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Case Studies of integrated hydrogen systems. International Energy Agency Hydrogen Implementing Agreement, Final report for Subtask A of task 11 - Integrated Systems

Description: Within the framework of the International Energy Agency Hydrogen Implementing Agreement, Task 11 was undertaken to develop tools to assist in the design and evaluation of existing and potential hydrogen demonstration projects. Emphasis was placed on integrated systems, from input energy to hydrogen end use. Included in the PDF document are the Executive Summary of the final report and the various case studies. The activities of task 11 were focused on near- and mid-term applications, with consideration for the transition from fossil-based systems to sustainable hydrogen energy systems. The participating countries were Canada, Italy, Japan, the Netherlands, Spain, Switzerland and the United States. In order for hydrogen to become a competitive energy carrier, experience and operating data need to be generated and collected through demonstration projects. A framework of scientific principles, technical expertise, and analytical evaluation and assessment needed to be developed to aid in the design and optimization of hydrogen demonstration projects to promote implementation. The task participants undertook research within the framework of three highly coordinated subtasks that focused on the collection and critical evaluation of data from existing demonstration projects around the world, the development and testing of computer models of hydrogen components and integrated systems, and the evaluation and comparison of hydrogen systems. While the Executive Summary reflects work on all three subtasks, this collection of chapters refers only to the work performed under Subtask A. Ten projects were analyzed and evaluated in detail as part of Subtask A, Case Studies. The projects and the project partners were: Solar Hydrogen Demonstration Project, Solar-Wasserstoff-Bayern, Bayernwerk, BMW, Linde, Siemens (Germany); Solar Hydrogen Plant on Residential House, M. Friedli (Switzerland); A.T. Stuart Renewable Energy Test Site; Stuart Energy Systems (Canada); PHOEBUS Juelich Demonstration Plant Research Centre, Juelich (FZJ) (Germany); Schatz Solar Hydrogen Project, Schatz Energy Research Centre, Humboldt State ...
Date: December 31, 1999
Creator: Schucan, T.

A Chaotic-Dynamical Conceptual Model to Describe Fluid flow and Contaminant Transport in a Fractured Vadose zone

Description: (1) To determine if and when dynamical chaos theory can be used to investigate infiltration of fluid and contaminant transport in heterogeneous soils and fractured rocks. (2) To introduce a new approach to the multiscale characterization of flow and transport in fractured basalt vadose zones and to develop physically based conceptual models on a hierarchy of scales. The following activities are indicative of the success in meeting the project s objectives: A series of ponded infiltration tests, including (1) small-scale infiltration tests (ponded area 0.5 m2) conducted at the Hell s Half Acre site near Shelley, Idaho, and (2) intermediate-scale infiltration tests (ponded area 56 m2) conducted at the Box Canyon site near Arco, Idaho. Laboratory investigations and modeling of flow in a fractured basalt core. A series of small-scale dripping experiments in fracture models. Evaluation of chaotic behavior of flow in laboratory and field experiments using methods from nonlinear dynamics; Evaluation of the impact these dynamics may have on contaminant transport through heterogeneous fractured rocks and soils, and how it can be used to guide remediation efforts; Development of a conceptual model and mathematical and numerical algorithms for flow and transport that incorporate (1) the spatial variability of heterogeneous porous and fractured media, and (2) the description of the temporal dynamics of flow and transport, both of which may be chaotic. Development of appropriate experimental field and laboratory techniques needed to detect diagnostic parameters for chaotic behavior of flow. This approach is based on the assumption that spatial heterogeneity and flow phenomena are affected by nonlinear dynamics, and in particular, by chaotic processes. The scientific and practical value of this approach is that we can predict the range within which the parameters of flow and transport change with time in order to design and manage the remediation, even when ...
Date: December 31, 1999
Creator: Faybishenko, Boris; Doughty, Christine; Stoops, Thomas M.; Wood, thomas R. & Wheatcraft, Stephen W.

