Nuclear Engineering Commons^™

An Automated Diagnostic Tool For Predicting Anatomical Response To Radiation Therapy, Carley Elizabeth Harris

Doctoral Dissertations

A "Clinical Decision Support System" (CDSS) is a concept which has advanced rapidly in health care over the last few decades, and it is defined as "an interactive computer program that is designed to assist physicians and other health professionals with decision-making tasks." Radiation therapy oncologists are required to make decisions that do not involve making a disease diagnosis. Therefore this work focuses on developing a modified CDSS which can be used to aid oncology staff in identifying cancer patients who will require adaptive radiation therapy (ART).

An image-guided radiation therapy (IGRT) tool was developed that consists of both diagnostic …

Radiation Detectors And Sources Enhanced With Micro/Nanotechnology, Chad Michael Whitney

Doctoral Dissertations

The ongoing threat of nuclear terrorism presents major challenges to maintaining national security. Currently, only a small percentage of the cargo containers that enter America are searched for fissionable bomb making materials. This work reports on a multi-channel radiation detection platform enabled with nanoparticles that is capable of detecting and discriminating all types of radiation emitted from fissionable bomb making materials. Typical Geiger counters are limited to detecting only beta and gamma radiation. The micro-Geiger counter reported here detects all species of radiation including beta particles, gamma/X-rays, alpha particles, and neutrons. The multi-species detecting micro-Geiger counter contains a hermetically sealed …

Forecasting Dose And Dose Rate From Solar Particle Events Using Locally Weighted Regression Techniques, Theodore Franklin Nichols

Doctoral Dissertations

Continued human exploration of the solar system requires the mitigating of radiation effects from the Sun. Doses from Solar Particle Events (SPE) pose a serious threat to the health of astronauts. A method for forecasting the rate and total severity of such events would give time for the astronauts to take actions to mitigate the effects from an SPE. The danger posed from an SPE depends on dose received and the temporal profile of the event. The temporal profile describes how quickly the dose will arrive (dose rate). Previously deployed methods used neural networks to predict the total dose from …

The Very Basics Of Sustainability - An Alternative Viewpoint (Slides With Audio) (Large File! To Speed Up Download, Right-Click On "Download" Link To Save To Own Pc.), Jim Mcgovern

Other resources

This presentation sets out the very basics of ‘sustainability’, although a definition of sustainability is not attempted. Some of the very basics are the context in which the Earth and humankind exist in space and time, the Earth’s climate, the Earth’s population and humankind’s options and choices. The author advocates keeping an open mind on all available options, including the use of oil, gas, coal, tar sands, carbon capture and sequestration, nuclear power etc., as well as the technologies that are more widely considered ‘green’. The author also argues that, in addressing the challenges that humankind faces, globally concerted effort …

Stochastic Methods For Uncertainty Quantification In Radiation Transport, Erin D. Fichtl

Nuclear Engineering ETDs

The use of stochastic spectral expansions, specifically generalized polynomial chaos (gPC) and Karhunen-Loeve (KL) expansions, is investigated for uncertainty quantification in radiation transport. The gPC represents second-order random processes in terms of an expansion of orthogonal polynomials of random variables. The KL expansion is a Fourier-type expansion that represents a second-order random process with known covariance function in terms of a set of uncorrelated random variables and the eigenmodes of the covariance function. The flux and, in multiplying materials, the k-eigenvalue, which are the problem unknowns, are always expanded in a gPC expansion since their covariance functions are also unknown. …

Time Dependent Non-Extinction Probability For Fast Burst Reactors, Michael Gregson

Nuclear Engineering ETDs

Sandia National Laboratories has successfully operated fast burst reactors over the past four decades. Fast burst reactors refer to a type of reactor that is able to achieve intense neutron pulses in very short periods of time using fissile material. Typically these systems are comprised of enriched metallic uranium fuel. During operation of a fast burst reactor, a phenomena known as a pre-initiation has been known to take place. A pre-initiation occurs when the neutron population exceeds some fiducial prior to achieving the final reactivity state in a pulse operation. Reactivity is determined from the physical configuration of the reactor …

Evaluation Of Low-Temperature Fluoride Routes To Synthesize Actinide Nitrides And Oxide Solid Solutions, Gunanda Waduge Chinthaka Silva

UNLV Theses, Dissertations, Professional Papers, and Capstones

Actinide mononitrides have been considered as a possible nuclear fuel for the Generation-IV nuclear reactor systems. In the process of evaluating these actinide mononitrides as nuclear fuel, it is important to study different chemical and physical characteristics of these compounds. Synthesis of the materials is thus important. Carbothermic reduction is one of the techniques that have been used to synthesize actinide mononitrides. In this method, a mixture of actinide oxide such as UO ₂ and excess carbon is heat treated at temperatures greater than 1700 °C under a nitrogen atmosphere. The technique is however not promising in synthesizing the actinide …

Demonstration Of A Completely Described Swirling Jet Experiment Used For Numerical Validation, Brandon M. Wilson

