Autosim is a software package written to control and trigger the programmable instruments that are used to supply simulated signals to the recording devices on underground nuclear weapons effects tests at the Nevada Test Site. These instruments are located either in the tunnel or at a remote site, and may be controlled from anywhere on the Department 9320 Computer Network. Autosim incorporates commands to control the operation of the Laser Calibrator that is a fiber optic device that transmits a signal from down-hole to the uphole recorders. Autosim also supports the task of characterizing the cable links by communicating to some high bandwidth digitizers that are used to input the pulse of the downhole simulator. To minimize the learning interval, Autosim utilizes menus and offers on-line help on most of the selections in the menu options.
Ceramic chip capacitors can potentially crack due to thermal stresses in a surface mount assembly process. The electrical performance of the cracked capacitors will degrade with time, and they will prematurely short. In high reliability applications, the cracked capacitors must be identified and eliminated. We have developed and demonstrated the temperature-humidity-bias (THB) aging technique to identify cracked capacitors. The initial phase of the study involved setting up automated test equipment to monitor 100 surface mounted capacitors at 85% relative humidity, 85{degree}C with 50 volts dc bias. The capacitors subjected to severe thermal shock were aged along with control samples. Failure mode analysis was done on the failed capacitors. The capacitors with surface cracks short-out within the first 8 hours of aging, whereas the capacitors that failed after a longer aging time (8 to 1000 hours) had a shorting path in an internal void. Internal voids are typical defects introduced during manufacturing of multilayer ceramic (MLC) capacitors. In the second phase of the study, we used the THB aging technique to study the effect of surface mount processes on capacitor cracking and, thus the reliability. The surface mount processes studied were vapor phase, infra-red (IR) and convection belt reflow soldering. The results shoed that 6.3% of vapor phase soldered capacitors, and 1.25% of the IR and convection belt soldered capacitors had cracks. In all capacitors, regardless of the solder process used, an additional 3 to 4% of the capacitors failed due to a shorting path in the internal void. The results of this study confirm that this technique can be used to screen cracked capacitors and compare different solder and manufacturing processes.
This report gives the results of a study of the production of electricity from geothermal energy with particular emphasis on the drilling of geothermal wells. A brief history of the industry, including the influence of the Public Utilities Regulatory Policies Act, is given. Demand and supply of electricity in the United States are touched briefly. The results of a number of recent analytical studies of the cost of producing electricity are discussed, as are comparisons of recent power purchase agreements in the state of Nevada. Both the costs of producing electricity from geothermal energy and the costs of drilling geothermal wells are analyzed. The major factors resulting in increased cost of geothermal drilling, when compared to oil and gas drilling, are discussed. A summary of a series of interviews with individuals representing many aspects of the production of electricity from geothermal energy is given in the appendices. Finally, the implications of these studies are given, conclusions are presented, and program recommendations are made.
In this paper we describe an algorithm by which obstructions and surface features in an underground storage tank can be modeled and used to generate virtual barrier functions for a real-time telerobotic system, which provides an aid to the operator for both real-time obstacle avoidance and for surface tracking. The algorithm requires that the slave's tool and every object in the waste storage tank be decomposed into convex polyhedral primitives, with the waste surface modeled by triangular prisms. Intrusion distance and extraction vectors are then derived at every time step by applying Gilbert's polyhedra distance algorithm, which has been adapted for the task. This information is then used to determine the compression and location of nonlinear virtual spring-dampers whose total force is summed and applied to the manipulator/teleoperator system. Experimental results using a PUMA 560 and a simulated waste surface validate the approach, showing that it is possible to compute the algorithm and generate smooth, realistic pseudo forces for the teleoperator system using standard VME bus hardware.
Low energy Ar and Xe ion bombardment of Ge (001) produces large numbers of point defects on the Ge surface and in the near-surface regions. Defect concentrations on the surface are detected and quantified in real time during bombardment using in situ Reflection High Energy Electron Diffraction (RHEED). We report the energy dependence of the defect yield for 70-500 eV Ar and Xe ion bombardment, and the temperature dependence of the defect yield (defects/ion) during 200 eV ion bombardment. The defect yield drops rapidly as the substrate temperature during bombardment is varied from 175 K to 400 K. We attribute the yield reduction to surface recombination of adatoms and vacancies produced in the same collision cascade.
