Publications

In particle methods, each particle represents a finite region over which there is a distribution of the field quantity of interest. The field value at any point is calculated by summing the distribution functions for all the particles. This summation procedure does not require the use of any connectivities to generate continuous fields. Various AVS modules and networks have been developed that enable us to visualize the results from particle methods. This will be demonstrated by visualizing a numerical simulation of a rising, chaotic bubble. In this fluid dynamics simulation, each particle represents a region with a specified vorticity distribution.

The paper discusses two aspects of Sandia`s Wind Energy Program. The first section of the paper presents a case study of fatigue in wind turbines. This case study was prepared for the American Society of Testing Material`s (ASTM) Standard Technical Publication (STP) on fatigue education. Using the LIFE2 code, the student is lead through the process of cumulative damage summation for wind turbines and typical data are used to demonstrate the range of life estimates that will result from typical parameter variations. The second section summarizes the results from a workshop held by Sandia and the National Renewable Energy Laboratory (NREL) to discuss fatigue life prediction methodologies. This section summarizes the workshop discussions on the use of statistical modeling to deduce the shape and magnitude of the low-probability-of-occurrence, high-stress tail of the load distribution on a wind turbine during normal operation.

The Mixed Waste Landfill Integrated Demonstration (MWLID) focuses on ``in-situ`` characterization, monitoring, remediation, and containment of landfills in arid environments that contain hazardous and mixed waste. The MWLID mission is to assess, demonstrate, and transfer technologies and systems that lead to faster, better, cheaper, and safer cleanup. Most important, the demonstrated technologies will be evaluated against the baseline of conventional technologies and systems. The comparison will include the cost, efficiency, risk, and feasibility of using these innovative technologies at other sites.

Two 75-kW{sub t} alkali-metal pool-boiler solar receivers have been successfully tested at Sandia National Laboratories` National Solar Thermal Test Facility. The first one, Sandia`s `` second-generation pool-boiler receiver,`` was designed to address commercialization issues identified during post-test assessment of Sandia`s first-generation pool-boiler receiver. It was constructed from Haynes alloy 230 and contained the alkali-metal alloy NaK-78. The absorber`s wetted side had a brazed-on powder-metal coating to stabilize boiling. This receiver was evaluated for boiling stability, hot- and warm-restart behavior, and thermal efficiency. Boiling was stable under all conditions. All of the hot restarts were successful. Mild transient hot spots observed during some hot restarts were eliminated by the addition of 1/3 torr of xenon to the vapor space. All of the warm restarts were also successful. The heat-transfer crisis that damaged the first receiver did not recur. Thermal efficiency was 92.3% at 750{degrees}C with 69.6 kW{sub t} solar input. The second receiver tested, Sandia`s ``advanced-concepts receiver,`` was a replica of the first-generation receiver except that the cavities, which were electric-discharge-machined in the absorber for boiling stability, were eliminated. This step was motivated by bench-scale test results that showed that boiling stability improved with increased heated-surface area, tilt of the heated surface from vertical, and added xenon. The bench-scale results suggested that stable boiling might be possible without heated-surface modification in a 75-kW{sub t} receiver. Boiling in the advanced-concepts receiver with 1/3 torr of xenon added has been stable under all conditions, confirming the bench-scale tests.

The Sandia Laser Tracker (LT) systems illuminate a cooperative target with a diverged Argon-ion laser beam and track the resulting bright target using a servo-controlled turning mirror. Raw data is digitally recorded in real time and analyzed later when more time is available. The recorded data consists of azimuth and elevation of the tracking mirror, tracking error signals, and range to the target. If the target is tracked perfectly, the error signals will always be zero. The data reduction for this simplified, zero-error condition can be accomplished with very few lines of code. To date, all data reduction for LTI has been done using this zero-error assumption. The more general data reduction problem using the tracking error signals is a much more involved calculation and is referred to as ``using the error foldback routine.`` Detailed theory and vector analysis behind the data reduction and error decoupling algorithms used in the LT systems are described. Errors and corrections to the original document uncovered in over ten years of use are also noted and corrected.

This report describes the layout and operation of the recently upgraded Sandia Lightning Early Warning Network, which was upgraded from an analog-based to a digital-based telemetry system.

