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Description: This report is one of four reports written to provide background information regarding immobilization technologies remaining under consideration for supplemental immobilization of Hanford's low-activity waste. This paper provides the reader a general understanding of joule-heated ceramic lined melters and their application to Hanford's low-activity waste.
Date: April 7, 2011
Creator: SE, KELLY
Partner: UNT Libraries Government Documents Department

Passive modal damping with piezoelectric shunts

Description: The use of piezoelectric materials in conjunction with passive inductance-resistance-capacitance (RLC) circuits to dampen specific vibration modes is explored. The piezoelectric materials convert mechanical energy to electrical energy, which is then dissipated in the RLC circuit through joule heating. An impulse is applied to a simple cantilevered beam and by varying the inductance and resistance values, the natural oscillation frequency fcir the RLC circuit is tuned to dampen the first mode of vibration.
Date: January 1, 2001
Creator: Granier, J. J. (John J.); Haundhausen, R. J. (R. Jason) & Gaytan, G. E. (Gabriel E.)
Partner: UNT Libraries Government Documents Department

Observation and calculation of trapped modes near cut-off in the ALS bellow-shield

Description: Observed heating of the RF shields in the bellows of the Advanced Light Source (ALS) storage ring has led to studies of possible causes. One such possibility is resonant impedances near the cut-off frequency of the beam-pipe that arise from small, localized, enlargements of the beampipe cross-section. Calculations of trapped modes in the elliptical-section vacuum chamber, approximated by a rectangular geometry, are described. Measurements of a bellows-shield in the test laboratory are also described, as are temperature measurements of a flexband in the storage ring.
Date: June 1, 1996
Creator: Corlett, J.N.
Partner: UNT Libraries Government Documents Department

Pseudo-MHD ballooning modes in tokamak plasmas

Description: The MHD description of a plasma is extended to allow electrons to have both fluid-like and adiabatic-regime responses within an instability eigenmode. In the resultant {open_quotes}pseudo-MHD{close_quotes} model, magnetic field line bending is reduced in the adiabatic electron regime. This makes possible a new class of ballooning-type, long parallel extent, MHD-like instabilities in tokamak plasmas for {alpha} > s{sup 2}(2 {sup 7/3}/9) (r{sub p}/R{sub 0}) or-d{radical}{Beta}/dr > (2{sup 1/6} /3)(s/ R{sub 0q}), which is well below the ideal-MHD stability boundary. The marginally stable pressure profile is similar in both magnitude and shape to that observed in ohmically heated tokamak plasmas.
Date: August 1, 1996
Creator: Callen, J.D. & Hegna, C.C.
Partner: UNT Libraries Government Documents Department

Notes on magnetic coil design

Description: This brief report summarizes work done which addressed the issue of sizing the USTX Ohmic heating solenoid by imposing some physical constraints on the TF and OH coil designs. A computer code is used for this study. The TF coil sets the solenoid inner radius at 0.10 meters. Allowing a 2.5 cm gap between the inner plasma radius and outer radius of the solenoid fixes the latter at 0.185 meters. The OH solenoid radial thickness is then 0.085 meters. The plasma current obtainable is I{sub p} = 1.05 megamp.
Date: May 11, 1995
Creator: Uglum, J.
Partner: UNT Libraries Government Documents Department

Restoration of the DIII-D solenoid

Description: The DIII-D tokamak has been operated since June 1995 with constrained ohmic heating capability as imposed by the abandonment of half of it`s solenoid system due to a cooling water leak. The solenoid is comprised of A and B windings with separate multiple power leads to each. The cooling water leak occurred in the lead of the B winding. This leak occurred in a remote area under the DIII-D vessel and is believed to be caused by magnetic forces developing cyclic bending loads on the conductor. Visual inspection of the lead using flexible bore scopes indicated that the structural fiberglass overwrap intended to band the supply and return leads into a primary-force canceling group had failed allowing individual conductors to become inadequately supported against bending loads. The overwrap failed as a result of poor epoxy encapsulation of the lead which was manufactured in 1978. Inspection of the A lead confirmed no overwrap failure and that the vacuum encapsulation of the A lead was proper and to specification. In order to continue operations, it was decided to abandon the B winding of the solenoid and operate under reduced (5 V-sec) capability. An in-situ repair approach was mandated by the extensive and lengthy effort required to disassemble, repair, and reassemble the tokamak. Access from outside the tokamak was severely limited. A plan to repair the damaged lead was developed and implemented over a 10 month period. This paper describes the repair of the solenoid lead. A VCR video tape of these remote installation efforts has been assembled and will be shown.
Date: November 1, 1997
Creator: Anderson, P.M.; Robinson, J.I.; Gonzales, E. & Rolens, G.W.
Partner: UNT Libraries Government Documents Department

