16,454 Matching Results

Search Results

Results: 1 - 24 next
open access

Local Effects of Biased Electrodes in the Divertor of NSTX

Description: The goal of this paper is to characterize the effects of small non-axisymmetric divertor plate electrodes on the local scrape-off layer plasma. Four small rectangular electrodes were installed into the outer divertor plates of NSTX. When the electrodes were located near the outer divertor strike point and biased positively, there was an increase in the nearby probe currents and probe potentials and an increase in the LiI light emission at the large major radius end of these electrodes. When an electrode located farther outward from the outer divertor strike point was biased positively, there was sometimes a significant decrease in the LiI light emission at the small major radius end of this electrode, but there were no clear effects on the nearby probes. No non-local effects were observed with the biasing of these electrodes.
Date: May 7, 2012
Creator: : S. Zweben, M.D. Campanell, B.C. Lyons, R.J. Maqueda, Y. Raitses, A.L. Roquemore and F. Scotti
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Physical effects of infrared quark eigenmodes in LQCD

Description: A truncated determinant algorithm is used to study the physical effects of the quark eigenmodes associated with eigenvalues below 300 MeV. This initial study focuses on coarse lattices (with O(a{sup 2}) improved gauge action), light internal quark masses and large physical volumes. Four bellweather full QCD processes are discussed: topological charge distributions, the eta prime propagator, string breaking as observed in the static energy and the rho decay into two pions.
Date: October 7, 1999
Creator: A. Duncan, E. Eichten and H. Thacker
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

GLASS FORMULATION TESTING TO INCREASE SULFATE INCORPORATION - Final Report VSL-04R4960-1, Rev 0, 2/28/05, Vitreous State Laboratory, The Catholic University of American, Washington, D.C.

Description: About 50 million gallons of high-level mixed waste is currently in storage in underground tanks at The United States Department of Energy's (DOE's) Hanford site in the State of Washington. The Hanford Tank Waste Treatment and Immobilization Plant (WTP) will provide DOE's Office of River Protection (ORP) with a means of treating this waste by vitrification for subsequent disposal. The tank waste will be separated into low- and high-activity fractions, which will then be vitrified respectively into Immobilized Low Activity Waste (ILAW) and Immobilized High Level Waste (IHLW) products. The ILAW product will be disposed of in an engineered facility on the Hanford site while the IHLW product will be directed to the national deep geological disposal facility for high-level nuclear waste. The ILAW and IHLW products must meet a variety of requirements with respect to protection of the environment before they can be accepted for disposal. The Office of River Protection is currently examining options to optimize the Low Activity Waste (LAW) facility and the LAW glass waste form. One option under evaluation is to enhance the waste processing rate of the vitrification plant currently under construction. It is likely that the capacity of the LAW vitrification plant can be increased incrementally by implementation of a variety of low-risk, high-probability changes, either separately or in combination. These changes include: (1) Operating at the higher processing rates demonstrated at the LAW Pilot Melter; (2) Increasing the glass pool surface area within the existing external melter envelope; (3) Increasing plant availability; (4) Increasing the glass waste loading; (5) Removing sulfate from the LAW stream; (6) Operating the melter at slightly higher temperature; (7) Installing the third LAW melter into the WTP plant; and (8) Other smaller impact changes. The melter tests described in this report utilized blended feed (glass formers plus …
Date: February 7, 2012
Creator: AA, KRUGER & KS, MATLACK
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

SMALL-SCALE MELTER TESTING WITH LAW SIMULANTS TO ASSESS THE IMPACT OF HIGHER TEMPERATURE MELTER OPERATIONS - Final Report, VSL-04R49801-1, Rev. 0, 2/13/03, Vitreous State Laboratory, The Catholic University of America, Washington, D.C.