Layered crystalline titanates (CT) [Anthony and Dosch, US Patent 5 177 045 (1993)] are pillared with tetraethyl orthosilicate, 3-aminopropyltrimethoxysilane, and aluminum acetylacetonate to prepare porous and high surface area supports for sulfided NiMo catalyst. Tetra-ethyl orthosilicate or aluminum acetylacetonate intercalated CT are prepared by stepwise intercalation. First, the basal distance is increased by n-alkylammonium ions prior to intercalation with inorganic compounds. However, an aqueous solution of 3-aminopropyltrimethoxysilane could directly pillar CT without first swelling the titanate with n-alkylamine. The catalytic activities for hydrogenation of pyrene of sulfided NiMo supported silica or alumina pillared CT were higher than those of commercial catalysts (Shell324 and Amocat1C). The silicon and aluminum contents of the pillared CT, used as supports, have a considerable effect on the catalytic activities and physical properties of the supports.

The use of laser ignited explosive components has been recognized as a safety enhancement over existing electrical explosive devices (EEDs). Sandia has been pursuing the development of optical ordnance for many years with recent emphasis on developing optical deflagration-to-detonation (DDT) detonators and pyrotechnic actuators. These low energy optical ordnance devices can be ignited with either a semiconductor diode laser, laser diode arrays or a solid state rod laser. By using a semiconductor laser diode, the safety improvement can be made without sacrificing performance since the input energy required for the laser diode and the explosive output are similar to existing electrical systems. The use of higher powered laser diode arrays or rod lasers may have advantages in fast DDT applications or lossy optical environments such as long fiber applications and applications with numerous optical connectors. Recent results from our continued study of optical ignition of explosive and pyrotechnic materials are presented. These areas of investigation can be separated into three different margin categories: (1) the margin relative to intended inputs ( i.e. powder performance as a function of laser input variation), (2) the margin relative to anticipated environments (i.e. powder performance as a function of thermal environment variation), and (3) the margin relative to unintended environments (i.e. responses to abnormal environments or safety).

Rapid evolution in the structure of military forces worldwide is resulting in the retirement of numerous weapon systems. Many of these systems include rocket motors containing highly energetic propellants based on hazardous nitrocellulose/nitroglycerin (NC/NG) mixtures. Even as the surplus quantities of such material increases, however, current disposal methods -- principally open burning and open detonation (OB/OD) -- are coming under close scrutiny from environmental regulators. Environmentally conscious alternatives to disposal of propellant and explosives are thus receiving renewed interest. Recycle and reuse alternatives to OB/OD appear particularly attractive because some of the energetic materials in the inventories of surplus weapon systems represent potentially valuable resources to the commercial explosives and chemical industries. The ability to reclaim such resources is therefore likely to be a key requirement of any successful technology of the future in rocket motor demilitarization. This document consists of view graphs from the poster session.

Cookoff modeling of confined energetic materials involves the coupling of thermal, chemical and mechanical effects. In the past, modeling has focussed on the prediction of thermal runaway with little regard to the effects of mechanical behavior of the energetic material. To address the mechanical response of the energetic material, a constitutive submodel has been developed which can be incorporated into thermal-chemical-mechanical analysis. This work presents development of this submodel and its incorporation into a fully coupled one-dimensional, thermal-chemical-mechanical computer code to simulate thermal initiation of energetic materials. Model predictions include temperature, chemical species, stress, strain, solid/gas pressure, solid/gas density, yield function, and gas volume fraction. Sample results from a scaled aluminum tube filled with RDX exposed to a constant temperature bath at 500 K will be displayed. The micromechanical submodel is based on bubble mechanics which describes nucleation, decomposition, and elastic/plastic mechanical behavior. This constitutive material description requires input of temperatures and reacted fraction of the energetic material as provided by the reactive heat flow code, XCHEM, and the mechanical response is predicted using a quasistatic mechanics code, SANTOS. A parametric sensitivity analysis indicates that a small degree of decomposition causes significant pressurization of the energetic material, which implies that cookoff modeling must consider the strong interaction between thermal-chemistry and mechanics. This document consists of view graphs from the poster session.

The chemical processes involved in the decomposition of energetic materials have been investigated theoretically using quantum chemical methods to determine the thermochemistry and reaction pathways. The Bond-Additivity-Corrected Moller-Plesset 4th order perturbation theory method (BAC-MP4) has been used to determine heats of formation and free energies of reaction intermediates of decomposition. In addition, the BAC-MP4 method has been used to determine action pathways involving these intermediates. A theoretical method for calculating solvation energies has been developed to treat the non-idealities of high pressure and the condensed phase. The resulting chemical processes involving decomposition and ignition are presented for nitrate compounds, nitramines, and nitromethane.