Thermal Fusing Model of Conducting Particle Composites

Description: Composites of carbon black particles in polyethylene are known to exhibit an unusually rapid increase in resistivity as the applied field is increased, making this material useful in automatically resettable fuses. In this application the composite is in series with the circuit it is protecting: at low applied voltages this circuit is the load, but at high applied voltages the composite becomes the load, limiting the current to the circuit. We present a simple model of this behavior in terms of a network of nonlinear conductors. Each conductor has a conductance that depends on its instantaneous Joule heating. It is shown that in the fusing regime, where the current through the composite decreases with increasing voltage, an plate-like dissipation instability develops normal to the applied field. Experimental evidence of this phenomena is described.
Date: June 24, 1999
Creator: Martin, James E.
Partner: UNT Libraries Government Documents Department

Energy and environmental research emphasizing low-rank coal: Task 6.2. Joining of advanced structural materials

Description: Silicon carbide (SiC) is considered an attractive material for structural applications in fossil energy systems because of its corrosion and wear resistance, high thermoconductivity, and high temperature strength. These same properties make it difficult to sinter or join SiC. Conventional sintering techniques require applying pressure and heating to temperatures near 2000{degree}C, or the use of binders with lower melting temperatures, or pressureless sintering with the aid of carbon and boron to near full density about 2100{degree}C. The sintering temperature can be reduced to 1850{degree}--2000{degree}C if SiC is sintered with the addition of small quantities of Al{sub 2}O{sub 3} and Al{sub 2}O{sub 3} {plus} Y{sub 2}O{sub 3}. In addition, reaction sintering has been used by mixing Si and C with SiC powder and heating the mixture to 1400{degree}C to cause the Si and C to react and form SiC, which bonds the aggregate together. Work proposed for this year was to center on determining gas compositions that could be used to increase the sinterability of oxide binders and on using the binder and gas combinations to join bars of SiC, alumina, and mullite (3Al{sub 2}O{center_dot}2SiO{sub 2}). During the course of the year the focus was shifted to SiC joining alone, because it was felt that alumina and mullite are too prone to thermal shock for use in structural applications in fossil energy systems. Because of a thermal expansion mismatch between alumina and SiC, only SiC and mullite were investigated as joining aides for SiC. Therefore, the objectives of this work evolved into examining the sintering phenomena of SiC and mullite-derived binders at and below 1500{degree}C in various atmospheres and determining which conditions are suitable to form strong joints in monolithic SiC structures to be used at temperatures of 1000{degree}--1400{degree}C.
Date: March 1, 1995
Creator: Nowok, J.W. & Hurley, J.P.
Partner: UNT Libraries Government Documents Department

A combined PLC and CPU approach to multiprocessor control

Description: A sophisticated multiprocessor control system has been developed for use in the E-Power Supply System Integrated Control (EPSSIC) on the DIII-D tokamak. EPSSIC provides control and interlocks for the ohmic heating coil power supply and its associated systems. Of particular interest is the architecture of this system: both a Programmable Logic Controller (PLC) and a Central Processor Unit (CPU) have been combined on a standard VME bus. The PLC and CPU input and output signals are routed through signal conditioning modules, which provide the necessary voltage and ground isolation. Additionally these modules adapt the signal levels to that of the VME I/O boards. One set of I/O signals is shared between the two processors. The resulting multiprocessor system provides a number of advantages: redundant operation for mission critical situations, flexible communications using conventional TCP/IP protocols, the simplicity of ladder logic programming for the majority of the control code, and an easily maintained and expandable non-proprietary system.
Date: October 1, 1995
Creator: Harris, J.J.; Broesch, J.D. & Coon, R.M.
Partner: UNT Libraries Government Documents Department

