25 Matching Results

Search Results

Advanced search parameters have been applied.

Trends vs. reactor size of passive reactivity shutdown and control performance

Description: The focus of the US advanced reactor program since the cancellation of CRBR has been on inherent safety and cost reduction. The notion is to so design the reactor that in the event of an off normal condition, it brings itself to a safe shutdown condition and removes decay heat by reliance on ''inherent processes'' i.e., without reliance on devices requiring switching and outside sources of power. Such a reactor design would offer the potential to eliminate costly ''Engineered Safety Features,'' to lower capital costs, and to assuage public unease concerning reactor safety. For LMR concepts, the goal of passive reactivity shutdown has been approached in the US by designing the reactors for favorable relationships among the power, power/flow, and inlet temperature coefficients of reactivity, for high internal conversion ratio (yielding small burnup control swing), and for a primary pump coastdown time appropriately matched to the delayed neutron hold back of power decay upon negative reactivity input. The use of sodium bonded metallic fuel pins has facilitated the achievement of the passive shutdown design goals as a consequence of their high thermal conductivity and high effective heavy metal density. Alternately, core designs based on derated oxide pins may be able to achieve the passive shutdown features at the cost of larger core volume and increased initial fissile inventory. 8 refs., 12 figs., 1 tab.
Date: January 1, 1988
Creator: Wade, D.C. & Fujita, E.K.
Partner: UNT Libraries Government Documents Department

The neutronic and fuel cycle performance of interchangeable 3500 MWth metal and oxide fueled LMRs

Description: This study summarizes the neutronic and fuel cycle analysis performed at Argonne National Laboratory for an oxide and a metal fueled 3500 MWth LMR. The oxide and metal core designs were developed to meet reactor performance specifications that are constrained by requirements for core loading interchangeability and for small burnup reactivity swing. Differences in the computed performance parameters of the oxide and metal cores, arising from basic differences in their neutronic characteristics, were identified and discussed. It is shown that metal and oxide cores designed to the same ground rules exhibit many similar performance characteristics; however, they differ substantially in reactivity coefficients, control strategies, and fuel cycle options. 12 refs., 25 figs.
Date: March 1, 1989
Creator: Fujita, E.K. & Wade, D.C.
Partner: UNT Libraries Government Documents Department

Trends vs. reactor size of passive reactivity shutdown and control performance

Description: For LMR concepts, the goal of passive reactivity shutdown has been approached in the US by designing the reactors for favorable relationships among the power, power/flow, and inlet temperature coefficients of reactivity, for high internal conversion ratio (yielding small burnup control swing), and for a primary pump coastdown time appropriately matched to the delayed neutron hold back of power decay upon negative reactivity input. The use of sodium bonded metallic fuel pins has facilitated the achievement of the massive shutdown design goals as a consequence of their high thermal conductivity and high effective heavy metal density. Alternately, core designs based on derated oxide pins may be able to achieve the passive shutdown features at the cost of larger core volume and increased initial fissile inventory. For LMR concepts, the passive decay heat removal goal of inherent safety has been approached in US designs by use of pool layouts, larger surface to volume ratio of the reactor vessel with natural draft air cooling of the vessel surface, elevations and redans which promote natural circulation through the core, and thermal mass of the pool contents sufficient to absorb that initial transient decay heat which exceeds the natural draft air cooling capacity. This paper describes current US ''inherently safe'' reactor design.
Date: January 1, 1987
Creator: Wade, D.C. & Fujita, E.K.
Partner: UNT Libraries Government Documents Department

CARBON DIOXIDE FIXATION.

