produced from the D-T reaction in kinematic coincidence. The results of these experiments …

Examination Of Color Center Formation In Caf2 Crystals When Exposed To Gamma And Mixed Neutron/Gamma Fields, Sara M. Pelka

Nuclear Engineering ETDs

Color centers in CaF₂ were studied in this work, in parallel with examinations of changes in the refractive index of the crystals by the larger research group, after they were subjected to radiation. Color centers induced by gamma rays and in mixed neutron-gamma fields were studied in CaF₂ and LiF using transmittance and absorbance spectra. The goals were to examine both neutron and neutron-gamma mixed field irradiations to be able to isolate neutron only effects and to correlate these color center effects with refractive index effects studied by our larger collaboration. Irradiation sources include ¹³⁷Cs, DD and …

Nuclear Weapons In A Changing Climate: Probability, Increasing Risks, And Perception, Adam Liska, Tyler R. White, Eric Holley, Robert J. Oglesby

Adam Liska Papers

Many people tend to think that the outcome of any nuclear weapons use today will result in an escalatory situation with apocalyptic outcomes for the countries involved. Yet many factors are increasing the probability of the limited use of nuclear weapons (e.g., 1 to 20 warheads) in a range of conflict scenarios. Previous atmospheric model simulations of regional nuclear conflicts employing many relatively small bombs have been estimated to cause a global “nuclear autumn,” with great reductions in agricultural productivity, stratospheric ozone loss, and spread of hazardous radioactive fallout. The totality of these effects would result in widespread damage …

High Precision Refractive Index Measurement Techniques Applied To The Analysis Of Neutron Damage And Effects In Caf2 Crystals, Joseph P. Morris Ph.D.

Nuclear Engineering ETDs

Neutron irradiation damages material by atomic displacements. The majority of these damage regions are microscopic and difficult to study, though they can cause a change in density and thus a change in refractive index in transparent materials. This work utilized CaF₂ crystals to track refractive index change based on neutron radiation dose. High precision refractive index measurements were performed utilizing a nested-cavity mode-locked laser where the CaF₂ crystal acted as a Fabry-Pérot Etalon (FPE). By comparing the repetition rate of the cavity and the repetition rate of the FPE, refractive index change was determined. Following several irradiation experiments, …

Initiating Event Analysis Of A Lithium Fluoride Thorium Reactor, Nicholas Charles Geraci

Engineering Management & Systems Engineering Theses & Dissertations

The primary purpose of this study is to perform an Initiating Event Analysis for a Lithium Fluoride Thorium Reactor (LFTR) as the first step of a Probabilistic Safety Assessment (PSA). The major objective of the research is to compile a list of key initiating events capable of resulting in failure of safety systems and release of radioactive material from the LFTR.

Due to the complex interactions between engineering design, component reliability and human reliability, probabilistic safety assessments are most useful when the scope is limited to a single reactor plant. Thus, this thesis will study the LFTR design proposed by …

Identification Of Key Drivers For Municipal Utility Performance, Jasmin Alsaied

Pursuit - The Journal of Undergraduate Research at The University of Tennessee

This report explores the various performance indicators for municipal electric utilities and the greatest impact financial investments can make for improving these indicators. A literature search provided key detail about performing an analysis that would prove useful to utilities. The analysis identifies key performance indicators that allowed for the most prudent of investments. Data mining techniques and statistical analyses were performed on data sets concerning the 51 North Carolina municipal electric utilities to identify several key ratios and performance indicators that have the greatest impact on cost of service, system reliability, and customer satisfaction. Statistical analyses were used to determine …

An Exact Analysis For Four-Order Acousto-Optic Bragg Diffraction Which Incorporates Both Incident Light Angle And Sound Frequency Dependencies, Adeyinka Sunday Ademola

Electrical Engineering Theses

This thesis extends the prior work which produced an exact solution to the four-order acousto-optic (AO) Bragg cell with assumed fixed center frequency and with exact Bragg angle incident light. The extension predicts the model that incorporates the dependencies of both the input angle of light and the sound frequency. Specifically, a generalized 4^th order linear differential equation (DE), is developed from a simultaneous analysis of four coupled AO system of DEs. Through standard methods, the characteristic roots, which requires solving a quartic equation, is produced. Subsequently, a derived system of homogeneous solutions, which absorbs the roots obtained using …

Computer Simulation Of Pore Migration Due To Temperature Gradients In Nuclear Oxide Fuel, Ian Wayne Vance