Analysis and testing of the DIII-D ohmic heating coil lead repair clamp

Description: DIII-D has been operating for the last year with limited volt-second capabilities due to structural failure of a conductor lead to one of the ohmic heating (OH) solenoids. The conductor failure was due to poor epoxy impregnation of the overwrap of the lead pack, resulting in copper fatigue and a water leak. A number of structural analyses were performed to assist in determining the failure scenario and to evaluate various repair options. A fatigue stress analysis of the leads with a failed epoxy overwrap indicated crack initiation after 1,000 cycles at the maximum operating conditions. The failure occurred in a very inaccessible area which restricted design repair options to concepts which could be implemented remotely. Several design options were considered for repairing the lead so that it can sustain the loads for 7.5 Vs conditions at full toroidal field. A clamp, along with preloaded banding straps and shim bags, provides a system that guarantees that the stress at the crack location is always compressive and prevents further crack growth in the conductor. Due to the limited space available for the repair, it was necessary to design the clamp system to operate at the material yield stress. The primary components of the clamp system were verified by load tests prior to installation. The main body of the clamp contains a load cell and potentiometer for monitoring the load-deflection characteristics of the clamp and conductors during plasma operation. Strain gages provides redundant instrumentation. If required, the preload on the conductors can be increased remotely by a special wrench attached to the clamp assembly.
Date: November 1, 1997
Creator: Reis, E.E.; Anderson, P.M.; Chin, E. & Robinson, J.I.
Partner: UNT Libraries Government Documents Department

FY-97 operations of the pilot-scale glass melter to vitrify simulated ICPP high activity sodium-bearing waste

Description: A 3.5 liter refractory-lined joule-heated glass melter was built to test the applicability of electric melting to vitrify simulated high activity waste (HAW). The HAW streams result from dissolution and separation of Idaho Chemical Processing Plant (ICPP) calcines and/or radioactive liquid waste. Pilot scale melter operations will establish selection criteria needed to evaluate the application of joule heating to immobilize ICPP high activity waste streams. The melter was fabricated with K-3 refractory walls and Inconel 690 electrodes. It is designed to be continuously operated at 1,150 C with a maximum glass output rate of 10 lbs/hr. The first set of tests were completed using surrogate HAW-sodium bearing waste (SBW). The melter operated for 57 hours and was shut down due to excessive melt temperatures resulting in low glass viscosity (< 30 Poise). Due to the high melt temperature and low viscosity the molten glass breached the melt chamber. The melter has been dismantled and examined to identify required process improvement areas and successes of the first melter run. The melter has been redesigned and is currently being fabricated for the second run, which is scheduled to begin in December 1997.
Date: November 1, 1997
Creator: Musick, C.A.
Partner: UNT Libraries Government Documents Department

Interaction of fast waves with ions

Description: To fully utilize the available power sources in DIII-D (FW, NBI, ECH), understanding of the synergism between the heating mechanisms is important. In this paper the ion distribution, under simultaneous application of NBI and FW, is calculated from Fokker-Planck code CQL3D coupled to ray-tracing code CURRAY. It is found that interaction between energetic ions and FW can be minimized or maximized by adjusting various parameters such as magnetic field, density, beam energy, and FW frequency. Specifically, in DIII-D, the authors find negligible interactions above 1.8 T and above 80 MHz, while the interaction increases at lower fields and frequencies. The results are compared with experiments in DIII-D including the calculated neutron rate. Energetic ion orbit losses may play an important role in the ion distribution, and this effect is being investigated.
Date: June 1, 1995
Creator: Chiu, S.C.; deGrassie, J.S. & Harvey, R.W.
Partner: UNT Libraries Government Documents Department

MHD Modeling of Conductors at Ultra-High Current Density

Description: In conjunction with ongoing high-current experiments on Sandia National Laboratories' Z accelerator we have revisited a problem first described in detail by Heinz Knoepfel. MITLs of previous pulsed power accelerators have been in the 1-Tesla regime. Z's disc transmission line (downstream of the current addition) is in a 100-1200 Tesla regime, so its conductors cannot be modeled simply as static infinite conductivity boundaries. Using the MHD code MACH2 we have been investigating conductor hydrodynamics, characterizing the joule heating, magnetic field diffusion, and material deformation, pressure, and velocity over a range of current densities, current rise-times, and conductor materials. Three purposes of this work are ( 1) to quantify power flow losses owing to ultra-high magnetic fields, (2) to model the response of VISAR diagnostic samples in various configurations on Z, and (3) to incorporate the most appropriate equation of state and conductivity models into our MHD computations. Certain features are strongly dependent on the details of the conductivity model. Comparison with measurements on Z will be discussed.
Date: June 30, 1999
Creator: Asay, J.R.; Desjarlais, M.P.; Douglas, M.R.; Frese, M.H.; Hall, C.A.; Morse, R.L. et al.
Partner: UNT Libraries Government Documents Department

