Publications

The use of focused laser beams and fiber optics to control the location and density of current filaments in GaAs photoconductive semiconductor switches (PCSS) is described in this paper. An intensified CCD camera is used to monitor the infrared photoluminescence of the filaments during fast initiation of high gain switching for several sizes of lateral GaAs PCSS (e.g. 0.5×5, 1×5, 2.5×5, 2×30, and 15×20 mm2). The switches are triggered with either a focused, mode-locked, Nd:YAG laser (532 and 1064 nm) or fiber-optically coupled semiconductor laser diodes (approximately 900 nm). The dependencies of the size, location, and density of the current filaments on the optical trigger, switch voltage, and switch current will be discussed. The impact of optically controlled current filaments on device design and lifetime is emphasized. Electro-optical switching amplification is demonstrated using the high gain switching mode of GaAs (lock-on). A single semiconductor laser diode is used to trigger a small GaAs PCSS. This PCSS is used to drive a 15-element laser diode array. Both electrical and optical pulse compression, sharpening, and amplification are achieved. Estimates for electrical and optical power gains are 8000 and 750 respectively.

A gridless numerical technique called smooth particle hydrodynamics (SPH) has been coupled the transient dynamics finite element code, PRONTO. In this paper, a new weighted residual derivation for the SPH method will be presented, and the methods used to embed SPH within PRONTO will be outlined. Example SPH-PRONTO calculations will also be presented. Smooth particle hydrodynamics is a gridless Lagrangian technique. Requiring no mesh, SPH has the potential to model material fracture, large shear flows, and penetration. SPH computes the strain rate and the stress divergence based on the nearest neighbors of a particle, which are determined using an efficient particle sorting technique. Embedding the SPH method within PRONTO allows part of the problem to be modeled with quadrilateral finite elements while other parts are modeled with the gridless SPH method. SPH elements are coupled to the quadrilateral elements through a contact like algorithm.

The response of thickness shear mode (TSM) resonators in liquids is examined. Smooth-surface devices, which viscously entrain a layer of contacting liquid, respond to the product of liquid density and viscosity. Textured-surface devices, which also trap liquid in surface features, exhibit an additional response that depends on liquid density alone. Combining smooth and textured resonators in a monolithic sensor allows simultaneous measurement of liquid density and viscosity.

The Yucca Mountain Site Characterization Project is studying Yucca Mountain in southwestern Nevada as a potential site for a high-level nuclear waste repository. Site characterization includes surface-based and underground testing. Analyses have been performed to support the design of site characterization activities so to have minimal impact on the ability of the site to isolate waste, and on tests performed as part of the characterization process. Two examples of site characterization activities are the construction of an Exploratory Studies Facility, which may include underground shafts, drifts, and ramps, and surface-based testing activities, which may require borehole drilling, excavation of test pits, and road watering for dust control. The information in this report pertains to two-dimensional numerical calculations modeling the movement of surficially applied water and the potential effects of that water on repository performance and underground experiments. This document contains information that has been used in preparing recommendations for two Yucca Mountain Site Characterization Project documents: Appendix I of the Exploratory Studies Facility Design Requirements document, and the Surface-Based Testing Field Requirements Document.

The Yucca Mountain Site Characterization Project is studying Yucca Mountain in southwestern Nevada as a potential site for a high-level radioactive waste repository. Analyses reported herein were performed to support the design of site characterization activities so that these activities will have a minimal impact on the ability of the site to isolate waste and a minimal impact on underground tests performed as part of the characterization process. These analyses examine the effect of water to be used in the underground construction and testing activities for the Exploratory Studies Facility on in situ conditions. Underground activities and events where water will be used include construction, expected but unplanned spills, and fire protection. The models used predict that, if the current requirements in the Exploratory Studies Facility Design Requirements are observed, water that is imbibed into the tunnel wall rock in the Topopah Springs welded tuff can be removed over the preclosure time period by routine or corrective ventilation, and also that water imbibed into the Paintbrush Tuff nonwelded tuff will not reach the potential waste storage area.

Synthesis of hybrid organic-inorganic materials with ionic functionality within the polymer backbone has been achieved. A new family of hypervalent spiro anionic polysiliconates and polygermylates has been prepared. These materials were shown to be thermally stable to moderate temperatures and are completely air and moisture stable. Analysis by solution and solid state NMR verified the presence of the hypervalent functionality. We are currently examining the effect that alteration of the condensing reagent and/or the counterion may have on bulk properties of the ionomeric material.

