Nuclear Engineering Commons^™

Measurements Of Dna Damage And Repair In Bacillus Anthracis Sterne Spores By Uv Radiation, Chelsea C. Marcum

Theses and Dissertations

Spores of Bacillus anthracis (Ba) sterne were irradiated with 267nm UV light using small light emitting diodes. The pRB373 plasmid with a red fluorescent protein was transformed into Ba sterne cells prior to irradiation. Following irradiation, germination media was added and the spores were incubated for various times, to allow for DNA repair. The pRB373 plasmid was isolated and analyzed using real-time PCR. Primers were designed across the RFP in the plasmid yielding two amplicons, 245bp and 547bp long. PCR amplification was not achieved for germinated samples. Spore samples isolated using bead beating methods were amplified. Results indicate a quicker …

Copper Doping Of Zinc Oxide By Nuclear Transmutation, Matthew C. Recker

Theses and Dissertations

This research verifies that neutron irradiation of zinc oxide leads to Cu-doping of the material by nuclear transmutation. After irradiation, both ⁶⁵Zn and ^69mZn were detected and positively identified. ⁶⁵Zn was visible at all times while ^69mZn was visible when the samples were measured within a few Zn-69m half-lifes. All decay paths of ⁶⁵Zn lead to ⁶⁵Cu and the detection of the 1115.5 keV characteristic gamma ray from this decay clearly indicated that ⁶⁵Cu was being created. Previous electron paramagnetic resonance (EPR) spectroscopic results were replicated to determine the spectrum of copper impurities …

System Analysis With Improved Thermo-Mechanical Fuel Rod Models For Modeling Current And Advanced Lwr Materials In Accident Scenarios, Ian Edward Porter

Theses and Dissertations

A nuclear reactor systems code has the ability to model the system response in an accident scenario based on known initial conditions at the onset of the transient. However, there has been a tendency for these codes to lack the detailed thermo-mechanical fuel rod response models needed for accurate prediction of fuel rod failure. This proposed work will couple today's most widely used steady-state (FRAPCON) and transient (FRAPTRAN) fuel rod models with a systems code TRACE for best-estimate modeling of system response in accident scenarios such as a loss of coolant accident (LOCA). In doing so, code modifications will be …

Implementation And Evaluation Of Fuel Creep Using Advanced Light-Water Reactor Materials In Frapcon 3.5, Spencer Carroll

Theses and Dissertations

As current reactors approach the end of their operable lifetime, new reactors are needed if nuclear power is to continue being generated in the United States. Some utilities have already began construction on newer, more advanced LWR reactors, which use the same fuel as current reactors and have a similar but updated design. Others are researching next generation (GEN-IV) reactors which have new designs that utilize alternative fuel, coolants and other reactor materials. Many of these alternative fuels are capable of achieving higher burnups and are designed to be more accident tolerant than the currently used UO2 fuel. However, before …

Modified Sodium Diuranate Process For The Recovery Of Uranium From Uranium Hexafluoride Transport Cylinder Wash Solution, Austin Dean Meredith

Theses and Dissertations

Uranium hexafluoride (UF₆) containment cylinders must be emptied and washed every five years in order to undergo recertification, according to ANSI standards. During the emptying of the UF₆ from the cylinders, a thin residue, or heel, of UF₆ is left behind. This heel must be removed in order for recertification to take place.

To remove it, the inside of the containment cylinder is washed with acid and the resulting solution generally contains three or four kilograms of uranium. Thus, before the liquid solution can be disposed of, the uranium must be separated. A modified sodium diuranate …

Predicting The Crack Response For A Pipe With A Complex Crack, Robert George Lukess

Theses and Dissertations

Traditional flaw evaluation in the nuclear field uses conservative methods to predict maximum load carrying capacity for flaws in a given pipe. There is a need in the nuclear industry for more accurate estimates of the load carrying capacity of nuclear piping such that probabilistic tools can be used to predict the time to failure for various types of cracks. These more accurate estimates will allow the nuclear industry to repair flaws at a more appropriate time considering external factors such as costs and man-rem planning along with the flaw repair. Analysis of the maximum load carrying capacity of a …

Evolution Of Microstructure Of Haynes 230 And Inconel 617 Under Mechanical Testing At High Temperatures, Kyle Hrutkay

