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Microstructure and Performance of Kovar/Alumina Joints Made with Silver-Copper Base Active Metal Braze Alloys

Description: Poor hermeticity performance was observed for Al{sub 2}O{sub 3}-Al{sub 2}O{sub 3} ceramic-ceramic joints having a Kovar{trademark} alloy interlayer. The active Ag-Cu-Ti filler metal was used to braze the substrates together. The Ti active element was scavenged from the filler metal by the formation of a (Fe, Ni, Co){sub x}Ti phase (x= 2-3) that prevented development of a continuous Ti{sub x}O{sub y} layer at the filler metal/Al{sub 2}O{sub 3} interface. Altering the process parameters did not circumvent the scavenging of Ti. Molybdenum barrier layers 1000, 2500, or 5000 {angstrom} thick on the Kovar{trademark} surfaces successfully allowed Ti{sub x}O{sub y} formation at the filler metal/Al{sub 2}O{sub 3} interface and hermetic joints. The problems with the Ag-Cu-Ti filler metal for Kovar{trademark}/Al{sub 2}O{sub 3} braze joints led to the evaluation of a Ag-Cu-Zr filler metal. The Zr (active element) in Ag-Cu-Zr filler metal was not susceptible to the scavenging problem.
Date: December 15, 1999
Creator: STEPHENS, JOHN J.; VIANCO,PAUL T.; HLAVA,PAUL F. & WALKER,CHARLES A.
Partner: UNT Libraries Government Documents Department

The impact of thermal loading on repository performance at Yucca Mountain

Description: In the unsaturated zone at Yucca Mountain, liquid flow along preferential fracture pathways is the only credible mechanism capable of bringing water to waste packages and transporting radionuclide to the water table. Three categories of features or mechanisms will mitigate the impact of flow along preferential fracture pathways: (1) discontinuity in fracture pathways, (2) liquid-phase dispersion in fracture networks, and (3) fracture-matrix interaction. For repository areal power densities (APDs) that are too low to result in significant boiling or rock dry-out effects, the primary mode of fracture-matrix interaction is matrix imbibition. For high APDs, boiling and enhanced matrix imbibition due to rock dry-out significantly add to the capacity of the unsaturated zone to retard fracture-dominated flow. With the use of V-TOUGH code, hydrothermal flow calculations are made for a range of APDs and spent fuel ages. For APD > 20 kW/acre, repository-heat-generated flow of vapor and liquid in fractures is found to dominate the ambient hydrological system. For high APDs, boiling conditions can persist for 10,000 yr or longer and rock-dry benefits for at least 100,000 yr.
Date: January 15, 1992
Creator: Buscheck, T.A. & Nitao, J.J.
Partner: UNT Libraries Government Documents Department

Corrosion performance of structural alloys.

Description: Component reliability and long-term trouble-free performance of structural materials are essential in power-generating and gasification processes that utilize coal as a feedstock. During combustion and conversion of coal, the environments encompass a wide range of oxygen partial pressures, from excess-air conditions in conventional boilers to air-deficient conditions in 10W-NO{sub x} and gasification systems. Apart from the environmental aspects of the effluent from coal combustion and conversion, one concern from the systems standpoint is the aggressiveness of the gaseous/deposit environment toward structural components such as waterwall tubes, steam superheaters, syngas coolers, and hot-gas filters. The corrosion tests in the program described in this paper address the individual and combined effects of oxygen, sulfur, and chlorine on the corrosion response of several ASME-coded and noncoded structural alloys that were exposed to air-deficient and excess-air environments typical of coal-combustion and gasification processes. Data in this paper address the effects of preoxidation on the subsequent corrosion performance of structural materials such as 9Cr-1Mo ferritic steel, Type 347 austenitic stainless steel, Alloys 800, 825, 625, 214, Hastelloy X, and iron aluminide when exposed at 650 C to various mixed-gas environments with and without HCI. Results are presented for scaling kinetics, microstructural characteristics of corrosion products, detailed evaluations of near-surface regions of the exposed specimens, gains in our mechanistic understanding of the roles of S and Cl in the corrosion process, and the effect of preoxidation on subsequent corrosion.
Date: July 15, 1999
Creator: Natesan, K.
Partner: UNT Libraries Government Documents Department

Concentration of uranium and plutonium in unsaturated spent fuel tests.

