Digital Commons Network^™

Radiation Transport Modeling Using Parallel Computational Techniques, William Culbreth, Denis Beller

Reactor Campaign (TRP)

The second year of this project involved modeling several aspects of the LANCSE beam experiments:

• Modeling targets of varying diameter in air, in a vacuum, and in the presence of humid air;
• Modeling various proton beam profiles;
• Modeling the effects of off-axis proton beam impingement on the target;
• Modeling the asymmetry introduced by the steel table below the target;
• Modeling the effect of varying ratios of Pb to Bi and the effect of impurities; and
• Modeling the system, including other structures within the test room.

With the experience gained through modeling these systems, the UNLV researchers plan, with the assistance …

Monte Carlo Verification And Modeling Of Lead-Bismuth Spallation Targets, Daniel R. Lowe

Reactor Campaign (TRP)

No abstract provided.

University Of Nevada, Las Vegas Transmutation Research Program Annual Report 2002, Anthony Hechanova, Elizabeth Johnson, Gary Cerefice

Transmutation Research Program Reports (TRP)

The UNLV Transmutation Research Program consists of four components: Program Support, Research Infrastructure Augmentation, International Collaboration, and Student Research.

In the first year of the program, the student research component was supported by the infrastructure augmentation and the program support components. In the second year of the program, the fourth leg of the support system, international collaborations, was added to the research support system.

Corrosion Of Steel By Lead Bismuth Eutectic, John Farley, Allen L. Johnson, Dale L. Perry

Transmutation Sciences Materials (TRP)

Materials for transmuter systems must be able to tolerate high neutron fluxes, great temperatures, and chemical corrosion. For lead bismuth eutectic (LBE) systems, there is an additional challenge in that the corrosive behaviors of materials in LBE are not well understood. Most of the available information on LBE systems has come from the Russians, who have over 80 reactor-years experience with LBE coolant in their Alpha-class submarine reactors. The Russians found that the presence of small amounts of oxygen (on the order of parts per million) in the LBE significantly reduced corrosion. However, a fundamental understanding and verification of its …

Surface Studies Of Corrosion Of Stainless Steel By Lead Bismuth Eutectic, Daniel Koury, Brian D. Hosterman, John Farley, Dale L. Perry, D. Parsons, J. Manzerova, Allen L. Johnson

Transmutation Sciences Materials (TRP)

Why is Lead Bismuth Eutectic Important?

• Changing national security stances have led to reexamination of nuclear waste reprocessing

• Dangerous actinides can be separated and

• Transmuted into safer products, creating a waste form dangerous for only hundreds of years, in addition to the production (up to 1/3 of the original fission energy) of useful energy

• Non-moderating coolants or spallation targets for production of fast neutrons is required for transmutation

• Russian experience with LBE coolants in their nuclear submarine fleet makes LBE an attractive possible transmutation coolant technology

• Corrosion of steel by LBE is an important …

Environment-Induced Degradation And Crack-Growth Studies Of Candidate Target Materials, Ajit K. Roy, Brendan O'Toole, Zhiyong Wang, David W. Hatchett

Transmutation Sciences Materials (TRP)

The primary objective of this task is to evaluate the potential for the environmentally-assisted cracking of candidate target materials for applications in spallation-neutron-target systems, such as accelerator-driven system for the transmutation of waste. The materials selected for evaluation and characterization are martensitic stainless steels (SS) including Alloys HT- 9, EP 823 and Type 422 stainless steel.

More recently, this experimental program has been expanded to evaluate the effect of molten lead-bismuth eutectic (LBE) on the corrosion behavior of target materials in the presence of oxygen. Since the materials performance laboratory (MPL) at UNLV currently cannot accommodate this type of testing, …

Modeling Corrosion In Oxygen Controlled Lbe Systems With Coupling Of Chemical Kinetics And Hydrodynamics, Samir Moujaes, Yitung Chen

Transmutation Sciences Materials (TRP)

The corrosion of structural materials is a major concern for the use of lead-bismuth eutectic (LBE) systems for nuclear applications such as in transmuter targets or fast reactors. Corrosion in liquid metal systems can occur through various processes, including, for example, dissolution, formation of inter-metallic compounds at the interface, and penetration of liquid metal along grain boundaries. Predicting the rate of these processes depends on numerous system operational factors: temperature, system geometry, thermal gradients, solid and liquid compositions, and velocity of the liquid metal, to name a few. Corrosion, along with mechanical and/or hydraulic factors, often contributes to component failure. …

Modeling Of Corrosion In Oxygen Controlled Lead Bismuth Eutectic Systems With The Coupling Of Chemical Kinetics And Hydrodynamics, Samir Moujaes, Yitung Chen, Kanthi Kiran Dasika, Chao Wu

Transmutation Sciences Materials (TRP)

Objectives:

• To simulate a 2-D model of the Materials Test Loop by approximating it to be a toroid with a pie cross section for the purpose of comparing the simulated results with the analytical results.
• The temperature and concentration profiles on the wall boundaries imposed are similar to the actual test model.
• Geometry effects have great influence on local corrosion rate.
• A 2-D benchmark problem and a sudden expansion case are studied which show good consistency to analytical solution.
• Results from 2-D sudden expansion problem are similar to experimental data obtained by other researchers.