Theses and Dissertations

Haynes 230 and Inconel 617 are austenitic nickel based superalloys, which are candidate structural materials for next generation high temperature nuclear reactors. High temperature deformation behavior of Haynes 230 and Inconel 617 have been investigated at the microstructural level in order to gain a better understanding of mechanical properties. Tensile tests were performed at strain rates ranging from 10-3-10-5 s-1 at room temperature, 600 °C, 800 °C and 950 °C. Subsequent microstructural analysis, including Scanning Electron Microscopy, Transmission Electron Microscopy, Energy-Dispersive X-ray Spectroscopy, and X-Ray Diffraction were used to relate the microstructural evolution at high temperatures to that of room …

The Study Of Alternate, Solid-Phase Fluorinating Agents For Use In Reactive Gas Recycle Of Used Nuclear Fuel, Dillon Inabinett

Theses and Dissertations

Surrogate oxides of the Used Nuclear Fuel (UNF) matrix were fluorinated using alternate, solid-phase fluorinating agents XeF2 and NH4HF2 to form volatile and non-volatile compounds and demonstrate the possibility of a chemical and thermal separations. A matrix of experiments was conducted at the milligram quantity scale using a Shimadzu DTG-60 TG/DTA installed at SRNL (Savannah River National Laboratory) for testing of all non-radioactive samples and a Netzsch STA 409 TGA installed in the laboratory at USC (University of South Carolina) for testing of all radioactive samples. The fluorination and subsequent volatilization potentials were analyzed by mixing excess fluorinating agent with …

Application Of Computational Fluid Dynamics Methods To Improve Thermal Hydraulic Code Analysis, Dennis Shannon Sentell, Jr.

Theses and Dissertations

A computational fluid dynamics code is used to model the primary natural circulation loop of a proposed small modular reactor for comparison to experimental data and best-estimate thermal-hydraulic code results. Recent advances in computational fluid dynamics code modeling capabilities make them attractive alternatives to the current conservative approach of coupled best-estimate thermal hydraulic codes and uncertainty evaluations. The results from a computational fluid dynamics analysis are benchmarked against the experimental test results of a 1:3 length, 1:254 volume, full pressure and full temperature scale small modular reactor during steady-state power operations and during a depressurization transient. A comparative evaluation of …

Advanced Fuels Modeling: Evaluating The Steady-State Performance Of Carbide Fuel In Helium-Cooled Reactors Using Frapcon 3.4, Luke H. Hallman

Theses and Dissertations

Uranium carbide (UC) has long been considered a potential alternative to uranium dioxide (UO2) fuel, especially in the context of Gen IV gas-cooled reactors. It has shown promise because of its high uranium density, good irradiation stability, and especially high thermal conductivity. Despite its many benefits, UC is known to swell at a rate twice that of UO2. However, the swelling phenomenon is not well understood, and we are limited to a weak empirical understanding of the swelling mechanism.

One suggested cladding for UC is silicon carbide (SiC), a ceramic that demonstrates a number of desirable properties. Among them are …

Characterization Of Two Ods Alloys: 18cr Ods And 9cr Ods, Julianne Kay Goddard

Theses and Dissertations

ODS alloys, or oxide dispersion strengthened alloys, are made from elemental or pre-alloyed metal powders mechanically alloyed with oxide powders in a high-energy attributor mill, and then consolidated by either hot isostatic pressing or hot extrusion causing the production of nanometer scale oxide and carbide particles within the alloy matrix; crystalline properties such as creep strength, ductility, corrosion resistance, tensile strength, swelling resistance, and resistance to embrittlement are all observed to be improved by the presence of nanoparticles in the matrix. The presented research uses various methods to observe and characterize the microstructural and microchemical properties of two experimental ODS …

Fabrication And Characterization Of Surrogate Fuel Particles Using The Spark Erosion Method, Kathryn Elizabeth Metzger

Theses and Dissertations

In light of the disaster at the Fukushima Daiichi Nuclear Plant, the Department of Energy's Advanced Fuels Program has shifted its interest from enhanced performance fuels to enhanced accident tolerance fuels. Dispersion fuels possess higher thermal conductivities than traditional light water reactor fuel and as a result, offer improved safety margins. The benefits of a dispersion fuel are due to the presence of the secondary non-fissile phase (matrix), which serves as a barrier to fission products and improves the overall thermal performance of the fuel. However, the presence of a matrix material reduces the fuel volume, which lowers the fissile …

