Nuclear Engineering Commons^™

Characterizing The Structure And Radiation Resistance Of Weberite-Type Complex Oxides, Igor M. Gussev

Doctoral Dissertations

Weberite-type A₃BO₇ oxides, where A is a trivalent rare earth and B is a pentavalent element like Ta, have been a focus of research due to the discovery of the weberite-type local atomic arrangement in ceramics with a defect-fluorite structure. Earlier studies primarily examined their long-range structures, leaving gaps in understanding their short-range atomic behavior. This thesis investigates various weberite-type tantalates across all structural scales. There has been debate over the long-range structure of Y₃TaO₇, a medium-sized rare earth tantalate oxide, particularly regarding its spacegroup symmetry. This work identifies Y₃TaO_{7 …}

Characterizing Local Order And Physical Properties Of Rare Earth Complex Oxides, Thomas Jacob Shamblin

Doctoral Dissertations

With more than 500 compositions, materials possessing the pyrochlore structure have a myriad of technological applications and physical phenomena. Three of the most noteworthy properties are the structure’s ability to resist amorphization making it a possible host matrix for spent nuclear fuel, its exotic magnetic properties arising from geometric frustration, and fast ionic conductivity for solid-oxide fuel cell applications. This work focuses on these three aspects of the pyrochlore’s many potential uses. Structural characterization revealed that pyrochlore-type oxides have a tendency to disorder from a high symmetry cubic structure to a lower symmetry orthorhombic arrangement in response to a variety …

Magnetron Sputtering And Corrosion Of Ti-Al-C And Cr-Al-C Coatings For Zr-Alloy Nuclear Fuel Cladding, Devin Alan Roberts

Masters Theses

The disaster at the Fukushima Daiichi Nuclear Power Plant in March 2011 bought renewed focus to the issue of corrosion in nuclear fuel cladding applications. This thesis reports on the background behind these issues, the investigation strategy, and the analysis of experiments focused on mitigating oxidation of Zr-alloy fuel cladding. This thesis seeks to develop magnetron sputtered Ti-Al-C and Cr-Al-C coatings for Zr-alloy substrates and characterize the as-deposited and corroded samples.

Ti-Al-C and Cr-Al-C coatings were deposited onto ZIRLO, Si, and Al₂O₃ [Aluminum Oxide] substrates under various sputtering conditions. A combinatorial sputtering method was employed to refine …

Ion Irradiation-Induced Microstructural Change In Sic, Chien-Hung Chen

Doctoral Dissertations

The high temperature radiation resistance of nuclear materials has become a key issue in developing future nuclear reactors. Because of its mechanical stability under high-energy neutron irradiation and high temperature, silicon carbide (SiC) has great potential as a structural material in advanced nuclear energy systems.

A newly developed nano-engineered (NE) 3C SiC with a nano-layered stacking fault (SFs) structure has been recently considered as a prospective choice due to enhanced point defect annihilation between layer-type structures, leading to outstanding radiation durability.

The objective of this project was to advance the understanding of gas bubble formation mechanisms under irradiation conditions in …

Ion Irradiation Characterization Studies Of Max Phase Ceramics, Daniel William Clark

Masters Theses

The family of layered carbides and nitrides known as MAX phase ceramics combine many attractive properties of both ceramics and metals due to their nanolaminate crystal structure and are promising potential candidates for application in future nuclear reactors. This thesis reports on the background, design, and analysis of an experiment focused on determining the effects of energetic heavy ion irradiations on polycrystalline samples of titanium silicon carbide 312, titanium aluminum carbide 312, and titanium aluminum carbide 211. The irradiation conditions consisted of ion doses between 10 and 30 displacements per atom at temperatures of 400 and 700 degrees Celsius, conditions …

Ion Irradiation Induced Damage And Dynamic Recovery In Single Crystal Silicon Carbide And Strontium Titanate, Haizhou Xue

Doctoral Dissertations

The objective of this thesis work is to gain better understanding of ion-solid interaction in the energy regime where electronic and nuclear energy loss are comparable. Such responses of materials to ion irradiations are of fundamental importance for micro-electronics and nuclear applications. The ion irradiation induced modification for the crystal structure, the physical and chemical properties etc. may strongly affect the performance of functional materials that needs to be better understood.