Development Of A Mechanistic Understanding Of High-Temperature Deformation Of Alloy Ep-823, Ajit K. Roy, Brendan O'Toole

Transmutation Sciences Materials (TRP)

The purpose of this task is to evaluate the mechanical properties of Alloy EP-823 at temperatures relevant to the transmutation processes. Testing has been initiated to evaluate the tensile properties of martensitic Alloy EP-823 stainless steel at temperatures ranging from ambient (25 °C) to 600°C. The test materials were thermally treated prior to the evaluation of their tensile properties. The deformation characteristics of these tensile specimens, upon completion of testing, will be evaluated by surface analytical techniques such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

Developing A Sensing System For The Measurement Of Oxygen Concentration In Liquid Pb-Bi Eutectic, Yingtao Jiang, Bingmei Fu, Woosoon Yim

Transmutation Sciences Materials (TRP)

Lead-bismuth eutectic (LBE) is a candidate as a spallation target in sub-critical transmutation systems and as a coolant in nuclear programs. One of the primary concerns with LBE systems is the corrosion of stainless steel, the primary structural material used in nuclear systems. To mitigate this problem, trace levels of oxygen can be introduced into the system, causing the formation of a protective oxide layer at the interface between the LBE and steel. To protect the steel components, this oxide layer must be properly maintained. However, too much oxygen will produce unwanted oxide precipitation within the coolant and elsewhere in …

Use Of Positron Annihilation Spectroscopy For Stress-Strain Measurements, Ajit K. Roy

Transmutation Sciences Materials (TRP)

One of the greatest challenges in evaluating the performance of materials in the real world is the determination of residual stresses, or the stresses induced in a material. Plastic deformation of metals and alloys produces an increase in the number of lattice imperfections known as dislocations, which by virtue of their interaction results in higher state of internal stress and reduces ductility. These stresses, if not properly annealed (released) can significantly degrade the long-term performance of the materials.

Due to the high temperatures and radiation fields typically encountered in most nuclear systems, such as accelerator-driven transmutation systems (ADS) and nuclear …

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

Transmutation Sciences Materials (TRP)

An innovative research program is proposed to investigate the corrosion of steel by lead alloys, and in particular lead-bismuth eutectic (LBE). In our previous work, some steels were found to be far more resistant to corrosion by LBE than others depending on surface preparation (cold working). This program would allow testing of crucial hypotheses about the causes of the observed increased corrosion resistance. We propose to build a new test facility at UNLV to expose steel samples to LBE as well as facilities to prepare steel samples as indicated by our work.

The unique capabilities of the test system will …

Effects Of Environmental Variables And Stress Concentration On Target Materials, Sudheer Sama

Transmutation Sciences Materials (TRP)

This paper presents a brief summary on stress corrosion cracking (SCC) behavior of alloy HT 9. The susceptibility of this alloy to SCC was evaluated by using constant load and slow strain rate test techniques in neutral and acidic solutions at ambient temperature and 90°C. A proof ring was used to apply tensile load to the smooth specimen for 30 days in constant load testing. In slow strain rate testing, the specimen was continuously strained in tension at a rate of 3.3 × 10^-6 sec^-1 until fracture.

Effects Of Environmental Variables And Stress Concentration On Cracking Of Spallation Target Materials, Ajit K. Roy, Ramprashad Prabhakaran, Mohammad K. Hossain

Transmutation Sciences Materials (TRP)

This paper presents the results of stress corrosion cracking (SCC) studies of two martensitic target materials, namely Alloy EP-823 and Type 422 stainless steel. The susceptibility to SCC was evaluated by using constantload and slow-strain-rate (SSR) test techniques in neutral (pH: 6-7) and acidic (pH: 2-3) aqueous solutions at ambient temperature and 90^oC. A proof ring was used to apply tensile load to the smooth cylindrical specimen for 30 days in constant-load testing. For SSR testing, the specimen was strained in tension until fracture at a strain rate of 3.3 x 10^-6 sec^-1.