Pellet Cladding Mechanical Interactions Of Ceramic Claddings Fuels Under Light Water Reactor Conditions, Bo-Shiuan Li

Theses and Dissertations

Ceramic materials such as silicon carbide (SiC) are promising candidate materials for nuclear fuel cladding and are of interest as part of a potential accident tolerant fuel design due to its high temperature strength, dimensional stability under irradiation, corrosion resistance, and lower neutron absorption cross-section. It also offers drastically lower hydrogen generation in loss of coolant accidents such as that experienced at Fukushima. With the implementation of SiC material properties to the fuel performance code, FRAPCON, performances of the SiC-clad fuel are compared with the conventional Zircaloy-clad fuel. Due to negligible creep and high stiffness, SiC-clad fuel allows gap closure …

Theoretical Study Of The Effects Of Di-Muonic Molecules On Muon-Catalyzed Fusion, Eugene V. Sheely

Theses and Dissertations

This document presents a theoretical study di-muonic hydrogen and helium molecules that have the potential of enhancing the muon-catalyzed fusion reaction rate. In order to study these di-muonic molecules a method of non-adiabatic quantum mechanics referred to as a General Particle Orbital (GPO) method was developed. Three mechanisms that have the possibility of enhancing the muon-catalyzed fusion rate were discovered. Two involve the formation of di-muonic hydrogen molecules, and the other uses di-muonic molecules to liberate muons stuck to ³He nuclei. The effects of muon spin on dimuonic hydrogen molecules was studied. The nuclear separation in di-muonic hydrogen molecules …

A Programmable Liquid Collimator For Both Coded Aperture Adaptive Imaging And Multiplexed Compton Scatter Tomography, Jack G. M. Fitzgerald

Theses and Dissertations

A novel, fully reconfigurable collimator device for gamma-ray and X-ray imaging was built and tested as a coded aperture. The device consisted of 10x10, 5x5x5 mm³ chambers. Each chamber either was filled with an attenuating liquid, stopping photons, or evacuated of the attenuating liquid, allowing the photons to pass through. As the pattern of on and off chambers was manipulated, different, semi-independent views of the gamma-ray source were found. Noise in reconstructed images decreased in all tests. Image reconstruction was performed with correlation methods and Maximum Likelihood Expectation Maximization (ML-EM). Using 10 mask patterns, the signal-to-noise ratio (SNR) in …

Neutron Detection Using Gadolinium-Based Diodes, Benjamin R. Thomas

Theses and Dissertations

P-n heterojunction diodes consisting of a thin n-type layer of Gd₂O₃ deposited on both p-type Si and p-type 4H SiC substrates were explored as possible solid-state neutron detectors. 79 keV internal conversion electrons from the de-excitation of the meta-stable Gd-158 nucleus can create ionization in the depletion region of the reverse-biased diodes resulting in a detectable signal. The diodes were modeled with Davinci software to determine the feasibility of signal detection above the reverse-bias leakage current. A CASINO simulation showed that less than one percent of the internal conversion electrons deposit their full energy within the achievable …

Gadolinium Oxide/Silicon Thin Film Heterojunction Solid-State Neutron Detector, Christopher M. Young

Theses and Dissertations

The internal conversion electron emission from the de-excitation of the Gd-158m nucleus was explored as a means for neutron detection. Thin film gadolinium oxide (Gd₂O₃) and p-type silicon heterojunction diodes were produced using a supercritical water deposition process. Pulse height spectroscopy was conducted on the novel diodes while they were subjected to a moderated plutonium-beryllium (PuBe) source flux of 10⁴ thermal neutrons/cm² s. Coincident gamma spectroscopy was employed to verify the 1107.6 keV photon emissions from the diode indicative of successful neutron capture by Gd-157 and the subsequent de-excitation of the Gd-158m nucleus. Neutron …

The Effects Of Temperature And Electron Radiation On The Electrical Properties Of Algan/Gan Heterostructure Field Effect Transistors, Jeffrey T. Moran

Theses and Dissertations

Al_xGa_1-xN/GaN Heterostructure Field Effect Transistors (HFETs) have come under increased study, in recent years, owing to their highly desirable material and electrical properties, ruggedness, and survivability even during and after exposure to extreme temperature and radiation environments. These devices or similar devices constructed of AlGaN and/or GaN materials are being researched for their potential applications in many military and space based systems. In this study, unpassivated and SiN passivated Al_0.27Ga_0.73N/GaN HFETs were subjected to electron radiation at incident energies of 0.5MeV and 1.0MeV and fluences from 5x10¹⁴ to 5x10¹⁵ [e-/cm …