Equilibrium system analysis in a tokamak ignition experiment. Final report

Description: The objective of the IGNITEX Project is to produce and control ignited plasmas for scientific study in the simplest and least expensive way possible. The original concept was proposed by both physics and engineering researchers along the following line of thought. Question: Is there any theoretically simple, compact and reliable way of achieving fusion ignition according to the results of the fusion research program for the last decades? Answer: Yes. An experiment to be carried out in an ohmically heated compact tokamak device with 20 T field on plasma axis. Question: Is there any practical way to carry out that experiment at low cost in the near term? Answer: Yes. Using a single-turn coil magnet system with homopolar power supplies.
Date: October 1, 1989
Creator: Carrera, R.; Weldon, W. F. & Woodson, H. H.
Partner: UNT Libraries Government Documents Department

Confinement improvement with rf poloidal current drive in the reversed-field pinch

Description: External control of the current profile in a reversed-field pinch (RFP), by means such as rf poloidal current drive, may have beneficial effects well beyond the direct reduction of Ohmic input power due to auxiliary heating. Reduction of magnetic turbulence associated with the dynamo, which drives poloidal current in a conventional RFP, may allow operation at lower density and higher electron temperature, for which rf current drive becomes efficient and the RFP operates in a more favorable regime on the n{tau} vs T diagram. Projected parameters for RFX at 2 MA axe studied as a concrete example. If rf current drive allows RFX to operate with {beta} = 10% (plasma energy/magnetic energy) at low density (3 {times} 10{sup 19} m{sup {minus}3}) with classical resistivity (i.e. without dynamo-enhanced power input), 40 ms energy confinement times and 3 keV temperatures will result, matching the performance of tokamaks of similar size.
Date: March 8, 1994
Creator: Hokin, S.; Sarff, J.; Sovinec, C. & Uchimoto, E.
Partner: UNT Libraries Government Documents Department

Princeton Fusion Power Plant superconducting magnet system and costs

Description: The Princeton University Reference Design of a proposed fusion power plant has been previously described. This paper describes details of the superconducting magnet system consisting of toroidal field, divertor, ohmic heating, equilibrium field and control field magnets, all of which are wound of Nb$sub 3$Sn conductor. The toroidal field coils are of the moment-free, ''D'' type, previously described. The toroidal field magnet is comprised of 48 discrete ''D'' coils, 12m x 19m bore. The magnet has a stored energy of 250 x 10$sup 9$ joules. The magnet which is operated at a maximum field of 16T is described in detail. Fault conditions are calculated and design conditions based on maximum fault forces are outlined. In addition, the Dewar System, the refrigeration plant (requiring 280 kW of refrigeration), the safety system, and the coil protection system for the magnets are described. Finally, an overview of the helium-steam generating plant and detailed cost data for the plant, the nuclear island and the magnet are presented. (auth)
Date: October 1, 1975
Creator: File, J.
Partner: UNT Libraries Government Documents Department

Electrical and thermal finite element modeling of arc faults in photovoltaic bypass diodes.

Description: Arc faults in photovoltaic (PV) modules have caused multiple rooftop fires. The arc generates a high-temperature plasma that ignites surrounding materials and subsequently spreads the fire to the building structure. While there are many possible locations in PV systems and PV modules where arcs could initiate, bypass diodes have been suspected of triggering arc faults in some modules. In order to understand the electrical and thermal phenomena associated with these events, a finite element model of a busbar and diode was created. Thermoelectrical simulations found Joule and internal diode heating from normal operation would not normally cause bypass diode or solder failures. However, if corrosion increased the contact resistance in the solder connection between the busbar and the diode leads, enough voltage potentially would be established to arc across micron-scale electrode gaps. Lastly, an analytical arc radiation model based on observed data was employed to predicted polymer ignition times. The model predicted polymer materials in the adjacent area of the diode and junction box ignite in less than 0.1 seconds.
Date: January 1, 2012
Creator: Bower, Ward Isaac; Quintana, Michael A. & Johnson, Jay
Partner: UNT Libraries Government Documents Department

A simplified model of TiH1.65/KClO4 pyrotechnic ignition.

