Digital Commons Network^™

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 …

Where Sin Abounds: A Religious History Of Las Vegas, Stanley Allen Steward

UNLV Retrospective Theses & Dissertations

Las Vegas has long been stigmatized with the label of "Sin City." While it is not difficult to understand how this image of Las Vegas came about, the power of this stereotype has masked one of the most interesting aspects of the local culture. It is a common assumption of many outsiders that Las Vegas is a spiritual wasteland devoid of any significant religious community and bereft of meaningful values or culture. But this is not the case. Las Vegas has a large, healthy, and expanding religious community. Within the religious milieu, there is a strong and rapidly expanding pentecostal …

The College Choice Phenomenon: An Exploration Of Parental Perceptions, Sandra Jean Lord Thomas

UNLV Retrospective Theses & Dissertations

Napoleon Bonaparte coined the maxim; "The future destiny of the child is always the work of the parent" (Evans, 1971, p. 18). A parent plays a key part in the development and progression of a child. Consequently, children often adopt parental perceptions of the world around them. The college choice phenomenon is no exception; parents perform a critical role. The purpose of this study was to examine the role parents played in the college choice phenomenon. The study employed a qualitative research approach with a quantitative component to explore parental perceptions and the interrelated roles of parents, students, high school …

Dialogical Inquiry In Critical Literacy: A Staff Development Intervention Study, Michelle Mcclellan Truman

UNLV Retrospective Theses & Dissertations

This study systematically examined the journey of a group of eight elementary school teachers and their administrator as they explored the social, political, and cultural world of critical literacy and its relationship to teaching. This expedition included using texts as social tools, which facilitated participants' critical reflections of personal beliefs and practices. They also investigated through dialogical inquiry the social, historical, and political elements that comprised their own cultural and historically situated identities. Data were collected through ethnographic methods, and four case studies were developed through artifacts, writing samples, transcriptions of discussions, observations, and interviews. Four individuals were chosen to …

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 …

A Study Of Post-Tenure Review *Policies Among Nevada Community Colleges And The Peer Institutions Of Ccsn, Thomas M Peacock

UNLV Retrospective Theses & Dissertations

This study carries forward the research of post-tenure review in selected community colleges. Administrators, faculty leadership, and faculty from the four (4) community colleges in Nevada and the seven (7) peer institutions of the Community College of Southern Nevada (CCSN) participated in this research; A descriptive survey instrument was used that was formatted using Likert-type items. The participants were asked to rate the degree to which they agreed or disagreed with the 27 statements; Statements 1--15 were designed to reflect the participant perceptions on how their institutions post-tenure review procedures comported with the AAUP's MINIMUM STANDARDS FOR GOOD PRACTICES IF …

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, …

Graphic Organizers, Activity, And The Positioning Of Language And Learners: An Ethnographic Case Study, John Allan Unger

UNLV Retrospective Theses & Dissertations

There were two main purposes for this research and one parallel purpose. One main purpose was to investigate how learners of English in an EFL/ESL context, who were also teachers of English and/or learning to be teachers of English, perceived and responded to different types of graphic organizers and associated activities. These graphic organizers and activities were presented at a university in Northern Thailand through an advanced reading comprehension course for preservice and inservice teachers taught by the primary researcher. The second main purpose was to explore, synthesize, and apply theories of mediated activity and research methods originating from or …

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 …

The Relationship Of Job Satisfaction To Role Ambiguity And Role Conflict Among School Counselors, Lisa Marie Violanti

UNLV Retrospective Theses & Dissertations

Elementary and secondary school counselors in the 16 smaller school districts in Nevada, excluding Clark County, were chosen for a study which investigated the nature and extent to which school counselors were experiencing role ambiguity and role conflict. It also investigated the extent to which these factors were related to counselors overall job satisfaction. A written instrument consisting of The Role Questionnaire (Rizzo, 1970) and the Teacher Job Satisfaction Questionnaire (Lester, 1984) was used with selected full-time K--12 counselors to measure role ambiguity and role conflict and their relationship to job satisfaction specifically in the areas of: colleagues, supervision, responsibility, …

"The German Arizonians": Ethnic Identity And Society Formation On A Southwestern Frontier, 1853--World War I, Gerhard Grytz

UNLV Retrospective Theses & Dissertations

This study discusses the experiences and the acculturation process of German immigrants in Arizona from the Gadsden Purchase of 1853 to World War I. German immigrants with distinct regional identities, Bavarians, Badeners, Wuerttembergers, Rhinelanders, and Prussians, made the transition to a regional New World identity and became Arizonans. Even though their history is ultimately the story of acculturation to a dominant society, it is the process that is important. Based on the analysis of census schedules, letters, newspaper reports, interviews, and other archival materials, this study tries to uncover the forces and mechanisms that determined the processes that formed American …

The Use Of Problem-Based Learning In Graduate Programs Of Higher Education, Lisa Ann Edler

UNLV Retrospective Theses & Dissertations

This study was intended to discover what Problem-Based Learning (PBL) looks like in graduate departments of higher education according to faculty who use PBL methodology in their curriculum and graduate students who experience PBL in their courses. This study also attempted to further understand the advantages, disadvantages, and challenges of PBL as perceived by both faculty and graduate students; After a comprehensive review of literature, two surveys were constructed, one for faculty and one for graduate students. The questions for both surveys were composed based on the information gleaned from the review of literature. The American Association of Higher Education …

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 …

The Effect Of Ambient Scent On Affiliation Behaviors And Social Interactions, Dina Marie Victoria Zemke

UNLV Retrospective Theses & Dissertations

The intent of the study was to explore if the focus group and the meetings industries can provide meeting environments that would be more conducive to communication and more productive. The concepts tested in this study are based in environmental psychology, or the study of how the physical environment affects individual and group behavior within the environment. Past studies have examined various ambient conditions and other aspects of the physical environment and their effects on retail environments. However, the characteristics that set services businesses apart from product marketing and retail businesses require new techniques to evaluate the effect of the …