Engineering Commons^™

Crystallographic Changes In Lead Zirconate Titanate Due To Neutron Irradiation, Alexandra Henriques, Joseph T. Graham, Sheldon Landsberger, Jon F. Ihlefeld, Geoff L. Brennecka, Donald W. Brown, Jennifer S. Forrester, Jacob L. Jones

Nuclear Engineering and Radiation Science Faculty Research & Creative Works

Piezoelectric and ferroelectric materials are useful as the active element in non-destructive monitoring devices for high-radiation areas. Here, crystallographic structural refinement (i.e., the Rietveld method) is used to quantify the type and extent of structural changes in PbZr_0.5Ti_0.5O₃ after exposure to a 1 MeV equivalent neutron fluence of 1.7x10¹⁵ neutrons/cm². The results showa measurable decrease in the occupancy of Pb and O due to irradiation, with O vacancies in the tetragonal phase being created preferentially on one of the two O sites. The results demonstrate a method by which the …

X-Ray Digital Industrial Radiography (Dir) For Local Liquid Velocity (Vll) Measurement In Trickle Bed Reactors (Tbrs): Validation Of The Technique, K. A. M. Salleh, M. F. A. Rahman, Hyoung-Koo Lee, Muthanna H. Al-Dahhan

Nuclear Engineering and Radiation Science Faculty Research & Creative Works

Local liquid velocity measurements in Trickle Bed Reactors (TBRs) are one of the essential components in its hydrodynamic studies. These measurements are used to effectively determine a reactor's operating condition. This study was conducted to validate a newly developed technique that combines Digital Industrial Radiography (DIR) with Particle Tracking Velocimetry (PTV) to measure the Local Liquid Velocity (V_LL) inside TBRs. Three millimeter-sized Expanded Polystyrene (EPS) beads were used as packing material. Three validation procedures were designed to test the newly developed technique. All procedures and statistical approaches provided strong evidence that the technique can be used to measure …

Development Of A Flat-Panel X-Ray Source, Edwin Joseph Grant

Doctoral Dissertations

"A novel flat-panel transmission type X-ray source was developed for both medical and industrial use. Depending on the geometry of the given situation, the flat-panel X-ray source could be used in tomography, radiography or tomosynthesis. Furthermore, the unit could be used as a portable X-ray scanner or an integral part of an existing detection system. The design incorporates a field emission cathode made of ultra-nanocrystalline diamonds (UNCD) doped with nitrogen. These field emitters show good electron output at low power and can be deposited over large areas as is the case with carbon nanotube "forest" (CNT) cathodes. This work presents …

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 …

Local Liquid Velocity Measurement Of Trickle Bed Reactor Using Digitial Industrial X-Ray Radiography, Khairul Anuar Mohd Salleh

Doctoral Dissertations

"Trickle Bed Reactors (TBRs) are fixed beds of particles in which both liquid and gas flow concurrently downward. They are widely used to produce not only fuels but also lubrication products. The measurement and the knowledge of local liquid velocities (VLL) in TBRs is less which is essential for advancing the understanding of its hydrodynamics and for validation computational fluid dynamics (CFD). Therefore, this work focused on developing a new, non-invasive, statistically reliable technique that can be used to measure local liquid velocity (V_LL) in two-dimensions (2-D). This is performed by combining Digital Industrial X-ray Radiography (DIR) and …

Thermal-Fluid Modeling Of The Missouri S&T Reactor, Susan Maria Sipaun

Doctoral Dissertations

"Thermal-fluid modeling of the Missouri University of Science and Technology Reactor (MSTR) was carried out using a computational fluid dynamics code (CFD), STAR-CCM+. First, a three-dimensional parallel-plate model was developed, and the cosine-shaped heat flux was applied to the MSTR core. Simulation results for fluid flow under natural convection condition show coolant temperature and velocity as a function of core power. A characteristic equation for the parallel-plate model was obtained based on Forchheimer's flow equation. The inertial resistance tensor and viscous resistance tensor were found to be 281005 kg/m^4 and 7121.6 kg/m^3 respectively. The MSTR core was then defined as …

Development Of A Nitrogen Incorporated Ultrananocrystalline Diamond Film Based Field Emitter Array For A Flat Panel X-Ray Source, Chrystian Mauricio Posada

Doctoral Dissertations

"As an alternative to conventional X-ray sources, a flat panel transmission X-ray source is being developed. A field emitter array (FEA) prototype to be incorporated as cold cathode in this flat panel X-ray source was fabricated for this work. Using the Particle-in-Cell code OOPIC Pro, an initial FEA was designed through simulations. Based on the simulation results, a FEA prototype was fabricated using conventional microfabrication techniques. Planar nitrogen-incorporated ultrananocrystalline diamond (N-UNCD) films were used as field emitters. This N-UNCD based FEA prototype was composed of 9 pixels distributed in a 3x3 array, with a pixel size of 225x225 µm, and …

Synthesis Of Radioactive And Nonradioactive Nanostructures Through Radiolytic And Wet Chemistry, Jessika Viviana Rojas Marin

Doctoral Dissertations

"In this work the synthesis of non radioactive and radioactive nanoparticles (NPs) through radiolytic and wet chemistry was studied. Non radioactive NPs of rhenium, iridium, and rhodium were synthesized from aqueous solutions containing the metal salt precursors by gamma irradiation. The solutions were irradiated to generate reducing species that led to the nucleation and growth of the nanoparticles. Amorphous rhenium oxide nanoparticles with average sizes ranging from 10 nm to 55 nm were obtained. Metallic iridium and rhodium nanoparticles were produced in polyvinyl-pyrrolidone (PVP) having narrow particle size distributions and average particle sizes from 2 nm to 6 nm. The …

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 …

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 …