Digital Commons Network^™

Combined Radiation Detection Methods For Assay Of Higher Actinides In Separation Processes, Denis Beller, Charlotta Sanders, Warnick Kernan

Safeguards Campaign (TRP)

In the MPAC project, faculty and students are investigating the potential to use combined neutron and gamma-ray detector systems to measure quantities and isotopic constituents contained during separations and intermediate storage. This will require knowledge of the nuclear and decay characteristics of materials during processing, the development of conceptual designs of monitoring systems, radiation transport studies to develop an understanding of operational regimes, and experiments to confirm performance. In addition, both passive and active concepts will be investigated, including collaborations with the Idaho Accelerator Center at Idaho State University (ISU) to use electron linear accelerators for producing photoneutrons in situ, …

Fundamental And Applied Experimental Investigations Of Corrosion Of Steel By Lbe Under Controlled Conditions: Kinetics, Chemistry Morphology, And Surface Preparation, John Farley, Allen L. Johnson

Transmutation Sciences Materials (TRP)

Advanced nuclear processes and facilities (e.g., transmutation of nuclear waste, fast reactors, and spallation neutron sources) impose special demands on materials, which must withstand high temperatures, high radiation fields, and chemical corrosion. Proposed schemes for transmuting nuclear waste require a nonmoderating coolant such as lead-bismuth eutectic (LBE) or liquid sodium. While LBE corrodes most steels, small amounts of oxygen in the LBE greatly reduces the corrosion rate, and could ideally re-grow a damaged oxide layer in situ. The protective oxide layer would thus be self-healing. However, a fundamental understanding of the role of oxygen and passivating oxide layers is presently …

Effect Of Silicon Content On The Corrosion Resistance And Radiation-Induced Embrittlement Of Materials For Advanced Heavy Liquid Metal Nuclear Systems, Ajit K. Roy

Transmutation Sciences Materials (TRP)

The beneficial effects of Si on both the metallurgical and corrosion properties of Cr-Mo steels have previously been demonstrated at UNLV. Therefore, additions of Si ranging from 0.5-2.0 weight percent (wt%) was attempted in this investigation to explore Si effect on both the high temperature tensile properties and corrosion behavior of T91 grade steel. Corrosion studies in the presence of molten LBE could not be performed due to a lack of proper experimental facilities at UNLV. Therefore, detailed corrosion studies involving Si-containing T91 grade steels were performed in an aggressive aqueous solution of acidic pH. Further, significant efforts have been …

Theoretical Modeling Of Protective Oxide Layer Growth In Non-Isothermal Lead Alloy Coolant Systems, Yitung Chen, Taide Tan, Jinsuo Zhang, Jichun Li

Transmutation Sciences Materials (TRP)

In advanced nuclear energy systems, lead alloys emerge as strong candidates for transmutation and advanced reactor systems as nuclear coolants and spallation neutron targets. However, it is widely recognized that corrosion of materials caused by lead alloys presents a critical barrier to their industrial use. A few experimental research and development projects have been set up by different groups such as at Los Alamos National Laboratory to study the corrosion phenomena in their test facilities and to develop mitigation techniques and materials. One of the central or main techniques under development is to use active control of oxygen thermodynamic activity …

Development Of Nanostructure Based Corrosion-Barrier Coatings On Steel For Transmutation Applications, Biswajit Das

Transmutation Sciences Materials (TRP)

Advanced transmutation systems require structural materials that are able to withstand high neutron fluxes, high thermal cycling, and high resistance to chemical corrosion. The current candidate materials for such structures are ferritic and ferritic-martensitic steels due to their strong resistance to swelling, good microstructural stability under irradiation, and the retention of adequate ductility at typical reactor operating temperatures.