In this presentation, we present modeling of DDT in porous energetic materials and experimental studies of a time-resolved, shock compression of highly porous inert and reactive materials. This combined theoretical and experimental studies explore the nature of the microscale processes of consolidation, deformation and reaction which are key features of the shock response of porous or damaged energetic materials. The theoretical modeling is based on the theory of mixtures in which multiphase mixtures are treated in complete nonequilibrium allowing for internal boundary effects associated mass/momentum and energy exchange between phases, relative flow, rate-dependent compaction behavior, multistage chemistry and interphase boundary effects. Numerous studies of low-velocity impacts using a high resolution adaptive finite element method are presented which replicate experimental observations. The incorporation of this model into multi-material hydrocode analysis will be discussed to address the effects of confinement and its influence on accelerated combustion behavior. The experimental studies will focus on the use of PVDF piezoelectric polymer stress-rate gauge to precisely measure the input and propagating shock stress response of porous materials. In addition to single constituent porous materials, such as granular HMX, we have resolved shock waves in porous composite intermetallic powders that confirm a dispersive wave nature which is highly morphologically and material dependent. This document consists of viewgraphs from the poster session.

``High consequence`` operations are systems, structures, and/or strategies for which it is crucial to provide assured protection against some potential catastrophe or catastrophes. The word ``catastrophe`` implies a significant loss of a resource (e.g., money, lives, health, environment, national security, etc.). The implementation of operations that are to be as catastrophe-free as possible must incorporate a very high level of protection. Unfortunately, real world limitations on available resources, mainly money and time, preclude absolute protection. For this reason, conventional ``risk analysis`` focuses on ``cost-effective`` protection, demonstrating through analysis that the benefits of any protective measures chosen outweigh their cost. This is a ``crisp`` one-parameter (usually monetary) comparison. A major problem with this approach, especially for high consequence operations, is that it may not be possible to accurately determine quantitative ``costs,`` and furthermore, the costs may not be accurately quantifiable. Similarly, it may not be possible to accurately determine or to quantify the benefits of protection in high consequence operations. These weaknesses are addressed in this paper by introducing multiple parameters instead of a single monetary measure both for costs of implementing protective measures and their benefits. In addition, a fuzzy-algebra comparison based on fuzzy number theory is introduced as a tool in providing cost/benefit tradeoff depiction, with the incorporation of measures of the uncertainty that necessarily exists in the input information. The result allows a more informative comparison to be made through use of fuzzy results, especially at the extreme bounds of the uncertainty.

In early October of 1993, an oil shipment of about 1 million barrels was made from the Bayou Choctaw Strategic Petroleum Reserve storage facility to St. James Terminal. During the shipment, oil temperatures and soil temperatures along the pipeline were recorded. The field data were used to make estimations of soil thermal properties, thermal conductivity and specific heat. These data were also used to validate and calibrate a heat transfer code, OILPIP, which has been used to calculate pipeline cooling of oil during a drawdown.

VISAR (Velocity Interferometer System for Any Reflector) is a system that uses the Doppler effect and is widely used for measuring the velocity of projectiles, detonations, flying plates, shock pressures (particle velocity) and other high speed/high acceleration motion. Other methods of measurement such as accelerometers and pressure gauges have disadvantages in that they are sensitive to radiation, electromagnetic pulses, and their mass can drastically alter the velocity of the projectile. VISAR uses single frequency-single mode laser fight focused onto a target of interest. Reflected fight from the target is collected and sent through a modified, unequal leg Michelson interferometer. In the interferometer the light is split into two components which travel through the legs of the interferometer cavity and are then recombined. When the light recombines, an interference pattern is created which can range from dark (destructive interference) to bright (constructive interference). When the target moves, the reflected laser light experiences a frequency shift (increase) with respect to the frequency from the target in a static condition. Since the Doppler shifted light is split and routed through an unequal leg interferometer cavity, there is a time lag of the light containing the Doppler information at the recombination point in the interferometer. The effect of the time lag is to create a sinusoidally changing interference pattern (commonly called fringes). Since the interferometer time delay, laser wavelength, and the speed of light are known, an accurate measurement of target velocity/acceleration may be measured by analyzing both the number of tinges and the speed of tinge generation (system accuracy is 3--4%).