Stress Corrosion Cracking Of Type 422 Stainless Steel, Ramprashad Prabhakaran

Transmutation Sciences Materials (TRP)

This paper presents the results of SCC tests of quenched and tempered martensitic Type 422 SS in neutral and acidic aqueous environments at ambient temperature and 90^oC.The susceptibility of smooth and notched tensile specimens to SCC was evaluated by using constant load (CL) and slow strain rate (SSR) test methods. During CL testing, a calibrated proof ring was used to apply a constant load to the test specimen. The magnitude of the applied stress was based on ambient temperature yield strength of the material. On the contrary, the test specimen during SSR testing was continuously strained in tension …

Neutron Multiplicity Measurements Of Target/Blanket Materials, Carter D. Hull, Denis Beller

Transmutation Sciences Physics (TRP)

To optimize the performance of accelerator driven transmutation systems (ADS), engineers will need to design the system to operate with a neutron multiplication factor just below that of a critical, or self-sustaining, system. This design criteria requires particle transport codes that instill the highest level of confidence with minimal uncertainty, because the larger the uncertainties in the codes, the larger the safety margin required in the design and the lower the efficiency of the ADS transmuter. For current design efforts, the MCNPX code is used to determine neutron production and transport for spallation neutron systems.

While providing a very useful …

Development Of Dose Coefficients For Radionuclides Produced In Spallation Targets, Phillip W. Patton, Mark Rudin

Transmutation Sciences Physics (TRP)

Dose coefficients permit simple determination of radiation dose associated with various exposure scenarios, and ultimately permit radiation safety personnel to assess the health risks to workers in a nuclear facility. Specifically, radiation safety personnel use dose coefficients to determine the radiation dose incurred to a tissue or organ system from a given exposure. These parameters are often expressed in terms of Annual Limits on Intake (ALIs) and Derived Air Concentrations (DACs).

Results from this study will be used to produce ALIs and DACs for these rare radionuclides created by spallation target systems that are not included in Federal Guidance Report …

Development Of Dose Coefficients For Radionulides Produced In Spallation Neutron Sources: Annual Report, Phillip W. Patton, Mark Rudin

Transmutation Sciences Physics (TRP)

The University of Nevada, Las Vegas (UNLV) Transmutation Research Program has been tasked to support U.S. Department of Energy (DOE) efforts to assess the health risks associated with the operation of each of their accelerator-driven nuclear facilities for both NEPA and PSAR development. Quantifying the radiological risks to workers will have to be addressed during the design and siting of each of these facilities. U.S. Environmental Protection Agency (EPA) Federal Guidance Report No. 11 “Limiting Values of Intake and Air Concentration and Dose Conversion Factors for Inhalation, Submersion, and Ingestion”, developed two derived guides, Annual Limit on Intake (ALI) and …

Nuclear Criticality, Shielding, And Thermal Analyses Of Separations Processes For The Transmutation Fuel Cycle, William Culbreth, Denis Beller

Separations Campaign (TRP)

The first step in any transmutation strategy is the separation of radionuclides in used nuclear fuel. The current separation strategy supporting the Advanced Fuel Cycle Initiative (AFCI) program is based on the use of a solvent extraction separation process to separate the actinides, fission products, and uranium from used commercial nuclear fuel, and on the use of pyrochemical separation technologies to process used transmuter fuels. To separate the fission products and transuranic elements from the uranium in used fuel, the national program is developing a new solvent extraction process, the Uranium Extraction Plus, or UREX+, process, based on the traditional …

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

Separations Campaign (TRP)

Fluorapatite, fluorinated calcium phosphate, has been identified as a potential matrix for the entombment of the zirconium fluoride fission product waste stream from the proposed FLEX process. If the efficacy of fluorapatite based waste-storage can be demonstrated, then new and potentially more-efficient options for handling and separating high-level wastes, based on fluoride-salt extraction, will become feasible. This proposal is for renewal of the UNLV portion of a dual-path research project to develop a process to fabricate a synthetic fluorapatite waste form for the ZrF₄, FP waste stream, characterize the waste form, examine its performance under environmental conditions, and …

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

Separations Campaign (TRP)

Argonne National Laboratory has proposed a new extraction procedure to handle TRISO-coated fuels, the Fluoride Extraction Process, or 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 …

Inside Unlv, Richard Jensen, Donna Mcaleer, Jennifer Vaughan, Cate Weeks, Carol C. Harter, Jeffrey Koep

Inside UNLV

No abstract provided.