In parallel, lead-bismuth eutectic (LBE) has emerged as a potential spallation target material for efficient production of neutrons, as well as a coolant in the accelerator system. While LBE has excellent properties as a nuclear coolant, it is also highly corrosive to …

Reactor Physics Studies For The Afci Reactor-Accelerator Coupling Experiments Project, Denis Beller

Transmutation Sciences Physics (TRP)

The specific research objective of this three-year project was to design and conduct accelerator driven experiments, to help demonstrate the ability to design, compute, and conduct ADS experiments and to predict and measure source importance, coupling efficiency, sub-critical reactor kinetics and source-driven transients. In addition, databases were created for both steady state and transient ADS experiments for the nuclear community to develop and test new computational codes and methods. The importance of a driving neutron source in various regions of different subcritical assemblies was mapped. Experiments were conducted and compared to calculations with radiation transport and thermal hydraulics codes such …

Immobilization Of Fission Iodine By Reaction With A Fullerene Containing Carbon Compound And Insoluble Natural Matrix, Spencer M. Steinberg, Gary Cerefice, David W. Emerson

Separations Campaign (TRP)

Observations related to the oxidation of iodide to iodine (I₂) or hypoiodic acid (HIO) by MnO₂ were continued. The formation of triiodide presumable involves the adsorption of iodide onto the MnO₂ surface (perhaps displacing a surface hydroxyl group). The iodide should be subsequently oxidized and released back into solution as IOH or I₂, which rapidly forms I₃ ^-. The kinetic data has been modeled as a first order process. First order rate constants have been obtained for the formation of iodine in the presence of MnO₂. The increase in iodide …

Evaluation Of Fluorapatite As A Waste-Form Material, Dennis W. Lindle, Oliver Hemmers, Dale L. Perry

Separations Campaign (TRP)

Argonne National Laboratory has proposed a new extraction procedure to handle TRISO-coated fuels, the Fluoride Extraction Process (FLEX). The FLEX process is designed to separate the uranium in the fuel from the actinides and most fission products by taking advantage of the unique properties of uranium hexafluoride (UF₆). In the FLEX process, the used TRISO fuel is reacted with zirconium fluoride salt, forming UF₆ and the fluoride salts of the actinides and fission products. At process temperatures, the UF₆ volatizes into a gas, and is released from the molten salt mixture. This leaves behind the actinides …

Electrochemical Separation Of Curium And Americium, David W. Hatchett, Kenneth Czerwinski

Separations Campaign (TRP)

The objective was to use electrochemical techniques to develop a thermodynamic understanding of actinide and lanthanide species in RTIL solutions, and use this data to effectively separate species with very similar chemical properties.

In consultation with a DOE collaborator, electrochemical methods and materials were evaluated and used to exploit the thermodynamic differences between similar chemical species enhancing the ability to selectively target and sequester individual species from mixtures. This project, in its third year, successfully completed phases 1, 2. Phase 3 was partially completed. The project expanded to include phase 4.

The following were specific goals for 2007-2008:

• To …

Fundamental Chemistry Of U And Pu In The Tbp-Dodecane-Nitric Acid System, Kenneth Czerwinski

Separations Campaign (TRP)

The research objective is to experimentally evaluate the fundamental speciation of Pu and U in the TBP-dodecane-nitric acid- AHA system and the effect of pertechnetate, specifically:

• To determine the influence of nitrate on the speciation of U and Pu in the TBP-dodecane-nitric acid system. The aqueous and organic speciation of U and Pu are examined as a function of the nitric acid concentration, nitrate concentration, actinide ion concentration, temperature, and time.

• To determine the speciation of U and Pu with AHA in the presence and absence of TBP-dodecane organic phase. The aqueous and organic speciation of U and …

Criticality Studies For Urex Processes, Denis Beller

Separations Campaign (TRP)

The completion of criticality experiments for mixtures of transuranic actinides (TRU; includes neptunium, plutonium, americium, and curium) that will be created during the separation of used nuclear fuel may be a requirement in order to construct prototype plants for the Global Nuclear Energy Partnership (GNEP). In this program and the Advanced Fuel Cycle Research and Development (AFC R&D) program that supports it, economic and environmental methods are being developed to reduce the impact of waste from commercial nuclear fuel cycles.