Description: A simplified model was developed and is presented in this report for simulating thermal transport coupled with chemical reactions that lead to the pyrotechnic ignition of TiH1.65/KClO4 powder. The model takes into account Joule heating via a bridgewire, thermal contact resistance at the wire/powder interface, convective heat loss to the surroundings, and heat released from the TiH1.65- and KClO4-decomposition and TiO2-oxidation reactions. Chemical kinetic sub-models were put forth to describe the chemical reaction rate(s) and quantify the resultant heat release. The simplified model predicts pyrotechnic ignition when heat from the pyrotechnic reactions is accounted for. Effects of six key parameters on ignition were examined. It was found that the two reaction-rate parameters and the thermal contact resistance significantly affect the dynamic ignition process whereas the convective heat transfer coefficient essentially has no effect on the ignition time. Effects of the initial/ambient temperature and electrical current load through the wire are as expected. Ignition time increases as the initial/ambient temperature is lowered or the wire current load is reduced. Lastly, critical needs such as experiments to determine reaction-rate and other model-input parameters and to measure temperature profiles, time to ignition and burn-rate data for model validation as well as efforts in incorporating reaction-rate dependency on pressure are pointed out.
Date: April 1, 2009
Creator: Chen, Ken Shuang
Partner: UNT Libraries Government Documents Department

Prospects for thermonuclear ignition in a ''collisional'' tokamak

Description: The parameters are described for a tokamak reactor plasma that attains ignition in the same regime of collisionality as present-day ohmic-heated tokamak plasmas, where the confinement scaling ntau$alpha$n$sup 2$ is observed. The use of Nb$sub 3$Sn toroidal field coils and a plasma elongation greater than or equal to 1.5 are necessary to attain the high plasma density (n approximately 10$sup 15$ cm$sup -3$) required for ignition in this collisional regime. Under these conditions, the fusion power density is of order 10 W/cm$sup 3$. This high value is probably necessary for an economic tokamak reactor. (auth)
Date: October 1, 1975
Creator: Cohn, D.R.; Jassby, D.L. & Parker, R.R.
Partner: UNT Libraries Government Documents Department

Effects of low Z impurities during the startup phase of a large tokamak

Description: The requirements placed on a tokamak ohmic heating system (i.e. loop voltage) to initiate the plasma become more severe as the size increases because of the current density decrease. During the startup phase even small concentrations of low Z impurities can affect the plasma energy balance very substantially and have very important effects on the evolution of the discharge. The startup phase has been studied using a simple zero dimensional computer code. Because the dominant energy loss mechanisms during startup, radiation, and ionization are a volume effect, the zero dimensional code was adequate to treat this phase. The results of this study which have been applied to TFTR indicate that the plasma evolution is a sensitive function of the applied loop voltage, impurity concentration, initial filling pressure and the manner in which gas is fed into the discharge. (auth)
Date: January 1, 1976
Creator: Hawryluk, R. J. & Schmidt, J. A.
Partner: UNT Libraries Government Documents Department

Initial assessment of the operability of the VHTR-HTSE nuclear hydrogen plant.

Description: The generation of hydrogen from nuclear power will need to compete on three fronts: production, operability, and safety to be viable in the energy marketplace of the future. This work addresses the operability of a coupled nuclear and hydrogen-generating plant while referring to other work for progress on production and safety. Operability is a measure of how well a plant can meet time-varying production demands while remaining within equipment limits. It can be characterized in terms of the physical processes that underlie operation of the plant. In this work these include the storage and transport of energy within components as represented by time constants and energy capacitances, the relationship of reactivity to temperature, and the coordination of heat generation and work production for a near-ideal gas working fluid. Criteria for assessing operability are developed and applied to the Very High Temperature Reactor coupled to the High Temperature Steam Electrolysis process, one of two DOE/INL reference plant concepts for hydrogen production. Results of preliminary plant control and stability studies are described. A combination of inventory control in the VHTR plant and flow control in the HTSE plant proved effective for maintaining hot-side temperatures near constant during quasi-static change in hydrogen production rate. Near constant electrolyzer outlet temperature is achieved by varying electrolyzer cell area to control cell joule heating. It was found that rates of temperature change in the HTSE plant for a step change in hydrogen production rate are largely determined by the thermal characteristics of the electrolyzer. It's comparatively large thermal mass and the presence of recuperative heat exchangers result in a tight thermal coupling of HTSE components to the electrolyzer. It was found that thermal transients arising in the chemical plant are strongly damped at the reactor resulting in a stable combined plant. The large Doppler reactivity component, ...
Date: November 1, 2007
Creator: Vilim, R. B.
Partner: UNT Libraries Government Documents Department