The Direct Absorption Receiver (DAR) concept was proposed in the mid-1970s as an alternative advanced receiver concept to simplify and reduce the cost of solar central receiver systems. Rather than flowing through tubes exposed to the concentrated solar flux, the heat absorbing fluid (molten nitrate salt) would flow in a thin film down a flat, nearly vertical panel and absorb the flux directly. Potential advantages of the DAR over conventional tubular designs include a substantially simplified design, improved thermal performance, increased reliability and operating life, as well as reduced capital and operating costs. However, before commercial-scale designs can be realized, a method for controlling droplet ejection from the panel must be developed. In this paper, we present a new DAR design, which has the potential to control these droplets. The design employs four flat panels that are sloped backwards 5 degrees, wind spoilers, and air curtains. A systems analysis is presented indicating that the levelized-energy cost of the quad geometry should be very similar to cylindrical geometry that was originally proposed for the DAR concept. 19 refs., 5 figs., 3 tabs.
A molten salt cavity receiver was solar tested at Sandia National Laboratories during a year-long test program. Upon completion of testing, an analysis was performed to determine the effect of thermal cycling on the receiver. The results indicate substantial fatigue damage accumulation for the receiver when the relatively short test time is considered. This paper describes the methodology used to analyze the cycling, the results, and how they affect future receiver design. The test receiver was configured as a C-shaped cavity with eight multipass heat absorption panels. The tubes were Alloy 800. The heat exchange medium was a molten nitrate salt mixture (60% sodium nitrate, 40% potassium nitrate by weight). The operating temperature range was from 288°C to 566°C.
A sodium reflux pool-boiler solar receiver has been tested on a nominal 75-kWt parabolic dish concentrator. The purpose was to demonstrate the feasibility of reflux receiver technology for application to Stirling engine dish electric systems. In this application, pool boilers (and more generally liquid metal reflux receivers) have advantages over directly illuminated tube receivers. The advantages include more uniform temperature, which results in longer lifetime and higher temperature available to the engine. The absorber was a 70° half-angle spherical segment with an 8.63 inches radius, positioned behind an 8.65 inches diameter aperture. The relatively small size of this receiver, which minimized thermal losses, fabrication costs, and sodium inventory, was possible because of its excellent internal heat transfer characteristics. Tests were run at sodium temperatures up to 800°C and receiver input power levels as high as 67 kWt. At maximum input power, the peak in the solar flux distribution on the absorber was calculated to be 73 Wt/cm2. Receiver efficiency was about 90% when the input power and sodium temperature were at their maximum values. To promote stable boiling, the receiver design included 35 equally spaced artificial cavities in the absorber wetted surface. In all tests, stable boiling was always observed. Under certain conditions during both real and simulated cloud transients, high incipient boiling superheats were observed. This behavior could be suppressed either actively by momentarily increasing the thermal load on the receiver or passively by the addition of a small amount of xenon into the boiler.
Over the next several decades, it is expected that the use of renewable energy technologies will greatly expand as these technologies mature, as the cost of conventional energy supply increases, and as the environmental impact of fossil fuel usage is better understood. A critical question is whether the impact of renewables, in terms of displaced fossil fuel use and reduced environmental effects, can be significant. Certainly, public policy will have dramatic effects on this question. Given a positive policy environment, renewables have the potential to displace a significant fraction of projected energy use within 30-40 years. For the United States, renewables could contribute as much as 25-55 exajoules of energy annually by the year 2030, or 15-35{percent} of the projected total US energy consumption. 12 refs., 6 figs.
Use of the MIT-SNL Period-Generated Minimum Time Control Laws for the automated increase of neutronic power from subcritical conditions has recently been demonstrated. The use of these laws is advantageous because they provide the speed at which a control device should be withdrawn in order to generate a specified period. Two strategies were investigated. The first was the direct use of the MIT-SNL laws for the entire transient, startup plus operation at power. The second was to add reactivity at a constant rate until criticality was achieved and then to transfer control to the MIT-SNL laws. Each was evaluated by both simulation and actual experiment under conditions of closed-loop digital control on the Annular Core Research Reactor that is operated by the Sandia National Laboratories. Both approaches were shown to be feasible. The former has the advantage that the power profile will be known during the startup. Its drawback is that an excessively high rate of reactivity change may be needed to initiate the transient. 16 refs., 9 figs.
