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BWR drywell behavior under steam blowdown.

Description: Historically, thermal hydraulics analyses on Large Break Loss of Coolant Accidents (LOCA) have been focused on the transients within the reactor or steam generator. Few have studied the effects of steam blowdown on the containment building. This paper discusses some theoretical issues as well as presenting numerical and experimental results of the blowdown tests performed at the Purdue University Multi-Dimensional Integrated Test Assembly (PUMA).
Date: May 8, 1998
Creator: NguyenLe, Q.
Partner: UNT Libraries Government Documents Department

Numerical relativity in a distributed environment.

Description: We have found that the hardware and software infrastructure exists to simulate general relativity problems in a distributed computational environment, at some cost in performance. We examine two different issues for running the Cactus code in such a distributed environment The first issue is running a Cactus simulation on multiple parallel computer systems. Our objective is to perform larger simulations than are currently possible on a single parallel computer. We distribute Cactus simulations across multiple supercomputers using the mechanisms provided by the Globus toolkit. In particular, we use Globus mechanisms for authentication, access to remote computer systems, file transfer, and communication. The Cactus code uses MPI for communication and makes use of an MPI implementation layered atop Globus communication mechanisms. These communication mechanisms allow a MPI application to be executed on distributed resources. We find that without performing any code optimizations, our simulations ran 48% to 100% slower when using an Origin at the National Center for Supercomputing Applications (NCSA) and an Onyx2 at Argonne National Laboratory (ANL). We also ran simulations between Cray T3Es in Germany and a T3E at the San Diego Supercomputing Center (SDSC). Running between the T3Es in Germany resulted in an increase in execution time of 79% to 133%, and running between a German T3E and a T3E at the San Diego Supercomputing Center resulted in an execution time increase of 114% to 186%. We are very encouraged that we are able to run simulations on parallel computers that are geographically distributed, and we have identified several areas to investigate to improve the performance of Cactus simulations in this environment. The second issue we examine here is remote visualization and steering of the Cactus code. Cactus is a modular framework and we have implemented a module for this task. This module performs isosurfacing operations on ...
Date: February 8, 1999
Creator: Benger, W.; Foster, I.; Novotny, J.; Seidel, E.; Shalf, J.; Smith, W. et al.
Partner: UNT Libraries Government Documents Department

Structural Modification of Sol-Gel Materials through Retro Diels-Alder Reaction

Description: Hydrolysis and condensation of organically bridged bis-triethoxysilanes, (EtO){sub 3}Si-R-Si(OEt){sub 3}, results in the formation of three dimensional organic/inorganic hybrid networks (Equation 1). Properties of these materials, including porosity, are dependent on the nature of the bridging group, R. Flexible groups (akylene-spacers longer than five carbons in length) polymerize under acidic conditions to give non-porous materials. Rigid groups (such as arylene-, alkynylene-, or alkenylene) form non-porous, microporous, and macroporous gels. In many cases the pore size distributions are quite narrow. One of the motivations for preparing hybrid organic-inorganic materials is to extend the range of properties available with sol-gel systems by incorporating organic groups into the inorganic network. For example, organically modified silica gels arc either prepared by co-polymerizing an organoalkoxysilane with a silica precursor or surface silylating the inorganic gel. This can serve to increase hydrophobicity or to introduce some reactive organic functionality. However, the type and orientation of these organic functionalities is difficult to control. Furthermore, many organoalkoxysilanes can act to inhibitor even prevent gelation, limiting the final density of organic functionalities. We have devised a new route for preparing highly functionalized pores in hybrid materials using bridging groups that are thermally converted into the desired functionalities after the gel has been obtained. In this paper, we present the preparation and characterization of bridged polysilsesquioxanes with Diels-Alder adducts as the bridging groups from the sol-gel polymerization of monomers 2 and 4. The bridging groups are constructed such that the retro Diela-Alder reaction releases the dienes and leaves the dienophiles as integral parts of the network polymers. In the rigid architecture of a xerogel, this loss of organic functionality should liberate sufficient space to modify the overall porosity. Furthermore, the new porosity will be functionalized with the dienophilic olefin bridging group. We also demonstrate that by changing the type of ...
Date: December 8, 1999
Partner: UNT Libraries Government Documents Department