Description: Solar carbon dioxide fixation offers the possibility of a renewable source of chemicals and fuels in the future. Its realization rests on future advances in the efficiency of solar energy collection and development of suitable catalysts for CO{sub 2} conversion. Recent achievements in the efficiency of solar energy conversion and in catalysis suggest that this approach holds a great deal of promise for contributing to future needs for fuels and chemicals.
Date: January 12, 2000
Creator: Fujita, E.
Partner: UNT Libraries Government Documents Department

Fuel management studies of small metal and oxide LMR's

Description: Fuel-cycle analyses performed at Argonne National Laboratory to evaluate and compare the neutronic performance characteristics of small oxide- and metal-fueled LMR's are described. Specific consideration is given to those analyses concerned with optimization of core and blanket configurations, selection of fuel residence time and refueling interval, determination of control rod worths and requirements, development of in-core fuel management strategy, and evaluation of performance characteristics both for startup cycles and for the equilibrium state reached via repeated recycle of discharged fuel. Differences in the computed performance parameters of oxide and metal cores, arising from basic differences in their neutronic characteristics, are identified and discussed. Metal-fueled cores are shown to offer some important performance advantages over oxide cores for small LMR's because of their harder spectrum, superior neutron economy, and greater breeding capacity. These advantages include smaller fissile and heavy metal loadings, lower control-system requirements, and greater adaptability to changes in fuel management scenarios.
Date: January 1, 1986
Creator: Khalil, H.; Fujita, E.K.; Yang, S. & Orechwa, Y.
Partner: UNT Libraries Government Documents Department

Core design and performance of small inherently safe LMRs

Description: Oxide and metal-fueled core designs at the 900 MWt level and constrained by a requirement for interchangeability are described. The physics parameters of the two cores studied here indicate that metal-fueled cores display attractive economic and safety features and are more flexible than are oxide cores in adapting to currently-changing deployment scenarios.
Date: January 1, 1986
Creator: Orechwa, Y.; Khalil, H.; Turski, R.B. & Fujita, E.K.
Partner: UNT Libraries Government Documents Department

Design and fuel management of PWR cores to optimize the once-through fuel cycle

Description: The once-through fuel cycle has been analyzed to see if there are substantial prospects for improved uranium ore utilization in current light water reactors, with a specific focus on pressurized water reactors. The types of changes which have been examined are: (1) re-optimization of fuel pin diameter and lattice pitch, (2) axial power shaping by enrichment gradation in fresh fuel, (3) use of 6-batch cores with semi-annual refueling, (4) use of 6-batch cores with annual refueling, hence greater extended (approximately doubled) burnup, (5) use of radial reflector assemblies, (6) use of internally heterogeneous cores (simple seed/blanket configurations), (7) use of power/temperature coastdown at the end of life to extend burnup, (8) use of metal or diluted oxide fuel, (9) use of thorium, and (10) use of isotopically separated low sigma/sub a/ cladding material. State-of-the-art LWR computational methods, LEOPARD/PDQ-7/FLARE-G, were used to investigate these modifications.
Date: August 1, 1978
Creator: Fujita, E.K.; Driscoll, M.J. & Lanning, D.D.
Partner: UNT Libraries Government Documents Department

REVERSIBLE CONVERSION BETWEEN CHEMICAL AND ELECTRICAL ENERGIES CATALYZED BY Ru COMPLEXES AIMED TO CONSTRUCT SUSTAINABLE SOCIETY.

Description: The present study demonstrates that [Ru{sup II}(NH{sub 3})(q)(trpy)]{sup +} has an ability to oxidize alcohols catalytically under very mild conditions under electrolysis at +0.35 V in MeOH. The elucidation of the reaction mechanisms in the alcohol-oxidation is underway.
Date: November 30, 2007
Creator: TANAKA,K.; WADA, T.; FUJITA, E. & MUCKERMAN, J.
Partner: UNT Libraries Government Documents Department

PHOTOCHEMICAL CO2 REDUCTION BY RHENUIM AND RUTHENIUM COMPLEXES.

