Engineering Commons^™

Methodology For Generating Simplified Cross Section Data Sets For Neutron Transport Calculations, Thomas Jay Harrison

Doctoral Dissertations

Neutron shielding problems involve radiation transport calculations over a wide range of energies. Fission neutrons have initial energy on the order of MeV, fusion neutrons have initial energy on the order of 10s of MeV, and space-origin neutrons have initial energy on the order of 100s of MeV or higher. Shielding calculations must track the neutrons from their initial energies until they are no longer of interest; for deep-penetration neutrons, this final energy can be on the order of eV before the neutron is no longer tracked. Thus, for deep-penetration space radiation shielding problems, the calculation may require tracking the …

Quantification Of Fast-Neutron Sources With Coded Aperture Imaging, Timothy Donald Jackson

Doctoral Dissertations

Quantification of the mass of plutonium in facilities that process plutonium is important for both nuclear safeguards concerns and safety concerns, and multiple methods to nondestructively quantify plutonium sample characteristics have been proposed, particularly when the sample is located directly adjacent to or within the measurement device. In prior work, coded-aperture fast neutron imaging has been developed to demonstrate the imaging of neutron emitting radiation sources in a qualitative fashion, where the sources may be located meters to tens of meters away. Building upon prior work, this work develops the use of a Maximum Likelihood Expectation Maximization (MLEM) reconstruction technique …

Study Of Secondary Particles Produced From Heavy-Ion Interactions, Pi-En Tsai

Doctoral Dissertations

The study of secondary particles produced from heavy-ion interactions is important in heavy ion radiotherapy, space radiation protection, and shielding at accelerator facilities. This dissertation focuses on the study of secondary neutron production as they are of special concern among all secondary particles.

The first part of this dissertation is the measurement of secondary neutrons created from ⁴He [helium] stopped in various target materials together with the model calculations accomplished by PHITS, FLUKA, and MCNP transport codes. The comparison results show that the physics models need improvements particularly in the predictions of 1) neutrons created from the ⁴He …

Development And Characterization Of A Directional Radiation Detection System Using A Fuzzy Logic Algorithm, Michael Joseph Willis

Doctoral Dissertations

Traditional radiation detection equipment consists of various types of devices that are capable of determining the presence of radioactive sources in the vicinity of the detection unit. Use of these systems typically consists of survey and search methods that employ broad area sweeps to narrow down the location of a radioactive source. Although these methods are effective, they are typically inefficient and lack the ability to produce a directional bearing of the source relative to the measurement location. More efficient methods that provide relative direction information for detected sources would facilitate a more timely response to a potential radiological threat. …

Ion Irradiation-Induced Microstructural Change In Sic, Chien-Hung Chen

Doctoral Dissertations

The high temperature radiation resistance of nuclear materials has become a key issue in developing future nuclear reactors. Because of its mechanical stability under high-energy neutron irradiation and high temperature, silicon carbide (SiC) has great potential as a structural material in advanced nuclear energy systems.

A newly developed nano-engineered (NE) 3C SiC with a nano-layered stacking fault (SFs) structure has been recently considered as a prospective choice due to enhanced point defect annihilation between layer-type structures, leading to outstanding radiation durability.

The objective of this project was to advance the understanding of gas bubble formation mechanisms under irradiation conditions in …

Ion Irradiation Characterization Studies Of Max Phase Ceramics, Daniel William Clark

Masters Theses

The family of layered carbides and nitrides known as MAX phase ceramics combine many attractive properties of both ceramics and metals due to their nanolaminate crystal structure and are promising potential candidates for application in future nuclear reactors. This thesis reports on the background, design, and analysis of an experiment focused on determining the effects of energetic heavy ion irradiations on polycrystalline samples of titanium silicon carbide 312, titanium aluminum carbide 312, and titanium aluminum carbide 211. The irradiation conditions consisted of ion doses between 10 and 30 displacements per atom at temperatures of 400 and 700 degrees Celsius, conditions …

Shielding Design For A Combined Accelerator And Physical Security Facility, Whitney J. Smith, Eric M. Welch, Zachary M. Weis, Jordan M. Parker, Isaac D. Mobley

Chancellor’s Honors Program Projects

No abstract provided.