Description: About 50 million gallons of high-level mixed waste is currently in storage in underground tanks at The United States Department of Energy's (DOE's) Hanford site in the State of Washington. The Hanford Tank Waste Treatment and Immobilization Plant (WTP) will provide DOE's Office of River Protection (ORP) with a means of treating this waste by vitrification for subsequent disposal. The tank waste will be separated into low- and high-activity fractions, which will then be vitrified respectively into Immobilized Low Activity Waste (ILAW) and Immobilized High Level Waste (IHLW) products. The ILAW product will be disposed of in an engineered facility on the Hanford site while the IHL W product will be directed to the national deep geological disposal facility for high-level nuclear waste. The ILAW and IHLW products must meet a variety of requirements with respect to protection of the environment before they can be accepted for disposal. The Office of River Protection is currently examining options to optimize the Low Activity Waste (LAW) facility and the LAW glass waste form. One option under evaluation is to enhance the waste processing rate of the vitrification plant currently under construction. It is likely that the capacity of the LAW vitrification plant can be increased incrementally by implementation of a variety of low-risk, high-probability changes, either separately or in combination. These changes include: (1) Operating at the higher processing rates demonstrated at the LAW Pilot Melter; (2) Increasing the glass pool surface area within the existing external melter envelope; (3) Increasing plant availability; (4) Increasing the glass waste loading; (5) Removing sulfate from the LAW stream; (6) Operating the melter at slightly higher temperature; (7) Installing the third LAW melter into the WTP plant; and (8) Other smaller impact changes. The tests describes in this report utilized blended feed (glass formers plus …
Date: February 7, 2012
Creator: AA, KRUGER & KS, MATLACK
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

EFFECT OF GLASS-BATCH MAKEUP ON THE MELTING PROCESS

Description: The response of a glass batch to heating is determined by the batch makeup and in turn determines the rate of melting. Batches formulated for a high-alumina nuclear waste to be vitrified in an all-electric melter were heated at a constant temperature-increase rate to determine changes in melting behavior in response to the selection of batch chemicals and silica grain-size as well as the addition of heat-generating reactants. The type of batch materials and the size of silica grains determine how much, if any, primary foam occurs during melting. Small quartz grains, 5 {micro}m in size, caused extensive foaming because their major portion dissolved at temperatures <800 C, contributing to the formation of viscous glass forming melt that trapped evolving batch gases. Primary foam did not occur in batches with larger quartz grains, {+-}75 {micro}m in size, because their major portion dissolved at temperatures >800 C when batch gases no longer evolved. The exothermal reaction of nitrates with sucrose was ignited at a temperature as low as 160 C and caused a temporary jump in temperature of several hundred degrees. Secondary foam, the source of which is oxygen from redox reactions, occurred in all batches of a limited composition variation involving five oxides, B{sub 2}O{sub 3}, CaO, Li{sub 2}O, MgO, and Na{sub 2}O. The foam volume at the maximum volume-increase rate was a weak function of temperature and melt basicity. Neither the batch makeup nor the change in glass composition had a significant impact on the dissolution of silica grains. The impacts of primary foam generation on glass homogeneity and the rate of melting in large-scale continuous furnaces have yet to be established via mathematical modeling and melter experiments.
Date: December 7, 2010
Creator: AA, KRUGER & P, HRMA
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

GLASSES CONTAINING IRON (II III) OXIDES FOR IMMOBILIZATION OF RADIOACTIVE TECHNETIUM

Description: Technetium-99 (Tc-99) has posed serious environmental threats as US Department of Energy's high-level waste. This work reports the vitrification of Re, as surrogate for Tc-99, by iron-borosilicate and iron-phosphate glasses, respectively. Iron-phosphate glasses can dissolve Re as high as {approx} 1.2 wt. %, which can become candidate waste forms for Tc-99 disposal, while borosilicate glasses can retain less than 0.1 wt. % of Re due to high melting temperature and long melting duration. Vitrification of Re as Tc-99's mimic was investigated using iron-borosilicate and iron-phosphate glasses. The retention of Re in borosilicate glasses was less than 0.1 wt. % and more than 99 wt. % of Re were volatilized due to high melting temperature and long melting duration. Because the retention of Re in iron-phosphate glasses is as high as 1.2 wt. % and the volatilization is reduced down to {approx}50 wt. %, iron-phosphate glasses can be one of the glass waste form candidates for Tc (or Re) disposal. The investigations of chemical durability and leaching test of iron-phosphate glasses containing Re are now underway to test the performance of the waste form.
Date: November 7, 2011
Creator: AA, KRUGER; J, HEO; K, XU; JK, CHOI; PR, HRMA & W, UM
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