Description: Photochemical conversion of CO{sub 2} to fuels or useful chemicals using renewable solar energy is an attractive solution to both the world's need for fuels and the reduction of greenhouse gases. Rhenium(I) and ruthenium(II) diimine complexes have been shown to act as photocatalysts and/or electrocatalysts for CO{sub 2} reduction to CO. We have studied these photochemical systems focusing on the identification of intermediates and the bond formation/cleavage reactions between the metal center and CO{sub 2}. For example, we have produced the one-electron-reduced monomer (i.e. Re(dmb)(CO){sub 3}S where dmb = 4,4'-dimethy-2,2'-bipyridine and S = solvent) either by reductive quenching of the excited states of fac-[Re(dmb)(CO){sub 3}(CH{sub 3}CN)]PF{sub 6} or by photo-induced homolysis of [Re(dmb)(CO){sub 3}]{sub 2}. We previously found that: (1) the remarkably slow dimerization of Re(dmb)(CO){sub 3}S is due to the absence of a vacant coordination site for Re-Re bond formation, and the extra electron is located on the dmb ligand; (2) the reaction of Re(dmb)(CO){sub 3}S with CO{sub 2} forms a CO{sub 2}-bridged binuclear species (CO){sub 3}(dmb)Re-CO(O)-Re(dmb)(CO){sub 3} as an intermediate in CO formation; and (3) the kinetics and mechanism of reactions are consistent with the interaction of the CO{sub 2}-bridged binuclear species with CO{sub 2} to form CO and CO{sub 3}{sup 2-}.
Date: November 30, 2007
Creator: FUJITA,E.; MUCKERMAN, J.T. & TANAKA, K.
Partner: UNT Libraries Government Documents Department

Toward Photochemical Water Splitting Using Band-Gap-Narrowed Semiconductors and Transition-Metal Based Molecular Catalysts

Description: We are carrying out coordinated theoretical and experimental studies of toward photochemical water splitting using band-gap-narrowed semiconductors (BGNSCs) with attached multi-electron molecular water oxidation and hydrogen production catalysts. We focus on the coupling between the materials properties and the H{sub 2}O redox chemistry, with an emphasis on attaining a fundamental understanding of the individual elementary steps in the following four processes: (1) Light-harvesting and charge-separation of stable oxide or oxide-derived semiconductors for solar-driven water splitting, including the discovery and characterization of the behavior of such materials at the aqueous interface; (2) The catalysis of the four-electron water oxidation by dinuclear hydroxo transition-metal complexes with quinonoid ligands, and the rational search for improved catalysts; (3) Transfer of the design principles learned from the elucidation of the DuBois-type hydrogenase model catalysts in acetonitrile to the rational design of two-electron hydrogen production catalysts for aqueous solution; (4) Combining these three elements to examine the function of oxidation catalysts on BGNSC photoanode surfaces and hydrogen production catalysts on cathode surfaces at the aqueous interface to understand the challenges to the efficient coupling of the materials functions.
Date: June 7, 2009
Creator: Muckerman,J.T.; Rodriguez, J.A. & Fujita, E.
Partner: UNT Libraries Government Documents Department

Photogeneration of Hydride Donors and Their Use Toward CO2 Reduction

Description: Despite substantial effort, no one has succeeded in efficiently producing methanol from CO2 using homogeneous photocatalytic systems. We are pursuing reaction schemes based on a sequence of hydride-ion transfers to carry out stepwise reduction of CO2 to methanol. We are using hydride-ion transfer from photoproduced C-H bonds in metal complexes with bio-inspired ligands (i.e., NADH-like ligands) that are known to store one proton and two electrons.
Date: June 7, 2009
Creator: Fujita,E.; Muckerman, J.T. & Polyansky, D.E.
Partner: UNT Libraries Government Documents Department

CARBON DIOXIDE AS A FEEDSTOCK.