Description: Commercial spent fuel is being tested under oxidizing conditions at 90 C in drip tests with simulated groundwater to evaluate its long-term performance in a potential repository at Yucca Mountain [1-4]. The tests allow us to monitor the dissolution behavior of the spent fuel matrix and the release rates of individual radionuclides. This paper reports the U and Pu concentrations in the leachates of drip tests during 3.7 years of reaction. Changes in these concentrations are correlated with changes in the measured pH and the appearance of alteration products on the fuel surface. Although there is little thermodynamic information at 90 C for either uranyl or plutonium compounds, some data are available at 25 C [5-8]. The literature data for the U and Pu solubilities of U and Pu compounds were compared to the U and Pu concentrations in the leachates. We also compare Wilson's [9] U and Pu concentrations in semi-static tests at 85 C on spent fuel with our results.
Date: April 15, 1998
Creator: Finn, P. A.
Partner: UNT Libraries Government Documents Department

Waste characterization for radioactive liquid waste evaporators at Argonne National Laboratory - West.

Description: Several facilities at Argonne National Laboratory - West (ANL-W) generate many thousand gallons of radioactive liquid waste per year. These waste streams are sent to the AFL-W Radioactive Liquid Waste Treatment Facility (RLWTF) where they are processed through hot air evaporators. These evaporators remove the liquid portion of the waste and leave a relatively small volume of solids in a shielded container. The ANL-W sampling, characterization and tracking programs ensure that these solids ultimately meet the disposal requirements of a low-level radioactive waste landfill. One set of evaporators will process an average 25,000 gallons of radioactive liquid waste, provide shielding, and reduce it to a volume of six cubic meters (container volume) for disposal. Waste characterization of the shielded evaporators poses some challenges. The process of evaporating the liquid and reducing the volume of waste increases the concentrations of RCIU regulated metals and radionuclides in the final waste form. Also, once the liquid waste has been processed through the evaporators it is not possible to obtain sample material for characterization. The process for tracking and assessing the final radioactive waste concentrations is described in this paper, The structural components of the evaporator are an approved and integral part of the final waste stream and they are included in the final waste characterization.
Date: February 15, 1999
Creator: Christensen, B. D.
Partner: UNT Libraries Government Documents Department

EVALUATION OF MODAL COMBINATION METHODS FOR SEISMIC RESPONSE SPECTRUM ANALYSIS.

Description: Regulatory Guide 1.92 ''Combining Modal Responses and Spatial Components in Seismic Response Analysis'' was last revised in 1976. The objective of this project was to re-evaluate the current regulatory guidance for combining modal responses in response spectrum analysis, evaluate recent technical developments, and recommend revisions to the regulatory guidance. This paper describes the qualitative evaluation of modal response combination methods.
Date: August 15, 1999
Creator: MORANTE,R.
Partner: UNT Libraries Government Documents Department

Fouling characteristics of compact heat exchangers and enhanced tubes.

Description: Fouling is a complex phenomenon that (1) encompasses formation and transportation of precursors, and (2) attachment and possible removal of foulants. A basic understanding of fouling mechanisms should guide the development of effective mitigation techniques. The literature on fouling in complex flow passages of compact heat exchangers is limited; however, significant progress has been made with enhanced tubes.
Date: July 15, 1999
Creator: Panchal, C. B. & Rabas, T. J.
Partner: UNT Libraries Government Documents Department

Coupled reactor physics and coolant dynamics of heavy liquid metal coolant systems.