Three concepts to measure incident flux (1) relative, real-time power measurement, (2) flux mapping and incident power measurement, and (3) real-time flux mapping) and two concepts to measure receiver surface temperatures low and high resolution temperature measurements) on an external central receiver are discussed along with the potential and shortcomings of these concepts to make the desired measurements and the uncertainties associated with the measurements caused by atmospheric and surface property variations. These concepts can aid in the operation and evaluation of the receiver and plant. Tests have shown that the incident flux distribution on a surface can be mapped out using a fixed, narrow white target and a CCD camera system by recording the images of the beam as it is passed over the target and by building a composite image. Tests with the infrared cameras have shown they are extremely valuable tools in determining temperature profiles during startup of the receiver and throughout operation. This paper describes each concept in detail along with the status of testing to determine the feasibility of these concepts.

The calculated valence charge density of the recently synthesized NaPd{sub 3}H{sub 2} compound is compared with that of palladium hydride, PdH, from which it can be derived.

Use of lead-indium solders in microelectronics packaging has increased over the last decade. Increased usage is due to improved properties, such as greater thermo-mechanical fatigue resistance, lower intermetallic formation rates with base metallizations, such as copper, and lower reflow temperatures. However, search of literature reveals no comprehensive studies on phase equilibrium relations between copper metal and lead-indium solder. Our effort involves a combination of experimental data acquisition and computer modeling to obtain the Cu-In-Pb ternary phase diagram. Isotherms and isopleths of interest at low temperatures are achieved by means of differential scanning calorimetry and electron probe microanalysis. Thermodynamic models of these sections served as a guide for efficient experimentation.

Nitrided gate oxides have been fabricated by furnace oxidation in N{sub 2}O with and without prior oxidation in O{sub 2}. SIMS nitrogen profiles show a sharp peak at the Si-insulator interface for both processes. Improved breakdown characteristics and reduced oxide damage after irradiation and charge injection are obtained.

The role of net positive oxide trapped charge and surface recombination velocity on excess base current in BJTs is identified. The effects of the two types of damage can be detected by plotting the excess base current versus base-emitter voltage. Differences and similarities between ionizing-radiation-induced and hot electron-induced degradation are discussed.

Short communication

The inertial confinement fusion (ICF) program at Sandia National Laboratories (SNL) is directed toward validating light ions as an efficient driver for ICF defense and energy applications. The light ion laboratory microfusion facility (LMF) is envisioned as a facility in which high gain ICF targets could be developed and utilized in defense-related experiments. The relevance of LMF technology to eventual inertial fusion energy (IFE) applications is assessed via a comparison of LMF technologies with those projected in the Light Ion Beam Reactor Assessment (LIBRA) conceptual reactor design study.

This paper summarizes the results of a study performed by the US and Germany to assess the technical and economic potential of central receiver power plants and to identify the necessary research and development (R&D) activities required to reach demonstration and commercialization. Second generation power plant designs, employing molten-salt and volumetric-air receivers, were assessed at the size of 30 and 100 MWe. The study developed a common guideline and used data from previous system tests and studies. The levelized-energy costs for the second generation plants were estimated and found to be competitive with costs from fossil-fueled power plants. Potential for further cost reductions exists if technical improvements can be introduced successfully in the long term. Additionally, the study presents results of plant reliability and uncertainty analyses. Mid- and long-term technical potentials are described, as well as recommendations for the R&D activities needed to reach the goal of large-scale commercialization. The results of this study have already helped direct research in the US and Europe. For example, the favorable potential for these technologies has led to the Solar Two molten-salt project in the US and the TSA volumetric receiver test in Spain. In addition, early analysis conducted within this study indicated that an advanced thermal storage medium was necessary to achieve favorable economics for the air plant. This led to the design of the thermal storage system currently being tested in Spain. In summary, each of the investigated receiver technologies has mid- and long-term potential for improving plant performance and reducing capital and energy costs (resulting in less than 10 cts/kWh given excellent insolation conditions) in an environmentally safe way and largely independent of fossil-fuel prices.

