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Final Project Report

Description: This report provides a description of the main accomplishments of the EMSP funded research, including products such as conference presentations and publications (including those still in preparation). The purpose of this study was to better understand the chemical interactions between dissolved aqueous contaminants and carbonate minerals occurring as coatings on mineral grains in the vadose zone beneath the Hanford reserve. This information is important for construction of improved reactive transport models intended to predict the subsurface migration of contaminants. We made improvements to the hydrothermal atomic force microscope (HAFM) design to be used in this project. The original HAFM was built with funding from the U.S. DOE, Office of Basic Energy Sciences. Improvements include operating limits of 70 bars and 170 C, from an original limit of 12 bars and 150 C. This product is patented. We completed a series of studies of magnesite, MgCO3, because this mineral is structurally equivalent to calcite but reacts much more slowly, allowing us to study carbonate reactivity under pH conditions (i.e., low pH) that are much more problematic for studies of calcite but which are nevertheless relevant to in-situ conditions. We found that dissolving magnesite exhibits a dramatic change in step orientation, and therefore etch pit shape, as pH is lowered through 4.2 to 3 and 2. This change in step orientation is NOT accompanied by an increase in step velocity with decreasing pH. We also found that, after growing magnesite on a magnesite substrate, the newly grown magnesite dissolved much more readily than the underlying substrate magnesite, and exhibited far larger etch pit densities. This effect may have been related to the rate of growth or to the presence of an Fe impurity in the growth solutions. We studied the dissolution of magnesite and calcite (104) surfaces under a wider variety of ...
Date: December 12, 2003
Creator: Eggleston, Carrick M.
Partner: UNT Libraries Government Documents Department

Coupled modeling of groundwater flow solute transport, chemical reactions and microbial processes in the 'SP' island

Description: The Redox Zone Experiment was carried out at the Aespoe HRL in order to study the redox behavior and the hydrochemistry of an isolated vertical fracture zone disturbed by the excavation of an access tunnel. Overall results and interpretation of the Redox Zone Project were reported by /Banwart et al, 1995/. Later, /Banwart et al, 1999/ presented a summary of the hydrochemistry of the Redox Zone Experiment. Coupled groundwater flow and reactive transport models of this experiment were carried out by /Molinero, 2000/ who proposed a revised conceptual model for the hydrogeology of the Redox Zone Experiment which could explain simultaneously measured drawdown and salinity data. The numerical model was found useful to understand the natural system. Several conclusions were drawn about the redox conditions of recharge waters, cation exchange capacity of the fracture zone and the role of mineral phases such as pyrite, calcite, hematite and goethite. This model could reproduce the measured trends of dissolved species, except for bicarbonate and sulfate which are affected by microbially-mediated processes. In order to explore the role of microbial processes, a coupled numerical model has been constructed which accounts for water flow, reactive transport and microbial processes. The results of this model is presented in this report. This model accounts for groundwater flow and reactive transport in a manner similar to that of /Molinero, 2000/ and extends the preliminary microbial model of /Zhang, 2001/ by accounting for microbially-driven organic matter fermentation and organic matter oxidation. This updated microbial model considers simultaneously the fermentation of particulate organic matter by yeast and the oxidation of dissolved organic matter, a product of fermentation. Dissolved organic matter is produced by yeast and serves also as a substrate for iron-reducing bacteria. Model results reproduce the observed increase in bicarbonate and sulfate concentration, thus adding additional evidence for ...
Date: December 1, 2003
Creator: Samper, Javier; Molinero, Jorg; Changbing, Yang & Zhang, Guoxiang
Partner: UNT Libraries Government Documents Department

Effect of ion mass and charge state on transport of vacuum ARC plasmas through a biased magnetic filter