The combustion behavior of energetic materials (e.g., solid propellants) has long been of interest in the fields of propulsion and pyrotechnics. In many such applications, it is becoming increasingly clear that two-phase flow effects play an important role, especially since, during combustion, most homogeneous solid propellants develop thin multi-phase layers at their surfaces in which finite-rate exothermic reactions occur. In addition, there is a growing interest in the behavior of porous energetic solids, since even initially dense materials can develop significant void fractions if, at any time, they are exposed to abnormal thermal environments. The deflagration characteristics of such ``damaged`` materials may then differ significantly from those of the pristine material due, at least in part, to gas flow in the solid/gas preheat region. The presence of gas in the porous solid in turn results in a more pronounced two-phase effect in the multi-phase surface layer, such as in the liquid melt region of nitramine propellants, which thus tend to exhibit extensive bubbling in an exothermic foam layer. The present analysis is largely applicable to this latter class of propellants.

To develop robust models for predicting the response of munitions under abnormal conditions associated with cookoff, it is necessary to be able to accurately characterize the following: the time to ignition, the location of the ignition point within the munition, and the combustive behavior of the damaged energetic material after ignition. For, the response of the munition, as controlled by these parameters, will determine whether its response will be characterized by a relatively mild deflagration or whether it will be characterized by a more damaging detonation. Several of the underlying properties of the energetic materials used in munitions that must be understood in order to accurately characterize these parameters are the chemical and physical changes that occur in these energetic materials as they are heated. The chemical changes involve overcoming the forces that tend to stabilize these materials, such as binding within the crystal lattice or intermolecular hydrogen bonding, and their transformation to less stable forms, such as mixtures of gases with high energy content. The physical changes typically involve phase changes of the material. One significant phase change is the slow transformation of the energetic materials from the solid reactant to gas phase products. This transformation can lead initially to the formation of high pressure gas bubbles within the solid particles and ultimately to changes in the porosity and gas permeability of the energetic material formulation. The presence of these reactive gases within high pressure bubbles can lead to increased hot spot formation of the material if it is compressed. The increased porosity can lead to significant increases in the burn rates of these materials at high pressures.

This paper discusses a thermochemical model for calculating equations of state (EOS) for the detonation products of explosives. This model, which was first presented at the Eighth Detonation Symposium, is available in the PANDA code and is referred to here as ``the Panda model``. The basic features of the PANDA model are as follows. (1) Statistical-mechanical theories are used to construct EOS tables for each of the chemical species that are to be allowed in the detonation products. (2) The ideal mixing model is used to compute the thermodynamic functions for a mixture of these species, and the composition of the system is determined from assumption of chemical equilibrium. (3) For hydrocode calculations, the detonation product EOS are used in tabular form, together with a reactive burn model that allows description of shock-induced initiation and growth or failure as well as ideal detonation wave propagation. This model has been implemented in the three-dimensional Eulerian code, CTH.

The enormity of the coal mine and extraction industries in Russia and the obvious need in both Russia and the US for cost savings and enhanced safety in those industries suggests that joint studies and research would be of mutual benefit. The author suggests that mine sites and well platforms in Russia offer an excellent opportunity for the testing of Sandia`s precise time-delay semiconductor bridge detonators, with the potential for commercialization of the detonators for Russian and other world markets by both US and Russian companies. Sandia`s semiconductor bridge is generating interest among the blasting, mining and perforation industries. The semiconductor bridge is approximately 100 microns long, 380 microns wide and 2 microns thick. The input energy required for semiconductor bridge ignition is one-tenth the energy required for conventional bridgewire devices. Because semiconductor bridge processing is compatible with other microcircuit processing, timing and logic circuits can be incorporated onto the chip with the bridge. These circuits can provide for the precise timing demanded for cast effecting blasting. Indeed tests by Martin Marietta and computer studies by Sandia have shown that such precise timing provides for more uniform rock fragmentation, less fly rock, reduce4d ground shock, fewer ground contaminants and less dust. Cost studies have revealed that the use of precisely timed semiconductor bridges can provide a savings of $200,000 per site per year. In addition to Russia`s vast mineral resources, the Russian Mining Institute outside Moscow has had significant programs in rock fragmentation for many years. He anticipated that collaborative studies by the Institute and Sandia`s modellers would be a valuable resource for field studies.