Conference Proceedings - 10th Anniv., IMTC 1994: Advanced Technologies in I and M. 1994 IEEE Instrumentation and Measurement Technology Conference
Deyst, J.P.; Souders, T.M.; Solomon, O.M.
Least-squares sine-fit algorithms are used extensively in signal processing applications. The parameter estimates produced by such algorithms are subject to both random and systematic errors when the record of input samples consists of a fundamental sine wave corrupted by harmonic distortion or noise. The errors occur because, in general, such sine-fits will incorporate a portion of the harmonic distortion or noise into their estimate of the fundamental. Bounds are developed for these errors for least-squares four-parameter (amplitude, frequency, phase, and offset) sine-fit algorithms. The errors are functions of the number of periods in the record, the number of samples in the record, the harmonic order, and fundamental and harmonic amplitudes and phases. The bounds do not apply to cases in which harmonic components become aliased.
FPT0 is the first of six tests that are scheduled to be conducted in an experimental reactor in Cadarache, France. The test apparatus consists of an in-pile fuel bundle, an upper plenum, a hot leg, a steam generator, a cold leg, and a small containment. Thus, the test is integral in the sense that it attempts to simulate all of the processes that would be operative in a severe nuclear accident. In FPT0, the fuel will be trace irradiated; in subsequent tests high burn-up fuel will be used. This report discusses separate pretest analyses of the FPT0 fuel bundle and primary circuit have been conducted using the USNRC`s source term code, VICTORIA-92. Predictions for release of fission product, control rod, and structural elements from the test section are compared with those given by CORSOR-M. In general, the releases predicted by VICTORIA-92 occur earlier than those predicted by CORSOR-M. The other notable difference is that U release is predicted to be on a par with that of the control rod elements; CORSOR-M predicts U release to be about 2 orders of magnitude greater.
DC and pulsed-DC electromigration tests were performed at the wafer level using standard and self-stressing test structures. DC characterization tests over a very large temperature range (180 to 560 °C) were consistent with an interface diffusion mechanism in parallel with lattice diffusion. That data allowed for extraction of the respective activation energies and the diffusion coefficient of the rapid mechanism. The ability to extract simultaneously a defect-based diffusion coefficient and activation energy is significant given the extreme difficulty in making those measurements in aluminum. The pulsed-DC experiments were conducted over a range that includes the highest frequency to date, from DC to 500 MHz. Measurements were also made as a function of duty factor from 15% to 100% at selected frequencies. The data shows that the pulsed-DC lifetime is consistent with the average current density model at high (>10 MHz) frequencies and showed no additional effects at the highest frequency tested (500 MHz). At low frequencies, we attribute the lessened enhancement to thermal effects rather than vacancy relaxation effects. Finally, the deviation in lifetime from the expected current density dependence, characterized over 1 1/2 orders of magnitude in current density, is explained in terms of a shift in the boundary condition for electromigration as the current density is decreased.
This report identifies and describes emerging nondestructive inspection (NDI) methods that can potentially be used to inspect commercial transport and commuter aircraft for structural damage. The nine categories of emerging NDI techniques are: acoustic emission, x-ray computed tomography, backscatter radiation, reverse geometry x-ray, advanced electromagnetics, including magnetooptic imaging and advanced eddy current techniques, coherent optics, advanced ultrasonics, advanced visual, and infrared thermography. The physical principles, generalized performance characteristics, and typical applications associated with each method are described. In addition, aircraft inspection applications are discussed along with the associated technical considerations. Finally, the status of each technique is presented, with a discussion on when it may be available for use in actual aircraft maintenance programs. It should be noted that this is a companion document to DOT/FAA/CT-91/5, Current Nondestructive Inspection Methods for Aging Aircraft.
This report describes efforts conducted under Tasks 3 and 4 of the second phase of the project to develop a single-element stretched-membrane dish concept to reduce the cost of a high-performance concentrating solar collector. We completed the detailed design for such a collector suitable to drive a 25-kWe Stirling motor generator. The design includes the collectors, optical element, the drive, and support systems. The aperture of the optical element was sized to provide the required energy to the engine based on test data and analytical models of the concentrator receiver, and engine. The design of the optical element was improved based on experience gained from the design, fabrication, and testing of several prototypes.