Description: The effect of ion mass and charge state on plasma transport through a 90{sup o}-curved magnetic filter is experimentally investigated using a pulsed cathodic arc source. Graphite, copper, and tungsten were selected as test materials. The filter was a bent copper coil biased via the voltage drop across a low-ohm, ''self-bias'' resistor. Ion transport is accomplished via a guiding electric field, whose potential forms a ''trough'' shaped by the magnetic guiding field of the filter coil. Evaluation was done by measuring the filtered ion current and determination of the particle system coefficient, which can be defined as the ratio of filter ion current, divided by the mean ion charge state, to the arc current. It was found that the ion current and particle system coefficient decreased as the mass-to-charge ratio of ions increased. This result can be qualitatively interpreted by a very simply model of ion transport that is based on compensation of the centrifugal force by the electric force associated with the guiding potential trough.
Date: December 1, 2003
Creator: Byon, Eungsun; Kim, Jong-Kuk; Kwon, Sik-Chol & Anders, Andre
Partner: UNT Libraries Government Documents Department

Leakage and Seepage in the Near-Surface Environment: An Integrated Approach to Monitoring and Detection

Description: Monitoring and detection of leakage and seepage of carbon dioxide (CO{sub 2}) in the near-surface environment is needed to ensure the safety and effectiveness of geologic carbon sequestration. Large leakage fluxes, e.g., through leaking wells, will be easier to detect and monitor than slow and diffuse leakage and seepage. The challenge of detecting slow leakage and seepage is discerning a leakage or seepage signal from within the natural background variations in CO{sub 2} concentration and flux that are controlled by a variety of coupled processes in soil. Although there are no direct examples of leaking geologic carbon sequestration sites on which to base a proposed verification approach, we have been guided by our prior simulation studies of CO{sub 2} leakage and seepage, which showed that large CO{sub 2} concentrations can develop in the shallow subsurface even for relatively small CO{sub 2} leakage fluxes. A variety of monitoring technologies exists for measuring CO{sub 2} concentration and flux, but there is a gap between instrument performance and the detection of a leakage or seepage signal from within large natural background variability. We propose an integrated approach to monitoring and verification. The first part of our proposed approach is to characterize and understand the natural ecosystem before CO{sub 2} injection occurs so that future anomalies can be recognized. Measurements of natural CO{sub 2} fluxes using accumulation chamber (AC) and eddy correlation (EC) approaches, soil CO{sub 2} concentration profiles with depth, and carbon isotope compositions of CO{sub 2} are needed to characterize the natural state of the system prior to CO{sub 2} injection. From this information, modeling needs to be carried out to enhance understanding of carbon sources and sinks so that anomalies can be recognized and subject to closer scrutiny as potential leakage or seepage signals. Long-term monitoring using AC, EC, and soil-gas ...
Date: December 18, 2003
Creator: Oldenburg, Curtis M. & Lewicki, Jennifer L.
Partner: UNT Libraries Government Documents Department

Comparison of particle simulation with j-parc linac mebt beam test results

Description: The construction of the initial part of the J-PARC linac has been started at KEK for beam tests before moving to the JAERI Tokai campus, where J-PARC facility is finally to be constructed. The RFQ and MEBT (Medium Energy Beam Transport) has already been installed at KEK, and the beam test has been performed successfully. In this paper, the experimental results of the beam test are compared with simulation results with a 3D PIC (Particle-In-Cell) code, IMPACT.
Date: December 16, 2003
Creator: Ikegami, M.; Kato, T., Igarashi, Z.; Ueno, A.; Kondo, Y.; Ryne, R. & Qiang, J.
Partner: UNT Libraries Government Documents Department

Optically Detected Magnetic Resonance and Thermal Activation Spectroscopy Study of Organic Semiconductors

Description: Organic electronic materials are a new class of emerging materials. Organic light emitting devices (OLEDs) are the most promising candidates for future flat panel display technologies. The photophysical characterization is the basic research step one must follow to understand this new class of materials and devices. The light emission properties are closely related to the transport properties of these materials. The objective of this dissertation is to probe the relation between transport and photophysical properties of organic semiconductors. The transport characteristics were evaluated by using thermally stimulated current and thermally stimulated luminescence techniques. The photoluminescence detected magnetic resonance and photoluminescence quantum yield studies provide valuable photophysical information on this class of materials. OLEDs are already in the market. However, detailed studies on the degradation mechanisms are still lacking. Since both optically detected magnetic resonance and thermal activation spectroscopy probe long-lived defect-related states in organic semiconductors, the combined study generates new insight on the OLED operation and degradation mechanisms.
Date: December 12, 2003
Creator: Kim, Chang-Hwan
Partner: UNT Libraries Government Documents Department