Experimentally, ion irradiation induced damage accumulation and dynamic recovery in SiC [silicon carbide] and SrTiO₃ [strontium titanate] were studied in this dissertation project. Five chapters are presented: Firstly, …

Disorder In Mg1-Xnixal2o4 Spinel And Its Impact On The Response To Swift Heavy Ion Irradiation, Brandon Alexander Perlov

Masters Theses

Spinels, which are currently used in optical applications, have many proposed functions in the nuclear industry, such as a nuclear waste form due to its radiation resistance. Disordering plays a key role in the response of spinel to a wide range of irradiation conditions. The first part of this research project was on characterizing the type and degree of disorder that can be induced by chemical substitution in the magnesium nickel aluminate spinel solid solution series (Mg(1-x)Ni(x)Al2O4). Neutron total scattering has been used to characterize the structure at both the cation and anion sublattices. High-resolution pair distribution function analysis was …

Electronic Energy Loss Of Heavy Ions And Its Effects In Ceramics, Ke Jin

Doctoral Dissertations

Energy loss of medium energy heavy ions (i.e. Cl, Br, I, and Au) in thin compound foils containing light elements (i.e. silicon carbide and silicon dioxide) is directly measured using a time-of-flight elastic recoil detection analysis (ToF-ERDA) technique. An improved data analysis procedure is proposed to provide the experimentally determined electronic stopping powers. This analysis procedure requires reliable predictions of nuclear stopping. Thus, the nuclear stopping predicted by the Stopping and Range of Ions in Matter (SRIM) code is validated by measuring the angular distribution of 1 MeV Au ions after penetrating a thin silicon nitride foil, using a secondary …

Impact Of Fuel Rod Coatings On Reactor Performance And Safety, Ian Robert Stewart

Masters Theses

This study evaluates the use of a ceramic coating on the Zr-alloy cladding within a PWR using four ceramic compounds of 5 and 10 micron thicknesses: ZrO2, TiAlN, Ti2AlC, and Ti3AlC2. The film’s impact is assessed for variation on: reactivity, fuel cycle length, maximum temperature, film’s roughness, and transient conditions. The reactivity is analyzed using the following methods: change in the multiplication factor (k) each film introduces to the system using the ABH method, and Monte Carlo software (MCNP). Both methods are in good agreement, yielding less than half a percent change from a reference, no-film fuel pin. In order …

Thermodynamic Modeling Of Uranium And Oxygen Containing Ternary Systems With Gadolinium, Lanthanum, And Thorium, Jacob Wesley Mcmurray

Doctoral Dissertations

The CALPHAD method is used to assess the thermodynamic properties and phase relations in the U-M-O system where M = Gd, La, and Th. A compound energy formalism (CEF) model for fluorite UO_2±x [urania] is extended to represent the complex U_1-yM_yO_2±x [urania solid solution] phases. The lattice stabilities for fictive GdO₂ [gadolinia] and LaO₂ [lanthana] fluorite structure compounds are calculated from density functional theory (DFT) for use in the CEF for U_1-yM_yO_2±x [urania solid solution phase] while U⁶⁺ [uranium 6 plus cation] is introduced into the …

Mehanical Characterization Of Ion-Iradiated Silicon Carbide By Nanoindentation, Alex Hackett, Kurt Johanns, Haizhou Xue, Yanwen Zhang, Erik Herbert, George Pharr

EURēCA: Exhibition of Undergraduate Research and Creative Achievement

Tests are done on various types of silicon carbide in order to analyze mechanical properties and radiation resistance.