Thin films of amorphous carbon/hydrogen, also known as diamond-like carbon or DLC, are of interest as an economical alternative to diamond in a variety of coatings applications. We have investigated the thermal stability of DLC films deposited onto tungsten and aluminum substrates via plasma CVD of methane. These films contain approximately 40 atom % hydrogen, and based on Auger spectra the carbon in the films is estimated to be approximately 60% sp3 hybridized and 40% sp2 hybridized. Thermal desorption, Auger, and Raman measurements all indicate that the DLC films are stable to 250-300 °C. Between 300 and 500 °C, thermal evolution of hydrogen from the films is accompanied by the conversion of carbon from sp3 to sp2 hybridization, and Raman spectra indicate the conversion of the overall film structure from DLC to micro-crystalline graphite or so-called `glassy' carbon. These results suggest that DLC of this type is potentially useful for applications in which the temperature does not exceed 250 °C.
This manual is intended to act as a working guide for setting up a Science Fair Volunteer Support Committee at your school. The Science Fair Volunteer Support Committee, or SFVSC, is the key component of the Science Fair Self-Help program, which was developed by Sandia National Laboratories and is designed to support a school`s science activities. The SFVSC is a team of parents and community volunteers who work in concert with a school`s teaching staff to assist and manage all areas of a school Science and Engineering Fair. The main advantage of creating such a committee is that it frees the science teachers from the organizational aspects of the fair and lets them concentrate on their job of teaching science. This manual is based on information gained through a Self-Help Development pilot program that was developed by Sandia National Laboratories during the 1991--92 school year at three Albuquerque, NM, middle schools. The manual describes the techniques that were successful in the pilot program and discusses how these techniques might be implemented in other schools. This manual also discusses problems that may be encountered, including suggestions for how they might be resolved.
The code HORSMIC was written to solve the problem of calculating the shape of hydrocarbon (gas or liquid) storage caverns formed by solution mining in bedded salt formations. In the past many storage cavems have been formed by vertically drilling into salt dome formations and solution mining large-aspect-ratio, vertically-axisymmetric caverns. This approach is generally not satisfactory for shallow salt beds because it would result in geomechanically-unstable, pancake-shaped caverns. In order to produce a high aspect ratio cavern in the horizontal direction a more complicated strategy must be employed. This report describes one such strategy, and documents the use of the computer model HORSMIC which can be used to estimate the shape of the cavern produced by a prescribed leaching schedule. Multiple trials can then be used to investigate the effects of various pipe hole configurations in order to optimize over the cavern shape.
The objective of the ``Hydrodynamics of Maneuvering Bodies`` LDRD project was to develop a Lagrangian, vorticity-based numerical simulation of the fluid dynamics associated with a maneuvering submarine. Three major tasks were completed. First, a vortex model to simulate the wake behind a maneuvering submarine was completed, assuming the flow to be inviscid and of constant density. Several simulations were performed for a dive maneuver, each requiring less than 20 cpu seconds on a workstation. The technical details of the model and the simulations are described in a separate document, but are reviewed herein. Second, a gridless method to simulate diffusion processes was developed that has significant advantages over previous Lagrangian diffusion models. In this model, viscous diffusion of vorticity is represented by moving vortices at a diffusion velocity, and expanding the vortices as specified by the kinematics for a compressible velocity field. This work has also been documented previously, and is only reviewed herein. The third major task completed was the development of a vortex model to describe inviscid internal wave phenomena, and is the focus of this document. Internal wave phenomena in the stratified ocean can affect an evolving wake, and thus must be considered for naval applications. The vortex model for internal wave phenomena includes a new formulation for the generation of vorticity due to fluid density variations, and a vortex adoption algorithm that allows solutions to be carried to much longer times than previous investigations. Since many practical problems require long-time solutions, this new adoption algorithm is a significant step toward making vortex methods applicable to practical problems. Several simulations are described and compared with previous results to validate and show the advantages of the new model. An overview of this project is also included.