Development And Evaluation Of Stable Isotope And Fluorescent Labeling And Detection Methodologies For Tracking Injected Bacteria During In Situ Bioremediation

Description: This report summarizes the results of a research project conducted to develop new methods to label bacterial cells so that they could be tracked and enumerated as they move in the subsurface after they are introduced into the groundwater (i.e., during bioaugmentation). Labeling methods based on stable isotopes of carbon (13C) and vital fluorescent stains were developed. Both approaches proved successful with regards to the ability to effectively label bacterial cells. Several methods for enumeration of fluorescently-labeled cells were developed and validated, including near-real time microplate spectrofluorometry that could be performed in the field. However, the development of a novel enumeration method for the 13C-enriched cells, chemical reaction interface/mass spectrometry (CRIMS), was not successful due to difficulties with the proposed instrumentation. Both labeling methodologies were successfully evaluated and validated during laboratory- and field-scale bacterial transport experiments. The methods developed during this research should be useful for future bacterial transport work as well as other microbial ecology research in a variety of environments. A full bibliography of research articles and meeting presentations related to this project is included (including web links to abstracts and full text reprints).
Date: December 17, 2003
Creator: Fuller, Mark E. & Onstott, Tullis C.
Partner: UNT Libraries Government Documents Department

The Use of Radar Methods to Determine Moisture Content in the Vadose Zone

Description: Water content is a critical parameter affecting both liquid-phase and vapor-phase contaminant transport in the vadose zone. This means that accurate estimate of in situ water content must be obtained in order to design for the appropriate handling or remediation of a contaminated region of the vadose zone. Traditional methods of sampling the subsurface by drilling and/or direct sampling are very time consuming, limited in terms of spatial coverage, and have the associated risk of contacting and increasing the size of the contaminated area. One solution is to use geophysical methods which can provide a high-resolution, non-invasive means of sampling or imagin the subsurface.
Date: December 28, 2003
Creator: Knight, Rosemary
Partner: UNT Libraries Government Documents Department

TEST & EVALUATION REPORT FOR THE HEDGEHOG-II PACKAGING SYSTEMS DOT-7A TYPE A CONTAINER

Description: This report documents the US. Department of Transportation Specification 7A (DOT-7A) Type A compliance test and evaluation results for the Hedgehog-II packaging systems. The approved Hedgehog-II packaging configurations provide primary and secondary containment. The approved packaging configurations described within this report are designed to ship Type A quantities of radioactive materials, normal form. Contents may be in solid or liquid form. Liquids transported in the approved 1 L glass bottle assembly shall have a specific gravity of less than or equal to 1.6. Liquids transported in all other approved configurations shall have a specific gravity of less than or equal to 2.0. The solid contents, including packaging, are limited in weight to the gross weight of the as-tested liquids and bottles. The approved Hedgehog-II packaging configurations described in this report may be transported by air, and have been evaluated as meeting the applicable International Air Transport Association/International Civil Aviation Organization (IATA/ICAO) Dangerous Goods Regulations in addition to the DOT requirements.
Date: December 29, 2003
Creator: Kelly, D. L.
Partner: UNT Libraries Government Documents Department

Fate and Transport of Radionuclides Beneath the Hanford Tank Farms: Unraveling Coupled Geochemical and Hydrological Processes in the Vadose Zone