Characterization of a new family of metal transporters

Description: Metal ions are critical nutrients, yet overaccumulation of these same metals can also be toxic. To maintain appropriate intracellular levels, cells require specific metal uptake systems that are subject to precise homeostatic regulation. The long-range goal of our research is to define the molecular mechanism(s) and regulation of metal ion uptake in eukaryotic cells. Integrating genetic, molecular biological and biochemical approaches, we have examined these processes in the yeast Saccharomyces cerevisiae and the plant Arabidopsis thaliana. Both are proven model systems for studying fundamental cellular processes. Our work has focused on the ZIP family of metal transporters which we identified; this family has representatives in bacteria, fungi,plants and animals. IRT1, one of the founding members of the ZIP family, is an essential cation transporter that is expressed in the epidermal cells of iron deficient plant roots and is responsible for uptake of iron from the soil. We now know that t here are 15 ZIP genes in the Arabidopsis genome which can be divided into four different classes, based on their intron/exon arrangements and the similarities among their encoded gene products. The ZIP family members display different substrate specificities for metals and different tissue distributions in Arabidopsis.Moreover, the family members respond differentially to metal deficiencies. For example, IRT1, ZIP6 and ZIP9 mRNA are expressed mainly in the roots of iron deficient plants whereas ZIP4 responds to both iron and zinc deficiency. Work in both yeast and Arabidopsis has addressed substrate specificity as well as how these transporters are regulated in response to metal availability. Our project was broken down into four specific aims. Significant progress was made on all four aims. I have listed the publications which have resulted under the relevant specific aim.
Date: December 31, 1999
Creator: Guerinot, Mary L. & Dide, David


Description: In the United States alone there are 100 million gallons of high-level nuclear wastes (HLWs) in various chemical forms awaiting eventual disposal in geologic repositories. For safety in handling and transport from their present underground storage tanks to their final burial sites, much of the HLWs are being immobilized by vitrification. A further virtue of HLW vitrification is the fact that the glass may serve as an additional, non-geologic barrier to the dispersal of these radio-toxins into the environment. For this reason, one of the criteria for selecting HLW glass compositions has been chemical durability against attack by ground water. While the effects of radiation on chemical durability have therefore been studied extensively, little consideration has been given to the possibility that self-irradiation of HLW glasses may lead to modes of chemical decomposition which render them unstable even in the absence of exposure to ground water. The worst-case threat would occur if the HLW glasses were to respond to irradiation in ways analogous to rock salt (NaCl). It has long been known that alkali halides irradiated to
Date: December 31, 1999
Creator: Griscom, Daavid L. & Merzbacher, Celia I.


Description: Photocatalysis could provide a cost-effective route to recycle CO{sub 2} to useful chemicals or fuels. Development of an effective catalyst for the photocatalytic synthesis requires (i) the knowledge of the surface band gap and its relation to the surface structure, (ii) the reactivity of adsorbates and their reaction pathways, and (iii) the ability to manipulate the actives site for adsorption, surface reaction, and electron transfer. The research tasks accomplished during first six months include setting up a photo-catalytic reactor, optical bench, calibration of gas chromatograph, catalyst preparation, and catalyst screening study. Addition of Pt and Cu on TiO{sub 2} was found to increase the activity of TiO{sub 2} catalysts for the synthesis of methanol and methane. The most active catalysts obtained from this study will be used for mechanistic study. The overall goal of this research is to provide a greater predictive capability for the design of visible light-photosynthesis catalysts by a deeper understanding of the reaction kinetics and mechanism as well as by better control of the coordination/chemical environment of active sites.
Date: December 31, 1999
Creator: Chuang, Steven S.C.

Colloidal Agglomerates in Tank Sludge: Impact on Waste Processing

Description: Disposal of millions of gallons of existing radioactive wastes in underground storage tanks is a major remediation activity for the United States Department of Energy. These wastes include a substantial volume of insoluble sludges consisting of submicron colloidal particles. Processing these sludges under the proposed processing conditions presents unique challenges in retrieval, transport, separation, and solidification of these waste streams. Depending on processing conditions, these colloidal particles can form agglomerated networks having high viscosities that could clog transfer lines or produce high volumes of low-density sediments that interfere with solid-liquid separations. Under different conditions, these particles can be dispersed to form very fine suspended particles that do not settle. Given the wide range of waste chemistries present at Department of Energy sites, it is impractical to measure the properties of all treatment procedures. The underlying principle s of colloid chemistry and physics were studied to provide data that would make it possible to predict and eventually control the physical properties of sludge suspensions and sediment layers in tank wastes and other waste processing streams.
Date: December 31, 1999
Creator: Tingey, Joel M.; Berg, John D.; Keefer, K.D.; Lea, A.S.; Rector, D.R.; Virden, J.W. et al.