This report documents results of a series of scoping experiments on boiling from downward-facing surfaces in support of the Sandia New Production Reactor, Vessel-Pool Boiling Heat Transfer task. Quenching experiments have been performed to examine the boiling processes from downward-facing surfaces using two 61-centimeter diameter test masses, one with a flat test surface and one with a curved test surface having a radius of curvature of 335 cm, matching that of the Cylindrical Boiling facility test vessel. Boiling curves were obtained for both test surfaces facing horizontally downward. The critical beat flux was found to be essentially the same, having an average value of approximately 0.5 MW/m{sup 2}. This value is substantially higher than current estimates of the heat dissipation rates required for in-vessel retention of core debris in the Heavy Water New Production Reactor as well as some of the advanced light water reactors under design. The nucleate boiling process was found to be cyclic with four relatively distinct phases: direct liquid/solid contact, nucleation and growth of bubbles, coalescence, and ejection.
We demonstrate the use of HAST and Assembly Test Chips to evaluate the susceptability of epoxy molding compounds to moisture induced corrosion of Al conductors. We show that the procedure is sufficiently sensitive to discriminate between assembly processes used by different molding facilities. Our data show that the location in time of the 'knee' in the failure distribution is dependent on material properties of the epoxy. Reducing the failure rate in the early or 'extrinsic' region of the time-failure distribution is key to achieving high reliability. We examine the failure modes in the extrinsic region for test chips encapsulated with a number of high quality molding compounds in an attempt to better understand this region.
This report describes the instrumentation locations of the Tore Supra Phase III Outboard Limiter, including the locations and signal names of the flowmeters and thermocouples. Shot 11044 was evaluated in some detail. The heat loads in the fourteen cooling tubes that form the limiter head were calculated from the data and the results compared with the heat loads predicted using a 3-D model heat transfer calculation that calculates the distribution of power on the limiter based upon the power scrape-off length, the mag magnetic configuration and the shape of the limiter.
We are studying carbon thin films by using a pulsed excimer laser to ablate pyrolytic graphite targets to form highly tetrahedral coordinated amorphous carbon (at-C) films. These films have been grown on room temperature p-type Si (100) substrates without the intentional incorporation of hydrogen. In order to understand and optimize the growth of at-C films, parametric studies of the growth parameters have been performed. We have also introduced various background gases (H2, N2 and Ar) and varied the background gas pressure during deposition. The residual compressive stress levels in the films have been measured and correlated to changes in the Raman spectra of the at-C band near 1565 cm-1. The residual compressive stress falls with gas pressure, indicating a decreasing atomic sp3-bonded carbon fraction. We find that reactive gases such as hydrogen and nitrogen significantly alter the Raman spectra at higher pressures. These effects are due to a combination of chemical incorporation of nitrogen and hydrogen into the film as well as collisional cooling of the ablation plume. In contrast, films grown in non-reactive Ar background gases show much less dramatic changes in the Raman spectra at similar pressures.
Granular salt can be used to construct high performance permanent seals in boreholes which penetrate rock salt formations. These seals are described as seal systems comprised of the host rock, the seal material, and the seal rock interface. The performance of these seal systems is defined by the complex interactions between these seal system components through time. The interactions are largely driven by the creep of the host formation applying boundary stress on the seal forcing consolidation of the granular salt. The permeability of well constructed granular salt seal systems is expected to approach the host rock permeability (<10-21 m2 (10"9 darcy)) with time. The immediate permeability of these seals is dependent on the emplaced density. Laboratory test results suggest that careful emplacement techniques could result in immediate seal system permeability on the order of 10'16 m2 to 10*1* m2 (10*4 darcy to 10"^ darcy). The visco-plastic behavior of the host rock coupled with the granular salts ability to "heal" or consolidate make granular salt an ideal sealing material for boreholes whose permanent sealing is required.
The Department of Energy’s Solar Thermal Electric Program is managed by the Solar Thermal and Biomass Power Division, which is part of the Office of Utility Technologies. The focus of the Program is to commercialize solar electric technologies. In this regard, three major projects are currently being pursued in trough, central receiver, and dish/Stirling electric power generation. This paper describes these three projects and the activities at the National Laboratories that support them.