Electrostatic Discharge Properties Of Irradiated Nanocomposites, Joshua D. Mcgary

Theses and Dissertations

Modernization in space systems requires employment of new light-weight, high performance composite materials that reduce bulk weight and increase structural integrity. This thesis explored the behavior of one such material prior to and following a 35-year simulated space radiation life-cycle. Select electrical properties of nickel nanostrand^TM-carbon composites in seven configurations were characterized prior to electron irradiation via surface and bulk resistivity measurements and contact electrostatic discharge (ESD) measurements. Following irradiation at a fluence of 10¹⁶ e^-/cm² at an average energy of 500 keV, measurements were repeated and compared against pre-irradiation data. Configuration D is …

Distribution Iteration: A Robust Alternative To Source Iteration For Solving The Discrete Ordinates Radiation Transport Equations In Slab And Xy- Geometries, Nicholas J. Prins

Theses and Dissertations

The discrete ordinates method is widely used to solve the Boltzmann transport equation for neutral particle transport for many engineering applications. Source iteration is used to solve the discrete ordinates system of equations, but can be slow to converge in highly scattering problems. Synthetic acceleration techniques have been developed to address this shortcoming; however, recent research has shown synthetic acceleration to lose effectiveness or diverge for certain problems. LTC Wager introduced an alternative to source iteration and demonstrated it in slab geometry. Here the method is further developed, enhancing efficiency in various ways, and demonstrated in XY-geometry as well as …

Neutron Detection Utilizing Gadolinium Doped Hafnium Oxide Films, Bryan D. Blasy

Theses and Dissertations

Gadolinium (Gd) doped hafnium oxide (HfO₂) was deposited onto a silicon substrate using pulsed laser deposition. Synchrotron radiation was used to perform Gd L3-edge extended X-ray absorption fine structure (EXAFS) measurements on 3%, 10%, and 15% doped HfO₂ samples. The interatomic distances determined from Fourier transformation and fitting the data show Gd occupying the hafnium site in the HfO₂ lattice, there was no clustering of Gd atoms, and the Gd ion retains monoclinic local symmetery for all levels of doping. Current as a function of voltage experiments identified the films as having poor diode characteristics with …

Evaluating The Response Of Polyvinyl Toluene Scintillators Used In Portal, Kelly D. Rakes

Theses and Dissertations

The goal of this research work was to determine if there exists, and to what extent, variability in the pulse-height spectrum, and resolution produced by ɤ-photon induced scintillation events in polyvinyl toluene scintillators. Scintillator panels of the same type as those used in portal detector units currently operated by the Department of Homeland Security, made of polyvinyl toluene and measuring 12 x 15 x 2 in were purchased from three vendors. Each vendor supplied two scintillators, one wrapped by the vendor with aluminum foil coated mylar, and two unwrapped. The scintillators where exposed to an ≈ 8µCi source collimated …

Micro-Etched Platforms For Thermal Inactivation Of Bacillus Anthracis And Bacillus Thuringiensis Spores, Leslie S. Hawkins

Theses and Dissertations

This research developed and applied microlithography techniques to etch microscope slide platforms in order to measure thermal inactivation of Bacillus thuringiensis and Bacillus anthracis spores, two closely related Bacillus species. B.t. is widely used as a surrogate for B.a. in response studies and in some field studies. This work addressed the previously identified problem of measuring both spore growth and spore thermal kill threshold using the traditional method of spreading a diluted spore solution on a plate. The micro-etched platforms forced spore separation thereby preventing neighbor growth from obscuring germination and initial vegetative growth measurements using a microscope. The technique …

Discrete Counting Of Short Lived Isotopes With Low Background Detectors, David E. Mather

Theses and Dissertations

We consider radiation counting experiments used to measure quantities of materials that are short-lived with respect to the count durations. The HPS 13.31 statistical analysis seriously overestimates the uncertainty when the quantity and background are very low. We consider the case in which the objective is to quantify the number of atoms, n, that were present in a sample when it was drawn. Mathews and Gerts [JRNC, 2008] analyzed this case and developed formulas for the probability distribution of n, in order to develop experiment design processes that minimize the smallest detectable quantity of material, thus maximizing sensitivity for the …