EVALUATION OF TEMPORAL VARIATIONS IN HYDRAULIC CAPTURE DUE TO CHANGING FLOW PATTERNS USING MAPPING AND MODELING TECHNIQUES

Description: Robust performance evaluation represents one of the most challenging aspects of groundwater pump-and-treat (P&T) remedy implementation. In most cases, the primary goal of the P&T system is hydraulic containment, and ultimately recovery, of contaminants to protect downgradient receptors. Estimating the extent of hydraulic containment is particularly challenging under changing flow patterns due to variable pumping, boundaries and/or other conditions. We present a systematic approach to estimate hydraulic containment using multiple lines of evidence based on (a) water-level mapping and (b) groundwater modeling. Capture Frequency Maps (CFMs) are developed by particle tracking on water-level maps developed for each available water level data set using universal kriging. In a similar manner, Capture Efficiency Maps (CEMs) are developed by particle tracking on water-levels calculated using a transient groundwater flow model: tracking is undertaken independently for each stress period using a very low effective porosity, depicting the 'instantaneous' fate of each particle each stress period. Although conceptually similar, the two methods differ in their underlying assumptions and their limitations: their use together identifies areas where containment may be reliable (i.e., where the methods are in agreement) and where containment is uncertain (typically, where the methods disagree). A field-scale example is presented to illustrate these concepts.
Date: April 7, 2011
Creator: AA, SPILIOTOPOULOS; LC, SWANSON; R, SHANNON & MJ, TONKIN
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Simulation of a Production Facility with an Automated Transport System

Description: A model was needed to assess material throughput and validate the conceptual design of a production facility, including equipment lists and layout. The initial desire was to use a commercially available discrete event simulation package. However, the available software was found to be too limited in capability. Database interface software was used to develop autonomous intelligent manufacturing workstations and material transporters. The initial Extend model used to assess material throughput and develop equipment lists for the preconceptual design effort was upgraded with software add-ons from Simulation Dynamics, Inc. (SDI). Use of the SDI database interface allowed the upgraded model to include: 1. a material mass balance at any level of detail required by the user, and 2. a transport system model that includes all transport system movements, time delays, and transfers between systems. This model will assist in evaluating transport system capacity, sensitive time delays in the system, and optimal operating strategies. An additional benefit of using the SDI database interface is dramatically improved run time performance. This allows significantly more runs to be completed to provide better statistics for overall plant performance. The model has all system and process parameters entered into sub-component accessible tables. All information for the manufactured items and process data is automatically generated and written to the database. The standard software is used for the movement of manufactured items between workstations, and for sequence and timing functions. Use of the database permits almost unlimited process control and data collection with an insignificant effect on run time.
Date: April 7, 2004
Creator: ABRAMCZYK, GLENN
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Temperature tests of high frequency SLIFER oscillator, LEA73-2176. [For monitoring underground nuclear detonations at Nevada Test Site]

Description: SLIFER (Short Location Indication by Frequency of Electrical Resonance) systems measure stress wave velocity in solid or liquid materials. They monitor underground nuclear detonations at the Nevada Test Site (NTS). A shorted length of coaxial cable is a component in an oscillator's tank circuit. This sensor cable is inductive when less than one-fourth wavelength long at the oscillator's resonant frequency. The stress wave from a detonation crushes and shorts this sensor cable. As the short proceeds, inductance decreases and oscillator frequency increases. Later we convert frequency vs time to shock-front position vs time. Some doubt existed about the reliable operation of the oscillators in cold weather. Therefore these tests were conducted to check their reliability under several conditions: (1) at temperatures from -40/sup 0/ to 60/sup 0/C; (2) with three sensor cable lengths; (3) with sensor cables shorted or open at the far end; and (4) at two input power voltages. Results are presented.
Date: June 7, 1976
Creator: Aaron, Carl C., Jr.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Early Fermi Gamma-ray Space Telescope Observations of the Quasar 3C454.3