We have developed a novel molecular beam mass spectrometry technique that can quantitatively analyze the gas-phase composition in a CVD reactor. The technique simultaneously monitors a wide variety of radical and stable species, and their concentrations can be determined with sensitivities approaching 1 ppM. Measurements performed in a diamond deposition system have given us keen insights into the important phenomena that affect the growth environment. This paper first discusses the primary gas sampling design issues. In the second part, the details of the experimental results and their implications will be described.

Hydrotalcite coatings on aluminum alloys are being developed for corrosion protection of aluminum in aggressive saline environments. Coating bath composition, surface pretreatment, and alloying elements in aluminum all influence the performance of these coatings during salt spray testing. The coating bath, comprised of lithium carbonate, requires aging by dissolution of aluminum into the bath in order to grow corrosion resistant coatings. Coatings formed in non- aged baths do not perform well in salt spray testing. The alloying elements in aluminum alloys, especially copper, influence the coating growth and formation leading to thin coatings. The effect of the alloy elements is to limit the supply of aluminum to the coating/electrolyte interface and hinder growth of hydrotalcite upon aluminum alloys.

Adsorption/desorption were studied using combined surface analytical techniques. An approximate initial sticking coefficient for Cs on sapphire was measured using reflection mass spectrometry and found to be 0.9. Thermal Desorption Mass Spectrometry (TDMS) and Auger Electron Spectroscopy (AES) were used to verify that a significant decrease in sticking coefficient occurs as the Cs coverage reaches a critical submonolayer value. TDMS analysis demonstrates that Cs is stabilized on a clean sapphire surface at temperatures (1200 K) in excess of the temperatures experienced by sapphire in a TOPAZ-2 thermionic fuel element (TFE). Surface contaminants on sapphire can enhance Cs adsorption relative to the clean surface. C contamination eliminates the high temperature state of Cs desorption found on clean sapphire but shifts the bulk of the C desorption from 400 to 620 K. Surface C is a difficult contaminant to remove from sapphire, requiring annealing above 1400 K. Whether Cs is stabilized on sapphire in a TFE environment will most likely depend on relation between surface contamination and surface structure.

Ortho-Chlorobenzylidene Malononitrile (CS) is one of a number of riot control agents referred to as tear gas, although it is in fact a particulate suspension. The toxicity of this material has been studied in various detail. The purpose of this study was to review and summarize the literature data available on the toxicity of CS.

Cold Smoke is a dense white smoke produced by the reaction of titanium tetrachloride and aqueous ammonia aerosols. Early studies on the toxicity of this nonpyrotechnically generated smoke indicated that the smoke itself is essentially non-toxic (i.e. exhibits to systemic toxicity or organ damage due to exposure) under normal deployment conditions. The purpose of this evaluation was to review and summarize the recent literature data available on the toxicity of Cold Smoke, its chemical constituents, and its starting materials.

The Microsoft (MS) Windows product is widely available for PC`s. There exists many thousands of them at Sandia. All of the MS applications in Windows have a Help file. This help file informs the user ``how to`` use and run that application. It is an ``on-line`` manual. The ``Help Compiler`` was obtained from Microsoft. Use of this compiler enables one to insert text in a form the MS ``Help Engine`` recognizes. This means all of the features of the Help file: Hypertext (hot links), browsing, searching, indexing, bookmarks, annotation, are available for your text. This turns a document into a ``Smart Document.`` The use of this Smart Document System (SDS) for Engineering Procedures (EPs) is described.

This item is a copy of the Dec., 1993 issue of Manufacturing Technology, a Sandia Technology Bulletin. It has information on a number of different projects being conducted by Sandia in the general area of manufacturing sciences. Topics addressed include the following: center for information-technology manufacturing gears up, luctrative flat-panel display market targeted; researchers make copper stick to teflon, patterned adhesion may provide ideal conductor/substrate combination for microcircuits; contact algorithm enhances simulation of manufacturing processes, algorithm efficiently handles previously difficult analyses of punching and cutting operations; national machine tool partnership rolls into action, national laboratories share technology to boost US machine-tool industry; closed-loop MAST system eyes robotic manufacturing, fast, accurate, low-cost sensor demonstrated on furnace brazing.

A brief history of lightning protection at Pantex nuclear explosive areas (NEAs) is given. An assessment of current Pantex lightning protection at NEAs is summarized. Recommendations for further improvements in lightning protection are described.