An experimental study is described that evaluates the potential for using an acoustic borehole television technique to measure fracture dimensions in lost circulation zones encountered in geothermal drilling. A simulated wellbore was constructed of sandstone blocks with adjustable, inclined fractures, stacked in a barrel filled with water. A slim-hole televiewer was used to log the wellbore, and a computer was used to digitize and analyze the data. Televiewer signal perturbations caused by the fractures were studied to evaluate the effects of fracture thickness and signal amplification on the width of the signal perturbation in the digital record. It was found that the signal amplification is applied. Two techniques for determining the correct amplification are described. With the televiewer used in the present study, fractures thicker than 0.15 inch in a 5.1-inch wellbore can be measured to within an accuracy of 5--15%. Fractures as small as 0.031 inch can be detected but cannot be accurately and reliably measured. 1 ref., 15 figs.
We are continuing to see significant progress in the development of photovoltaic (PV) concentrator technology. New record cell and module efficiencies have been achieved, and improvements in cells, cell assemblies, and modules are increasing reliability and decreasing cost. The number of firms actively pursuing PV concentrator module technology has increased substantially in the last three years. Two new concentrator systems were installed last year, and more are likely to be installed in the near future. This paper describes the most significant developments of the last two years, including descriptions of advances in PV concentrator cell technology, module development and reliability activities, the new installations, a new Concentrator Initiative Program, and results of the latest costing study. 26 refs., 8 figs., 1 tab.
The cost goals and calculations in the Five-Year Plan for the National Photovoltaics Program assume that photovoltaic (PV) concentrator modules will have a reliable output and an operational life expectancy of 30 years.'' Although the modules in the few PV concentrator systems fielded to date have so far been reliable, they have not been in the field long enough to establish performance levels for 30 years and are not necessarily representative of newer concentrator designs. Thus, extensive testing and analysis are required to evaluate and establish the reliability of current concentrator module designs. Considerable research has been done to establish appropriate qualification tests, to understand component failure mechanisms, and to obtain reliable materials and designs. Surveys of fielded systems have been conducted and new test and analysis techniques have been developed in the process. This paper discusses the reliability of photovoltaic concentrator modules with an emphasis on the issues that are currently of most concern. 12 refs., 5 figs.
Erosion of POCO graphite by helium in PISCES-A was measured by carbon spectroscopy for a temperature range from 900{degree}-- 2000{degree}C, ion energies of 30--300 eV, ion fluxes of 1 {minus} 6 {times} 10{sup 22} m{sup {minus}2} s{sup {minus}1} and electro temperatures of 4--22 eV. Yields at low energies were higher than predicted in current models. The role of redeposition is discussed. 15 refs., 4 figs.
Under compressive stresses, brittle polycrystalline materials fail as the result of the growth, interaction and coalesence of microcracks. To predict the deformation of damaging material, constitutive laws developed for such materials must incorporate the effects of crack size, density, orientation, and interaction.A method of incorporating the accumulation and growth of microcracks into a continuum model is to use a measure of microcrack growth and interaction defined as damage. Although a number of damage theories have been proposed, there is no generally accepted experimental technique for detecting and measuring damage. Acoustic emissions (AE) have been correlated with microcrack nucleation and growth. We propose that AE locations and density are useful measures of damage that can be correlated with calculated damage. Our approach is to use acoustic emissions (AE) and computer modeling to study the development of damage in geomaterials.
The In-situ Permeable Flow Sensor is a new type of implantable instrument under development at Sandia National Laboratories that uses thermal boundary layer pertubation techniques to rapidly determine the three-dimensional velocity vector of groundwater flow in soils or permeable geologic media. This sensor is based on the refinement of previous technology, the Convective Heat Flow Probe, developed for the scientific study of the flow of geothermal fluids in thermally active regions of the earth's crust. The Convective Heat Flow Probe was designed as a logging tool for use in open or uncased boreholes. The newer In-situ Permeable Flow Sensor is based on the same theoretical principles but is designed to be permanently buried at waste or cleanup sites where long term monitoring of groundwater flow is of interest. This instrument is sensitive to permeable flows as low as a few meters per year.