Combustion 2000

Description: This report presents work carried out under contract DE-AC22-95PC95144 ''Combustion 2000 - Phase II.'' The goals of the program are to develop a coal-fired high performance power generation system (HIPPS) that is capable of: {lg_bullet} thermal efficiency (HHV) {ge} 47% {lg_bullet} NOx, SOx, and particulates {le} 10% NSPS (New Source Performance Standard) {lg_bullet} coal providing {ge} 65% of heat input {lg_bullet} all solid wastes benign {lg_bullet} cost of electricity {le} 90% of present plants Phase I, which began in 1992, focused on the analysis of various configurations of indirectly fired cycles and on technical assessments of alternative plant subsystems and components, including performance requirements, developmental status, design options, complexity and reliability, and capital and operating costs. Phase I also included preliminary R&D and the preparation of designs for HIPPS commercial plants approximately 300 MWe in size. Phase II, had as its initial objective the development of a complete design base for the construction and operation of a HIPPS prototype plant to be constructed in Phase III. As part of a descoping initiative, the Phase III program has been eliminated and work related to the commercial plant design has been ended. The rescoped program retained a program of engineering research and development focusing on high temperature heat exchangers, e.g. HITAF development (Task 2); a rescoped Task 6 that is pertinent to Vision 21 objectives and focuses on advanced cycle analysis and optimization, integration of gas turbines into complex cycles, and repowering designs; and preparation of the Phase II Technical Report (Task 8). This rescoped program deleted all subsystem testing (Tasks 3, 4, and 5) and the development of a site-specific engineering design and test plan for the HIPPS prototype plant (Task 7). Work reported herein is from: {lg_bullet} Task 2.2.4 Pilot Scale Testing {lg_bullet} Task Laboratory and Bench Scale Activities
Date: December 31, 1999

Cooled silicon nitride stationary turbine vane risk reduction. Final report

Description: The purpose of this program was to reduce the technical risk factors for demonstration of air cooled silicon nitride turbine vanes. The effort involved vane prototype fabrication efforts at two U.S. based gas turbine grade silicon nitride component manufacturers. The efficacy of the cooling system was analyzed via a thermal time/temperature flow test technique previously at UTRC. By having multiple vendors work on parts fabrication, the chance of program success increased for producing these challenging components. The majority of the effort under this contract focused on developing methods for, and producing, the complex thin walled silicon nitride vanes. Components developed under this program will undergo engine environment testing within N00014-96-2-0014.
Date: December 31, 1999
Creator: Holowczak, John

Determination of Transmutation Effects in Crystalline Waste Forms

Description: The overall goal of this Environmental Management Science Program project was to develop research tools to investigate the effect of transmutation, that is, the radioactive decay of a radioisotope to an isotope of another element, on the stability of a crystalline matrix. This process is an important issue in the assessment of the long-term stability, and hence performance, of a waste form. Most work on radiation effects in waste forms has focused on alpha radiation, which produces more displacements than beta radiation. However, beta radiation results in transmutation, which changes both the valence and the ionic radius of the element undergoing decay. These changes in coordination chemistry may destabilize the waste form and hence permit higher releases of the radionuclide contaminants to the accessible environment. Little is known about the mobility of Cs in pollucite. Only a few studies [1-3] have examined leaching following transmutation or irradiation of pollucite or closely related aluminosilicates. These studies seem to have contradictory results. The results may indicate that prior to radiation-induced amorphization, the accumulated defects may lead to higher leachability of Cs [3], whereas once amorphization occurs, the Cs becomes trapped in the collapsed structure [2]. A more thorough analysis of the effect of accumulated defects from both transmutation and ionization processes on the pollucite structure is needed to assess to the impact on Cs mobility. In this three- year research program, we used cutting-edge experimental approaches to investigate this little-understood issue. The work was a collaboration between Argonne National Laboratory (ANL) and Pacific Northwest National Laboratory (PNNL). We focused on the effects of transmutation on pollucite (CsAlSi2O6), a cesium aluminosilicate that has been proposed for the long-term immobilization of radioactive cesium. In this ceramic waste form, the 137Cs decays to 137Ba, causing barium to build up in the pollucite samples over time. ...
Date: December 31, 1999
Creator: Fortner, Jeffrey A.

