Nuclear Engineering Commons^™

Determination Of Critical Experiment Correlations Via The Monte Carlo Sampling Technique, William Jay Marshall

Doctoral Dissertations

Critical benchmark experiments are the foundation of validation of the computational codes used in criticality safety analyses because they provide a basis for comparison between the calculated results and the physical world. These experiments are often performed in series varying a limited number of parameters to isolate the effect of the independent parameter. The use of common materials, geometries, machines, procedures, detectors, or other shared features can create correlations among the resulting experiments. Most validation techniques used in criticality safety practice do not treat these correlations explicitly, and the effect of this is unclear as the correlations themselves are not …

Double Differential Neutron Yields Produced By Proton, Helium, And Iron Interactions In Thick Aluminum Targets, Natalie Ann Mcgirl

Doctoral Dissertations

Recent calculations of galactic cosmic ray (GCR) transport in enclosed, shielded space environments indicate that a minimum dose equivalent is achieved with aluminum shielding thicknesses near 20 g/cm² [grams per centimeter squared]. Increases in the absorbed dose and dose equivalent with shielding thicknesses above 20 g/cm² are believed to be caused by the production of light ions and neutrons in the thick shielding. However, uncertainties surround these calculations due to limited cross section and yield data for high-energy projectiles incident on thick targets. Thick-target neutron yields are particularly valuable measurements since they are produced over a wide range …

Novel Fission Track Detection For Identification And Characterization Of Special Nuclear Materials, Jonathan Allen Gill

Doctoral Dissertations

Fission track detection and analysis is used primarily in nuclear safeguards to identify special nuclear material. Identification of isotopic ratios is a crucial step in understanding the intended use of nuclear material and the nature of the materials production cycle. Unfortunately, this methodology uses etchable track detectors that require significant expertise and intensive labor to process.

This study developed a novel method using lithium fluoride (LiF) as a fluorescing nuclear track detector to conduct fission track analysis for isotopic prediction of uranium enrichment. Individual latent tracks produced by fission products were observed in LiF for the first time. These tracks …

Nestle To Origami Coupling: A Nuclear Non-Proliferation Tool For Lwr Fuel Assembly Isotope Analysis, Margaret Alva Kurtts

Doctoral Dissertations

NESTLE to ORIGAMI coupling is a versatile nuclear modeling tool that allows researchers to directly observe the impact of operator induced changes on LWR assembly isotope production. The paper presents an experimental method by which to test the ability of an operator to manipulate the core neutron spectrum in order to produce higher quality plutonium for weapons use. The paper presents two plutonium production scenarios and evaluates their feasibility based on potential for detection and production capacity. Reactor modeling of a VVER-1000 uses NESTLE core simulation software. NESTLE outputs burnup and relative power information for all nodes in the core. …

Determining 235u Enrichment Using A Dual-Energy Approach For Delayed Neutron Measurements, Angela Lynn Lousteau

Doctoral Dissertations

Bulk uranium items are often measured using active neutron interrogation systems to take advantage of the relatively high penetrability of neutrons, providing the ability to quickly and accurately measure uranium masses in large, dense configurations. Active techniques employ an external neutron source to induce fission in the uranium and subsequently measure emitted prompt fission or delayed neutrons. Unfortunately, the emitted neutrons from ²³⁵U [uranium-235] and ²³⁸U [uranium-238] are, for all practical purposes, indistinguishable; therefore, commonly used systems such as the Active Well Coincidence Counter, the ²⁵²Cf [californium-252] Shuffler, and other systems based on measurement of prompt or …

Methodology For An Advanced Risk Assessment Of Crud Induced Power Shift Using Coupled Multi-Physics Simulations And A Monte Carlo Scenario Analysis Of The Potential Financial Benefits, Travis Louis Lange

Doctoral Dissertations

Beginning in the 1970's, power uprates in nuclear power plants began to cause an operational problem called Crud Induced Power Shift (CIPS). Over decades, a method has been developed and refined that has allowed industry to effectively avoid CIPS. However, increasingly challenging economic environments have caused power plants to utilize more aggressive core designs. The problem of CIPS still looms over many reactors as a potential hazard requiring conservative measures. CIPS is due to complex physical and chemical interactions. Current industry methods use multiple single-physics simulations in their analyses. However, improved 3D multi-physics models of CIPS can provide a better …

