Nuclear Engineering Commons^™

Nuclear Energy As A Reliable And Safe Source Of Power Generation, Sarup Dhungana

Honors Theses

There is a high demand of energy for generating civil applicable power in the world and in the USA, correspondingly. The world has been consuming various sources to extract the power to meet its demands. Most of the power sources include renewable and non-renewable sources like fossil fuels, natural gas, coal, water, solar, wind, and nuclear power. Although most of these sources have many advantages in terms of their capacity and cost of production, nuclear power can be categorized as the emerging driving force in the United States and in the world for power generation, because of its reliability and …

Reactive Thin Film Polymers And Thin Film Composite Membranes For The Rapid Screening Of Uranium Isotopes, Abenazer W. Darge

All Dissertations

Traditional radiochemistry approaches for the detection of trace-level alpha-emitting radioisotopes in water require lengthy offsite sample preparations and do not lend themselves to rapid quantification. Therefore, a novel platform is needed that combines onsite purification, concentration, and isotopic screening with a fieldable detection system. My dissertation research objective was to develop novel reactive thin polymer films and thin film composite membranes for the selective separation of uranium from environmental water followed by direct isotopic analysis by alpha spectroscopy. Chapter 1 reviews progress made on uranium separation from aqueous matrices and discusses methods used for the determination of isotopic composition.

Chapter …

Thermochemical And Continuum Modeling To Understand The Chemical Composition Of Pwr Fuel Crud, Jason T. Rizk

Doctoral Dissertations

Computational modeling of Chalk River Undesirable Deposits (CRUD) allows for the prediction of associated phenomena that impact nuclear power plant performance, reliability, and safety. It also provides insight into the physical mechanisms by which CRUD forms and affects plant performance. A major concern in pressurized water reactors (PWRs) is Axial Offset Anomaly (AOA) which is caused by CRUD’s proficiency at trapping boron within the reactor core. The ability to predict AOA and other phenomena requires a detailed explanation of the chemical composition of CRUD. By pairing computational models that can simulate the structure and species trapping with detailed thermochemical models, …

Thorium Dioxide Extraction From Monazite Ore, Jason Pan, Niall Phelan Terry, Katherine Glass, Eli Jenkins, Connor High

Chancellor’s Honors Program Projects

No abstract provided.

Numerical Study Of Spacer Grid Geometry In A 5 X 5 Nuclear Fuel Rod Bundle, Wan Chuan Fan

UNLV Theses, Dissertations, Professional Papers, and Capstones

Reactor fuel rod bundles serve as the primary heat source in light water reactors (LWRs), commonly found in the aforementioned PWR plants. The fuel rod bundles’ structure consists of a collection of fuel rods put into a parallel grid configuration. The bundles also include fuel rod spacers, which hold the fuel rods in place, in accordance with the grid. Repeating structures of the fuel bundles create the meta-structure in the reactor. In other words, the grid configuration repeats until it fills the entire space of the reactor. This results in reactor fuel rods suspended in the working fluid domain, oriented …

An Experimental And Numerical Investigation Of Flow Accelerated Flibe Corrosion, David B. Weitzel

Nuclear Engineering ETDs

Renewed interest in molten salt reactor technology has brought to light the need for a better understanding of FLiBe corrosion. To this end a flowing FLiBe corrosion test loop was designed to test the flow effects of FLiBe corrosion. The loop consists of a pump, melt tank, and stainless-steel tubing assembly that heats the molten salt to high temperatures and circulates it over test specimens. The experiment has been constructed and has completed initial shakedown testing.