Simplified ATPG and fault simulation algorithms, reduced test set sizes, and increased fault coverage are achieved with I {sub DDQ} testing for stuck-at faults. In addition, I {sub DDQ} testing will detect logically redundant and multiple stuck-at faults, and improve the detection of non-stuck-at fault defects. 17 refs., 6 figs., 6 tabs.
The Department of Energy's Multiwell Experiment (MWX) is a field laboratory in the Piceance Basin of Colorado which has two overall objectives: to characterize the low permeability gas reservoirs in the Mesaverde Formation and to develop technology for their production. Different depositional environments have created distinctly different reservoirs in the Mesaverde, and MWX has addressed each of these in turn. This report presents a comprehensive summary of results from the fluvial interval which lies between 4400 ft and 6000 ft at the MWX site. The reservoirs consist of heterogeneous, amalgamated point-bar sequences which form broad meanderbelts which create irregular, but roughly tabular, reservoirs with widths of 1000--2500 ft. Separate sections of this report are background and summary; site descriptions and operations; geology; log analysis; core analysis; in situ stress; well testing, stimulation, fracture diagnostics, and reservoir evaluation in two separate sandstones; stress, fracture diagnostic, and stimulation experiments in an additional sandstone; supporting laboratory studies; and a bibliography. Additional detailed data, results, analyses, and data file references are presented as appendices which are included on microfiche. The results show that stimulation of fluvial reservoirs can be successful if proper care is taken to minimize damage to the natural fracture system. Both an accelerated leakoff phenomenon and the ability to alter the in situ stress were quantified. Overall, the fluvial interval offers the highest production potential of the three nonmarine intervals studied. 116 refs., 230 figs., 28 tabs.
This paper presents a discussion of the use of the Nijssen Information Analysis Methodology (NIAM) in the design of an experimenters database. This database is used by physicists and technicians to describe the configuration and diagnostic systems used on Sandia National Laboratories Particle Beam Fusion Accelerator II (PBFA II). The design of this database presented some unique challenges because of the large degree of flexibility required to enable timely response to changing experimental configurations. The NIAM user-oriented technique proved to be invaluable in translating experimenter's requirements into an information model and then to a normalized relational design.
The theory and practice of information engineering is being actively developed at Sandia National Laboratories. The main output of Sandia is information. Information is created, analyzed and distributed. It is the life blood of our design laboratory. The proper management of information will have a large, positive impact on staff productivity. In order to achieve the potential benefits of shared information a commonly understood approach is needed, and the approach must be implemented in a CASE (Computer-Aided Software Engineering) tool that spans the entire life cycle of information. The commonly understood approach used at Sandia is natural language. More specifically, it is a structured subset of English. Users and system developers communicate requirements and commitments that they both understand. The approach is based upon NIAM (Nijssen's Information Analysis Methodology). In the last three years four NIAM training classes have been given at Sandia. The classes were all at the introductory level, with the latest class last October having an additional seminar highlighting successful projects. The continued growth in applications using NIAM requires an advanced class. The class will develop an information model for the Ultimate CASE Tool.'' This paper presents the requirements that have been established for the Ultimate CASE Tool'' and presents initial models. 4 refs., 1 tab.
Consideration is given to the problem of stabilizing a plant using a suboptimal stable compensator of fixed order. The resulting equations are a modified form of the optimal projection equations, with the separation principle not holding in either the full- or reduced-order case. An overbounding technique on the state covariance guarantees that the compensator is stable if nonnegative definite solutions exist to the design equations.
Sandia National Laboratories joined with two other laboratories, Los Alamos National Laboratory and Naval Research Laboratory, to study and implement a highly parallelized tracker/correlator algorithm. Significant progress was made at Sandia on a specific algorithm and code. This report summarizes the accomplishments by Sandia during FY '89 on this project. 12 refs., 4 figs., 2 tabs.