Modeling Of Dislocation Channel Formation And Evolution In Irradiated Metals, Peter James Doyle

Masters Theses

Defect-free dislocation channel formation has been reported to promote plastic instability during tensile testing via localized plastic flow, leading to a distinct loss of ductility and strain hardening in many low-temperature irradiated materials. In order to study the underlying mechanisms governing dislocation channel width and formation, the channel formation process is modeled via a simple stochastic dislocation-jog process dependent upon grain size, defect cluster density, and defect size. Dislocations traverse a field of defect clusters and jog stochastically upon defect interaction, forming channels of low defect-density. Based upon prior molecular dynamics (MD) simulations and in-situ experimental transmission electron microscopy (TEM) …

Positron Emission Particle Tracking Software Maturation Project, Eric Michael Moore

Masters Theses

Positron Emission Particle Tracking (PEPT) software at the University of Tennessee (MultiPEPT) has demonstrated promising performance in multiple measurement domains. In order to contribute to its further development, a full codebase audit and three focused performance assessments were undertaken. Several improvements were made to the codebase as a result of the audit. The assessments demonstrated a linear axial detector- MultiPEPT response, the effect of mesh size variation, and the effect of temporal overlap variation. A number of best practices are compiled for effective use of MultiPEPT.

Improvements To Nestle: Cross Section Interpolation And N-Group Extension, William Matthews Kirkland

Masters Theses

The NESTLE program is a few-group neutron diffusion reactor core simulator code utilizing the nodal expansion method (NEM). This thesis presents two improvements made to NESTLE regarding cross-section interpolation and multigroup capability.

To quickly and accurately obtain cross sections from lattice physics input data, a new cross section interpolation routine was developed utilizing multidimensional radial basis function interpolation, also known as thin plate spline interpolation. Testing showed that, for existing NESTLE lattice physics input, accuracy was retained but not improved and processing time was longer. However, the new interpolation routine was shown allow much greater exibility in the case matrix …

The Development Of Cesium Calcium Bromo-Iodide Scintillator For X-Ray And Gamma Ray Detection, Matthew Starr Loyd

Masters Theses

CsCaI₃:Eu [cesium calcium iodide doped with europium] is a promising scintillator material that can be grown from the melt, but undergoes a tetragonal to orthorhombic phase transition upon cooling at 255 °C [degrees Celsius], causing twinning and cloudiness. The purpose of this work is to suppress this solid to solid phase transition in the CsCaI₃:Eu scintillator, which has a light yield of ~40000 ph/Mev and energy resolution at 662keV of ~4%, by halide replacement to form the compound CsCaBr_xI_3-x:Eu [cesium calcium bromo-iodide doped with europium]. Crystals 8 cm³ [cubic centimeters] in …

The Inverse Kinetics Method And Its Application To The Annular Core Research Reactor, Thomas A. Ball

Nuclear Engineering ETDs

The inverse kinetics method, is a method to calculate a reactor’s reactivity profile from its power profile. In this thesis, the reactivity profile corresponding to pulse operations of the Annular Core Research Reactor (ACRR) was sought. Of specific interest was the shutdown reactivity of the reactor following the pulse. This required accounting for delayed beryllium photoneutrons that are present in the ACRR in addition to U-235 delayed neutron precursors. The power profiles of the pulses were experimentally measured using a diamond photoconductive detector (PCD). Using the inverse kinetics equation, a computer code was written to numerically calculate the reactivity corresponding …

Evaluation Of Energy Released From Nuclear Criticality Excursions In Process Solutions, Corey Michael Skinner

Nuclear Engineering ETDs

Typically, the staff of a nonreactor nuclear facility or a processing facility involving nuclear material are not expected to have a strong technical background in nuclear criticality physics, as that is not the purpose of these sites, yet handle material with the potential to undergo a criticality excursion. Such excursions have occurred 22 times in the past, 21 of which involved an aqueous solution material. Therefore, it would be useful to have a general model capable of providing a quick estimation of the consequences of a criticality excursion in a processing plant. To this end, correlations developed utilizing experimental data …