Recycling of used fuel by chemically separating it into U, fission products, and TRU would be the first step in …

F-Element Electrochemistry In Rtil Solutions: Electrochemical Separation Of Lanthanides And Actinides, David W. Hatchett

Separations Campaign (TRP)

Electrochemical methods can be used to effectively separate actinide and lanthanide species from complex mixtures. This is based on the unique electrochemical properties of each specific target species. In studies it has been found that, with the exception of Ce, aqueous solutions provide unsuitable electrochemical windows to effectively evaluate the thermodynamic properties that are useful for chemical separations. Therefore, a more novel approach was examined which eliminated the aqueous solution with a room temperature ionic liquid (RTIL) solution. RTIL solutions do not suffer from the side reactions that are prominent in aqueous environments. In addition, the potential window is much …

Evaluation Of Fundamental Radionuclide Extraction Data For Urex, Kenneth Czerwinski

Separations Campaign (TRP)

The speciation of technetium and actinides in advanced solvent extraction systems is the basis for their manipulation in separations. The ability to understand and predict radionuclide speciation is paramount to successful modeling of proposed separation systems. This project will examine the speciation of radionuclides in different stages of the uranium extraction (UREX) separation scheme, providing data useful to modeling. The areas to be examined include the speciation of uranium and plutonium with tributylphosphate and the kinetics and thermodynamics of lanthanides and actinides in the TALSPEAK (Trivalent actinide lanthanide separation by phosphorous reagent extraction from aqueous complexes) system. The complexation constants …

Separation Of Technetium From Uranium And Waste Form Synthesis, Kenneth Czerwinski

Waste Forms Campaign (TRP)

In this project, systematic investigations on the Tc-Zr binary metal system will be evaluated for the first time. The synthesis of metallic Tc as well as its alloys with Zr will be evaluated. In order to provide valuable data to AFC R&D, the thermodynamic equilibrium phases, as well as their performance under repository conditions, will be examined.

The research objectives of this project are as follows:

• Evaluate anion exchange methods for achieving the separation of Tc from U.

• Synthesize metallic Tc from the separated product.

• Synthesize and characterize Tc alloys.

• Investigate Tc-corrosion and Tc-leaching of binary …

Evaluation Of Cs/Sr Waste Form For Long Term Storage And Disposal, Gary Cerefice, Longzhou Ma

Waste Forms Campaign (TRP)

To facilitate long-term storage, the disposal containers will need to be able to survive for the entire storage interval. The first aspect of the project will explore the potential interaction of the aluminosilicate waste form with the storage canister materials to determine if there is any corrosion or chemical interaction concerns for the storage of the materials. At the end of the storage interval, most of the cesium (¹³⁷Cs) in the waste form will have decayed to its daughter, barium (¹³⁷Ba). While this decay provides a significant reduction in the decay heat generated by the waste …

Mojave Applied Ecology Notes Winter 2008, Scott R. Abella, E. Cayenne Engel, Jill E. Craig

Mojave Applied Ecology Notes

Mojave Desert collaborative projects, fire history in Spring Mountains, Northshore Road rehabilitation, wildfires and invasive plants in American deserts conference, weed sentry surveys

Magnetohydrodynamics In Microchannels And Adhesion Properties Of Nanoporous Alumina Films, Hussameddine Kabbani

UNLV Retrospective Theses & Dissertations

In the first part of this dissertation, RedOx-based magnetohydrodynamic (MHD) flows in three-dimensional (3D) microfluidic channels are investigated theoretically with a coupled mathematical model consisting of the Nernst-Planck equations for the concentrations of ionic species, the local electroneutrality condition of the electric potential, and the Navier-Stokes equations for the flow field. The induced currents and flow rates in 3D planar channels are compared with the experimental data obtained from the literature and those obtained from the previous two-dimensional mathematical model. Then a new approximate closed form solution for the velocity profile of steady incompressible MHD flows in a rectangular micro-channel …

Experimental And Theoretical Control Of A Smart Projectile Fin Using Piezoelectric Bimorph Actuator, Venkat R Mudupu

UNLV Retrospective Theses & Dissertations

The goal of this work is to develop efficient control algorithms for the control of a smart projectile fin. Smart fins are deployed as soon as the projectile reaches the apogee and are used to steer the projectile towards its target by controlling the rotation angle of the fin. The fin is actuated using the piezoelectric macro-fiber composite (MFC) bimorph actuator which is completely enclosed within the aero-shell. The actuator is composed of two Macro Fiber Composites (MFC's), manufactured by Smart Material Co. The presented smart fin design minimizes the volume and weight of the unit; Two different models of …