Graduate Theses and Dissertations

A phase-field simulation model is being presented that captures the thermal-gradient-driven migration of pores in oxide fuel associated with fuel restructuring. The model utilizes a Cahn-Hilliard equation supplemented with an advection term to describe the vapor transport of fuel material through the pore interior due to gradients in vapor pressure. In addition, the model also captures changes in a migrating pores’ morphology. Simulations demonstrate that the model successfully predicts pore migration towards the hottest portion of the fuel, the centerline. The simulations also demonstrate changes in pore shape that are in agreement with previous experimental observations. Initially isotropic pores are …

Numerical Simulation Of Metallic Uranium Sintering, Bruce Berry

Graduate Theses and Dissertations

Conventional ceramic oxide nuclear fuels are limited in their thermal and life-cycle properties. The desire to operate at higher burnups as is required by current utility economics has proven a formidable challenge for oxide fuel designs. Metallic formulations have superior thermal performance but are plagued by volumetric swelling due to fission gas buildup. In this study, we consider a number of specific microstructure configurations that have been experimentally shown to exhibit considerable resistance to porosity loss. Specifically, a void sizing that is bimodally distributed was shown to resist early pore loss and could provide collection sites for fission gas buildup. …

Fast Neutron Detection In Nuclear Material Photofission Assay Using A 15 Mev Linear Electron Accelerator, Matthew Steven Hodges

UNLV Theses, Dissertations, Professional Papers, and Capstones

The purpose of this research was to use a 15 MeV (K15 model by Varian) linear electron accelerator (linac) for the photon assay of special nuclear materials (SNM). First, the properties of the photon radiation probe were determined. The stochastic radiation transport code, MCNP5, was used to develop computational models for the linac. The spectral distribution of photons as well as dose rate contour maps of the UNLV accelerator facility were computed for several linac operating configurations. These computational models were validated through comparison with experimental measurements of dose rates.

The linac model was used to simulate the photon interrogation …

Analysis Of The Temporal Response Of Coupled Asymmetrical Zero-Power Subcritical Bare Metal Reactor Systems, Kimberly Lynn Klain

UNLV Theses, Dissertations, Professional Papers, and Capstones

The behavior of symmetrical coupled-core systems has been extensively studied, yet there is a dearth of research on asymmetrical systems due to the increased complexity of the analysis of such systems. In this research, the multipoint kinetics method is applied to asymmetrical zero-power, subcritical, bare metal reactor systems. Existing research on asymmetrical reactor systems assumes symmetry in the neutronic coupling; however, it will be shown that this cannot always be assumed. Deep subcriticality adds another layer of complexity and requires modification of the multipoint kinetics equations to account for the effect of the external neutron source. A modified set of …

Applications Of Elpasolites As A Multimode Radiation Sensor, Amber Lynn Guckes

UNLV Theses, Dissertations, Professional Papers, and Capstones

This study consists of both computational and experimental investigations. The computational results enabled detector design selections and confirmed experimental results. The experimental results determined that the CLYC scintillation detector can be applied as a functional and field-deployable multimode radiation sensor.

The computational study utilized MCNP6 code to investigate the response of CLYC to various incident radiations and to determine the feasibility of its application as a handheld multimode sensor and as a single-scintillator collimated directional detection system. These simulations include:

• Characterization of the response of the CLYC scintillator to gamma-rays and neutrons;

• Study of the isotopic enrichment of …

Experimental And Computational Investigations Of Heat Transfer Systems In Fluoride Salt-Cooled High-Temperature Reactors, Joel T. Hughes

Nuclear Engineering ETDs

Fluoride salt-cooled high-temperature reactors (FHRs) face a number of challenges similar to those faced by other Generation IV advanced reactor concepts. Predicting heat transfer in these systems accurately and reliably is one major challenge. Another is ensuring the safety of these systems during challenging operating conditions across the design basis envelope. Finally, achieving good economics to compete in a modern power generation portfolio is necessary for moving any nuclear power plant concept past the pre-conceptual stage. This dissertation attempts to support, from a thermal-hydraulics research standpoint, the case that the FHR can attain these goals. The dissertation focuses on several …

Structural Evolution Of Tungsten Surface Exposed To Sequential Low-Energy Helium Ion Irradiation And Transient Heat Loading, G Sinclair, J K. Tripathi, P K. Diwakar, M Wirtz, J Linke, A Hassanein

School of Nuclear Engineering Faculty Publications

Structural damage due to high flux particle irradiation can result in significant changes to the thermal strength of the plasma facing component surface (PFC) during off-normal events in a tokamak. Low-energy He+ ion irradiation of tungsten (W), which is currently the leading candidate material for future PFCs, can result in the development of a fiber form nanostructure, known as “fuzz”. In the current study, mirror-finished W foils were exposed to 100 eV He+ ion irradiation at a fluence of 2.6 × 1024 ions m−2 and a temperature of 1200 K. Then, samples were exposed to two different types of …