Structural analysis of ORNL underground gunite waste storage tanks

Description: The North Tank Farm (NTF) and the South Tank Farm (STF) located at ORNL contains 8 underground waste storage tanks which were built around 1943. The tanks were used to collect and store the liquid portion of the radioactive and/or hazardous chemical wastes produced as part of normal facility operations at ORNL, but are no longer part of the active Low Level Liquid Waste system of the Laboratory. The tanks were constructed of gunite. The six STF tanks are 50 ft in diameter, and have a 12 ft sidewall, and an arched dome rising another 6.25 ft. The sidewall are 6 in. thick and have an additional 1.5 in. gunite liner on the inside. There is a thickened ring at the wall-dome juncture. The dome consists of two 5 in. layers of gunite. The two tanks in the NTF are similar, but smaller, having a 25 ft diameter, no inner liner, and a dome thickness of 3.5 in. Both sets of tanks have welded wire mesh and vertical rebars in the walls, welded wire mesh in the domes, and horizontal reinforcing hoop bars pre-tensioned to 35 to 40 ksi stress in the walls and thickened ring. The eight tanks are entirely buried under a 6 ft layer of soil cover. The present condition of the tanks is not accurately known, since access to them is extremely limited. In order to evaluate the structural capability of the tanks, a finite element analysis of each size tank was performed. Both static and seismic loads were considered. Three sludge levels, empty, half-full, and full were evaluated. In the STF analysis, the effects of wall deterioration and group spacing were evaluated. These analyses found that the weakest element in the tanks is the steel resisting the circumferential (or hoop) forces in the dome ring, ...
Date: November 8, 1995
Creator: Fricke, K.E. & Chung, T.C.
Partner: UNT Libraries Government Documents Department

Microbial Population Changes During Bioremediation of an Experimental Oil Spill

Description: A field experiment was conducted in Delaware (USA) to evaluate three crude oil bioremediation techniques. Four treatments were studied: no oil control, oil alone, oil + nutrients, and oil + nutrients + an indigenous inoculum. The microbial populations were monitored by standard MPN techniques, PLFA profile analysis, and 16S rDNA DGGE analysis for species definition. Viable MPN estimates showed high but steadily declining microbial numbers and no significant differences among treatments during the 14-weeks. Regarding the PLFA results, the communities shifted over the 14-week period from being composed primarily of eukaryotes to Gram-negative bacteria. The Gram-negative communities shifted from the exponential to the stationary phase of growth after week 0. All Gram-negative communities showed evidence of environmental stress. The 16S rDNA DGGE profile of all plots revealed eight prominent bands at time zero. The untreated control plots revealed a simple, dynamic dominant population structure throughout the experiment. The original banding pattern disappeared rapidly in all oiled plots, indicating that the dominant species diversity changed and increased substantially over 14 weeks. The nature of this change was altered by nutrient-addition and the addition of the indigenous inoculum.
Date: August 8, 1998
Creator: Chang, Y. J.; Davis, G. A.; Macnaughton, S. J.; Stephen, J. R.; Venosa, A. D. & White, D. C.
Partner: UNT Libraries Government Documents Department

Owner Involvement in Construction at a National Laboratory

Description: In a construction project, the contractor and the owner each have a responsibility for ensuring the health and safety of personnel on a project site. The contractor has the responsibility for ensuring that the provisions of OSHA'S safety and health regulations are followed and that the work is conducted in a safe and well thought out manner (Kohn 1996). The owner has a responsibility for disclosing to the contractor those owner-controlled hazards that are present in the work area due to ongoing and past operations (OSHA 1997). With the owner taking an active role in disclosing the potential hazards, the contractor is able to account for, plan, and mitigate potential health and safety issues during the performance phase of the project. At Sandia National Laboratories, this disclosure is made early in the project through the use of processes developed specifically for this purpose.
Date: March 8, 1999
Creator: Lipka, G.
Partner: UNT Libraries Government Documents Department