Description: Although the accelerated transport of {sup 99}Tc, {sup 137}Cs, and {sup 235}U within the vadose zone beneath the 200-West Area of the Hanford tank-farm area has been recognized, the mechanisms responsible for the vertical migration of the radionuclides is unclear. Does horizontal stratification enhance the lateral movement of contaminants, which in turn enhances vertical preferential flow due to perched water dynamics? Do physical heterogeneities, such as stratification and pore regime connectivity, influence the retardation and degree of geochemical nonequilibrium during contaminant transport? Recent modeling efforts of the problem have failed to yield answers to this question since they are inadequately parameterized due to the lack of sufficient quality data. Fundamental experimental research is needed that will improve the conceptual understanding and predictive capability of radionuclide migration in the Hanford tankfarm environment. Since geochemical reactions are directly linked to the system hydrodynamics, coupled geochemical and hydrological processes must be investigated in order to resolve the key mechanisms contributing to vadose zone and groundwater contamination at Hanford. Our research group has performed extensive investigations on time-dependent contaminant interactions with subsurface media using dynamic flow techniques which more closely simulate conditions in-situ. Of particular relevance to this proposal is the work of Barnett et al. (2000) who showed that U(VI) transport through Hanford sediments was highly retarded and extremely sensitive to changes in pH and total carbonate. What remains elusive are the geochemical mechanisms for uranium retention-necessary information for accurately simulating transport-and are thus the focus of this study. The experimental and numerical results from this research will provide knowledge and information in previously unexplored areas of vadose zone fate and transport to support EM's performance/risk assessment and decision-making process for Tank Farm restoration. By unraveling fundamental contaminant transport mechanisms in complex porous media, we provide an improved conceptual understanding and predictive capability ...
Date: December 31, 2003
Creator: Jardine, Philip M.; Ainsworth, Calvin C. & Fendorf, Scott
Partner: UNT Libraries Government Documents Department

Sensitivity of Global Modeling Initiative CTM predictions of Antarctic ozone recovery to GCM and DAS generated meteorological fields

Description: We use the Global Modeling Initiative chemistry and transport model to simulate the evolution of stratospheric ozone between 1995 and 2030, using boundary conditions consistent with the recent World Meteorological Organization ozone assessment. We compare the Antarctic ozone recovery predictions of two simulations, one driven by meteorological data from a general circulation model (GCM), the other using the output of a data assimilation system (DAS), to examine the sensitivity of Antarctic ozone recovery predictions to the characteristic dynamical differences between GCM and DAS-generated meteorological data. Although the age of air in the Antarctic lower stratosphere differs by a factor of 2 between the simulations, we find little sensitivity of the 1995-2030 Antarctic ozone recovery between 350 K and 650 K to the differing meteorological fields, particularly when the recovery is specified in mixing ratio units. Relative changes are smaller in the DAS-driven simulation compared to the GCM-driven simulation due to a surplus of Antarctic ozone in the DAS-driven simulation which is not consistent with observations. The peak ozone change between 1995 and 2030 in both simulations is {approx}20% lower than photochemical expectations, indicating that changes in ozone transport at 450 K between 1995 and 2030 constitute a small negative feedback. Total winter/spring ozone loss during the base year (1995) of both simulations and the rate of ozone loss during August and September is somewhat weaker than observed. This appears to be due to underestimates of Antarctic Cl{sub y} at the 450 K potential temperature level.
Date: December 4, 2003
Creator: Rotman, D & Bergmann, D
Partner: UNT Libraries Government Documents Department

Large deformation solid-fluid interaction via a level set approach.

Description: Solidification and blood flow seemingly have little in common, but each involves a fluid in contact with a deformable solid. In these systems, the solid-fluid interface moves as the solid advects and deforms, often traversing the entire domain of interest. Currently, these problems cannot be simulated without innumerable expensive remeshing steps, mesh manipulations or decoupling the solid and fluid motion. Despite the wealth of progress recently made in mechanics modeling, this glaring inadequacy persists. We propose a new technique that tracks the interface implicitly and circumvents the need for remeshing and remapping the solution onto the new mesh. The solid-fluid boundary is tracked with a level set algorithm that changes the equation type dynamically depending on the phases present. This novel approach to coupled mechanics problems promises to give accurate stresses, displacements and velocities in both phases, simultaneously.
Date: December 1, 2003
Creator: Schunk, Peter Randall; Noble, David R.; Baer, Thomas A.; Rao, Rekha Ranjana; Notz, Patrick K. & Wilkes, Edward Dean
Partner: UNT Libraries Government Documents Department

Photonic encryption using all optical logic.