Description: Cooling of advanced nuclear designs with heavy liquid metals such as lead or lead-bismuth eutectic offers the potential for plant simplifications and higher operating efficiencies compared to previously considered liquid metal coolants such as sodium or NaK. Such applications would however also introduce additional safety concerns and design challenges, therefore necessitating a verifiable computational tool for transient design-basis analysis of heavy liquid metal coolant (HLMC) systems. This capability would enable analysts to compare operational and safety characteristics of design alternatives, and to evaluate relative performance advantages with a consistent, deterministic measure.
Date: July 15, 1999
Creator: Cahalan, J. E.; Dunn, F. E. & Taiwo, T. A.
Partner: UNT Libraries Government Documents Department

High rate PLD of diamond-like-carbon utilizing high repetition rate visible lasers

Description: Pulsed Laser Deposition (PLD) has been shown to be an effective method for producing a wide variety of thin films of high-value-added materials. The high average powers and high pulse repetition frequencies of lasers under development at LLNL make it possible to scale-up PLD processes that have been demonstrated in small systems in a number of university, government, and private laboratories to industrially meaningful, economically feasible technologies. A copper vapor laser system at LLNL has been utilized to demonstrate high rate PLD of high quality diamond-like-carbon (DLC) from graphite targets. The deposition rates for PLD obtained with a 100 W laser were {approx} 2000 {mu}m{center_dot}cm{sup 2}/h, or roughly 100 times larger than those reported by chemical vapor deposition (CVD) or physical vapor deposition (PVD) methods. Good adhesion of thin (up to 2 pm) films has been achieved on a small number of substrates that include SiO{sub 2} and single crystal Si. Present results indicate that the best quality DLC films can be produced at optimum rates at power levels and wavelengths compatible with fiber optic delivery systems. If this is also true of other desirable coating systems, this PLD technology could become an extremely attractive industrial tool for high value added coatings.
Date: September 15, 1994
Creator: McLean, W. II; Fehring, E.J.; Dragon, E.P. & Warner, B.E.
Partner: UNT Libraries Government Documents Department

Methods for incorporating effects of LWR coolant environment into ASME code fatigue evaluations.

Description: The ASME Boiler and Pressure Vessel Code provides rules for the construction of nuclear power plant components. Appendix I to Section HI of the Code specifies design fatigue curves for structural materials. However, the effects of light water reactor (LWR) coolant environments are not explicitly addressed by the Code design curves. Recent test data illustrate potentially significant effects of LWR environments on the fatigue resistance of carbon and low-alloy steels and austenitic stainless steels (SSs). Under certain loading and environmental conditions, fatigue lives of carbon and low-alloy steels can be a factor of {approx}70 lower in an LWR environment than in air. These results raise the issue of whether the design fatigue curves in Section III are appropriate for the intended purpose. This paper presents the two methods that have been proposed for incorporating the effects of LWR coolant environments into the ASME Code fatigue evaluations. The mechanisms of fatigue crack initiation in carbon and low-alloy steels and austenitic SSs in LWR environments are discussed.
Date: April 15, 1999
Creator: Chopra, O. K.
Partner: UNT Libraries Government Documents Department

Sorption and diffusion studies of Pu(IV) and Pu(V)-EDTA onto and through Hanford soil

Description: Plutonium production at U.S. Department of Energy Hanford site has created massive amounts of radioactive and mixed wastes. Over 1.3 trillion liters of liquid waste have been discharged into the ground, the largest part of which has been absorbed by the upper soil layers with a small fraction migrating into the groundwater. Approximately 350 million liters of other low and high-level mixed wastes were stored in underground tanks between 1944 and 1980. These tanks contain organic materials that were introduced during the production and processing of plutonium, such as ethylenediametetraacetic acid (EDTA), tributyl phosphate, hexone, paraffin hydrocarbon and other minor organic and inorganic components. The quantity of EDTA is estimated to be 83 metric tons in the underground tanks. Several single-shell tanks are known or suspected to have leaked. It was reported that since 1995, approximately four million liters of mixed waste might have entered the soil beneath the single-shell tanks. This volume of waste is estimated to contain as much as one million curies of radioactivity.
Date: September 15, 1999
Creator: Allen, P G; Hakem, N L & Sylwester, E R
Partner: UNT Libraries Government Documents Department

A sparse superlinearly convergent SQP with applications to two-dimensional shape optimization.