Development of a High Fluence Neutron Source for Nondestructive Characterization of Nuclear Waste

Description: We are addressing the need to measure nuclear wastes, residues, and spent fuel in order to process these for final disposition. For example, TRU wastes destined for the WIPP must satisfy extensive characterization criteria outlined in the Waste Acceptance Criteria, the Quality Assurance Program Plan, and the Performance Demonstration Plan. Similar requirements exist for spent fuel and residues. At present, no nondestructive assay (NDA) instrumentation is capable of satisfying all of the PDP test cycles (particularly for Remote-Handled TRU waste). One of the primary methods for waste assay is by active neutron interrogation. The objective of this project is to improve the capability of all active neutron systems by providing a higher intensity neutron source (by about a factor of 1,000) for essentially the same cost, power, and space requirements as existing systems. This high intensity neutron source is an electrostatically confined (IEC) plasma device. The IEC is a symmetric sphere that was originally developed in the 1960s as a possible fusion reactor. It operates as DT neutron generator. Although it is not likely that this device will scale to fusion reactor levels, previous experiments1 have demonstrated a neutron yield of 2 x 1010 neutrons/second on a table-top device that can be powered from ordinary laboratory circuits (9 kilowatts). Subsequently, the IEC physics has been extensively studied at the University of Illinois and other locations. We have established theoretically the basis for scaling the output up to 1 x 1011 neutrons/second. In addition, IEC devices have run for cumulative times approaching 10,000 hours, which is essential for practical application to NDA. They have been operated in pulsed and continuous mode. The essential features of the IEC plasma neutron source, compared to existing sources of the same cost, size and power consumption, are: Table 1: Present and Target Operating Parameters for ...
Date: December 31, 1999
Creator: Pickrell, Mark M.

Development of METHANE de-NOX reburning process. Quarterly report, October 1 - December 31, 1999

Description: The use of biomass and wood waste solids and sludges as fuel is often hampered by their low heating values and the presence of bound nitrogen that result in inefficient combustion and high NOx emission. Cofiring supplemental fuel through auxiliary burners helps with improving the combustion effectiveness and NOx reduction, but the benefits are limited to the fractional heat input of the auxiliary fuel. Demonstration tests have shown over 60% reduction in NOx, CO and VOC emissions, and a 2% increase in boiler thermal efficiency using only 8 to 13% natural gas.
Date: December 31, 1999

Engineering Development of Coal-Fired High-Performance Power Systems

Description: A High Performance Power System (HIPPS) is being developed. This system is a coal-fired, combined cycle plant with indirect heating of gas turbine air. Foster Wheeler Development Corporation and a team consisting of Foster Wheeler Energy Corporation, Bechtel Corporation, University of Tennessee Space Institute and Westinghouse Electric Corporation are developing this system. In Phase 1 of the project, a conceptual design of a commercial plant was developed. Technical and economic analyses indicated that the plant would meet the goals of the project which include a 47 percent efficiency (HHV) and a 10 percent lower cost of electricity than an equivalent size PC plant. The concept uses a pyrolysis process to convert coal into fuel gas and char. The char is fired in a High Temperature Advanced Furnace (HITAF). The HITAF is a pulverized fuel-fired boiler/air heater where steam is generated and gas turbine air is indirectly heated. The fuel gas generated in the pyrolyzer is then used to heat the gas turbine air further before it enters the gas turbine. The project is currently in Phase 2 which includes engineering analysis, laboratory testing and pilot plant testing. Research and development is being done on the HIPPS systems that are not commercial or being developed on other projects. Pilot plant testing of the pyrolyzer subsystem and the char combustion subsystem are being done separately, and after each experimental program has been completed, a larger scale pyrolyzer will be tested at the Power Systems Development Facility (PSDF) in Wilsonville, AL. The facility is equipped with a gas turbine and a topping combustor, and as such, will provide an opportunity to evaluate integrated pyrolyzer and turbine operation. This report addresses the areas of technical progress for this quarter. Detailed design of the components to be used to for the circulating bed gasification tests ...
Date: December 31, 1999
Creator: Tsuo, York