Description: With the build-out of large transport networks utilizing optical technologies, more and more capacity is being made available. Innovations in Dense Wave Division Multiplexing (DWDM) and the elimination of optical-electrical-optical conversions have brought on advances in communication speeds as we move into 10 Gigabit Ethernet and above. Of course, there is a need to encrypt data on these optical links as the data traverses public and private network backbones. Unfortunately, as the communications infrastructure becomes increasingly optical, advances in encryption (done electronically) have failed to keep up. This project examines the use of optical logic for implementing encryption in the photonic domain to achieve the requisite encryption rates. In order to realize photonic encryption designs, technology developed for electrical logic circuits must be translated to the photonic regime. This paper examines two classes of all optical logic (SEED, gain competition) and how each discrete logic element can be interconnected and cascaded to form an optical circuit. Because there is no known software that can model these devices at a circuit level, the functionality of the SEED and gain competition devices in an optical circuit were modeled in PSpice. PSpice allows modeling of the macro characteristics of the devices in context of a logic element as opposed to device level computational modeling. By representing light intensity as voltage, 'black box' models are generated that accurately represent the intensity response and logic levels in both technologies. By modeling the behavior at the systems level, one can incorporate systems design tools and a simulation environment to aid in the overall functional design. Each black box model of the SEED or gain competition device takes certain parameters (reflectance, intensity, input response), and models the optical ripple and time delay characteristics. These 'black box' models are interconnected and cascaded in an encrypting/scrambling algorithm based on ...
Date: December 1, 2003
Creator: Blansett, Ethan L.; Schroeppel, Richard Crabtree; Tang, Jason D.; Robertson, Perry J.; Vawter, Gregory Allen; Tarman, Thomas David et al.
Partner: UNT Libraries Government Documents Department

Summary of Vadose -- Zone Conceptual Models for Flow and Contaminant Transport and 1999 - 2003 Progress on Resolving Deficiencies in Understanding the Vadose Zone at the INEEL

Description: The thick vadose zone that underlies the Idaho National Engineering and Environmental Laboratory has been recognized both as an avenue through which contaminants disposed at or near the ground surface can migrate to groundwater in the underlying Eastern Snake River Plain aquifer, and as a barrier to the movement of contaminants into the aquifer. Flow and contaminant transport in the vadose zone at the INEEL is complicated by the highly heterogeneous nature of the geologic framework and by the variations in the behavior of different contaminants in the subsurface. The state of knowledge concerning flow and contaminant transport in the vadose zone at and near the INEEL IN 1999 was summarized in Deficiencies in Vadose Zone Understanding at the Idaho National Engineering and Environmental Laboratory (Wood et al., 2000). These authors identified deficiencies in knowledge of flow and contaminant transport processes in the vadose zone, and provided recommendations for additional work that should be conducted to address these deficiencies. In the period since (Wood et al., 2000) was prepared, research has been published that, to some degree, address these deficiencies. This document provides a bibliography of reports, journal articles, and conference proceedings published 1999 through mid-2003 that are relevant to the vadose zone at or near the INEEL and provides a brief description of each work. Publications that address specific deficiencies or recommendations are identified, and pertinent information from selected publications is presented.
Date: December 1, 2003
Creator: Starr, Robert C.; Dettmers, Dana L.; Orr, Brennon R. & Wood, Thomas R.
Partner: UNT Libraries Government Documents Department