Description: This report is an overview on the subject of carbon dioxide as a starting material for organic syntheses of potential commercial interest and the utilization of carbon dioxide as a substrate for fuel production. It draws extensively on literature sources, particularly on the report of a 1999 Workshop on the subject of catalysis in carbon dioxide utilization, but with emphasis on systems of most interest to us. Atmospheric carbon dioxide is an abundant (750 billion tons in atmosphere), but dilute source of carbon (only 0.036 % by volume), so technologies for utilization at the production source are crucial for both sequestration and utilization. Sequestration--such as pumping CO{sub 2} into sea or the earth--is beyond the scope of this report, except where it overlaps utilization, for example in converting CO{sub 2} to polymers. But sequestration dominates current thinking on short term solutions to global warming, as should be clear from reports from this and other workshops. The 3500 million tons estimated to be added to the atmosphere annually at present can be compared to the 110 million tons used to produce chemicals, chiefly urea (75 million tons), salicylic acid, cyclic carbonates and polycarbonates. Increased utilization of CO{sub 2} as a starting material is, however, highly desirable, because it is an inexpensive, non-toxic starting material. There are ongoing efforts to replace phosgene as a starting material. Creation of new materials and markets for them will increase this utilization, producing an increasingly positive, albeit small impact on global CO{sub 2} levels. The other uses of interest are utilization as a solvent and for fuel production and these will be discussed in turn.
Date: December 9, 2000
Creator: CREUTZ,C. & FUJITA,E.
Partner: UNT Libraries Government Documents Department

CARBON DIOXIDE AS A FEEDSTOCK.

Description: This report is an overview on the subject of carbon dioxide as a starting material for organic syntheses of potential commercial interest and the utilization of carbon dioxide as a substrate for fuel production. It draws extensively on literature sources, particularly on the report of a 1999 Workshop on the subject of catalysis in carbon dioxide utilization, but with emphasis on systems of most interest to us. Atmospheric carbon dioxide is an abundant (750 billion tons in atmosphere), but dilute source of carbon (only 0.036 % by volume), so technologies for utilization at the production source are crucial for both sequestration and utilization. Sequestration--such as pumping CO{sub 2} into sea or the earth--is beyond the scope of this report, except where it overlaps utilization, for example in converting CO{sub 2} to polymers. But sequestration dominates current thinking on short term solutions to global warming, as should be clear from reports from this and other workshops. The 3500 million tons estimated to be added to the atmosphere annually at present can be compared to the 110 million tons used to produce chemicals, chiefly urea (75 million tons), salicylic acid, cyclic carbonates and polycarbonates. Increased utilization of CO{sub 2} as a starting material is, however, highly desirable, because it is an inexpensive, non-toxic starting material. There are ongoing efforts to replace phosgene as a starting material. Creation of new materials and markets for them will increase this utilization, producing an increasingly positive, albeit small impact on global CO{sub 2} levels. The other uses of interest are utilization as a solvent and for fuel production and these will be discussed in turn.
Date: December 9, 2000
Creator: CREUTZ,C. & FUJITA,E.
Partner: UNT Libraries Government Documents Department

ANL pre analysis of the SHEBA/CERES experiments.

Description: The French and British nuclear programs have prepared a series of natural uranium oxide fuel samples spiked with small amounts of the individual fission products which makeup a large fraction of the total neutron absorption by fission products in spent nuclear fuel. Both programs have utilized these samples in experimental reactors and have inferred the worth of the individual fission products. These results have been used to validate the cross sections used in criticality safety calculations. These measurements constitute a major element in support of spent fuel burnup credit in these countries.
Date: May 5, 2000
Creator: Palmiotti, G.; Smith, M.; Klann, R.; Fujita, E. & Imel, G.
Partner: UNT Libraries Government Documents Department

Physics studies of higher actinide consumption in an LMR

Description: The core physics aspects of the transuranic burning potential of the Integral Fast Reactor (IFR) are assessed. The actinide behavior in fissile self-sufficient IFR closed cycles of 1200 MWt size is characterized, and the transuranic isotopics and risk potential of the working inventory are compared to those from a once-through LWR. The core neutronic performance effects of rare-earth impurities present in the recycled fuel are addressed. Fuel cycle strategies for burning transuranics from an external source are discussed, and specialized actinide burner designs are described. 4 refs., 4 figs., 3 tabs.
Date: January 1, 1990
Creator: Hill, R.N.; Wade, D.C.; Fujita, E.K. & Khalil, H.S.
Partner: UNT Libraries Government Documents Department