Supercomputing `93, a high-performance computing and communications conference, was held November 15th through 19th, 1993 in Portland, Oregon. For the past two years, Sandia National Laboratories has used this conference to showcase and focus its communications and networking endeavors. At the 1993 conference, the results of Sandia`s efforts in exploring and utilizing Asynchronous Transfer Mode (ATM) and Synchronous Optical Network (SONET) technologies were vividly demonstrated by building and operating three distinct networks. The networks encompassed a Switched Multimegabit Data Service (SMDS) network running at 44.736 megabits per second, an ATM network running on a SONET circuit at the Optical Carrier (OC) rate of 155.52 megabits per second, and a High Performance Parallel Interface (HIPPI) network running over a 622.08 megabits per second SONET circuit. The SMDS and ATM networks extended from Albuquerque, New Mexico to the showroom floor, while the HIPPI/SONET network extended from Beaverton, Oregon to the showroom floor. This paper documents and describes these networks.

An analysis of the impact of the Minuteman III Payload Transporter Type III into a nonyielding target at 46 m.p.h. and 30 m.p.h., and into a yielding target at 46 m.p.h. is presented. The analysis considers the structural response of the tiedown system which secures the Minuteman III re-entry system to the floor of the payload transporter. A finite element model of the re-entry system, its tiedown system, which includes tie-rods and shear pins, and the pallet plate which is attached to the transporter floating plate, was constructed. Because accelerations of the payload transporter are not known, acceleration data from one-quarter scale testing of the Safe Secure Trailer was used to investigate the response of the tiedown system. These accelerations were applied to the pallet plate. The ABAQUS computer code was used to predict the forces in the members of the tiedown system.

SAFSIM (System Analysis Flow SIMulator) is a FORTRAN computer program for simulating the integrated performance of complex flow systems. SAFSIM provides sufficient versatility to allow the engineering simulation of almost any system, from a backyard sprinkler system to a clustered nuclear reactor propulsion system. In addition to versatility, speed and robustness are primary SAFSIM development goals. SAFSIM contains three basic physics modules: (1) a fluid mechanics module with flow network capability; (2) a structure heat transfer module with multiple convection and radiation exchange surface capability; and (3) a point reactor dynamics module with reactivity feedback and decay heat capability. Any or all of the physics modules can be implemented, as the problem dictates. SAFSIM can be used for compressible and incompressible, single-phase, multicomponent flow systems. Both the fluid mechanics and structure heat transfer modules employ a one-dimensional finite element modeling approach. This document contains a description of the theory incorporated in SAFSIM, including the governing equations, the numerical methods, and the overall system solution strategies.

Preliminary estimates of national benefits from electric utility applications of battery energy storage through the year 2010 are presented along with a discussion of the particular applications studied. The estimates in this report were based on planning information reported to DOE by electric utilities across the United States. Future studies are planned to refine these estimates as more application-specific information becomes available.

The integrity of the electrostatic bonding procedures used to equilibrate operating technicians and weapon components was questioned during the course of the quality evaluation assessments of the W70, W68, and B57 dismantlement programs. A multi-disciplined, interlaboratory team was convened on an ad hoc basis to resolve certain static bonding issues. The accomplishments of this team in upgrading the integrity of the bonding process include recommendations on the proper use of wrist straps, training of technicians in their use, and procedures to reduce accumulation of static charge on components during routine handling operations.

The On-Line Aerosol Monitor (OLAM) is a light attenuation device designed and built at the Idaho National Engineering Laboratory (INEL) by EG&G Idaho. Its purpose is to provide an on-line indication of aerosol concentration in the PHEBUS-FP tests. It does this by measuring the attenuation of a light beam across a tube through which an aerosol is flowing. The OLAM does not inherently give an absolute response and must be calibrated. A calibration has been performed at Sandia National Laboratories` (SNL) Sandia Aerosol Research Laboratory (SARL) and the results are described here. Ammonium chloride and sodium chloride calibration aerosols are used for the calibration and the data for the sodium chloride aerosol is well described by a model presented in this report. Detectable instrument response is seen over a range of 0.1 cm{sup 3} of particulate material per m{sup 3} of gas to 10 cm{sup 3} of particulate material per m{sup 3} of gas.

Pressure-pulse, constant-pressure flow, and pressure-buildup tests have been performed in bedded evaporites of the Salado Formation at the Waste Isolation Pilot Plant (WIPP) site to evaluate the hydraulic properties controlling brine flow through the Salado. Transmissivities have been interpreted from six sequences of tests conducted on five stratigraphic intervals within 15 m of the WIPP underground excavations.