TRUPACT-II 157 Examination Report

Description: This report presents the results of examination and recovery activities performed on the TRUPACT-II 157 shipping container. The container was part of a contact-handled transuranic waste shipment being transported on a truck to the Waste Isolation Pilot Plant in New Mexico when an accident occurred. Although the transport vehicle sustained only minor damage, airborne transuranic contamination was detected in air samples extracted from inside TRUPACT-II 157 at the Waste Isolation Pilot Plant. Consequently, the shipping container was rejected, resealed, and returned to the Idaho National Engineering and Environmental Laboratory where the payload was disassembled, examined, and recovered for subsequent reshipment to the Waste Isolation Pilot Plant. This report documents the results of those activities.
Date: December 1, 2003
Creator: O'Brien, Barry H.; Lacy, Jeffrey M. & Archibald, Kip E.
Partner: UNT Libraries Government Documents Department

III-antimonide/nitride based semiconductors for optoelectronic materials and device studies : LDRD 26518 final report.

Description: The goal of this LDRD was to investigate III-antimonide/nitride based materials for unique semiconductor properties and applications. Previous to this study, lack of basic information concerning these alloys restricted their use in semiconductor devices. Long wavelength emission on GaAs substrates is of critical importance to telecommunication applications for cost reduction and integration into microsystems. Currently InGaAsN, on a GaAs substrate, is being commercially pursued for the important 1.3 micrometer dispersion minima of silica-glass optical fiber; due, in large part, to previous research at Sandia National Laboratories. However, InGaAsN has not shown great promise for 1.55 micrometer emission which is the low-loss window of single mode optical fiber used in transatlantic fiber. Other important applications for the antimonide/nitride based materials include the base junction of an HBT to reduce the operating voltage which is important for wireless communication links, and for improving the efficiency of a multijunction solar cell. We have undertaken the first comprehensive theoretical, experimental and device study of this material with promising results. Theoretical modeling has identified GaAsSbN to be a similar or potentially superior candidate to InGaAsN for long wavelength emission on GaAs. We have confirmed these predictions by producing emission out to 1.66 micrometers and have achieved edge emitting and VCSEL electroluminescence at 1.3 micrometers. We have also done the first study of the transport properties of this material including mobility, electron/hole mass, and exciton reduced mass. This study has increased the understanding of the III-antimonide/nitride materials enough to warrant consideration for all of the target device applications.
Date: December 1, 2003
Creator: Kurtz, Steven Ross; Hargett, Terry W.; Serkland, Darwin Keith; Waldrip, Karen Elizabeth; Modine, Normand Arthur; Klem, John Frederick et al.
Partner: UNT Libraries Government Documents Department

Anisotropy in magnetic and transport properties of GdCrSb3

Description: We report the first measurements of anisotropy in magnetic susceptibility, magnetization, and electrical resistivity using single crystals of GdTSb3 (T=Cr, V). GdTSb{sub 3} is a quasi-two dimensional system with orthorhombic crystal structure (space group Pbcm). Unlike the other light rare earth chromium antimonides (R = Ce-Nd, Sm), in which two magnetic transitions are observed, GdCrSb3 undergoes a single ferrimagnetic transition at T{sub C}=86 K, which is evident in both the magnetic susceptibility and electrical resistivity. Within the b-c plane, GdCrSb{sub 3} is found to have metallic behavior from 5 K to 300 K, but it is found to have insulating behavior (dp{sub a}/dT < 0) along the stacking axis. GdVSb3 is found to have a N{acute e}el transition at 5 K due to the localized Gd ions, but no ferromagnetic transition.
Date: December 16, 2003
Creator: Jackson, D D & Fisk, Z
Partner: UNT Libraries Government Documents Department

Technical Basis for Also Using Health-Risk Assessment to Establish Contaminant Boundaries for Corrective Action Units (CAUs) of the Underground Test Area (UGTA) at the Nevada Test Site (NTS)