Enhanced Sludge Processing of HLW: Hydrothermal Oxidation of Chromium, Technetium, and Complexants by Nitrate

Description: The objective of this project is to develop the scientific basis for hydrothermal separation of chromium from High Level Waste (HLW) sludges. Our worked is aimed at attaining a fundamental understanding of chromium speciation, oxidation/reduction and dissolution kinetics, reaction mechanisms, and transport properties under hydrothermal conditions in both simple and complex salt solutions that will ultimately lead to an efficient chromium leaching process.
Date: December 31, 1999
Creator: Buelow, Steven J. & Robinson, Jeanne M.

Evaluation Of Isotopic Diagnostics For Subsurface Characterization And Monitoring : Field Experiments At The Tan And RWMC (SDA) Sites, Ineel

Description: The purpose of this project was to explore and refine applications of isotope measurements for guiding environmental remediation strategies. The isotopic compositions of samples from field sites were analyzed to address both basic scientific issues and site-specific problems. Initial efforts were concentrated on two sites at the Idaho National Engineering and Environmental Laboratory (INEEL). During the final year of the project, the focus of work was shifted to the Hanford site in Washington. The Test Area North (TAN) site at INEEL consists of a 2 km-long plume of mixed wastes containing low-level radionuclides, sewage and chlorinated solvents that were injected into the groundwater between 1955 and 1972. Isotopic measurements of groundwater samples were made to address questions about the source of the groundwater and the regional hydrology at TAN. These data show that there is a significant input to the groundwater from playa lakes that were located west of the TAN site prior to the 1950s (since that time, inflow to the playas has been diverted for agricultural uses). Radiocarbon dates of the playa waters indicate a mean infiltration rate of 3-5 cm/year. These results explain the groundwater flow patterns observed in the plume and provide constraints on transport rates.
Date: December 31, 1999
Creator: DePaolo, Donald J.


Description: During the FY96-FY99 funding cycle we examined the uptake of aqueous strontium onto goethite, kaolinite, and amorphous silica surfaces as a function of pH, total strontium, and temperature. Our overall goal was to produce a mechanistic sorption model that can be used in reaction-transport calculations to predict the mobility and attenuation of radioactive strontium (90Sr) in the environment. Our approach was to combine structural information derived from synchrotron-based x-ray absorption spectroscopic analysis together with macroscopic uptake data and surface complexation models to clarify the physical and chemical structure of sorbed complexes. We chose to study these solids because of the prevalence of clays and iron hydroxides in natural systems, and because silica colloids probably form beneath leaking tanks at Hanford as caustic waste is neutralized. We have published the spectroscopic work in two papers in the Journal of Colloid and Interface Science [1, 2], and will soon submit at third manuscript to Geochemical Transactions [3] combining the sorption and spectroscopic data with a mechanistic complexation model.
Date: December 31, 1999
Creator: Carroll, Susan A. & O'Day, Peggy A.

Extraction and Recovery of Mercury and Lead from Aqueous Waste Streams using Redox-Active Layered Materials

Description: The goals of this program have been to develop a series of new compounds that act as redox recyclable heavy metal ion selective materials. This has been a preliminary exploration into the viability of creating materials that act as selective exchange media. We have historically been involved in the separation of ionic pollutants such as radionuclides or toxic heavy metal ions from water by designing extractants with high selectivities and large capacities. We have also recognized that there is a more urgent need to develop processes that allow the target pollutants to be recovered in a minimal volume of secondary waste and that allow the extractants to be reused or recycled. We have been studying redox active transition-metal-containing extractants that undergo reversible electron transfer activation and deactivation as the target ions are extracted and recovered or that undergo efficient, selective ion exchange.
Date: December 31, 1999
Creator: Dorhout,P.K & Strauss, S.H.