This report responds to the Department of Energy`s request that Sandia National Laboratories compare existing technologies against several advanced technologies as they apply to DOE needs to monitor the movement of material, weapons, or personnel for safety and security programs. The authors describe several material control systems, discuss their technologies, suggest possible applications, discuss assets and limitations, and project costs for each system. The following systems are described: WATCH system (Wireless Alarm Transmission of Container Handling); Tag system (an electrostatic proximity sensor); PANTRAK system (Personnel And Material Tracking); VRIS (Vault Remote Inventory System); VSIS (Vault Safety and Inventory System); AIMS (Authenticated Item Monitoring System); EIVS (Experimental Inventory Verification System); Metrox system (canister monitoring system); TCATS (Target Cueing And Tracking System); LGVSS (Light Grid Vault Surveillance System); CSS (Container Safeguards System); SAMMS (Security Alarm and Material Monitoring System); FOIDS (Fiber Optic Intelligence & Detection System); GRADS (Graded Radiation Detection System); and PINPAL (Physical Inventory Pallet).

An essential component of a horizontal, underground nuclear test setup at the Nevada Test Site is the auxiliary closure system. The massive gates that slam shut immediately after a device has been detonated allow the prompt radiation to pass, but block debris and hot gases from continuing down the tunnel. Thus, the gates protect experiments located in the horizontal line-of-sight steel pipe. Sandia National Laboratories has been the major designer and developer of these closure systems. This report records the history of SNL`s participation in and contributions to the technology of auxiliary closure systems used in horizontal tunnel tests in the underground test program.

VICTORIA is a mechanistic computer code that treats fission product behavior in the reactor coolant system during a severe accident. During an accident, fission products that deposit on structural surfaces produce heat loads that can cause fission products to revaporize and possibly cause structures, such as a pipe, to fail. This mechanism had been lacking from the VICTORIA model. This report describes the structural heat-up model that has recently been implemented in the code. A sample problem shows that revaporization of fission products can occur as structures heat up due to radioactive decay. In the sample problem, the mass of deposited fission products reaches a maximum, then diminishes. Similarly, temperatures of the deposited film and adjoining structure reach a maximum, then diminish.

This performance assessment characterized plausible treatment options conceived by the Idaho National Engineering Laboratory (INEL) for its spent fuel and high-level radioactive waste and then modeled the performance of the resulting waste forms in two hypothetical, deep, geologic repositories: one in bedded salt and the other in granite. The results of the performance assessment are intended to help guide INEL in its study of how to prepare wastes and spent fuel for eventual permanent disposal. This assessment was part of the Waste Management Technology Development Program designed to help the US Department of Energy develop and demonstrate the capability to dispose of its nuclear waste, as mandated by the Nuclear Waste Policy Act of 1982. The waste forms comprised about 700 metric tons of initial heavy metal (or equivalent units) stored at the INEL: graphite spent fuel, experimental low enriched and highly enriched spent fuel, and high-level waste generated during reprocessing of some spent fuel. Five different waste treatment options were studied; in the analysis, the options and resulting waste forms were analyzed separately and in combination as five waste disposal groups. When the waste forms were studied in combination, the repository was assumed to also contain vitrified high-level waste from three DOE sites for a common basis of comparison and to simulate the impact of the INEL waste forms on a moderate-sized repository, The performance of the waste form was assessed within the context of a whole disposal system, using the U.S. Environmental Protection Agency`s Environmental Radiation Protection Standards for Management and Disposal of Spent Nuclear Fuel, High-Level and Transuranic Radioactive Wastes, 40 CFR 191, promulgated in 1985. Though the waste form behavior depended upon the repository type, all current and proposed waste forms provided acceptable behavior in the salt and granite repositories.

The purpose of this document is to present technical information that should be useful for understanding and applying locking systems for physical protection and control. There are major sections on hardware for locks, vaults, safes, and security containers. Other topics include management of lock systems and safety considerations. This document also contains notes on standards and specifications and a glossary.