Description: This technical basis document serves two purposes. First, it provides a detailed discussion of the rationale and procedures suitable for deriving a risk-based contaminant boundary that will protect public health unambiguously, along with examples that are intended as illustrative only to facilitate understanding. Second, it explains the benefits of using such information as the framework for fostering risk communication to educate, inform, and enlighten, and importantly, to fully disclose the goals and structure of contaminant boundaries. To determine a contaminant boundary within a CAU, standards or criteria must be adopted that establish whether groundwater is safe or unsafe for public (and worker) use. For purposes of this discussion, drinking water consumption is considered the pathway of exposure. However, in practice, a realistic land-use scenario must be described and agreed upon before a prospective, realistic risk-based calculation is performed. Otherwise, it will not be clear whether consumption of drinking water is a even appropriate. For example, the future land use that is defined may not even permit access to the contaminated water (e.g., denial of use by law and stewardship; or a lack of accessibility), and in that situation there would be no exposure and no potential health consequences. Taking into consideration that consumption of the groundwater is feasible, the groundwater is deemed unsafe if it contains radionuclide contamination that exceeds the criteria that the United States Environmental Protection Agency (EPA) considers in establishing regulatory standards for drinking water contaminants, including radionuclides generally (i.e., a target range for lifetime excess-cancer risk that is not to exceed 10{sup -4} [1/10,000] and ideally is less than 10{sup -6} [1/1,000,000]) (see EPA, 2000a). Thus, the maximum contaminant levels (MCLs) for substances in drinking water are considered to be health-protective and generally are derived on the basis of acceptable level of risk. Revision 1 to ...
Date: December 29, 2003
Creator: Daniels, J I & Tompson, A F
Partner: UNT Libraries Government Documents Department

Effects of the Use of Pore Formers on Performance of an Anode supported Solid Oxide Fuel Cell

Description: The effects of amount of pore former used to produce porosity in the anode of an anode supported planar solid oxide fuel cell were examined. The pore forming material utilized was rice starch. The reduction rate of the anode material was measured by Thermogravimetric Analysis (TGA) to qualitatively characterize the gas transport within the porous anode materials. Fuel cells with varying amounts of porosity produced by using rice starch as a pore former were tested. The performance of the fuel cell was the greatest with an optimum amount of pore former used to create porosity in the anode. This optimum is believed to be related to a trade off between increasing gas diffusion to the active three-phase boundary region of the anode and the loss of performance due to the replacement of active three-phase boundary regions of the anode with porosity.
Date: December 4, 2003
Creator: Haslam, J J; Pham, A; Chung, B W; DiCarlo, J F & Glass, R S
Partner: UNT Libraries Government Documents Department

Magnetic field perturbartions in closed-field-line systems with zero toroidal magnetic field

Description: In some plasma confinement systems (e.g., field-reversed configurations and levitated dipoles) the confinement is provided by a closed-field-line poloidal magnetic field. We consider the influence of the magnetic field perturbations on the structure of the magnetic field in such systems and find that the effect of perturbations is quite different from that in the systems with a substantial toroidal field. In particular, even infinitesimal perturbations can, in principle, lead to large radial excursions of the field lines in FRCs and levitated dipoles. Under such circumstances, particle drifts and particle collisions may give rise to significant neoclassical transport. Introduction of a weak regular toroidal magnetic field reduces radial excursions of the field lines and neoclassical transport.
Date: December 2, 2003
Creator: Mauel, M; Ryutov, D & Kesner, J
Partner: UNT Libraries Government Documents Department