Final Report: High Spectral Resolution Atmospheric Emitted Radiance Studies with the ARM UAV

Description: The active participation in the Atmospheric Radiation Measurement (ARM) Unmanned Airborne Vehicle (UAV) science team that was anticipated in the grant proposal was indefinitely delayed after the first year due to a programmatic decision to exclude the high spectral resolution observations from the existing ARM UAV program. However, this report shows that substantial progress toward the science objectives of this grant have made with the help of separate funding from NASA and other agencies. In the four year grant period (including time extensions), a new high spectral resolution instrument has been flown and has successfully demonstrated the ability to obtain measurements of the type needed in the conduct of this grant. In the near term, the third water vapor intensive observing period (WVIOP-3) in October 2000 will provide an opportunity to bring the high spectral resolution observations of upwelling radiance into the ARM program to complement the downwelling radiance observations from the existing ARM AERI instruments. We look forward to a time when the ARM-UAV program is able to extend its scope to include the capability for making these high spectral resolution measurements from a UAV platform.
Date: December 31, 1999
Creator: Revercomb, Henry E.

The Government-University-Industry Research Roundtable. Annual reports for 1997, 1998, 1999

Description: The Roundtable was created in 1984 to provide a unique forum for dialog among top government, university, and industry leaders of the national science and technology enterprise. The purpose is to facilitate personal working relationships and exchange of ideas regarding issues, problems, and promising opportunities that are facing those charged with developing and deploying science and technology resources. These annual reports begin by describing the purpose, structure, and mode of operation of the Roundtable. There follow sections devoted to the council activities, major projects, and follow-up planning, and the activities of the Roundtable working groups. Meeting agendas and publications lists are also included.
Date: December 31, 1999

High Temperature Condensed Phase Mass Spectrometric Analysis Program

Description: This program (EMSP Project No.60424) was funded by the EM Science Program for the development of an integrated mass spectrometric analysis system (see Figure 1.) capable of analyzing materials from room up to high temperatures, with the practical upper temperature limit to be experimentally determined. A primary objective of the program was the development of techniques to analyze waste materials during vitrification processing to produce waste forms. The sample is heated in the ion formation region of the mass spectrometer. This instrument geometry allows the atoms and molecules that volatilize from the sample as neutrals to be ionized before they have a chance to condense on surfaces that generally are cooler that the sample. In addition, this geometry facilitates more efficient focusing of SIMS and thermal ions into the quadrupole mass analyzer. Instrumental capabilities include the detection of volatilizing neutral species by electron bombardment, ions forming on the surface by surface ionization, and surface species by static SIMS. In addition, the instrument has elemental analysis capability (by dynamic SIMS).
Date: December 31, 1999
Creator: Delmore, James E.

Hydrologic and Geochemical Controls on the Transport of Radionuclides in Natural Undisturbed Arid Environments as Determined by Accelerator Mass Spectrometry Measurements