Description: Discretization of optimal shape design problems leads to very large nonlinear optimization problems. For attaining maximum computational efficiency, a sequential quadratic programming (SQP) algorithm should achieve superlinear convergence while preserving sparsity and convexity of the resulting quadratic programs. Most classical SQP approaches violate at least one of the requirements. We show that, for a very large class of optimization problems, one can design SQP algorithms that satisfy all these three requirements. The improvements in computational efficiency are demonstrated for a cam design problem.
Date: April 15, 1998
Creator: Anitescu, M.
Partner: UNT Libraries Government Documents Department

Exploiting the power of DSM and SMP clusters for parallel CFD

Description: The new generation of powerful DSM and SMP cluster computers enables simulations of fluid dynamics at sufficient resolution to compute the complex nonlinear interactions of small-scale turbulent motions with a large-scale driving flow. With a new programming model of hierarchical shared memory multitasking, it is possible to exploit these new systems without disrupting the flow of small and medium-sized jobs that makes their existence possible.
Date: March 15, 1999
Creator: Anderson, S. E.; Cohen, R. H.; Curtis, B. C.; Dannevik, W. P.; Dimits, A. M.; Dinge, D. et al.
Partner: UNT Libraries Government Documents Department

Experimental Demonstration of Guiding and Bending of Electromagnetic Waves in a Photonic Crystal

Description: The routing and interconnection of optical signals through narrow channels and around sharp corners is important for large-scale all-optical circuit applications. A recent computational result suggests that photonic crystals may offer a novel way of achieving this goal by providing a mechanism for guiding light that is fundamentally different from traditional index guiding. Waveguiding in a photonic crystal, and near 100% transmission of electromagnetic waves around sharp 90o corners were observed experimentally. Bend- ing radii were made smaller than one wavelength.
Date: October 15, 1998
Creator: Chow, E.; Hietala, .; Joannopoulos, J.D.; Lin, S. & Villeneuve, P.R.
Partner: UNT Libraries Government Documents Department

Ball lens reflections by direct solution of Maxwell`s equations

Description: Ball lenses are important for many applications. For example, ball lenses can be used to match the mode of a laser diode (LD) to a single mode fiber (SMF), essential for low-loss, high bit rate communication systems. Modeling the propagation of LD light through a ball lens presents a challenge due to the large angular divergence of the LD field (typically > 20{degrees} HWHM) and the subsequent significant effect of spherical aberration. Accurately calculating the reflected power is also difficult, but essential, since reflections as small as {minus}30 dB can destabilize the LID. A full-wave analysis of this system using, e.g., a finite-difference time-domain method is not practical because of the size of the ball lens, typically hundreds of wavelengths in diameter. Approximate scalar methods can give good results in some cases, but fail to calculate reflected power and miss polarization effects entirely. The authors` approach exploits the fact that the scattering of an arbitrary electromagnetic beam from a sphere is an exactly solvable problem. The scattering of a plane wave from a sphere is a classical problem which was solved by Mie in 1908. More recently, various workers have considered the scattering of a Gaussian beam from a sphere and its numerical implementation for other applications. To the authors knowledge, this is the first time this approach has been applied to a problem in optical design. They are able to calculate reflection and transmission accurately with modest computational effort.
Date: February 15, 1995
Creator: Ratowsky, R.P.; Deri, R.J. & Kallman, J.S.
Partner: UNT Libraries Government Documents Department