NOx Control for Utility Boiler OTR Compliance

Description: Under sponsorship of the Department of Energy's National Energy Technology Laboratory (NETL), the Babcock and Wilcox Company (B and W), and Fuel Tech teamed together to investigate an integrated solution for NO{sub x} control. The system is comprised of B and W's DRB-4Z{trademark} ultra low-NO{sub x} pulverized coal (PC) burner technology and Fuel Tech's NOxOUT{reg_sign}, a urea-based selective non-catalytic reduction (SNCR) technology. Development of the low-NO{sub x} burner technology has been a focus in B and W's combustion program. The DRB-4Z{trademark} burner is B and W's newest low-NO{sub x} burner capable of achieving very low NO{sub x}. The burner is designed to reduce NO{sub x} by controlled mixing of the fuel and air. Based on data from several 500 to 600 MWe boilers firing PRB coal, NOx emissions levels of 0.15 to 0.20 lb/ 106 Btu have been achieved from the DRB-4Z{trademark} burners in combination with overfire air ports. Although NOx emissions from the DRB-4Z{trademark} burner are nearing the Ozone Transport Rule (OTR) level of 0.15 lb NO{sub x}/106 Btu, the utility boiler owners can still benefit from the addition of an SNCR and/or SCR system in order to comply with the stringent NO{sub x} emission levels facing them. Large-scale testing is planned in B and W's 100-million Btu/hr Clean Environment Development Facility (CEDF) that simulates the conditions of large coal-fired utility boilers. The objective of the project is to achieve a NO{sub x} level below 0.15 lb/106 Btu (with ammonia slip of less than 5 ppm) in the CEDF using PRB coal and B and W's DRB-4Z{trademark} low-NO{sub x} pulverized coal (PC) burner in combination with dual zone overfire air ports and Fuel Tech's NO{sub x}OUT{reg_sign}. During this period B and W prepared and submitted the project management plan and hazardous substance plan to DOE. The negotiation of a ...
Date: December 31, 2003
Creator: Farzan, Hamid
Partner: UNT Libraries Government Documents Department

Active Cathodes for Super-High Power Density Solid Oxide Fuel Cells Through Space Charge Effects Quarterly Report: July-September 2003

Description: This report summarizes the work done during the fourth quarter of the project. Effort was directed in two areas, namely, continued further development of the model on the role of connectivity on ionic conductivity of porous bodies, including the role of grain boundaries and space charge, and its relationship to cathode polarization; and fabrication of samaria-doped ceria porous (SDC). The work on the model development involves calculation of the effect of space charge on transport through porous bodies. Three specific cases have been examined: (1) Space charge resistivity greater than the grain resistivity, (2) Space charge resistivity equal to the grain resistivity, and (3) Space charge resistivity lower than the grain resistivity. The model accounts for transport through three regions: the bulk of the grain, the space charge region, and the structural part of the grain boundary. The effect of neck size has been explicitly incorporated. In future work, the effective resistivity will be incorporated into the effective cathode polarization resistance. The results will then be compared with experiments.
Date: December 12, 2003
Creator: Virkar, Anil V.
Partner: UNT Libraries Government Documents Department

PROTON-CONDUCTING DENSE CERAMIC MEMBRANES FOR HYDROGEN SEPARATION

Description: Dense perovskite-type structured ceramic membranes, SrCe{sub 0.95}Tm{sub 0.05}O{sub 3} (SCTm), of different thickness, were prepared by the dry-press method. Membrane thickness was varied from 3 mm to 150 {micro}m. The hydrogen permeation flux was found to be inversely proportional to the thickness of the dense films, indicating that the bulk diffusion rather than the surface reaction played a dominant role in the H{sub 2} transport through these dense membranes within the studied thickness range. Hydrogen permeation flux increases with increasing upstream hydrogen partial pressure and decreasing downstream hydrogen partial pressure. The activation energy for hydrogen permeation through the SCTm membrane is about 116 kJ/mol in 600-700 C and 16 kJ/mol in 750-950 C. This indicates a change in the electrical and protonic conduction mechanism at around 700 C. Pd-Cu thin films were synthesized with elemental palladium and copper targets by the sequential R.F. sputter deposition on porous substrates. Pd-Cu alloy films could be formed after proper annealing. The deposited Pd-Cu films were gas-tight. This result demonstrated the feasibility of obtaining an ultrathin SCTm film by the sequential sputter deposition of Sr, Ce and Tm metals followed by proper annealing and oxidation. Such ultrathin SCTm membranes will offer sufficiently high hydrogen permeance for practical applications.
Date: December 1, 2003
Creator: Lin, Jerry Y. S.; Cheng, Scott & Gupta, Vineet
Partner: UNT Libraries Government Documents Department