Description: This is the first report of Fermi Gamma-ray Space Telescope observations of the quasar 3C 454.3, which has been undergoing pronounced long-term outbursts since 2000. The data from the Large Area Telescope (LAT), covering 2008 July 7-October 6, indicate strong, highly variable {gamma}-ray emission with an average flux of {approx} 3 x 10{sup -6} photons cm{sup -2} s{sup -1}, for energies > 100 MeV. The {gamma}-ray flux is variable, with strong, distinct, symmetrically-shaped flares for which the flux increases by a factor of several on a time scale of about three days. This variability indicates a compact emission region, and the requirement that the source is optically thin to pair-production implies relativistic beaming with Doppler factor {delta} > 8, consistent with the values inferred from VLBI observations of superluminal expansion ({delta} {approx} 25). The observed {gamma}-ray spectrum is not consistent with a simple power-law, but instead steepens strongly above {approx} 2 GeV, and is well described by a broken power-law with photon indices of {approx} 2.3 and {approx} 3.5 below and above the break, respectively. This is the first direct observation of a break in the spectrum of a high luminosity blazar above 100 MeV, and it is likely direct evidence for an intrinsic break in the energy distribution of the radiating particles. Alternatively, the spectral softening above 2GeV could be due to -ray absorption via photonphoton pair production on the soft X-ray photon field of the host AGN, but such an interpretation would require the dissipation region to be located very close ({approx}< 100 gravitational radii) to the black hole, which would be inconsistent with the X-ray spectrum of the source.
Date: May 7, 2009
Creator: Abdo, A. A.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Chamber and target technology development for inertial fusion energy

Description: Fusion chambers and high pulse-rate target systems for inertial fusion energy (IFE) must: regenerate chamber conditions suitable for target injection, laser propagation, and ignition at rates of 5 to 10 Hz; extract fusion energy at temperatures high enough for efficient conversion to electricity; breed tritium and fuel targets with minimum tritium inventory; manufacture targets at low cost; inject those targets with sufficient accuracy for high energy gain; assure adequate lifetime of the chamber and beam interface (final optics); minimize radioactive waste levels and annual volumes; and minimize radiation releases under normal operating and accident conditions. The primary goal of the US IFE program over the next four years (Phase I) is to develop the basis for a Proof-of-Performance-level driver and target chamber called the Integrated Research Experiment (IRE). The IRE will explore beam transport and focusing through prototypical chamber environment and will intercept surrogate targets at high pulse rep-rate. The IRE will not have enough driver energy to ignite targets, and it will be a non-nuclear facility. IRE options are being developed for both heavy ion and laser driven IFE. Fig. 1 shows that Phase I is prerequisite to an IRE, and the IRE plus NIF (Phase II) is prerequisite to a high-pulse rate. Engineering Test Facility and DEMO for IFE, leading to an attractive fusion power plant. This report deals with the Phase-I R&D needs for the chamber, driver/chamber interface (i.e., magnets for accelerators and optics for lasers), target fabrication, and target injection; it is meant to be part of a more comprehensive IFE development plan which will include driver technology and target design R&D. Because of limited R&D funds, especially in Phase I, it is not possible to address the critical issues for all possible chamber and target technology options for heavy ion or laser fusion. On the …
Date: April 7, 1999
Creator: Abdou, M.; Besenbruch, G.; Duke, J.; Forman, L.; Goodin, D.; Gulec, K. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Electricity Restructuring Background: Public Utility Holding Company Act of 1935 (PUHCA)

Description: This report provides background information on PUHCA, including its history and impact. It also discusses how PUHCA reform fits into the current electric utility industry restructuring debate. This report will be updated as events warrant. For related information on electricity restructuring, see the CRS Electronic Briefing Book.
Date: January 7, 1999
Creator: Abel, Amy
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Electricity: The Road Toward Restructuring