To support the flowing FLiBe experiment, a numerical corrosion model that couples FLiBe electrochemistry, solid metal diffusion, and mass transport was implemented. The model …

Computational Fluid Dynamics Modeling And Comparison Of Advanced Techniques For Heat Transfer Augmentation For Nuclear Applications, Salman Mohammed Alzahrani

Doctoral Dissertations

“Passive safety is the most important feature of NuScale’s reactor designs. Twist tape is one passive heat enhance heat technique. The present research investigated thermo-hydraulic characteristics of natural and forced convection of water under different configurations of twisted tape inserted in tube as well as NuScale rod bundles for uniform wall heat flux using computational fluid dynamics (CFD) using ANSYS Fluent 18.1. Results for twist tape inserted in tube under natural circulation showed that heat transfer enhanced and pressure drop increased to 28% and 102.8% over the plain tube respectively. Regularly spaced tapes, and different widths of the twisted tapes …

Experimental Investigation Of Liquid Contact In The Developing Post-Dryout Chf Flow Boiling Regime Using Surface Mounted Thermistors, Hiralkumar Harshadbhai Patel

Doctoral Dissertations

"Understanding heat transfer in the post-critical heat flux (CHF) flow boiling regime is important for determining the performance of the heat transfer equipment for various industrial applications requiring high heat transfer rates, e.g., heat exchangers, boilers, chemical and nuclear reactors. Liquid can be present in the core of the flow channel in the form of entrained liquid droplets, especially immediately downstream of film dryout. These droplets are suspected to provide an important heat transfer mechanism as they impinge on the heated wall. The objective of the current study is to investigate liquid contact with the heated wall in this flow …

Air Ingress And Heat-Driven Flow Relaminarization In A Very High Temperature Reactor (Vhtr), Apoorva Rudra

Dissertations and Theses

Very High Temperature Reactors (VHTRs) are one of six Generation IV reactors that have been proposed for DOE’s Next Generation Nuclear Plant. In addition to using gaseous coolants, VHTRs also display benefits of passive safety systems including intra-core natural circulation for heat removal in accident scenarios. However, a number of substantial engineering challenges are expected in VHTRs, and due to the high temperatures of the coolant involved, material behavior in various components needs to be better understood. Our work focuses mainly on two key phenomena that could lead to localized hot spots in the VHTR reactor core if not addressed …

Plenum-To-Plenum Heat Transfer Characteristics Under Natural Circulation In A Scaled-Down Prismatic Modular Reactor, Salman Mohammed Alshehri

Doctoral Dissertations

“Gas-cooled reactor (GCR) is being developed under the Next Generation Nuclear Plant Program (NGNP) in nuclear engineering studies. As the world searches for an energy source with high energy density, clean, abundant, and storable nature to avoid global warming issues, GCR seems to be a promising solution, particularly the possibility of producing hydrogen. Studying and developing the safety analysis and GCR technologies are required for the optimum design and safety of GCR system. Multiphase Reactors Engineering and Applications Laboratory (mReal) at Missouri University of Science and Technology (S&T) has developed a natural convection heat transfer test facility with one riser …

Computational Design And Numerical Analyses Of Thermal-Hydraulics In A Pwr-Type Small Modular Nuclear Reactor, Vivek Murlidhar Rao

Doctoral Dissertations

"This dissertation focuses on computational design of a PWR-type small modular nuclear reactor (SMR), and analysis of coolant thermal-hydraulics during steady-state operation. Physical design of the SMR is based on the existing AP-1000 and Small Modular Reactor designs by Westinghouse Nuclear.

The first paper discusses a two-stage simulation of turbulent flow in the lower plenum of the RPV. In the first stage, four time-dependent Reynolds-Averaged Navier-Stokes (RANS) based turbulence models were used to simulate turbulent flow, compare predictions and identify an appropriate turbulence model. In the second stage, the selected turbulence model was once again used to simulate flow on …

The Significance Of Grouping And Missed Bubbles On Interfacial Area Concentration And Void Fraction, Chandller Stephen-Leslie Mills

Doctoral Dissertations

"The two-fluid model is used in nuclear reactor safety codes. Two of the important constitutive relations will be discussed in this study, the interfacial area concentration and void fraction. The Interfacial area concentration is directly affected by the number of bubbles and how these bubbles are categorized into groups. In this study, a new algorithm was implemented to account for trailing bubbles, bubbles with short response times, and the categorization of bubbles based upon diameter for all group 1 bubbles. The optical and conductivity probes were used to determine the void fraction and interfacial area concentration in a bubble column. …