Gamma-Radiation Induced Corrosion Of Alloy 800, Mojtaba Momeni

Electronic Thesis and Dissertation Repository

This thesis presents a newly developed mechanism and predictive model for the corrosion of Alloy 800. The Fe-Cr-Ni Alloy (Incoloy 800) is mainly used for steam generator (SG) tubing in CANDU and PWR reactors and is a candidate material for the proposed Canadian Supercritical Water Reactor (SCWR) in which it will be exposed to extreme conditions of high radiation flux and large temperature gradients. The influence of gamma radiation and water chemistry conditions on the corrosion behaviour of Alloy 800 are studied in this work. Ionizing radiation creates reducing (•e_aq^–, •H, •O₂^-) and oxidizing …

Time-Of-Flight And Energy Loss Analysis On The Unm Fission Fragment Spectrometer, Shelby Fellows

Nuclear Engineering ETDs

The University of New Mexico spectrometer experimental work has been used to provide an event-by-event fission product measurement to aid in filling in the gaps in existing fission product yield data, as part of the Los Alamos National Lab Spectrometer for Ion Detection in Fission Research project (SPIDER) collaboration. This thesis examines the time-of-flight (TOF) component of the spectrometer towards improving the resolution of the system. Different thicknesses of TOF conversion foils were examined with alpha particles and fission fragments: 20, 55, and 100 µg/cm² carbon foils. For the thinnest carbon foil studied, a timing resolution of 160 ps …

Asymptotic Neutronic Solutions For Fast Burst Reactor Design, Edward L. Hobbs

Nuclear Engineering ETDs

Deterministic numerical methodologies for solving time-eigenvalue problems are valuable in characterizing the inherent rapid transient neutron behavior of a Fast Burst Reactor (FBR). New nonlinear solution techniques used to solve eigenvalue problems show great promise in modeling the neutronics of reactors. This research utilizes nonlinear solution techniques to solve for the dominant time-eigenvalue associated with the asymptotic (exponential) solution to the neutron diffusion and even-parity form of the neutron transport equation, and lays the foundation for coupling with other physics phenomena associated with FBRs.

High security costs and proliferation risks associated with Highly Enriched Uranium (HEU) fueled FBRs are the …

Improvements To The Predictive Capability Of Fcm Fuel Performance Modeling, Daniel Philip Schappel

Doctoral Dissertations

A proposed fuel type for improved accident performance in LWRs (Light Water Reactors) involves TRISO (Tristructural-Isotropic) particles embedded in a NITE (Nano Infiltrated Eutectic) silicon carbide matrix. TRISO fuel particles contain a spherical fuel kernel of about 500 to in excess of 800 microns in diameter. The kernel and buffer layer are then coated with three isotropic layers consisting of a dense inner pyrolytic carbon (IPyC), a silicon carbide (SiC) layer, and an outer pyrolytic carbon (OPyC) layer. These layers are about 40 microns thick. The TRISO particle packing fraction in the NITE-SiC matrix is expected to be about 40 …

Intrusion Detection Of A Simulated Scada System Using A Data-Driven Modeling Approach, Brien Alen Jeffries

Doctoral Dissertations

Supervisory Control and Data Acquisition (SCADA) are large, geographically distributed systems that regulate help processes in industries such as nuclear power, transportation or manufacturing. SCADA is a combination of physical, sensing, and communications equipment that is used for monitoring, control and telemetry acquisition actions. Because SCADA often control the distribution of vital resources such as electricity and water, there is a need to protect these cyber-physical systems from those with possible malicious intent. To this end, an Intrusion Detection System (IDS) is utilized to monitor telemetry sources in order to detect unwanted activities and maintain overall system integrity.