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This thesis demonstrates the standard for the design of an experimental model to be used for numerical validation purposes. It is proposed that numerical models may be assessed more accurately and directly by validation with a completely described experimental model, consisting of accurate descriptions of the operating conditions, fluid properties, and experimental uncertainties. This idea is demonstrated using an experimental model of a swirling jet at three Reynolds numbers (Re = 550, 2560, and 3650), with vortex breakdown existing in the higher two Reynolds number cases. Measurements of the swirling jet were obtained at two locations upstream of the jet …

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 …

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 …

Interaction Between Supersonic Disintegrating Liquid Jets And Their Shock Waves, K.-S. Im, S.-K. Cheong, Xin Liu, J. Wang, M.-C. Lai, M. W. Tate, A. Ercan, M. J. Renzi, D. R. Schuette, S. M. Gruner

Nuclear Engineering and Radiation Science Faculty Research & Creative Works

The use of additional spectral filtration for dual-energy (DE) imaging using a dual-source CT (DSCT) system was investigated and its effect on the material-specific DEratio was evaluated for several clinically relevant materials. The x-ray spectra, data acquisition, and reconstruction processes for a DSCT system (Siemens Definition) were simulated using information provided by the system manufacturer, resulting in virtual DE images. The factory-installed filtration for the 80 kV spectrum was left unchanged to avoid any further reductions in tube output, and only the filtration for the high-energy spectrum was modified. Only practical single-element filter materials within the atomic number range of …

System And Method For Quantitative Imaging Of Chemical Composition To Decompose More Than Two Materials, Xin Liu, L. Yu, C. H. Mccollough

Nuclear Engineering and Radiation Science Faculty Research & Creative Works

A system and method for decomposing more than two materials in an imaging object includes performing a CT imaging acquisition of a portion of an imaging object using at least two energy levels to acquire imaging data associated with each of the at least two energy levels. A total mass attenuation of the imaging data is expressed as a weighted sum of constituent element mass attenuation coefficients and an effective atomic number and density of the constituent elements in the portion of the imaging object is determined by one of a number of methods. Accordingly, concentration of the constituent elements …

Hydrothermal Preparation Of Gd+3 -Doped Titanate Nanotubes: Magnetic Properties And Photovoltaic Performance, Hoda S. Hafez, M Saif, James T. Mcleskey Jr., M.S.A. Abdel-Mottaleb, I S. Yahia, T Story, W Knoff

Mechanical and Nuclear Engineering Publications

Pure and Gd+3 -doped titanate nanotubes (TNTs) materials were synthesized by a hydrothermal method. Their morphology, optical properties, thermal stability, and magnetic properties were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), UV-Vis spectroscopy, thermal analysis, and magnetic measurements. It was found that doping renders Gd+3-TNT visible light active and results in smaller crystallite size and larger surface area as well as higher thermal stability compared to pure titanate nanotubes. The estimated magnetic moments point to presence of weak antiferromagnetic interaction. Application of the prepared Gd+3-TNT for modifying conventional photoanodes in polymer solar cells was attempted. Preliminary results show …

Nanostructured Solid-State Hybrid Photovoltaic Cells Fabricated By Electrostatic Layer-By-Layer Deposition, Rolf Kniprath, James T. Mcleskey Jr., Jürgen P. Rabe, Stefan Kirstein

Mechanical and Nuclear Engineering Publications

We report on the fabrication of hybrid organic/inorganic photovoltaic cells utilizing layer-by-layer deposition of water-soluble polyions and nanocrystals. A bulk heterojunction structure was created consisting of alternating layers of the p-conductive polythiophene derivative poly[2-(3-thienyl)-ethoxy-4-butylsulfonate] and n-conductive TiO2nanoparticles. We fabricated working devices with the heterostructure sandwiched between suitable charge carrier blocking layers and conducting oxide and metal electrodes, respectively. We analyzed the influence of the thickness and nanostructure of the active layer on the cell performance and characterized the devices in terms of static and transient current response with respect to illumination and voltage conditions. We observed reproducible and stable photovoltaic …

Study Of A Nanoscale Water Cluster By Atomic Force Microscopy, Manhee Lee, Baekman Sung, Nicole N. Hashemi, Wonho Jhe

Nastaran Hashemi

We present a novel method for investigating a nanometric cluster of water molecules, which includes the formation and manipulation of nanometric water, and the measurement of its mechanical properties. The atomic force microscope based on the quartz tuning-fork sensor is employed to form and manipulate the nanometric water, and the theoretical tool of amplitude-modulation atomic force microscopy is used to obtain the elasticity, viscosity and dissipation energy of it. With high vertical resolution less than [similar]0.1 nm and high force sensitivity of [similar]0.01 N m−1, this tool facilitates the stable formation and manipulation of a nano-water cluster ([similar]104 molecules) in …

Energy Security: An Australian Nuclear Power Industry, Geoff I. Swan

Australian Security and Intelligence Conference

Climate change and energy security are driving a worldwide renaissance in nuclear power. An Australian nuclear power industry has also been seriously investigated by the Australian government and its agencies. This paper provides a broad overview of the nuclear fuel cycle and the nuclear power industry. It identifies aspects that are sensitive to nuclear terrorism and nuclear weapons proliferation to help security professionals identify threats and prepare for a possible Australian nuclear power industry.