Issues and opportunities: beam simulations for heavy ion fusion

Description: UCRL- JC- 134975 PREPRINT code offering 3- D, axisymmetric, and ''transverse slice'' (steady flow) geometries, with a hierarchy of models for the ''lattice'' of focusing, bending, and accelerating elements. Interactive and script- driven code steering is afforded through an interpreter interface. The code runs with good parallel scaling on the T3E. Detailed simulations of machine segments and of complete small experiments, as well as simplified full- system runs, have been carried out, partially benchmarking the code. A magnetoinductive model, with module impedance and multi- beam effects, is under study. experiments, including an injector scalable to multi- beam arrays, a high- current beam transport and acceleration experiment, and a scaled final- focusing experiment. These ''phase I'' projects are laying the groundwork for the next major step in HIF development, the Integrated Research Experiment (IRE). Simulations aimed directly at the IRE must enable us to: design a facility with maximum power on target at minimal cost; set requirements for hardware tolerances, beam steering, etc.; and evaluate proposed chamber propagation modes. Finally, simulations must enable us to study all issues which arise in the context of a fusion driver, and must facilitate the assessment of driver options. In all of this, maximum advantage must be taken of emerging terascale computer architectures, requiring an aggressive code development effort. An organizing principle should be pursuit of the goal of integrated and detailed source- to- target simulation. methods for analysis of the beam dynamics in the various machine concepts, using moment- based methods for purposes of design, waveform synthesis, steering algorithm synthesis, etc. Three classes of discrete- particle models should be coupled: (1) electrostatic/ magnetoinductive PIC simulations should track the beams from the source through the final- focusing optics, passing details of the time- dependent distribution function to (2) electromagnetic or magnetoinductive PIC or hybrid PIG/ ...
Date: July 15, 1999
Creator: Friedman, A
Partner: UNT Libraries Government Documents Department

MCFC component development at ANL.

Description: Argonne National Laboratory is developing advanced cathode and electrolyte components for the molten carbonate fuel cell (MCFC). Working in support of the MCFC developers, the goal of this effort is to extend the life of the MCFC cell and to improve its performance.
Date: September 15, 1998
Creator: Bloom, I.
Partner: UNT Libraries Government Documents Department

NRC-BNL BENCHMARK PROGRAM ON EVALUATION OF METHODS FOR SEISMIC ANALYSIS OF COUPLED SYSTEMS.

Description: A NRC-BNL benchmark program for evaluation of state-of-the-art analysis methods and computer programs for seismic analysis of coupled structures with non-classical damping is described. The program includes a series of benchmarking problems designed to investigate various aspects of complexities, applications and limitations associated with methods for analysis of non-classically damped structures. Discussions are provided on the benchmarking process, benchmark structural models, and the evaluation approach, as well as benchmarking ground rules. It is expected that the findings and insights, as well as recommendations from this program will be useful in developing new acceptance criteria and providing guidance for future regulatory activities involving licensing applications of these alternate methods to coupled systems.
Date: August 15, 1999
Creator: XU,J.
Partner: UNT Libraries Government Documents Department

Imaging sciences workshop

Description: This workshop on the Imaging Sciences sponsored by Lawrence Livermore National Laboratory contains short abstracts/articles submitted by speakers. The topic areas covered include the following: Astronomical Imaging; biomedical imaging; vision/image display; imaging hardware; imaging software; Acoustic/oceanic imaging; microwave/acoustic imaging; computed tomography; physical imaging; imaging algorithms. Selected papers are indexed separately for inclusion in the Energy Science and Technology Database.
Date: November 15, 1994
Creator: Candy, J.V.
Partner: UNT Libraries Government Documents Department

Magnetic correlations in doped transition metal oxides

Description: The authors review recent reactor- and spallation-source-based neutron scattering experiments on the magnetic fluctuations and order in a variety of doped transition metal oxides. In particular, data are shown for the NiO chain compound, Y{sub 2{minus}x}Ca{sub x}BaNiO{sub 5}, the two-dimensional cuprate superconductors La{sub 2{minus}x}Sr{sub x}CuO{sub 4} and YBa{sub 2}Cu{sub 3} O{sub 6+x}, and the classical three-dimensional ``Mott-Hubbard`` system V{sub 2{minus}y}O{sub 3}.
Date: February 15, 1995
Creator: Aeppli, G.; Bao, W. & Broholm, C.
Partner: UNT Libraries Government Documents Department