Rapid Dissolution For Destructive Assay Of Nuclear Melt Glass, Jonathan Allen Gill

Masters Theses

This study evaluates four methods for dissolving complex glassy debris resulting from nuclear detonations. The samples of interest simulate the glassy debris generated from a nuclear detonation’s fireball coming in contact with solid masses. Each method attempts to achieve dissolution through different approaches involving either acid digestion, alkaline digestion, or molten salt fusion. Two of the four methods were modified to retain all elements of the debris or surrogate debris. This retention is critical to the proportional relationships used in identifying fuel types and designs of nuclear weapons. Analysis is conducted with an inductively coupled time of flight mass spectrometer …

Modeling And Simulation Of A Prototypical Advanced Reactor, Xiaotong Liu

Masters Theses

Current online risk monitors provide a point-in-time estimate of the system risk given the current plant configuration (e.g., equipment availability, operational regime, environmental conditions). However, these risk monitors do not account for plant- specific normal, abnormal, and deteriorating states of active components and systems. The lack of operating experience with proposed advanced reactor designs limits our ability to estimate the probability of failure (POF) of key components. Incorporation of unit-specific estimates of POF into dynamic probabilistic risk assessment (PRA) has the potential to enable real-time decisions about stress relief and to support effective maintenance planning while ensuring investment protection. The …

Kinetic And Thermodynamic Modeling Of Long Term Phase Stability In Alloy 800h Subjected To Lwr Core Conditions, Wayne Ethan Pratt

Masters Theses

An in depth literature review of Incoloy Alloy 800H was conducted and presented to summarize the current understanding of microstructural evolution under irradiation and secondary phase precipitate stability. Due to a lack of radiation induced segregation (RIS) data for Alloy 800H, Isopleth sections varying Cr, Ni, Ti, and Si were generated from a computational thermodynamics approach using ThermoCalc and analyzed to compensate for knowledge related to radiation induced precipitates (RIP’s). These isopleths were analyzed for a composition range based off previous knowledge of RIS tendencies in austenitic stainless steels. Analysis of four major binary phase diagrams and complex phase diagrams …

Template-Based Imaging Analysis Of Arbitrary Nuclear Material Configurations Using Time And Directionally-Tagged Fast Neutrons, Kirsten Elise Pena

Doctoral Dissertations

Reduction of nuclear material worldwide requires that robust methods for template measurement systems be developed. For nuclear material in metal form, two scenarios where it is necessary to verify and account for the material include storage and treaty verification. In both of these scenarios, the nuclear material’s high density, as well as possible heavy shielding or high radiation background, are obstacles to verifying the materials and configuration of an object with a high degree of confidence in a timely manner.

Addressing the need for confident verification, the template analysis method investigated in this work— the Kolmogorov-Smirnov (K-S) goodness-of-fit test—uses tagged …

Ion Irradiation Induced Damage And Dynamic Recovery In Single Crystal Silicon Carbide And Strontium Titanate, Haizhou Xue

Doctoral Dissertations

The objective of this thesis work is to gain better understanding of ion-solid interaction in the energy regime where electronic and nuclear energy loss are comparable. Such responses of materials to ion irradiations are of fundamental importance for micro-electronics and nuclear applications. The ion irradiation induced modification for the crystal structure, the physical and chemical properties etc. may strongly affect the performance of functional materials that needs to be better understood.

Experimentally, ion irradiation induced damage accumulation and dynamic recovery in SiC [silicon carbide] and SrTiO₃ [strontium titanate] were studied in this dissertation project. Five chapters are presented: Firstly, …

Disorder In Mg1-Xnixal2o4 Spinel And Its Impact On The Response To Swift Heavy Ion Irradiation, Brandon Alexander Perlov

Masters Theses

Spinels, which are currently used in optical applications, have many proposed functions in the nuclear industry, such as a nuclear waste form due to its radiation resistance. Disordering plays a key role in the response of spinel to a wide range of irradiation conditions. The first part of this research project was on characterizing the type and degree of disorder that can be induced by chemical substitution in the magnesium nickel aluminate spinel solid solution series (Mg(1-x)Ni(x)Al2O4). Neutron total scattering has been used to characterize the structure at both the cation and anion sublattices. High-resolution pair distribution function analysis was …

Sensitivity Analysis Of Fuel Cladding Temperature To Dry Cask Loading And Storage Conditions, Remy Russell Devoe

Masters Theses

Dry cask safety analyses and material degradation studies depend on reliable best- estimate thermal models. Gaps in design data and storage site conditions require analysts to frequently rely on bounding assumptions in thermal models that introduce bias to the results. Efforts to gather physical attributes of cask designs from vendors or experimental measurements can be costly and to determine all the uncertain parameters for a number of different cask designs is impractical. Measuring the sensitivity of peak cladding temperature to cask and fuel depletion modeling parameters was done to inform decision makers of which parameters that have the most impact …