Northern Research and Engineering Corp. (NREC) is currently under contract to Sandia National Laboratories to solarize a 30 kWe Brayton engine that is based on turbo-charger technology. This program is also supported by the German Aerospace Research Establishment (DLR), which is supplying the solar receiver through an agreement with the International Energy Agencyl Solar PACES. The engine is a low pressure, highly recuperated engine. The turbo-machinery is built up from commercial turbo-chargers, which ensures low cost and high reliability. A combustor will be included in the system to allow for full power production during cloud transients. Current estimates are that the engine/alternator thermal-to-electric efficiency will be 30+%. The solar receiver to be supplied by DLR will be an advanced version of their VOBREC volumetric receiver. This receiver has a parabolic quartz window and ceramic foam absorber. The estimated efficiency of the receiver is 9W%. Sandia has developed an economic model to estimate the levelized energy cost (LEC) of energy produced by dish/engine systems. The model includes both the operating characteristics of the dishes and engines as well as a detailed economic model. The results of the analysis indicate that the dish/Brayton systems compare favorably with dishlstirling systems.
The National Ignition Facility (NIF), which is expected to resolve important Defense Program and inertial fusion energy issues for energy production in the future, will consist of a laser system with 192 independent beamlets transported to a target chamber. The target chamber is a multi-purpose structure that provides the interface between the target and the laser optics. The chamber must be capable of achieving moderate vacuum levels in reasonable times; it must remain dimensionally stable within micron tolerances, provide support for the optics, diagnostics, and target positioner; it must minimize the debris from the x-ray and laser light environments; and it must be capable of supporting external neutron shielding. The chamber must also be fabricated from a low neutron activation material. This paper describes the conceptual design of the target chamber, target positioner, and shielding for the NIF.
Highly tetrahedral-coordinated-amorphous-carbon (a-tC) films deposited by pulsed-laser deposition (PLD) on silicon substrates are studied. These films are grown at room-temperatures in a high-vacuum ambient. a-tC films grown in this manner have demonstrated stability to temperatures in excess of T = 1000 °C, more than sufficient for any post-processing treatment or application. Film surfaces are optically smooth as determined both visually and by atomic-force microscopy. PLD growth parameters can be controlled to produce films with a range of sp2 - sp3 carbon-carbon bond ratios. Films with the highest yield of sp3 C-C bonds have high resistivity, with a dielectric permittivity constant ε to approximately 4, measured capacitively at low frequencies (1 - 100 kHz). These a-tC films are p-type semiconductors as grown. Schottky barrier diode structures have been fabricated.
Pool-boiler reflux receivers have been considered as an alternative to heat pipes for the input of concentrated solar energy to Stirling-cycle engines in dish-Stirling electric generation systems. Pool boilers offer simplicity in design and fabrication. The operation of a full-scale pool-boiler receiver has been demonstrated for short periods of time. However, to generate cost-effective electricity, the receiver must operate without significant maintenance for the entire system life, as much as 20 to 30 years. Long-term liquid-metal boiling stability and materials compatibility with refluxing NaK-78 is not known and must be determined for the pool boiler receiver. No boiling system has been demonstrated for a significant duration with the current porous boiling enhancement surface and materials. At least one theory explaining lncipientboiling behavior of alkali metals indicates that favorable start-up behavior should deteriorate over time. Many factors affect the stability and startup behavior of the boiling system. Therefore, it is necessary to simulate the full-scale pool boiler design as much as possible, including flux levels, materials, and operating cycles. On-sun testing is impractical because of the limited test time available. A test vessel was constructed with a Friction Coatings Inc, porous boiling enhancement surface. The boiling surface consisted of a brazed stainless steel powder with about 50% porosity. The vessel was heated with a quartz lamp array providing about 90 Wlcm2 peak incident thermal flux. The vessel was charged with NaK-78, which is liquid at room temperature. This allows the elimination of costly electric preheating, both on this test and on fullscale receivers. The vessel was fabricated from Haynes 230 alloy, selected for its high temperature strength and oxidation resistance. The vessel operated at 750°C around the clock, with a 112-hour shutdown cycle to ambient every 8 hours. Temperature data was continually collected. The test completed 7500 hours of lamp-on operation time, and over 1000 startups from ambient. The test was terminated when a small leak in an lnconel 600 thermowell was detected. The test design and data are presented here. Metallurgical analysis of virgin and tested materials has begun, and initial results are also presented.