Nuclear Engineering Commons^™

A Sensor For Oxygen In A Potassium-Sodium Alloy, Michael George Pastis

Masters Theses

This project supports a research project to determine the configuration for heat exchanger welds in a space reactor. The reactor is a sodium-potassium (NaK) cooled reactor for use on future missions on the lunar surface or on Mars. Various types of welds in Type 316L stainless steel have been positioned in a furnace which is part of a NaK test loop. The specimens are bathed in circulating NaK at 600 degrees centigrade.

Since the oxygen concentration in the NaK is a major factor in corrosion of the weld specimens, it must be carefully monitored and controlled. However, few techniques are …

Characterization Of Lithium-6 As A Commercial Helium-3 Alternative For Nuclear Safeguards And Security, Alexander Martin Okowita

Masters Theses

Helium-3 detectors are efficient, reliable neutron detectors, but their high demand has reduced their supply to a very miniscule level, making them very expensive. The goal of this project is to test and evaluate an alternative produced by industry. Current testing is being done with a Lithium Zinc Sulfide (⁶LiF:ZnS(Ag)) detector from Aspect used in their portal monitors.

There are three basic requirements for neutron detectors used in nuclear safeguards and security: 1) high absolute detection efficiency, 2) maintaining neutron detection efficiency when simultaneously exposed to a high gamma ray exposure rate, and 3) the ability to maintain …

Modeling Integral Fuel Burnable Absorbers Using The Method Of Characteristics, Erik Daniel Walker

Masters Theses

Modern core designs that utilize Westinghouse fuel technology employ the use of Integral Fuel Burnable Absorbers (IFBA) that consists of very thin coatings of boron absorber material on the fuel pellets. While IFBA has proven to be an effective burnable absorber, it does present a neutronics modeling challenge. The difficulty of modeling IFBA using the Method of Characteristics (MOC) transport method is well known, and arises from the fact that IFBA is a very small, but also very important, region in nuclear fuel. Experience in modeling IFBA at the pin cell and single assembly lattice level requires a decrease in …

Thick Target Yield Of Th-229 Via Low Energy Proton Bombardment Of Th-232, Justin Reed Griswold

Masters Theses

Actinium-225 is one of the more effective radioisotopes used in alpha radioimmunotherapy. Due to its ten-day half-life, it is more efficient to create its precursor, ²²⁹Th [Thorium-229] (t_1/2[half-life] = 7932 ± 55 years). In this work, ²²⁹Th was produced via 40 MeV [Mega electron Volts] proton bombardment of a thick ²³²Th [Thorium-232] target. The irradiation took place at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Lab (ORNL). The target, consisting of 23 stacked natural thorium foils (137 mg/cm² [milligrams per square centimeter] each), was irradiated with 50 nA [nanoamps] of …

Production Of Nuclear Debris Surrogates For Forensic Methods Development, Joshua James Molgaard

Masters Theses

A novel method for producing synthetic debris similar to the melt glass produced by nuclear surface testing is demonstrated. Melt glass from the first nuclear weapon test (commonly referred to as trinitite) is used as the benchmark for this study. These surrogates can be used to simulate a variety of scenarios and will serve as a tool for developing and validating forensic analysis methods.

The ultimate goal is to provide the nuclear forensics community with a robust method to supply realistic yet non-sensitive surrogate materials simulating a variety of detonation scenarios. This work will also allow for the development of …

Verification Of The Shift Monte Carlo Code Using The C5g7 And Casl Benchmark Problems, Nicholas Cameron Sly

Masters Theses

While Monte Carlo simulation has been recognized as a powerful numerical method for use in radiation transport, it has required a mixture of methods development and hardware advancement to meet these expectations in practical applications. In an effort to continue this advancement for uses of Monte Carlo simulation in ever larger capacities, Oak Ridge National Laboratory is developing the Shift hybrid deterministic/Monte Carlo code to be massively-parallel for use on parallel computing systems of all sizes. As part of this development, verification of the Monte Carlo parts of the code is needed to confirm that the current version of the …

The Effects Of Shielding On Non-Destructive Analysis (Nda) And The Use Of Small-Angle Compton Scattering To Overcome Those Effects, Cory Jake Hudson

Masters Theses

The use of passive Non-Destructive Analysis (NDA) equipment and techniques are very beneficial tools in the nuclear industry that have a plethora of applications and advantages over destructive or more invasive measurement methods. Of course, NDA techniques also have many limitations including dealing with many unknown parameters, overcoming the effects of gamma ray shielding, and the reliance on making many gross assumptions in the analysis of non-destructively acquired data. These limitations can lead to biased results or extremely difficult analysis which often introduces inaccurate conclusions and/or high levels of uncertainty.

This thesis paper will focus on specific NDA equipment and …

A Benchmark Comparison Of Epa Computer Models For Demonstrating Compliance To The Regulatory Effluent Dose Constraint At A Radioactive Waste Processing Facility, Debra Ann Mccroskey

Masters Theses

The U.S. Environmental Protection Agency (EPA) and the Nuclear Regulatory Commission (NRC), or NRC agreement states, establish radiation dose limits to members of the public from airborne radionuclide emissions released from facilities licensed to use and/or handle radioactive material. These regulations specify that the licensee ensure that the individual member of the public likely to receive the highest dose shall not be expected to receive a total effective dose equivalent (EDE) in excess of 10 mrem (0.1 mSv) per year. Doses to members of the public from airborne effluents are evaluated using EPA-approved computer programs, such as COMPLY or CAP88. …