Comparative neutronic analysis of Pb-versus Na-cooled LMR cores

Description: A comparative neutronic study has been conducted on several LMR cores using both lead-magnesium eutectic alloy (97.7% Pb -- 2.3% Mg) and sodium as coolant. In order to have a consistent comparison for these two coolants on a common basis, i.e. interchangeable designs, this study used exactly the same reactor core layout, assembly design parameters, and compositions for structure material. Only driver fuel enrichments were adjusted respectively for these two coolants in order to meet the same set of requirements for specified burnup cycles. Equilibrium cycle performance and coolant void worth were calculated for five different lattice designs, first for sodium coolant and then for Pb-Mg coolant. Our results indicated a better neutron economy is achieved in cores using Pb-Mg as coolant which generally have higher breeding performance, small burnup reactivity swing, and lower fissile enrichment. On the otherhand, linear heat rate goes up, power peaking worsens, and peak fast fluence increases in Pb-Mg cooled cores. Some of these problems may be mitigated if the design constraint of interchangeability were relaxed. Special emphasis has been put on the void worth comparison between Na and Pb-Mg coolant. quite large negative void worths were obtained for several cases using Pb-Mg as coolant where the Na coolant would have otherwise yielded positive values. The difference is void worths were explained from basic physical principles involved in voiding these two coolants. The large negative void worth with Pb-Mg coolant is mainly caused by the enhanced leakage component rather than the direct spectral hardening effects of heavy coolants.
Date: January 1, 1992
Creator: Liaw, J.R.; Fujita, E.K. & Wade, D.C.
Partner: UNT Libraries Government Documents Department

Physics considerations in the design of liquid metal reactors for transuranium element consumption

Description: The management of transuranic nuclides in liquid metal reactors (LMR's) is considered based on the use of the Integral Fast Reactor (IFR) concept. Unique features of the IFR fuel cycle with respect to transuranic management are identified. These features are exploited together with the hard spectrum of LMR's to demonstrate the neutronic feasibility of a wide range of transuranic management options ranging from efficient breeding to pure consumption. Core physics aspects of the development of a low sodium void worth transuranic burner concept are described. Neutronics performance parameters and reactivity feedback characteristics estimated for this core concept are presented.
Date: January 1, 1992
Creator: Khalil, H.; Hill, R.; Fujita, E. & Wade, D.
Partner: UNT Libraries Government Documents Department

Catalyzed Water Oxidation by Solar Irradiation of Band-Gap-Narrowed Semiconductors (Part 1. Overview).

Description: The objectives of this report are: (1) Investigate the catalysis of water oxidation by cobalt and manganese hydrous oxides immobilized on titania or silica nanoparticles, and dinuclear metal complexes with quinonoid ligands in order to develop a better understanding of the critical water oxidation chemistry, and rationally search for improved catalysts. (2) Optimize the light-harvesting and charge-separation abilities of stable semiconductors including both a focused effort to improve the best existing materials by investigating their structural and electronic properties using a full suite of characterization tools, and a parallel effort to discover and characterize new materials. (3) Combine these elements to examine the function of oxidation catalysts on Band-Gap-Narrowed Semiconductor (BGNSC) surfaces and elucidate the core scientific challenges to the efficient coupling of the materials functions.
Date: March 18, 2008
Creator: Fujita, E.; Khalifah, P.; Lymar, S.; Muckerman, J. T. & Rodgriguez, J.
Partner: UNT Libraries Government Documents Department

Catalyzed Water Oxidation by Solar Irradiation of Band-Gap-Narrowed Semiconductors (Part 2. Overview).