This dissertation …

Integrating Disparate Nuclear Data Sources For Improved Predictive Maintenance Modeling: Maintenance-Based Prognostics For Long-Term Equipment Operation, Zachary Allen Welz

Doctoral Dissertations

The United States (US) nuclear industry is one of the most heavily regulated businesses in the world, creating a culture of world-class design, operation, and maintenance. In an article published on modern maintenance technologies, Terrence OHanlon (past Chief Asset Manager for Reliabilityweb.com) stated, “world class companies often devote up to 50 percent of their entire maintenance resources to condition based monitoring and the planned work that is required as a result of the findings” [1]. One would expect US nuclear power plants to constantly upgrade, improve, and expand their operations and maintenance departments and tactics. Since the early 1990s, US …

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 …

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 …

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, …

Thermal Kinetics Of Helium Irradiation Hardening In Selected Alloys For The Canadian Gen. Iv Nuclear Reactor Concept, Feifei Nie

Electronic Thesis and Dissertation Repository

In this thesis, we present nano-indentation measurements performed to quantify the increase in hardness as a result of He⁺ and Fe⁴⁺ implantation in both Inconel 800H and AISI 310 alloys. After annealing, the softening rate of He⁺ and Fe⁴⁺ implanted samples were compared, and it is found that Ni can slow the helium diffusion. Thermal activation energy Q characterizing this process was similar to the computed thermal activation energy Q_He for interstitial helium diffusion within pure nickel. Indentation hardness tests were also performed at various indentation strain rates, to further study the effect of implanted …

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 …

Non-Destructive Assay Of Uranium Enrichment Facilities, Kathryn E. Bales, Weston Bogart, Tyler Camarena, Sarah Creasman, Eric W. Nelius

Chancellor’s Honors Program Projects

No abstract provided.

Thermodynamic Characterization And Isothermal Separability Of Heavy Fission Product Chelates For Post-Detonation Nuclear Forensic Analysis, Steven Adam Stratz

Doctoral Dissertations

Nuclear terrorism, one of the most critical threats to national security, exhibits complexities that do not exist with similar threats from sanctioned state actors. Responding to a domestic nuclear terrorism strike is difficult when the original source of the weapon may be unknown, given that terrorist organizations (at the time of writing) do not themselves have nuclear technology sufficient to design and build nuclear weapons. Consequently, the development of forensic techniques to help source and characterize nuclear weapons after detonation has recently become an area of interest. This relatively new field of science, known as post-detonation nuclear forensics, aims to …

Sensitivity Of Vver-1000 Spent Fuel Pin Nuclide Inventory To Operational Parameters, Nicholas Patrick Luciano

Doctoral Dissertations

Tools that can rapidly compute the isotopic composition of spent nuclear fuel (SNF) are useful for many reasons, including safety and security. Although tools exist to compute approximate isotopic compositions, detailed fuel composition requires reactor simulation that result from normal and off-normal operations. Reactor simulation is typically performed using nodal core simulators. These codes perform their calculations rapidly, but they may not compute isotopic composition.

The Russian designed VVER is a pressurized water reactor that uses hexagonal fuel assemblies with triangularly pitched fuel rods and annular pellets. The international expansion of VVER-1000 reactor technology has motivated a renewed interest in …

Improved Sample Utilization In Thermal Ionization Mass Spectrometry Isotope Ratio Measurements: Refined Development Of Porous Ion Emitters For Nuclear Forensic Applications, Matthew Louis Baruzzini

Doctoral Dissertations

The precise and accurate determination of isotopic composition in nuclear forensic samples is vital for assessing origin, intended use and process history. Thermal ionization mass spectrometry (TIMS) is widely accepted as the gold standard for high performance isotopic measurements and has long served as the workhorse in the isotopic ratio determination of nuclear materials. Nuclear forensic and safeguard specialists have relied heavily on such methods for both routine and atypical efforts. Despite widespread use, TIMS methods for the assay of actinide systems continue to be hindered by poor ionization efficiency, often less than tenths of a percent; the majority of …

An Optimization Method For Matched Abundance-Ratio Cascades By Varying The Key Weight, Richard Dale Harvey

Doctoral Dissertations

The theory of multicomponent isotope separation in matched abundance-ratio cascades (MARC) has been well established by Cohen, de la Garza, von Halle, and others. Because separation factors of different isotopes vary in the same separator, isotopic weight fractions cannot be matched in the same sense as in a two-component ideal system. Therefore, the abundance ratios of the desired isotope and a selected key isotope are matched, hence the name. These ratios are matched by choosing a key weight between the two selected components of separation.

Desirable stable isotopes for separation can exist as minor components of a natural, multicomponent isotope …