Low Pressure Chemical Vapor Deposition Of Semiconducting Boron Carbide Thin Films On Silicon, Thomas Gregory Wulz

Masters Theses

Boron carbide thin films were grown on the (100) plane of n-type silicon in a low pressure chemical vapor deposition (CVD) system from the thermal decomposition of boron trichloride and methane reactant gases with hydrogen as a carrier gas. Boron trichloride to methane molar ratio was 5, while the boron trichloride to hydrogen molar ratio was 3.5. Thin film deposition was carried out at 900 degrees Celsius at 25 Torr. The thin films were analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Energy Dispersive X-Ray Spectroscopy (EDS), Laser Induced Breakdown Spectroscopy (LIBS), and current-voltage characteristics. The crystallography of …

Multidimensional Cfd Modeling Of A Liquid Salt Pebble Bed Heat Transfer Loop, Richard B. Cunningham

Masters Theses

The Pebble Bed Advanced High Temperature Reactor (PB-AHTR) is a next generation reactor design proposed by the University of California at Berkeley. Oak Ridge National Laboratory’s Liquid Salt Test Loop (LSTL) is designed to simulate AHTR operating conditions for component testing. In this study, COMSOL Multiphysics is used to model the LSTL. Full 3D modeling of the LSTL is computationally expensive. However, COMSOL allows users to combine 1D, 2D, and 3D fluid flow physics in order to design models that are both representative and efficient. 1D pipe flow calculations are used for the piping sections. COMSOL’s porous media module is …

A Nuclear Solution For The Energy Security Vulnerabilities Of The Department Of Defense: Using A Small Modular Reactor To Power Military Installations, Margaret Alva Kurtts

Masters Theses

Due to its reliance on the civil electrical grid, the Department of Defense has significant energy security vulnerabilities. DoD does not have energy production capabilities within its organization necessary to sustain the operations of a military installation. Its current installation energy strategy is a combination of energy reduction measures and renewable production efforts. Therefore, increased threats from cyber attacks combined with an aging electrical infrastructure threaten DoD’s energy supply to its installations. The electrical grid provides aggressors an opportune target for weakening military response capabilities in the event of a natural or man-made disaster. While DoD is successfully using energy …

Metal Chronometry For Pre-Detonation Nuclear Forensics Applications, Edward Thomas Peskie

Masters Theses

The ability to determine the time since forming of seized nuclear material would provide crucial data to be used in its investigation. This paper examines the time dependent processes of diffusion; to include grain boundary diffusion, and discontinuous precipitation, and assess the utility of examination of impurity and alloying element concentration profiles, for use as a pre-detonation nuclear forensics tool for determining the age of a metal sample. Several examples provided illustrate the effects of time on both binary alloys and multi-component systems. This study draws parallels from studies of diffusion in mineral samples under geologic time and proposes modifications …

Particle Image Velocimetry (Piv) For Positron Emission Particle Tracking (Pept) And Turbulence Modeling Validation, Sarah Ridley Rupert

Masters Theses

A Particle Image Velocimetry (PIV) experiment is designed and data collected with intention to validate Positron Emission Particle Tracking (PEPT) methods. The PIV data are collected in a narrow rectangular channel for flow Reynolds number near 20,000. The narrow channel and attendant pump, header tanks and flow instrumentation are portable and designed to allow identical tests in a Concord Microsystems MicroPET P4 pre-clinical PET scanner at the pre-clinical Imaging Suite at the UT Hospital. The PIV data are instantaneous velocity field data, allowing statistics on the flow turbulence to be collected in the Eulerian frame. The PEPT method measures activated …

Determination Of Minor And Trace Elements Concentration In Kidney Stones Using Elemental Analysis Techniques, Anjali Srivastava

Masters Theses

"The determination of accurate material composition of a kidney stone is crucial for understanding the formation of the kidney stone as well as for preventive therapeutic strategies. Radiations probing instrumental activation analysis techniques are excellent tools for identification of involved materials present in the kidney stone. The X-ray fluorescence (XRF) and neutron activation analysis (NAA) experiments were performed and different kidney stones were analyzed. The interactions of X-ray photons and neutrons with matter are complementary in nature, resulting in distinctly different materials detection. This is the first approach to utilize combined X-ray fluorescence and neutron activation analysis for a comprehensive …

Experimental Investigation Of The Pebble Bed Structure By Using Gamma Ray Tomography, Fadha Shakir Ahmed

Masters Theses

"Pebble Bed Reactors offer a future for new nuclear energy plants. They are small, inherently safe, and can be competitive with fossil fuels. The fuel forms a randomly stacked pebble with non-uniform fuel densities. The thermal-mechanical behavior of pebble bed reactor core is depends strongly on the spatial variation of packing fraction in the bed and in particular on the number of contacts between pebbles, and between the pebbles and the blanket walls. To investigate these effects, experimental data to characterize bed structure are needed along with other numerical simulation and computational tools for validation.

In this study, a powerful …

Feasibility Study Of A Two-Fluid Small Modular Molten Salt Reactor With In Core Heat Removal Capability, Brandon James Lahmann

Masters Theses

"A feasibility study of a two-fluid small modular molten salt reactor (MSR) with in core heat removal was performed. The initial fuel block dimension for the configuration was based on the Fuji MSR. The fuel was a mixed fluoride salt of density 3.25 g/cc, composed of 71 LiF - 16 BeF₂ - 12 ThF₄- 1 ²³³UF₄ molar percentages. The coolant salt was Li₄(FLiBe) of density 1.94 g/cc. The work set out to establish whether or not such a reactor is thermodynamically feasible when optimized for various neutronics parameters. A Java based API was …