Description: This project developed low-level analytical methods for the measurement of radionuclides by accelerator mass spectrometry. The contaminant radionuclides potentially measurable by AMS include: 14C, 36Cl, 59Ni, 63Ni, 90Sr, 93Zr, 99Tc, 129I, 239Np, 239Pu, and other actinides. We chose to concentrate on 36Cl, 99Tc, 90Sr, and 129I. These nuclides were globally distributed as fallout during the era of atmospheric nuclear testing, and occur today in almost every environment. They also are prominent contaminant nuclides at a variety of DOE sites. There is a need to develop these low-level methods to observe the migration of radionuclides in natural environments. There are at least three advantages of this: (1) the ability to conduct migration studies in locations most like those of concern to public health, e.g., a ''far-field'' environment; (2) migration research does not have to be conducted at sites of multiple contamination, e.g., by VOC's, which can produce hard-to-interpret results; and (3) it becomes unnecessary to collect research samples that are themselves radioactive waste and are therefore difficult to handle and dispose of in the laboratory. Our approach of examining globally distributed, fallout radionuclides provides another advantage: (4) since the nuclides are globally distributed, migration research can be conducted in any chosen environment. Arid environments can be examined for purposes of nuclear waste storage; riverine systems can be examined for the effects of long-range transport; forested or agricultural regions can be examined for the effects of vegetative mediation; even accessible arctic regions could be examined to better understand the fate of radionuclides in remote northern Russia. The innovative aspect of this research project was that it developed methods by which field studies of radionuclide migration could take place virtually anywhere, making the research easier to conduct, less expensive, and better controlled scientifically. Science is still in the process of trying to characterize ...
Date: December 31, 1999
Creator: Nimz, Gregory J.; Caffee, Marc W. & McAninch, Jeffrey


Description: Carbon tetrachloride has been used extensively within the DOE nuclear weapons facilities. Rocky Flats was formerly the largest volume consumer of CCl4 in the United States using 5000 gallons in 1977 alone (Ripple, 1992). At the Hanford site, several hundred thousand gallons of CCl4 were discharged between 1955 and 1973 into underground cribs for storage. Levels of CCl4 in groundwater at highly contaminated sites at the Hanford facility have exceeded 8 the drinking water standard of 5 ppb by several orders of magnitude (Illman, 1993). High levels of CCl4 at these facilities represent a potential health hazard for workers conducting cleanup operations and for surrounding communities. The level of CCl4 cleanup required at these sites and associated costs are driven by current human health risk estimates, which assume that CCl4 is a genotoxic carcinogen. The overall purpose of these studies was to improve the scientific basis for assessing the health risk associated with human exposure to CCl4. Specific research objectives of this project were to: (1) compare the rates of CCl4 metabolism by rats, mice and hamsters in vivo and extrapolate those rates to man based on parallel studies on the metabolism of CCl4 by rat, mouse, hamster and human hepatic microsomes in vitro; (2) using hepatic microsome preparations, determine the role of specific cytochrome P450 isoforms in CCl4-mediated toxicity and the effects of repeated inhalation and ingestion of CCl4 on these isoforms; and (3) evaluate the toxicokinetics of inhaled CCl4 in rats, mice and hamsters. This information has been used to improve the physiologically based pharmacokinetic (PBPK) model for CCl4 originally developed by Paustenbach et al. (1988) and more recently revised by Thrall and Kenny (1996). Another major objective of the project was to provide scientific evidence that CCl4, like chloroform, is a hepatocarcinogen only when exposure results in ...
Date: December 31, 1999
Creator: Benson, Janet M. & Springer, David L.


Description: The growing concerns for the environment and increasingly stringent standards for NO emission have presented a major challenge to control NO emissions from electric utility plants and automobiles. Catalytic decomposition of NO is the most attractive approach for the control of NO emission for its simplicity. Successful development of an effective catalyst for NO decomposition will greatly decrease the equipment and operation cost of NO control. Due to lack of understanding of the mechanism of NO decomposition, efforts on the search of an effective catalyst have been unsuccessful. Scientific development of an effective catalyst requires fundamental understanding of the nature of active site, the rate-limiting step, and an approach to prolong the life of the catalyst. The authors have investigated the feasibility of two novel approaches for improving catalyst activity and resistance to sintering. The first approach is the use of silanation to stabilize metal crystallites and supports for Cu-ZSM-5 and promoted Pt catalysts; the second is utilization of oxygen spillover and desorption to enhance NO decomposition activity. The silanation approach failed to stabilize Cu-ZSM-5 activity under hydrothermal condition. Silanation blocked the oxygen migration and inhibited oxygen desorption. Oxygen spillover was found to be an effective approach for promoting NO decomposition activity on Pt-based catalysts. Detailed mechanistic study revealed the oxygen inhibition in NO decomposition and reduction as the most critical issue in developing an effective catalytic approach for controlling NO emission.
Date: December 31, 1999