Performance of keck adaptive optics with sodium laser guide star

Description: The Keck telescope adaptive optics system is designed to optimize performance in he 1 to 3 micron region of observation wavelengths (J, H, and K astronomical bands). The system uses a 249 degree of freedom deformable mirror, so that the interactuator spacing is 56 cm as mapped onto the 10 meter aperture. 56 cm is roughly equal to r0 at 1.4 microns, which implies the wavefront fitting error is 0.52 ({lambda}/2{pi})({ital d}/{ital r}{sub 0}){sup 5/6} = 118 nm rms. This is sufficient to produce a system Strehl of 0.74 at 1.4 microns if all other sources of error are negligible, which would be the case with a bright natural guidestar and very high control bandwidth. Other errors associated with the adaptive optics will however contribute to Strehl degradation, namely, servo bandwidth error due to inability to reject all temporal frequencies of the aberrated wavefront, wavefront measurement error due to finite signal-to-noise ratio in the wavefront sensor, and, in the case of a laser guidestar, the so-called cone effect where rays from the guidestar beacon fail to sample some of the upper atmosphere turbulence. Cone effect is mitigated considerably by the use of the very high altitude sodium laser guidestar (90 km altitude), as opposed to Rayleigh beacons at 20 km. However, considering the Keck telescope`s large aperture, this is still the dominating wavefront error contributor in the current adaptive optics system design.
Date: March 8, 1996
Creator: Gavel, D.T.; Olivier, S. & Brase, J.
Partner: UNT Libraries Government Documents Department

Molten salt destruction of energetic material wastes as an alternative to open burning

Description: The Lawrence Livermore National Laboratory in conjunction with the Energetic Materials Center (a partnership of Lawrence Livermore and Sandia National Laboratories), is developing methods for the safe and environmentally sound destruction of explosives and propellants as a part of the Laboratory`s ancillary demilitarization mission. As a result of the end of the Cold War and the shift in emphasis to a smaller stockpile, many munitions, both conventional and nuclear, are scheduled for retirement and rapid dismantlement and demilitarization. major components of these munitions are the explosives and propellants, or energetic materials. The Department of Energy has thousands of pounds of energetic materials which result from dismantlement operations at the Pantex Plant. The Department of Defense has several hundred million pounds of energetic materials in its demilitarization inventory, with millions more added each year.
Date: September 8, 1994
Creator: Upadhye, R.S.; Brummond, W.A.; Pruneda, C.O. & Watkins, B.E.
Partner: UNT Libraries Government Documents Department

NdFeB magnets aligned in a 9-T superconducting solenoid.

Description: Commercial-grade magnet powder (Magnequench UG) was uniaxial die-pressed into cylindrical compacts, while being aligned in the 1-T to 8-T DC field of a superconducting solenoid at Argonne National Laboratory. Then, the compacts were added to normal Magnequench UG production batches for sintering and annealing. The variations in magnet properties for different strengths of alignment fields are reported for 15.88-mm (5/8-in.) diameter compacts made with length-to-diameter (L/D) ratios in the range {ge} 0.25 and {le} 1. The best magnets were produced when the powder-filled die was inserted into the active field of the solenoid and then pressed. Improvements in the residual flux density of 8% and in the energy product of 16% were achieved by increasing the alignment field beyond the typical 2-T capabilities of electromagnets. The most improvement was achieved for the compacts with the smallest L/D ratio. The ability to make very strong magnets with small L/D, where self-demagnetization effects during alignment are greatest, would benefit most the production of near-final-shape magnets. Compaction of the magnet powder using a horizontal die and a continuously active superconducting solenoid was not a problem. Although the press was operated in the batch mode for this proof-of-concept study, its design is intended to enable automated production.
Date: May 8, 2002
Creator: Mulcahy, T. M.; Hull, J. R.; Rozendaal, E. & Wise, J. H.
Partner: UNT Libraries Government Documents Department


Description: We are developing a computer code, ORBIT, specifically for beam dynamics calculations in high-intensity rings. Our approach allows detailed simulation of realistic accelerator problems. ORBIT is a particle-in-cell tracking code that transports bunches of interacting particles through a series of nodes representing elements, effects, or diagnostics that occur in the accelerator lattice. At present, ORBIT contains detailed models for strip-foil injection, including painting and foil scattering; rf focusing and acceleration; transport through various magnetic elements; longitudinal and transverse impedances; longitudinal, transverse, and three-dimensional space charge forces; collimation and limiting apertures; and the calculation of many useful diagnostic quantities. ORBIT is an object-oriented code, written in C++ and utilizing a scripting interface for the convenience of the user. Ongoing improvements include the addition of a library of accelerator maps, BEAMLINE/MXYZPTLK, the introduction of a treatment of magnet errors and fringe fields; the conversion of the scripting interface to the standard scripting language, Python; and the parallelization of the computations using MPI. The ORBIT code is an open source, powerful, and convenient tool for studying beam dynamics in high-intensity rings.
Date: April 8, 2002
Partner: UNT Libraries Government Documents Department