Proton Decay Studies of the Light Lu, Tm and Ho Isotopes

Description: A double-sided Si-strip detector system has been installed and commissioned at the focal plane of the Recoil Mass Spectrometer at the Holifield Radioactive Ion Beam Facility. The system can be used for heavy charged particle emission studies with half-lives as low as a few {micro}sec. In this paper the authors present identification and study of the decay properties of the five new proton emitters: {sup 140}Ho, {sup 141m}Ho, {sup 145}Tm, {sup 150m}Lu and {sup 151m}Lu.
Date: October 15, 1998
Creator: Akovali, Y.; Batchelder, J.C.; Bingham, C.R.; Davinson, T.; Ginter, T.N.; Gross, C.J. et al.
Partner: UNT Libraries Government Documents Department

The MINOS long-baseline experiment at Fermilab.

Description: The MINOS long-baseline experiment will search for neutrino oscillations by measuring an intense {nu}{sub {mu}} beam at the end of a 730 km flight path. The 10,000 ton MINOS far detector will utilize magnetized steel plates interleaved with track chambers to reconstruct event topologies and to measure the energies of the muons, hadrons and electromagnetic showers produced by neutrino interactions. The experiment is designed to detect {nu}{sub {mu}} {r_arrow} {nu}{sub {tau}} and {nu}{sub {mu}} {r_arrow} {nu}{sub e} oscillations with {Delta}m{sup 2} {ge} 0.001 eV{sup 2} and sin{sup 2}(2{theta}) {ge} 0.01. Any oscillation signal observed can be verified and studied by several independent tests: a near/far rate comparison, the NC/CC event ratio, the CC and NC event energy spectra, and the identification of electrons and {tau} leptons. The neutrino beam can be operated in both wide-band and narrow-band configurations, allowing the detailed study oscillation phenomena. The experiment is scheduled to begin operation in 2001.
Date: October 15, 1997
Creator: Ayres, D. S.
Partner: UNT Libraries Government Documents Department

Use of Dissolved and Colloidal Actinide Parameters within the 1996 Waste Isolation Pilot Plant Compliance Certification Application

Description: Many of the papers in this volume present detailed descriptions of the chemical analyses and methodologies that have been used to evaluate the maximum dissolved and colloid concentrations of actinides within the WIPP repository as part of the performance assessment. This paper describes the program fcm collecting experimental data and provides an overview of how the PA modeled the release of radionuclides to the accessible environment, and how volubility and colloid parameters were used by the PA models.
Date: October 15, 1998
Creator: Moore, R.C. & Stockman, C.T.
Partner: UNT Libraries Government Documents Department

ALPS - advanced limiter-divertor plasma-facing systems.

Description: The Advanced Limiter-divertor Plasma-facing Systems (ALPS) program was initiated in order to evaluate the potential for improved performance and lifetime for plasma-facing systems. The main goal of the program is to demonstrate the advantages of advanced limiter/divertor systems over conventional systems in terms of power density capability, component lifetime, and power conversion efficiency, while providing for safe operation and minimizing impurity concerns for the plasma. Most of the work to date has been applied to free surface liquids. A multi-disciplinary team from several institutions has been organized to address the key issues associated with these systems. The main performance goals for advanced limiters and diverters are a peak heat flux of >50 MW/m{sup 2},elimination of a lifetime limit for erosion, and the ability to extract useful heat at high power conversion efficiency ({approximately}40%). The evaluation of various options is being conducted through a combination of laboratory experiments, modeling of key processes, and conceptual design studies. The current emphasis for the work is on the effects of free surface liquids on plasma edge performance.
Date: September 15, 1999
Creator: Allain, J. P.; Bastasz, R.; Brooks, J. N.; Evans, T.; Hassanein, A.; Luckhardt, S. et al.
Partner: UNT Libraries Government Documents Department