A Realistic Modeling Of Fluid Infiltration In Thin Fibrous Sheets, Sudhakar Jaganathan, Hooman Vahedi Tafreshi, Behnam Pourdeyhimi

Mechanical and Nuclear Engineering Publications

In this paper, a modeling study is presented to simulate the fluid infiltration in fibrous media. The Richards’ equation of two-phase flow in porous media is used here to model the fluid absorption in unsaturated/partially saturated fibrous thin sheets. The required consecutive equations, relative permeability, and capillary pressure as functions of medium’s saturation are obtained via fiber-level modeling and a long-column experiment, respectively. Our relative permeability calculations are based on solving the Stokes flow equations in partially saturated three-dimensional domains obtained by imaging the sheets’ microstructures. The Richards’ equation, together with the above consecutive correlations, is solved for fibrous media …

System And Method For Quantitative Imaging Of Chemical Composition To Decompose Multiple Materials, Xin Liu, L. Yu, C. H. Mccollough

Nuclear Engineering and Radiation Science Faculty Research & Creative Works

The present invention provides a material decomposition method capable of determining the distribution of density and constituent material concentration throughout an imaged object. The concentration, in the form of a mass fraction, mass percent, weight fraction, or weight percent, is determined from CT images acquired at different energy levels. The ratio of attenuation coefficients associated with one energy level to attenuation coefficients associated with another energy level is determined and used as an index in a lookup table to determine the concentration of a given material throughout the imaged object.

Criticality Studies Of Actinides Within Fissures, Trevor Wilcox

UNLV Theses, Dissertations, Professional Papers, and Capstones

The storage of nuclear waste in underground storage facilities presents numerous engineering challenges and risks. Experimental verification of engineered underground storage is impractical or prohibitively expensive, leaving scientists with few options. A 1995 report by Bowman and Venneri of the Los Alamos National Laboratory generated considerable controversy by hypothesizing that wastes composed of fissionable plutonium leached from underground storage containers could pose a nuclear criticality hazard. They proposed cases where plutonium collected in underground fractures could lead to sustained nuclear fission. In overmoderated cases, they argued that the resulting release of energy from fission could result in steam explosions, or …

Oxidation Modeling By Means Of Molecular Dynamics, Chaiyod Soontrapa

UNLV Theses, Dissertations, Professional Papers, and Capstones

Oxidation modeling is normally engineered to study systems at macroscopic scales, mostly in analytical forms based on diffusion theories. The associated time scale is usually in months, days, or minutes, and the length scale is in the order of microns. In this dissertation, oxidation modeling is performed at atomistic scale with the time and length scales in picoseconds and angstroms, respectively, using molecular dynamics. Molecular dynamics simulations generate trajectories of each atom or particle in a system according to the laws of physics. Studying oxidations under the atomistic point of view can offer new insights on atomic behaviors and influencing …

Zirconia-Magnesia Inert Matrix Fuel And Waste Form: Synthesis, Characterization And Chemical Performance In An Advanced Fuel Cycle, Kiel Steven Holliday

UNLV Theses, Dissertations, Professional Papers, and Capstones

There is a significant buildup in plutonium stockpiles throughout the world, because of spent nuclear fuel and the dismantling of weapons. The radiotoxicity of this material and proliferation risk has led to a desire for destroying excess plutonium. To do this effectively, it must be fissioned in a reactor as part of a uranium free fuel to eliminate the generation of more plutonium. This requires an inert matrix to volumetrically dilute the fissile plutonium. Zirconia-magnesia dual phase ceramic has been demonstrated to be a favorable material for this task. It is neutron transparent, zirconia is chemically robust, magnesia has good …

Update To Ansi/Ans-6.4.3-1991 For Low-Z And Compound Materials And Review Of Particle Transport Theory, Luis Durani

UNLV Theses, Dissertations, Professional Papers, and Capstones

The ANSI/ANS-6.4.3-1991 Gamma-Ray Attenuation Coefficients and Buildup Factors for Engineering Materials Standard (herein known as ANS Standard), contains derived gamma-ray attenuation coefficients and buildup factors for selected engineering materials and elements for use in shielding calculations (ANSI/ANS-6.1.1, 1991). The current status of the ANS Standard is withdrawn due to the lack of any updates since its last publication. Since the last update of the ANS standard, more accurate codes for particle transport and cross sectional data have become available. As a result, this study was carried out to update gamma-ray buildup factors for iron and water as a function of …

Analogy Based Modeling Of Natural Convection, Vaibhav Khane

Masters Theses

"This research is an extension of previous work on the development of an integrator or resistance-capacitance circuit analogy for natural convection. As a part of a larger project to enhance transport phenomenon on a micro-scale using radiation, this work studied the phenomenon of natural convection. Using experimental techniques and numerical simulations (FLUENT code), it investigated the transient response of a natural convection system. It proposes an integrator circuit analogy for a natural convection system. Experimental investigation with three different fluids indicated that the characteristic time constant of the system is related to the Prandtl number of the fluid. The project …