Description: The Public Utility Holding Company Act of 1935 (PUHCA) and the Federal Power Act (FPA) were enacted to eliminate unfair practices and other abuses by electricity and gas holding companies by requiring federal control and regulation of interstate public utility holding companies. Comprehensive energy legislation has passed the House and Senate. The House passed H.R. 6 on April 11, 2003. On July 31, 2003, the Senate suspended debate on S. 14, inserted the text of H.R. 4 (107th Congress) as a substitute, and passed H.R. 6. A conference agreement was reached November 17, 2003, and passed by the House the next day. H.R. 6 includes an electricity title that would, in part, repeal PUHCA, would prospectively repeal the mandatory purchase requirement under PURPA, and would create an electric reliability organization. On June 15, 2004, H.R. 4503, a comprehensive energy policy bill, passed the House.
Date: September 7, 2001
Creator: Abel, Amy & Parker, Larry
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Interagency Geothermal Coordinating Council fifth annual report. Final draft

Description: Geothermal energy is the natural heat of the earth, and can be tapped as a clean, safe, economical alternative source of energy. Much of the geothermal energy resource is recoverable with current or near-current technology and could make a significant contribution both to increasing domestic energy supplies and to reducing the US dependence on imported oil. Geothermal energy can be used for electric power production, residential and commercial space heating and cooling, industrial process heat, and agricultural process applications. This report describes the progress for fiscal year 1980 (FY80) of the Federal Geothermal Program. It also summarizes the goals, strategy, and plans which form the basis for the FY81 and FY82 program activities and reflects the recent change in national policy affecting Federal research, development and demonstration programs. The Interagency Geothermal Coordinating Council (IGCC) believes that substantial progress can and will be made in the development of geothermal energy. The IGCC goals are: (1) reduce the institutional barriers so that geothermal projects can be on-line in one-half the current time; (2) make moderate temperature resources an economically competitive source of electricity; (3) remove the backlog of noncompetitive lease applications; (4) competitive lease all KGRA lands; and (5) cut the cost of hydrothermal technology by 25%.
Date: July 7, 1981
Creator: Abel, Fred H.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

[RE: Time for Reform]

Description: Photocopy of a memo from Julie Abel, program associate for the Getty Center for Education in the Arts, to the Regional Institute Directors, Sheila Brown, Phyllis Scott Johnson, Jessie Lovano-Kerr, William McCarter, Joyce Wright, Virginia Gembica, Anne Lindsey, Nancy MacGregor and Susan Rotilie. The memo is in regards to an enclosed copy of the Time for Reform by Susanna Purnell and Paul Hill, published by RAND that Vicki Rosenberg thought the directors would find interesting and beneficial. cc'd on the memo, Jack Davis, Edith Curtis Johnson, Margaret DiBlasio and Nancy Roucher.
Date: April 7, 1993
Creator: Abel, Julie
Item Type: Refine your search to only Letter
Partner: UNT Libraries Special Collections
open access

The H II Region of a Primordial Star

Description: The concordance model of cosmology and structure formation predicts the formation of isolated very massive stars at high redshifts in dark matter dominated halos of 10{sup 5} to 10{sup 6} Msun. These stars photo-ionize their host primordial molecular clouds, expelling all the baryons from their halos. When the stars die, a relic H II region is formed within which large amounts of molecular hydrogen form which will allow the gas to cool efficiently when gravity assembles it into larger dark matter halos. The filaments surrounding the first star hosting halo are largely shielded and provide the pathway for gas to stream into the halo when the star has died. We present the first fully three dimensional cosmological radiation hydrodynamical simulations that follow all these effects. A novel adaptive ray casting technique incorporates the time dependent radiative transfer around point sources. This approach is fast enough so that radiation transport, kinetic rate equations, and hydrodynamics are solved self-consistently. It retains the time derivative of the transfer equation and is explicitly photon conserving. This method is integrated with the cosmological adaptive mesh refinement code enzo, and runs on distributed and shared memory parallel architectures. Where applicable the three dimensional calculation not only confirm expectations from earlier one dimensional results but also illustrate the multi-fold hydrodynamic complexities of H II regions. In the absence of stellar winds the circumstellar environments of the first supernovae and putative early gamma-ray bursts will be of low density {approx}1 cm{sup -3}. Albeit marginally resolved, ionization front instabilities lead to cometary and elephant trunk like small scale structures reminiscent of nearby star forming regions.
Date: June 7, 2006
Creator: Abel, Tom; Wise, John H.; /KIPAC, Menlo Park; Bryan, Greg L. & /Columbia U., Astron. Astrophys.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
Back to Top of Screen