Pressure diffusion waves in porous media

Description: Pressure diffusion wave in porous rocks are under consideration. The pressure diffusion mechanism can provide an explanation of the high attenuation of low-frequency signals in fluid-saturated rocks. Both single and dual porosity models are considered. In either case, the attenuation coefficient is a function of the frequency.
Date: April 8, 2003
Creator: Silin, Dmitry; Korneev, Valeri & Goloshubin, Gennady
Partner: UNT Libraries Government Documents Department


Description: A recirculating accelerator accelerates the beam by passing through accelerating cavities multiple times. An FFAG recirculating accelerator uses a single arc to connect the linacs together, as opposed to multiple arcs for the different energies. For most scenarios using high-frequency RF, it is impractical to change the phase of the RF on each pass, at least for lower energy accelerators. Ideally, therefore, the WAG arc will be isochronous, so that the particles come back to the same phase (on-crest) on each linac pass. However, it is not possible to make the FFAG arcs isochronous (compared to the RF period) over a large energy range. This paper demonstrates that one can nonetheless make an WAG recirculating accelerator work. Given the arc's path length as a function of energy and the number of turns to accelerate for, one can find the minimum voltage (and corresponding initial conditions) required to accelerate a reference particle to the desired energy. I also briefly examine how the longitudinal acceptance varies with the number of turns that one accelerates.
Date: April 8, 2002
Creator: BERG,J.S.
Partner: UNT Libraries Government Documents Department

Aluminosilicate Formation in High Level Waste Evaporators: A Mechanism for Uranium Accumulation

Description: High level waste Evaporators at the Savannah River Site (SRS) process radioactive waste to concentrate supernate and thus conserve tank space. In June of 1997, difficulty in evaporator operation was initially observed. This operational difficulty evidenced itself as a plugging of the evaporator's gravity drain line (GDL). The material blocking the GDL was determined to be a sodium aluminosilicate. Following a mechanical cleaning of the GDL, the evaporator was returned to service until October 1999. At this time massive deposits were discovered in the evaporator pot. As a result of the changes in evaporator chemistry and the resulting formation of aluminosilicate deposits in the evaporator, a comprehensive research and development program has been undertaken. This program is underway in order to assist in understanding the new evaporator chemistry and gain insight into the deposition phenomena. Key results from testing in FY01 have demonstrated that the chemistry of the evaporator feed favors aluminosilicate formation. Both the reaction kinetics and particle growth of the aluminosilicate material under SRS evaporator conditions has been demonstrated to occur within the residence times utilized in the SRS evaporator operation. Batch and continuous-flow experiments at known levels of supersaturation have shown a significant correlation between the deposition of aluminosilicates and mixing intensity in the vessel. Advances in thermodynamic modeling of the evaporator chemistry have been accomplished. The resulting thermodynamic model has been related to the operational history of the evaporator, is currently assisting in feed selection, and could potentially assist in expanding the operating envelopes technical baselines for evaporator operation.
Date: February 8, 2002
Creator: Wilmarth, W.R.
Partner: UNT Libraries Government Documents Department

Carbon sequestration in natural gas reservoirs: Enhanced gas recovery and natural gas storage

Description: Natural gas reservoirs are obvious targets for carbon sequestration by direct carbon dioxide (CO{sub 2}) injection by virtue of their proven record of gas production and integrity against gas escape. Carbon sequestration in depleted natural gas reservoirs can be coupled with enhanced gas production by injecting CO{sub 2} into the reservoir as it is being produced, a process called Carbon Sequestration with Enhanced Gas Recovery (CSEGR). In this process, supercritical CO{sub 2} is injected deep in the reservoir while methane (CH{sub 4}) is produced at wells some distance away. The active injection of CO{sub 2} causes repressurization and CH{sub 4} displacement to allow the control and enhancement of gas recovery relative to water-drive or depletion-drive reservoir operations. Carbon dioxide undergoes a large change in density as CO{sub 2} gas passes through the critical pressure at temperatures near the critical temperature. This feature makes CO{sub 2} a potentially effective cushion gas for gas storage reservoirs. Thus at the end of the CSEGR process when the reservoir is filled with CO{sub 2}, additional benefit of the reservoir may be obtained through its operation as a natural gas storage reservoir. In this paper, we present discussion and simulation results from TOUGH2/EOS7C of gas mixture property prediction, gas injection, repressurization, migration, and mixing processes that occur in gas reservoirs under active CO{sub 2} injection.
Date: April 8, 2003
Creator: Oldenburg, Curtis M.
Partner: UNT Libraries Government Documents Department