Requirements For A Computer Code System For The Development And Maintenance Of Target Sets, Christopher Chwasz

Masters Theses

In the field of commercial nuclear reactor security, the concept of target sets has matured since its invention in the late 1980s and early 1990s to the codification of target set regulations by the United States Nuclear Regulatory Commission in 2009 and publishing of official guidance in 2010. Target sets have evolved into a complex and useful tool to develop and test a protective strategy. By their definition, target sets are the “minimum combination of equipment or operator actions which, if all are prevented from performing their intended safety function or prevented from being accomplished, would likely result in significant …

Characterization Of Mechanically Cooled High Purity Germanium (Hpge) Detectors At Elevated Temperatures, Joseph Benjamin Mccabe

Doctoral Dissertations

High resolution gamma spectroscopy is a tool used in nuclear security applications due to its achievable energy resolution and associated ability to identify special nuclear material. This identification ability is achieved by identifying the characteristic gamma-rays of a material. The challenges that have confronted industry concerning the use of hand-held high purity germanium (HPGe) in homeland security applications have centered on weight, geometry, and cool-down time. Typical liquid nitrogen cooled detectors ranging in size from 10% to 150% detectors will cool down sufficiently within 2-6 hours of filling. The cool-down time achieved in this research ranges from 45 min on …

Electronic Energy Loss Of Heavy Ions And Its Effects In Ceramics, Ke Jin

Doctoral Dissertations

Energy loss of medium energy heavy ions (i.e. Cl, Br, I, and Au) in thin compound foils containing light elements (i.e. silicon carbide and silicon dioxide) is directly measured using a time-of-flight elastic recoil detection analysis (ToF-ERDA) technique. An improved data analysis procedure is proposed to provide the experimentally determined electronic stopping powers. This analysis procedure requires reliable predictions of nuclear stopping. Thus, the nuclear stopping predicted by the Stopping and Range of Ions in Matter (SRIM) code is validated by measuring the angular distribution of 1 MeV Au ions after penetrating a thin silicon nitride foil, using a secondary …

Hybrid K-Edge Densitometry As A Method For Materials Accountancy Measurements In Pyrochemical Reprocessing, Matthew Tyler Cook

Doctoral Dissertations

Pyrochemical reprocessing is a proven method to recover useful fissile material from spent nuclear fuel. The process requires high temperatures and an inert atmosphere thus complicating the prospect of making materials accountancy measurements. Development of a measurement method for materials accountancy measurements has become necessary since pyroprocessing is receiving more attention as a possible compliment to aqueous reprocessing methods. If pyroprocessing is to be adapted from the engineering scale to a commercially viable reprocessing method a comprehensive safeguards measurement method and strategy must be developed.

Hybrid k-edge densitometry (HKED) has been applied to aqueous reprocessing measurements in commercial facilities. This …

Assessment Of Reactivity Equivalence For Enhanced Accident Tolerant Fuels In Light Water Reactors, Nathan Michael George

Doctoral Dissertations

The neutronic behavior of accident tolerant fuel (ATF) concepts was simulated in light water reactors (LWRs) to establish design parameters to match reactivity lifetime requirements of standard UO₂ [uranium dioxide]/Zircaloy fuel. The two concepts discussed in this dissertation are fully ceramic micro-encapsulated (FCM) fuel and alternate cladding concepts. To compare the required fuel alterations against standard UO₂/Zircaloy fuel, a 2D lattice-physics based reactivity equivalence method was established to estimate excess reactivity at the completion of each weighted batch cycle.

In the case of FCM fuel, the uranium-based tristructural isotropic (TRISO) kernel and the surrounding particle layers/matrix material …

Evaluation, Construction, And Verification Of A Subchannel Steady State Heat Transfer Code For Plate-Fueled Reactors, Cory Landon Griffard

Doctoral Dissertations

Several high performance research reactors use plate fuel that is clad with aluminum and cooled with forced convection of subcooled water. High resolution multiphysics simulation tools have been developed to allow the performance of the core in these reactors to be assessed in more detail. The high resolution multiphysics (HRMP) simulation tools must go through verification and validation (V&V) to ensure the additional detail of the outcomes is accompanied with quantifiable uncertainties and confidence intervals. As an example of V&V, a one-dimensional subchannel code with conventional engineering flow and heat transfer models may be used to check the performance of …

Molecular Dynamics Simulation Of Irradiation Damage In Multicomponent Alloys, Wei Guo