A Systematic Approach To An Integrated Curriculum Model For Dental Education, Tanis Maria Stewart

UNLV Retrospective Theses & Dissertations

The purpose of this quantitative study was to determine the degree of curriculum integration within dental schools in North America. The intent of the study was to determine how an adaptation of the Fogarty (1991) framework of integration exhibits itself in dental education; An electronic survey conducted of the Academic Deans of dental schools in the United States and Canada resulted in a response rate of 54.09% (33/61). Frequencies, chi-square and Spearman rho (p) correlation coefficient were used for the statistical analyses of data; All survey respondents reported that their curricula include all levels of integration which comprise the adapted …

Estimates At Infinity For Positive Solutions To Problems Involving The P-Laplacian, Ralph W Thomas

UNLV Retrospective Theses & Dissertations

There has been much study of finding positive solutions to various logistic problems involving the Laplacian and the p-Laplacian; problems which, loosely speaking, contain a nonlinear term that behaves like lambdau p-1(1 - u gamma); In this paper we will first look for positive solutions to -Dpu=ax lup-2u-a xgu x∈RN 0.3 where g(s) behaves like sgamma-1, gamma > p, for s large. We will employ many of the same methods as Costa, Drabek and Tehrani, and in doing so will not only prove the existence of positive (weak) solutions, but will also have estimates for the behavior of these solutions at …

Microscopic And Spectroscopic Studies Of Metal Deposition On Carbon-Based Materials, Ich C Tran

UNLV Retrospective Theses & Dissertations

This dissertation is focused on studying the atomic and electronic structure of carbon-based materials, namely highly-ordered pyrolytic graphite (HOPG), single-walled carbon nanotubes (SWNT), and C60 fullerenes, with and without metal (Ti and Li) deposition. The work is motivated by ongoing efforts to understand and improve the hydrogen storage capability of carbon-based nanomaterials as well as their potential applications for developing novel electronic devices; Ti and Li deposition on the surface of SWNT, C60, and HOPG samples have been performed in ultra-high vacuum. The morphology and local geometric and electronic structure of the samples was investigated by scanning tunneling microscopy and …

Mentoring Novice Elementary Teachers In Science Teaching, Mary Sowder

UNLV Retrospective Theses & Dissertations

This dissertation explored how novice elementary teachers learn to teach science, how their preparation for teaching affects their classroom practice and their students' learning, and how they may be mentored toward more reform-based science practice. The instructional practices of four novice elementary teachers, two from traditional and two from alternative preparation programs, were studied as they worked with mentor teachers toward building pedagogical content knowledge for reform-based instruction in science. Data collected from interviews of novice and mentor teachers, from classroom observations of science lessons, from observations of mentor-novice conferences, and from student work were analyzed to discover patterns of …

Assessment In Higher Education: A Case Study On Assessment Of Student Learning In Three States, Hyla Winters

UNLV Retrospective Theses & Dissertations

This study examined how state participation in the National Forum on College-Level Learning project changed higher education system policy and institutional practices on assessment of student learning. The purpose of this study examined state higher education implementation practices for assessing student learning outcomes in selected land grant and community colleges before and after participation in the National Forum on College-Level Learning project; The results of this study are limited to the states of Nevada, Oklahoma, and Kentucky. To determine the implementation of state assessment policy at the institutional level, this study's theoretical framework was implementation theory. The research questions which …

Policies For Highway Financing: Gasoline Taxes And Other Alternatives, Vinod Vasudevan

UNLV Retrospective Theses & Dissertations

The development and maintenance of highway infrastructure in the US is becoming an important challenge due to increasing costs and revenues that are not adequate to meet the costs. Traditionally, fuel taxes have provided a significant portion of the revenues for the highway network. This research evaluates the impacts of changes in automobile and light truck fleet fuel economies, as well as hybrid and alternative fuel vehicles in the fleet, on gasoline tax based revenues. Vehicle sales, vehicle survivability, and fuel consumption data from 1980 to 2005 were used to estimate the fleet mix, Vehicle Miles Travel (VMT) by fleet …

The Development Of A Replicable Model For Implementation Of A High School Minimum Competency Program, Nils Golden Bayles

UNLV Retrospective Theses & Dissertations

Problem. A twenty year decline on college entrance examination test scores achieved by high school students and two massive national studies of education in the United States, the Coleman Report and the National Assessment of Educational Progress, highlighted a nationwide concern about student.