Identifying The Barriers To Access To Higher Education For African -American Students: Opinions Of Successful African -American Educators, William Lewis Taylor

UNLV Retrospective Theses & Dissertations

The purpose of this study was to examine past and present social, educational, and financial barriers to African American access to and success within United States higher educational institutions, and identify and recommend ways of ameliorating those barriers for African American students in the future. Based on a comprehensive literature review and analysis of responses to an author-designed survey questionnaire mailed to a cross-section of current United States African American higher education administrators, the study identified and analyzed past and present impacts, on African Americans, of social, educational, and economic factors possibly impeding their higher education entry and success. These …

Postsecondary Readiness Skills: Perceptions Of Students With And Without Disabilities, Carol Mae White

UNLV Retrospective Theses & Dissertations

The purpose of this study was to investigate the differences in the perceptions of postsecondary readiness skills between students with emotional disorders, students with learning disabilities, and students with no disabilities. Participants consisted of 91 students, 12 students with emotional disorders, 47 students with learning disabilities, and 32 students without disabilities in grades 11 and 12 who were planning on transitioning to postsecondary education. Data were collected to determine if there were significant differences in perceptions of postsecondary readiness skills among the three groups of students, specifically on eight domains: general preparation, academic preparation, self-determination and advocacy, academic accommodations and …

Effects Of Classwide Peer Tutoring (Cwpt) On Social Interactions Of Children With And Without English Proficiency, Yaoying Xu

UNLV Retrospective Theses & Dissertations

Learning and Education occur in social contexts. The quality of children's peer relationships is an important indication of children's current and later social adjustment. Children with peer problems tend to experience higher levels of loneliness and other undesirable affective consequences, including social dissatisfaction and worrying about peer relations. Because of the limited language proficiency and cultural and ethnic differences among children with LEP, some of their social behaviors are considered inappropriate by their non-LEP teachers and peers. On the other hand, children with LEP may feel that they do not fit in a group or class activity. As a result, …

Modeling Of The Reciprocating, Pneumatic Impact Hammer, William Allan Bloxsom

UNLV Retrospective Theses & Dissertations

The motion of the reciprocating, pneumatic impact tool, the air-driven piston inside the tool, the chisel mounted into the tool, and the specifically designed single degree-of-freedom spring-damper-mass test fixture were modeled with a MATLAB computer code. The three tools modeled and evaluated experimentally were the Ingersoll-Rand IR-121 impact tool, the Sears Craftsman Medium Duty impact tool, and the ATSCO No.2 impact tool; The computer model of the accelerations of the tool and the test fixture mass were compared to the experimental data obtained on the actual test fixture by the three tools modeled. The correlation between the experimental data and …

Proposed Intra-District Methodology For Funding School Sites, Eva Marie White

UNLV Retrospective Theses & Dissertations

The purpose of this study was to develop an intra-district allocation-funding model for the Clark County School District (CCSD). Two models, a linear formula and a formula with a non-linear component, were developed and evaluated against a set of criteria from the research literature on characteristics of optimal funding formulas. Simulations of these models' impact on elementary, middle, and high schools in the Clark County School District were performed to ascertain the redistributive effect under two separate conditions, the first keeping current funding levels constant, and the second considering additional funding; The simulations indicated that under Model II, a linear …

Thermal Method For Measuring Perfusion In Transplanted Organs, Fredericka Delores Brown

UNLV Retrospective Theses & Dissertations

Adequate blood flow to the graft kidney is critical in the postoperative care of the transplant patient. Many factors can lead to disturbance in blood flow to the kidney, including the various effects of medication or volume status of the patient. Current methods to monitor blood flow depend on either duplex ultrasound or nuclear medicine renal flow scan. These modalities do not provide continuous monitoring of renal blood flow; A non-invasive technique to the organ is developed that will allow for the continuous qualitative and quantitative monitoring of blood perfusion in a kidney during postoperative periods utilizing an easily extracted …

Development Of Computer Science Online And Preliminary Validation Of Its Efficacy As An Instructional Environment, Gregory Paul Halopoff

UNLV Retrospective Theses & Dissertations

CS Online was developed as an instructional environment to address many issues facing computer science education. One of these is the need to rekindle interest in introductory computer science. CS Online seeks to accomplish this by offering active learning experiences set in real-world contexts. The intended outcomes are increased interest in computer science as an academic discipline, increased enrollments in related courses, and increased achievement resulting from cognitive skills growth; The CS Online system generated data while 36 high school students solved programming problems, and questionnaires administered by the system were used to collect information about students' self-regulatory skills and …

Comparing Web-Based Instruction To Traditional Instruction For Teaching Special Education Content To General Education Preservice Teachers, Kelly Elizabeth O'Neal

UNLV Retrospective Theses & Dissertations

It has been documented that there are multiple ways to offer teacher preparation course work. Incorporating technology into teacher preparation programs using Web-based instruction may help address obstacles involving distance and time. The purpose of this study was to investigate the efficacy of using Web-based instruction as an appropriate method for disseminating information and teaching undergraduates in the college of education about appropriate teaching practices for students with disabilities. Data were collected to answer three specific research questions related to student achievement, student satisfaction, and quality and quantity of discussions; There were 44 undergraduate participants in the study who were …