To extend the life of gas delivery systems and improve wafer yields, there is a need for an in-line monitor of H{sub 2}O contamination. Goal of this project is to develop such an instrument, based on infrared spectroscopy, that has a detection limit of 30 ppB or better and costs $50K or less. This year`s work considered the application of Fourier transform infrared (FTIR) spectroscopy to H{sub 2}O detection in N{sub 2} and HCl. Using a modified commercial FTIR spectrometer and a long-path gas cell, a detection limit of about 10 ppB was demonstrated for H{sub 2}O in N{sub 2} and HCl. This includes about a factor of three improvement achieved by applying quantitative multivariate calibration methods to the problem. Absolute calibration of the instrument was established from absorptivities of prominent H{sub 2}O bands between 3600 and 3910 cm{sup {minus}1}. Methods are described to minimize background moisture in the beam path. Spectral region, detector type, resolution, cell type, and path length were optimized. Resolving the narrow H{sub 2}O bands (FWHM {approx} 0.20 cm{sup {minus}1}) is not necessary to achieve optimal sensitivity. In fact, optimal sensitivity is achieved at 2 to 4 cm{sup {minus}1} resolution, allowing the use of an inexpensive interferometer. A much smaller, second generation instrument is described that will have a conservatively estimated detection limit of 1 ppB. Since the present laboratory instrument can be duplicated in its essential parts for about $90K, it is realistic to project a cost of $50K for the new instrument. An accessory for existing FTIR spectrometers was designed that may be marketed for as little as $10K.

A dynamic simulator of the TOPAZ II reactor system has been developed for the Nuclear Electric Propulsion Space Test Program. The simulator combines first-principle modeling and empirical correlations in its algorithm to attain the modeling accuracy and computational through-put that are required for real-time execution. The overall execution time of the simulator for each time step is 15 ms when no data is written to the disk, and 18 ms when nine double precision data points are written to the disk once in every time step. The simulation program has been tested and it is able to handle a step decrease of $8 worth of reactivity. It also provides simulations of fuel, emitter, collector, stainless steel, and ZrH moderator failures. Presented in this paper are the models used in the calculations, a sample simulation session, and a discussion of the performance and limitations of the simulator. The simulator has been found to provide realistic real-time dynamic response of the TOPAZ II reactor system under both normal and casualty conditions.

Samples of chemically-vapor-deposited micrometer and sub-micrometer-thick films of polysilicon were analyzed by transmission electron microscopy (TEM) in cross-section and by Raman spectroscopy with illumination at their surface. TEM and Raman spectroscopy both find varying amounts of polycrystalline and amorphous silicon in the wafers. Raman spectra obtained using blue, green and red excitation wavelengths to vary the Raman sampling depth are compared with TEM cross-sections of these films. Films showing crystalline columnar structures in their TEM micrographs have Raman spectra with a band near 497 cm{sup {minus}1} in addition to the dominant polycrystalline silicon band (521 cm{sup {minus}1}). The TEM micrographs of these films have numerous faulted regions and fringes indicative of nanometer-scale silicon structures, which are believed to correspond to the 497cm{sup {minus}1} Raman band.

Optical communication is likely to significantly speed up parallel computation because the vast bandwidth of the optical medium can be divided to produce communication networks of very high degree. However, the problem of contention in high-degree networks makes the routing problem in these networks theoretically (and practically) difficult. In this paper we examine Valiant`s h-relation routing problem, which is a fundamental problem in the theory of parallel computing. The h-relation routing problem arises both in the direct implementation of specific parallel algorithms on distributed-memory machines and in the general simulation of shared memory models such as the PRAM on distributed-memory machines. In an h-relation routing problem each processor has up to h messages that it wishes to send to other processors and each processor is the destination of at most h messages. We present a lower bound for routing an h-relation (for any h > 1) on a complete optical network of size -n. Our lower bound applies to any randomized distributed algorithm for this task. Specifically, we show that the expected number of communication steps required to route an arbitrary h-relation is {Omega}(h + {radical}log log n). This is the first known lower bound for this problem which does not restrict the class of algorithms under consideration.

The combined dynamic environments of vibration and linear acceleration are common to a large number of spacecraft components and other devices. Testing such devices has normally been a two-step process in which independent vibration and centrifuge tests are performed. There is a concern that the combined effects from these two dynamic environments could cause unexpected operational failures that were not predicted from either analysis or independent testing. This paper describes the design and performance of a testing facility that combines vibration and centrifuge testing in a single operation. The test facility is called the Vibrafuge and utilizes Sandia National Laboratories' (SNL) 29-ft underground centrifuge with an attached electrodynamic shaker. Also addressed are activities underway at SNL on development of a combined vibration and acoustic test facility (ATF).