The Development Of A Consensus Management By Objectives Model And A Comparison To The Clark County School District Management And Accountability System For Secondary Schools, Agustin A Orci

UNLV Retrospective Theses & Dissertations

The purpose of the study was to examine selected business and education management by objectives (MBO) models and identify the common elements. These elements resulted in a consensus MBO model which was compared to determine agreement with the Clark County School District's Management and Accountability System for Secondary Schools. Educational accountability, the theoretical bases for MBO and MBO models in business and education were treated in the review of the literature. Graphic models developed in the study included the Clark County District's Management and Accountability System for Secondary Schools and a consensus MBO model; A management process based on the …

Solution Of Heat Transfer And Fluid Flow Problems Using Meshless Radial Basis Function Method, Nagamani Devi Kalla

UNLV Retrospective Theses & Dissertations

In the past, the world of numerical solutions for Heat Transfer and Fluid Flow problems has been dominated by Finite Element Method, Finite Difference Method, Finite Volume Method, and more recently the Boundary Element Method. These methods revolve around using a mesh or grid to solve problems. However, problems with irregular boundaries and domains can be difficult to properly discretize; In this thesis, heat transfer and fluid flow problems are solved using Radial Basis Functions. This method is meshless, easy to understand, and even easier to implement. Radial Basis Functions are used to solve lid-driven cavity flow, natural convection in …

Titanium Hydride Up To 90 Gpa: Synchrotron X-Ray Diffraction Studies, Patricia E Kalita

UNLV Retrospective Theses & Dissertations

The structure and behavior of titanium hydride was studied on compression to about a megabar. Angle-dispersive as well as energy-dispersive synchrotron X-ray diffraction studies were carried out in situ, in diamond anvil cells, in several compression and decompression sequences. A phase transition from a cubic to a tetragonal structure was observed. The pressure evolution of the diffraction patterns revealed that the cubic (Fm-3m) to tetragonal ((4/mmm) phase transition occurs at about 0.6 GPa. The transition was found to be reversible on decompression from 34 GPa but irreversible on decompression from 90 GPa. The influence of the pressure transmitting medium on …

Numerical Modeling Of High Temperature Shell And Tube Heat Exchanger And Chemical Decomposer For Hydrogen Production, Gayatri Kuchi

UNLV Retrospective Theses & Dissertations

This thesis deals with the development of a three-dimensional numerical model of high temperature shell and tube heat exchanger and chemical decomposer to examine the percentage decomposition of a sulfur trioxide gaseous mixture for the production of hydrogen by the sulfur-iodine thermochemical water splitting cycle, a candidate cycle in the U.S. Department of Energy Nuclear Hydrogen Initiative. A counter flow type straight tube shell and heat exchanger concept is chosen for the analysis. The reacting fluid is a mixture of sulfur trioxide gas and water vapor inside the tubes of the heat exchanger and high temperature helium is the gas …

Neutron Cross-Section Sensitivity Studies In Higher Actinides For Criticality Safety In Reprocessing, Lawrence J Lakeotes

UNLV Retrospective Theses & Dissertations

During reprocessing, the spent fuel rod can be divided up into its component parts for separation into different waste streams. These radioactive streams are then directed appropriately toward low-level waste (LLW) storage, high-level waste (HLW) storage, or reuse into a recycled fuel pin. [1]; The issue that requires evaluation is the nuclear reaction of the higher actinides in reprocessing in an aqueous solution with regard to small temperature changes. This will need an analysis of neutron cross section, which is the measure of the probability that a nuclear reaction will occur; The isotopes' cross sections need to be temperature corrected. …