Doctoral Dissertations

The development of the generation IV reactors calls for radiation resistant materials. This thesis proposes that the newly developed single phase solid solution of high-entropy alloys (HEAs) can be such candidates. HEAs can undergo the crystalline to amorphous to crystalline (C-A-C) transitions under radiation. The radiation induced amorphous structure is a highly radiation resistant medium as shown by previous studies, and it further transforms to crystalline phases without much structural defects. In this thesis, by reviewing the formation rules of solid solutions and amorphous metallic glasses, it is suggested that the atomic size plays a key role affecting the C-A-C …

Doping Of Fluorchlorozirconate And Borate-Silica Glass Ceramics For Medical Imaging And Fast Neutron Scintillation, Julie Elizabeth Swafford

Masters Theses

Borate silica glass ceramics were produced for neutron scintillation. The Glass ceramics were doped with europium fluoride [EuF₂] and cerium chloride [CeCl₃]. Isotopic lithium fluoride [⁶LiF] and boron oxide [¹⁰B₂O₃] were used in most samples while non-isotopic lithium fluoride [LiF] and boron oxide [ B₂O₃] were used in the rest. When exposed to a neutron beam, samples doped with europium fluoride [EuF₂] scintillated while samples doped with cerium chloride [CeCl₃] did not. This contradicts current literature on fast scintillation. What …

User Perspective And Analysis Of The Continuous-Energy Sensitivity Methods In Scale 6.2 Using Tsunami-3d, Elizabeth Lauryn Jones

Masters Theses

The Tools for Sensitivity and UNcertainty Analysis Methodology Implementation (TSUNAMI) suite within the SCALE code system makes use of eigenvalue sensitivity coefficients to enable several capabilities, such as quantifying the data-induced uncertainty in calculated eigenvalues and assessing the similarity between different critical systems. The TSUNAMI-3D code is one tool within the TSUNAMI suite used to calculate eigenvalue sensitivity coefficients in three-dimensional models. The SCALE 6.1 code system includes only the multigroup (MG) mode for three-dimensional sensitivity analyses; however, the upcoming release of SCALE 6.2 will feature the first implementation of continuous-energy (CE) sensitivity methods in SCALE. For MG calculations, TSUNAMI-3D …

Modeling Radiation-Induced Segregation In Ferritic-Martensitic Steels, Aaron Patrick Selby

Masters Theses

As ferritic-martensitic (FM) steels receive increasing interest, due to the development of Generation IV fission reactors and fusion reactors, it is imperative to understand how the metals will behave under irradiation. Of the radiation effects, radiation-induced segregation (RIS) is of particular concern as it can lead to the formation of intermetallic phases, stress corrosion cracking, and other detrimental effects. However, predicting RIS in FM steels is more complex due to the lack of consistent trends in experimental results. Therefore, we developed a program to simulate RIS in FM alloys. By performing a sensitivity analysis of the input parameters, we found …

Impact Of Fuel Rod Coatings On Reactor Performance And Safety, Ian Robert Stewart

Masters Theses

This study evaluates the use of a ceramic coating on the Zr-alloy cladding within a PWR using four ceramic compounds of 5 and 10 micron thicknesses: ZrO2, TiAlN, Ti2AlC, and Ti3AlC2. The film’s impact is assessed for variation on: reactivity, fuel cycle length, maximum temperature, film’s roughness, and transient conditions. The reactivity is analyzed using the following methods: change in the multiplication factor (k) each film introduces to the system using the ABH method, and Monte Carlo software (MCNP). Both methods are in good agreement, yielding less than half a percent change from a reference, no-film fuel pin. In order …

Accelerator Facility Shielding Design, Kaitlyn Hope Darby, Tucker Caden Mcclanaha, Adrian Moore, Christopher Tyler Crutcher, Melissa Alexis Megonigal

Chancellor’s Honors Program Projects

No abstract provided.

Dynamic Modeling Of A Small Modular Reactor For Control And Monitoring, Jeffrey Robert Kapernick

Masters Theses

A system model of the Babcock & Wilcox Generation mPower small modular reactor (SMR) was developed within the MATLAB-Simulink environment. A detailed physical configuration of this SMR was established based on the limited information available for the mPower reactor. This is an important step in the development of the simulation model. Three mathematical models were combined to simulate the control dynamics. A lumped-parameter approximation of fuel-to-coolant heat transfer is combined with vessel upper plenum and lower plenum coolant masses to represent the core power and heat transfer dynamics. A nodalized moving boundary steam generator model balances mass, momentum, and energy …