This paper and a companion paper show the traditional limits on amplitude and frequency that can be generated in a laboratory test on a vibration exciter can be substantially extended. This is accomplished by attaching a device to the shaker that permits controlled metal to metal impacts that generate high frequency, high acceleration environment on a test surface. A companion paper (Reference 1) shows that a sinusoidal or random shaker input can be used to generate a random vibration environment on the test surface. This paper derives the three response components that occur on the test surface due to an impact on the bottom surface and the base driven response from the shaker input. These response components are used to generate impulse response functions and frequency response functions which are used in the companion paper to derive power spectral density functions for the overall response. 9 refs., 8 figs.
High average power magnetic pulse compression systems are now being considered for use in several applications such as the High Power Radiation Source (HiPoRS) project. Such systems will require high reliability magnetic switches (saturable inductors) that are very efficient and have long lifetimes. One of the weakest components in magnetic switches is their interlaminar insulation. Considerations related to dielectric breakdown, thermal management of compact designs, and economical approaches for achieving these needs must be addressed. Various dielectric insulation and coating materials have been applied to Metglas foil in an attempt to solve the complex technical and practical problems associated with large magnetic switch structures. This work reports various needs, studies, results, and proposals in selecting and evaluating continuous coating approaches for magnetic foil. Techniques such as electrophoretic polymer deposition and surface chemical oxidation are discussed. We also propose continuous photofabrication processes for applying dielectric ribs or spacers to the foil which permit circulation of dielectric liquids for cooling during repetitive operation. 10 refs., 8 figs., 11 tabs.
This paper and a companion paper show that the traditional limits on amplitude and frequency that can be generated in a laboratory test on a vibration exciter can be substantially extended. This is accomplished by attaching a device to the shaker that permits controlled metal to metal impacts that generate a high acceleration, high frequency environment on a test surface. A companion paper derives some of the mechanical relations for the system. This paper shows that a sinusoidal shaker input can be used to excite deterministic chaotic dynamics of the system yielding a random vibration environment on the test surface, or a random motion of the shaker can be used to generate a random vibration environment on the test surface. Numerical examples are presented to show the kind of environments that can be generated in this system. 9 refs., 9 figs.
Charged-particle simulations in three dimensions are now performed routinely in the Pulsed Power Sciences Directorate at Sandia with the QUICKSILVER suite of codes. QUICKSILVER is a multitasked, finite-difference, three-dimensional, fully relativistic, electromagnetic, particle-in-cell code developed at Sandia. It is targeted for use on current and near-term supercomputers, such as the Cray X-MP/416, which are characterized by large, shared central memories and multiple processors. QUICKSILVER has already been used to simulate ion diodes, magnetically insulated transmission lines, microwave devices, and electron beam propagation. QUICKSILVER is actually a suite of codes; in addition to the main simulation code there are several support codes. The problem geometry is generated with a preprocessor and the simulation results are examined with one or more postprocessors. The MERCURY preprocessor assists the user in defining the mesh, boundary conditions, and other input parameters. The FLASH and AVS postprocessors are used to examine a wide variety of simulation output, including 3D rendering of particle positions, conductor surfaces, and scalar and vector quantities. The PLOTPFF postprocessor displays 2D slices and 1D pencils derived from 3D scalar and vector quantities. Additionally, time histories of various simulation quantities can be examined and manipulated with the IDR postprocessor. This paper describes the suite in detail. 9 refs., 4 figs.
This is a brief report about a Sandia National Laboratory facility which can provide high-thermal flux for simulation of nuclear thermal flash, measurements of the effects of aerodynamic heating on radar transmission, etc
This paper summarizes a cost-benefit assessment of the seismic design of the waste-handling facilities associated with the prospective high-level waste repository at Yucca Mountain, Nevada. It provides a very brief description of the methodology used and the costs and benefits of varying design levels for vibratory ground motions and surface fault displacements for structures, components, and equipment that are important to safety in the waste-handling facilities. 3 refs., 7 figs.
The semiconductor product engineers job requires knowledge and expertise related to many different subjects. This report provides guidance for newcomers to product engineering and is a consise reference for all others involved in product engineering. Subjects addressed are Customer/Supplier interactions, component development sequence, production schedule support, component characterization, product specifications, test equipment requirements, product qualification, characterization and development reports, preferred parts list, standard packaging, and finally, classification and security considerations. This guide is intended to help standardize and simplify the component development sequence presently used in the semiconductor product engineering department. 3 figs., 2 tabs.