Improving Predictive Capabilities Of Classical Cascade Theory For Nonproliferation Analysis, David Allen Vermillion

Doctoral Dissertations

Uranium enrichment finds a direct and indispensable function in both peaceful and nonpeaceful nuclear applications. Today, over 99% of enriched uranium is produced by gas centrifuge technology. With the international dissemination of the Zippe archetypal design in 1960 followed by the widespread illicit centrifuge trafficking efforts of the A.Q. Khan network, traditional barriers to enrichment technologies are no longer as effective as they once were. Consequently, gas centrifuge technology is now regarded as a high-priority nuclear proliferation threat, and the international nonproliferation community seeks new avenues to effectively and efficiently respond to this emergent threat.

Effective response first requires an …

Preliminary Investigation For The Development Of Surrogate Debris From Nuclear Detonations In Marine-Urban Environments, Adam G. Seybert

Masters Theses

No nuclear weapon has ever been detonated in a United States city. However, this also means the nuclear forensic community has no actual debris from which to develop analytical methods for source attribution, making the development of surrogate nuclear debris a vital undertaking. Moreover, the development of marine-urban debris presents an unusual challenge because unlike soil and urban structures, which remain compositionally consistent, the elemental composition of harbor and port waters fluctuates considerably due to natural phenomenon and human activity. Additionally, marine vessel composition and cargo can vary dramatically. While early US nuclear tests were carried out in shallow-water coastal …

Particle Entrainment Studies From Dry And Wet Bed, Saber Ayatollahi

Electronic Thesis and Dissertation Repository

During the Fluid Coking Process™ bitumen is sprayed into a fluidized bed of hot coke particles. The bitumen undergoes thermal cracking and is converted into gasses, condensable vapors, and solid coke, which deposits on the coke particles. These vapors rise through the vessel and result in entrainment of coke particles. Wet fine coke particles from the freeboard region enter the cyclone and contribute to the fouling of the Coker cyclones which can lead to the premature shut-down of Fluid Cokers.

The primary objective of this research is to determine how bed wetness affects entrainment.

First, a new fluidized bed was …

Cd Transport In Eutectic Licl-Kcl And Contamination Of Zr Metal And Thermal Dehydration Of Bulk Licl-Kcl, Nicholas Azoy Earle

Masters Theses

Researchers at Idaho National Labs have noted unexpectedly high Cd content in empty cladding hulls after processing in the Mark-IV ER. It has been theorized that Cd metal is transporting from the LCC pool through the eutectic LiCl-KCl salt bath to the anode baskets containing the empty hull where it is retained as a Zr-Cd intermetallic. This study sought to replicate the Cd contamination in a dry Ar glovebox using small-scale analogue of the Mark-IV ER salt-Cd metal system.

Anhydrous eutectic LiCl-KCl was an essential regent in this research and experiments were conducted to investigate the feasibility of dehydrating nominally …

Study Of Heat Transfer Phenomenon During Natural Convection, Muhammad Yousaf

Doctoral Dissertations

"The purpose of the present study was to numerically investigate the effects of the roughness elements on the heat transfer during natural convection. A computational algorithm was developed based on the Lattice Boltzmann method to conduct numerical study in two-dimensional rectangular cavities and Rayleigh-Bénard cell. A single relaxation time Bhatnagar-Gross-Krook model of Lattice Boltzmann method was used to solve the coupled momentum and energy equations in two-dimensional lattices. Computational model was validated against previous benchmark solutions, and a good agreement was found to exist. A Newtonian fluid of Prandtl (Pr) number 1.0 was considered for this numerical study. The range …

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 …

Investigation And Modeling Of Uranium Polarization For The Electrorefining Of Scrap U-Mo Foils, Melissa Rose