Description: The SNS Ring off-line parallel simulation environment based on the Unified Accelerator Libraries (UAL) has en implemented and used for extensive full-scale beam dynamics studies arising in high-intensity ring. The paper describes the structure of this environment and its application to various high-intensity topics and diagnostics modeling.
Date: April 8, 2002
Partner: UNT Libraries Government Documents Department

New developments in photdectection in particle physics and nuclear physics

Description: Photodetectors are widely used in particle and nuclear physics research. Since the beginning of the modern era of photoelectric transducers in the late 1930�s, many types of devices have been developed and exploited for physics research. New performance requirements arising in physics experiments have often provided very interesting technological drivers for industry. New ideas for photo-detection are rapidly adapted by the physics community to enable more powerful experimental capabilities. This report gives a sampling of new developments in photodetection for physics research in the period since the first conference in this series, Beaune 96. Representative examples of advances in vacuum devices, solid-state devices and gaseous photodetectors are described including, where appropriate, an indication of areas where technological improvements are needed or expected.
Date: October 8, 1999
Creator: Elias, John E.
Partner: UNT Libraries Government Documents Department

Initial results from the Lick Observatory Laser Guide Star Adaptive Optics System

Description: A prototype adaptive optics system has been installed and tested on the 3 m Shane telescope at Lick Observatory. The adaptive optics system performance, using bright natural guide stars, is consistent with expectations based on theory. A sodium-layer laser guide star system has also been installed and tested on the Shane telescope. Operating at 15 W, the laser system produces a 9th magnitude guide star with seeing-limited size at 589 nm. Using the laser guide star, the adaptive optics system has reduced the wavefront phase variance on scales above 50 cm by a factor of 4. These results represent the first continuous wavefront phase correction using a sodium-layer laser guide star. Assuming tip-tilt is removed using a natural guide star, the measured control loop performance should produce images with a Strehl ratio of 0.4 at 2.2 {mu}m in 1 arc second seeing. Additional calibration procedures must be implemented in order to achieve these results with the prototype Lick adaptive optics system.
Date: November 8, 1995
Creator: Olivier, S.S.; An, J. & Avicola, K.
Partner: UNT Libraries Government Documents Department

Evaluation of concrete masonry unit walls for lateral natural phenomena hazards loads

Description: Older single-story facilities (Pre-1985 vintage) are commonly constructed of structural steel framing with concrete masonry unit (CMU) walls connected to columns and roof girders of the steel framing system. The CMU walls are designed for lateral wind and seismic loads (perpendicular to the wall) and transmit shear loads from the roof diaphragm to the foundation footings. The lateral loads normally govern their design. The structural framing system and the roof diaphragm system are straight forward when analyzing or upgrading the structure for NPH loads. Because of a buildings design vintage, probable use of empirical methodology, and poor design basis documentation (and record retention); it is difficult to qualify or upgrade CMU walls for lateral Natural Phenomena Hazards (NPH) loads in accordance with References 1, 2 and 3. This paper discusses three analytical approaches and/or techniques (empirical, working stress and yield line) to determine the collapse capacity of a laterally loaded CMU wall, and compares their results
Date: March 8, 1996
Creator: Faires, W.E. Jr.
Partner: UNT Libraries Government Documents Department

Gist: A scientific graphics package for Python

Description: {open_quotes}Gist{close_quotes} is a scientific graphics library written by David H. Munro of Lawrence Livermore National Laboratory (LLNL). It features support for three common graphics output devices: X Windows, (Color) PostScript, and ANSI/ISO Standard Computer Graphics Metafiles (CGM). The library is small (written directly to Xlib), portable, efficient, and full-featured. It produces X versus Y plots with {open_quotes}good{close_quotes} tick marks and tick labels, 2-dimensional quadrilateral mesh plots with contours, vector fields, or pseudo color maps on such meshes, with 3-dimensional plots on the way. The Python Gist module utilizes the new {open_quotes}Numeric{close_quotes} module due to J. Hugunin and others. It is therefore fast and able to handle large datasets. The Gist module includes an X Windows event dispatcher which can be dynamically added (e.g., via importing a dynamically loaded module) to the Python interpreter after a simple two-line modification to the Python core. This makes fast mouse-controlled zoom, pan, and other graphic operations available to the researcher while maintaining the usual Python command-line interface. Munro`s Gist library is already freely available. The Python Gist module is currently under review and is also expected to qualify for unlimited release.
Date: May 8, 1996
Creator: Busby, L.E.
Partner: UNT Libraries Government Documents Department