Description: The objectives of this report are: (1) Investigate the catalysis of water oxidation by cobalt and manganese hydrous oxides immobilized on titania or silica nanoparticles, and dinuclear metal complexes with quinonoid ligands in order to develop a better understanding of the critical water oxidation chemistry, and rationally search for improved catalysts. (2) Optimize the light-harvesting and charge-separation abilities of stable semiconductors including both a focused effort to improve the best existing materials by investigating their structural and electronic properties using a full suite of characterization tools, and a parallel effort to discover and characterize new materials. (3) Combine these elements to examine the function of oxidation catalysts on Band-Gap-Narrowed Semiconductor (BGNSC) surfaces and elucidate the core scientific challenges to the efficient coupling of the materials functions.
Date: March 18, 2008
Creator: Fujita, E.; Khalifah, P.; Lymar, S.; Muckerman, J. T. & Rodriguez, J.
Partner: UNT Libraries Government Documents Department

Collaborative Lubricating Oil Study on Emissions: November 28, 2006 - March 31, 2011

Description: The Collaborative Lubricating Oil Study on Emissions (CLOSE) project was a pilot investigation of how fuels and crankcase lubricants contribute to the formation of particulate matter (PM) and semi-volatile organic compounds (SVOC) in vehicle exhaust. As limited vehicles were tested, results are not representative of the whole on-road fleet. Long-term effects were not investigated. Pairs of vehicles (one normal PM emitting, one high-PM emitting) from four categories were selected: light-duty (LD) gasoline cars, medium-duty (MD) diesel trucks, heavy-duty (HD) natural-gas-fueled buses, and HD diesel buses. HD vehicles procured did not exhibit higher PM emissions, and thus were labeled high mileage (HM). Fuels evaluated were non-ethanol gasoline (E0), 10 percent ethanol (E10), conventional low-sulfur TxLED diesel, 20% biodiesel (B20), and natural gas. Temperature effects (20 degrees F, 72 degrees F) were evaluated on LD and MD vehicles. Lubricating oil vintage effects (fresh and aged) were evaluated on all vehicles. LD and MD vehicles were operated on a dynamometer over the California Unified Driving Cycle, while HD vehicles followed the Heavy Duty Urban Dynamometer Driving Schedule. Regulated and unregulated emissions were measured. Chemical markers from the unregulated emissions measurements and a tracer were utilized to estimate the lubricant contribution to PM.
Date: October 1, 2011
Creator: Carroll, J. N.; Khalek, I. A.; Smith, L. R.; Fujita, E. & Zielinska, B.
Partner: UNT Libraries Government Documents Department

Towards the photoreduction of CO{sub 2} with Ni(bpy){sub n}{sup 2+} complexes

Description: When an acetonitrile solution containing Ni(bpy){sub 3}{sup 2+}, trithylamine and CO{sub 2} is irradiated at 313 nm, CO is produced with a quantum yield {approximately} 0.1% (defined as CO produced/photons absorbed). Flash photolysis, electrochemistry, and pulse radiolysis experiments provide evidence for the formation of Ni{sup I}(bpy){sub 2+}, as an intermediate, in the photochemical Ni(bpy){sub 3}{sup 2+}/TEA/CO{sub 2} system. Although Ni{sup 0}(bpy){sub 2} does react with CO{sub 2}, Ni{sup I}(bpy){sub 2+} seems unreactive toward CO{sub 2} addition. The x-ray structure of [Ni{sub 3}(bpy){sub 6}](ClO{sub 4}), which crystallize as blue-violet needles, reveals the existence of a dimer in the solid. UV-vis spectra also indicate that reduced Ni(bpy){sub 3}{sup 2+} solutions contain Ni{sup I}(bpy){sub 2+}, Ni{sup 0}(bpy){sub 2} and [Ni(bpy){sub 2}]{sub 2} complexes in equilibrium.
Date: August 1, 1995
Creator: Mori, Y.; Szalda, D.J.; Brunschwig, B.S.; Schwarz, H.A. & Fujita, E.
Partner: UNT Libraries Government Documents Department