Open Access Dissertations

A uranium molybdenum alloy fuel has been proposed to convert research and test reactors from highly enriched uranium to low enriched uranium to increase the proliferation resistance at such reactors. Pyroprocessing has been selected to recover uranium from the scrap produced in the manufacture of this novel fuel type. Electrorefining, the main separation process of pyroprocessing, is modeled through a novel approach using corrosion theory. To use corrosion theory, knowledge of uranium polarization and kinetic parameters such as Tafel constant, transfer coefficient and exchange current density are required. Uranium polarization was investigated at five temperatures and three scan rates in …

Development Of A Monitoring Framework For The Detection Of Diversion Of Intermediate Products In A Generic Natural Uranium Conversion Plant, Jennifer L. Ladd-Lively

Doctoral Dissertations

The objective of this work is the development of an on-line monitoring and data analysis framework that could detect the diversion of intermediate products such as uranium dioxide, uranium tetrafluoride, and uranium hexafluoride in a natural uranium conversion plant (NUCP) using a multivariate statistical approach. This was an initial effort to determine the feasibility of this approach for safeguards applications. This study was limited to a 100 metric ton of uranium (MTU) per year NUCP using the wet solvent extraction method for the purification of uranium ore concentrate. A key component in the multivariate statistical methodology was the Principal Component …

Studies Of Reaction Processes For Voloxidation Methods, Jared Allen Johnson

Doctoral Dissertations

Various facets of the voloxidation process and processes that have been derived from the voloxidation process have been investigated since its development over four decades ago. Despite the numerous studies performed, gaps remain in understanding of particular fundamental aspects of the reaction processes. In this work, several of these specific aspects of the oxidation processes for standard voloxidation and NO₂ [nitrogen dioxide] voloxidation are studied experimentally and modeled.

In the case of standard voloxidation, the oxidation rates of simulant UO_­2 [uranium dioxide] pressurized water reactor pellets in oxygen-rich environments were studied with an emphasis on the controlling phenomena …

An Adaptive Nonparametric Modeling Technique For Expanded Condition Monitoring Of Processes, Matthew John Humberstone

Doctoral Dissertations

New reactor designs and the license extensions of the current reactors has created new condition monitoring challenges. A major challenge is the creation of a data-based model for a reactor that has never been built or operated and has no historical data. This is the motivation behind the creation of a hybrid modeling technique based on first principle models that adapts to include operating reactor data as it becomes available.

An Adaptive Non-Parametric Model (ANPM) was developed for adaptive monitoring of small to medium size reactors (SMR) but would be applicable to all designs. Ideally, an adaptive model should have …

Design And Analysis For Melt Casting Metallic Fuel Pins Incorporating Volatile Actinides, Xiaolong Wu

UNLV Theses, Dissertations, Professional Papers, and Capstones

Fundamental issues related to the selection of a metallic fuel casting furnace design are presented and discussed including heating mechanisms, casting issues, crucible design, and issues related to the mass transport of americium. The process of evaluating all of these different criteria is undertaken to select a concept that would have the greatest chance of success for casting americium in a metallic fuel rod. Based on this evaluation process, a concept for the casting of metallic fuel pins containing high vapor pressure materials is selected and discussed. The important physics of this concept include mass transport of americium from the …

Modeling And Simulation Of The Chemical Etching Process In Niobium Cavities, Qin Xue

UNLV Theses, Dissertations, Professional Papers, and Capstones

Niobium Cavities are important parts of the integrated NC/SC high-power linear accelerator (linac) that can accelerate over 100 mA of protons to several GeV. Surface finish of the niobium cavity plays an important role of achieving the best performance of niobium cavity. The chemical etching techniques have been widely used.

Chemical etching of the inner surface of the cavity is achieved by circulating acid through it. The acid interacts with the surface and eliminates imperfections. During the etching process, a pipe with baffles is inserted within the cavity to direct the flow along the surfaces.

A 2-D, axisymmetric, steady state, …