This report discusses the Sandia Pulse Reactor-IIIM (SPR-IIIM) is a modernized, improved version of the SPR-III burst reactor. Fast burst reactors are bare metal reactors that have very short neutron lifetimes (10--20 nanos) and pulse widths (50--100 {mu}s full width half maximum). The Sandia National Laboratories SPR reactors have been used to produce bursts of fast neutrons to simulate certain hostile weapon environments. Generations of weapon-related electronic components and subsystems have been tested for radiation vulnerability and hardness at the SPR Facility. The reactor consists of two right circular hollow cylinder core halves separated by about 3.5 inches when the reactor is shutdown (scrammed). To operate, the movable lower core half (safety block) is driven vertically upward until it makes contact with the stationary upper core half. Final reactivity is added by four external reflector elements, three are nickel control elements and one is an aluminum pulse element. The reflector elements travel up and down just beyond the outer diameter of the cylindrical reactor core and conform to the curvature of the outer vertical surface. The ``pulse`` element adds reactivity at a rate of $10/s. Experiments can be placed in the central cavity (usable space is 7.5-in. OD by 14.5-in. height). The integrated dose in the central cavity is 6{times}10{sup 14} n/cm{sup 2} on a nominal size burst (300{degrees}C{Delta}T). The dose at the closest approach outside the reactor is 1{times}10{sup 14} n/cm{sup 2}. The unmoderated neutron spectrum peaks at {approximately}350 keV.

Interest in the characteristics of urban street networks is increasing at the same time new monitoring technologies are delivering detailed traffic data. These emerging streams of data may lead to the dilemma that airborne remote sensing has faced: how to select and access the data, and what meaning is hidden in them? computer-assisted visualization techniques are needed to portray these dynamic data. Of equal importance are controls that let the user filter, symbolize, and replay the data to reveal patterns and trends over varying time spans. We discuss a prototype software system that addresses these requirements.

Using a real-time, Surface Acoustic Wave (SAW) sensing instrument supplied by Femtometrics, we have measured organic contamination, or nonvolatile residues (NVR), in both a cleanroom and a microenvironment. To demonstrate the {open_quotes}real-time{close_quotes} NVR detectability and sensitivity of the SAW instrument, controlled contamination experiments with photoresist material were also conducted. In addition, two cleaning methods for removing contamination from used sensors have been evaluated. One technique uses the on-board temperature varying capability of the SAW instrument, while the other technique utilizes a uv-ozone cleaner for the sensor cleaning. Preliminary results from SAW measurements in the cleanroom and in a microenvironment and tests to evaluate sensor cleaning techniques are presented in this report. A concluding summary with an assessment of the current SAW instrument and potential future applications for this technology is also presented.

Significant progress has occurred lately regarding the classification, characterization, and formation of white spots during vacuum arc remelting (VAR). White spots have been generally split into three categories: discrete white spots, which are believed to be associated with undissolved material which has fallen in from the shelf, crown, or torus regions; dendritic white spots, usually associated with dendrite clusters having fallen from the electrode; and solidification white spots, believed to be caused by local perturbations in the solidifications conditions. Characteristics and proposed formation mechanisms of white spots are reviewed and discussed in context of physical processes occurring during VAR, such as fluid flow and arc behavior. Where possible, their formation mechanisms will be considered with respect to specific operating parameters. In order to more fully understand the formation of solidification white spots, an experimental program has been begun to characterize the solidification stability of Alloy 718 and variants with respect to changes in growth rate and thermal environment. A description of the experimental program and preliminary results are included.

In this report, we reconsider the various approximations made to the full equations of motion and energy transport for treating low-speed flows with significant temperature induced property variations. This entails assessment of the development of so-called anelastic for low-Mach number flows outside the range of validity of the Boussinesq equations. An integral part of this assessment is the development of a finite element-based numerical scheme for obtaining approximate numerical solutions to this class of problems. Several formulations were attempted and are compared.

H1224A weapons containers have been used for years by the Department of Energy and Department of Defense to transport and store W78 warhead midsections. Although designed to protect these midsections only in low-energy handling drop and impact accidents, a recent transportation risk assessment effort has identified a need to evaluate the container`s ability to protect weapons in higher-energy environments. Four impact tests were performed on H1224A containers with W78 Mod 6c mass mockup midsections inside, onto an essentially unyielding target. Dynamic acceleration and strain levels were recorded during the side-on and end-on impacts, each at 12.2 m/s (40 ft/s) and 38.1 m/s (125 ft/s). Measured peak accelerations experienced by the midsections during lower velocity impacts ranged from 250 to 600 Gs for the end-on impact and 350 to 600 Gs for the side-on impact. Measured peak accelerations of the midsections during the higher velocity impacts ranged from 3,000 to 10,000 Gs for the end-on impact and 8,000 to 10,000 Gs for the side-on impact. Deformations in the H1224A container ranged from minimal to severe buckling and weld tearing. At higher impact velocities, the H1224A container may not provide significant energy absorption for the re-entry vehicle midsection but can provide some confinement of potentially damaged components.