Time Dependent Discrete Ordinates Neutron Transport Using Distribution Iteration In Xyz Geometry, James R. Dishaw

Theses and Dissertations

The DI algorithm is an alternative to source iteration that, in our testing, does not require an accelerator. I developed a formal verification plan and executed it to verify the results produced by my code that implemented DI with the above features. A new, matrix albedo, boundary condition treatment was developed and implemented so that infinite-medium benchmarks could be included in the verification test suite. The DI algorithm was modified for parallel efficiency and the prior instability of the refinement sweep was corrected. The testing revealed that DI performed as well or faster than source iteration with DSA and that …

A Multireference Density Functional Approach To The Calculation Of The Excited States Of Uranium Ions, Eric V. Beck

Theses and Dissertations

An accurate and efficient hybrid Density Functional Theory (DFT)/Multireference Configuration Interaction (MRCI) model for computing electronic excitation energies in heavy element atoms and molecules was developed. This model incorporated relativistic effects essential for accurate qualitative and quantitative spectroscopic predictions on heavy elements, while simultaneously removing spin-multiplicity limitations inherent in the original model on which it is based. This model was used to successfully compute ground and low-lying electronic states for atoms in the first two rows of the period table, which were used for calibration. Once calibrated, calculations on carbon monoxide, bromine fluoride, the bromine atom, uranium +4 and +5 …

Precise Calculation Of Complex Radioactive Decay Chains, Logan J. Harr

Theses and Dissertations

This thesis documents a new approach to investigate the gamma radiation activity of the fission products of three different fuels (U-235, U-238, and U-239) exposed to three different incident neutron energy spectra (thermal, fast spectrum, and high energies). An application of the exponential moments function is used with a transmutation matrix in the calculation of complex radioactive decay chains to achieve greater precision than can be attained through current methods. The result of this research is a code which can calculate the decay products from complex radioactive decay chains with a high degree of precision while quantifying the uncertainty in …

High Resolution Mesoscale Weather Data Improvement To Spatial Effects For Doserate Contour Plot Predictions, Christopher P. Jones

Theses and Dissertations

Reanalysis weather data is obtained for dates surrounding historical nuclear tests and processed through Regional Atmospheric Modeling System (RAMS) software to produce a high-resolution weather forecast. Output from RAMS is visualized to check for validity and input into Hazard Prediction and Assessment Capability (HPAC) software and modeled predictions are compared to historical observation data. Simulations are conducted using constant high resolution weather and varying terrain resolution. The HPAC prediction is numerically compared to historical observation data. The result of this research culminated in the knowledge that early-time, low-altitude wind data was neglected by HPAC's incorporation of the Defense Land Fallout …

Terrain And Spatial Effects On Hazard Prediction And Assessment Capability (Hpac) Software Dose-Rate Contour Plot Predictions As Compared To A Sample Of Local Fallout Data From Test Detonations In The Continental United States, 1945-1962, Kevin D. Pace

Theses and Dissertations

Hazard Prediction and Capability (HPAC) Software is validated by comparing modeled predictions to historical test data. Reanalysis weather data is acquired and reformatted for use in HPAC. Simulations are made using various amounts of weather data by use of a spatial domain. Simulations are also varied by levels of terrain resolution. The predicted output of the software is numerically compared to historical test data. The result of this research culminated in the knowledge that HPAC prediction accuracy is improved by using terrain resolutions beyond the flat earth assumption. Furthermore, this research establishes that domain size variation produces no significant advantage …

Improved Multinuclide Imaging Of Special Nuclear Material Using A High Purity Germanium Double Sided Strip Detector, Fred D. Rothenbush Jr.

Theses and Dissertations

The purpose of this research is to improve the ability to image Special Nuclear Material (SNM) using a High Purity Germanium Double Sided Strip Detector (HPGeDSSD) for use in the field of nuclear nonproliferation. When used for gamma spectrometry, HPGe detectors can efficiently distinguish various isotopes because of their good energy resolution. The detector used for this research is a liquid nitrogen cooled germanium detector with five charge collection strips on each face. The strips are orthogonal to each other, creating a five by five array of data collection pixels. When the 25 mm by 25 mm detector array is …