An Integrated Demonstration Program, hosted by the Fernald Environmental Restoration Management Corporation (FERMCO), has been established for investigating technologies applicable to the characterization and remediation of soils contaminated with uranium. An important part of this effort is the evaluation of field screening tools capable of acquiring high resolution information on the distribution of uranium contamination in surface soils in a cost-and-time efficient manner. Consistent with this need, four field screening technologies have been demonstrated at two hazardous waste sites at the FERMCO. The four technologies tested are wide-area gamma spectroscopy, beta scintillation counting, laser ablation-inductively coupled plasma-atomic emission spectroscopy (LA-ICP-AES), and long-range alpha detection (LRAD). One of the important findings of this demonstration was just how difficult it is to compare data collected by means of multiple independent measurement techniques. Difficulties are attributed to differences in measurement scale, differences in the basic physics upon which the various measurement schemes are predicated, and differences in the general performance of detector instrumentation. It follows that optimal deployment of these techniques requires the development of an approach for accounting for the intrinsic differences noted above. As such, emphasis is given in this paper to the development of a methodology for integrating these techniques for use in site characterization programs as well as the development of a framework for interpreting the collected data. The methodology described here also has general application to other field-based screening technologies and soil sampling programs.

This paper describes the development and use of the Multi-Axis Seam Tracking (MAST) sensor for tracking seams or other features in real-time. Four independent, spatially-distributed electric fields are used to sense changes in the relative position of the sensor and the workpiece. The MAST sensor is very inexpensive compared with commercially available seam tracking sensors. It can be used in systems to perform cost-effective small-lot manufacturing operations in a faster, more consistent manner. The MAST sensor is used in an automated system for dispensing braze paste during a rocket nozzle fabrication process.

Pitting of 1100 Al(Al-1.0(Fe,Cu,Si)) due to Al{sub 3}Fe constituent particles has been studied by examining a variety of intrinsic, extrinsic, and environmental factors that contribute to localized corrosion. Consistent with results from other studies, Al{sub 3}Fe is noble with respect to its microstructural surroundings and pitting is localized to the particle periphery. Polarization curves indicate that cathodic electron transfer reactions are supported on Al{sub 3}Fe at high rates, however, a anodic electron transfer reactions are not. Interparticle spacing appears to play a strong role in determining where pitting will occur, while Al{sub 3}Fe particle area plays a lesser role. Solution pH, applied potential, and exposure time each have measurable effects on the electrochemical behavior of Al{sub 3}Fe and the {alpha}-Al matrix phase which can impact either the galvanic potential of the Al{sub 3}Fe/{alpha}-Al couple, or charge transfer processes on Al{sub 3}Fe particles.

Using surface acoustic wave (SAW) devices, three approaches to the effective use of chemically sensitive interfaces that are not highly chemically selective have been examined: (1) molecular identification from time-resolved permeation transients; (2) using multifrequency SAW devices to determine the frequency dependence of analyte/film interactions; (3) use of an array of SAW devices bearing diverse chemically sensitive interfaces to produce a distinct response pattern for each analyte. In addition to their well-known sensitivity to mass changes (0.0035 monolayer of N{sub 2} can be measured), SAW devices respond to the mechanical and electronic properties of thin films, enhancing response information content but making a thorough understanding of the perturbation critical. Simultaneous measurement of changes in frequency and attenuation, which can provide the information necessary to determine the type of perturbation, are used as part of the above discrimination schemes.

We present a global motion planner for tracing curves in three dimensions with robot manipulator tool frames. This planner generates an efficient motion satisfying three types of constraints; constraints on the tool tip for curve tracing, robot kinematic constraints and robot-link collision constraints. Motions are planned using a global search algorithm and a local planner based on a potential-field approach. This planner can be used with potential-field approach. This planner can be used with any robots including redundant manipulators, and can any robots including redundant manipulators, and can control the trade-offs between its algorithmic completeness and computation time. It can be applied in many robotic tasks such as seam welding, caulking, edge deburrring and chamfering, and is expected to reduce motion programming times from days to minutes.

Robotic systems are often very complex and difficult to operate, especially as multiple robots are integrated to accomplish difficult tasks. In addition, training the operators of these complex robotic systems is time-consuming and costly. In this paper, a virtual reality based robotic control system is presented. The virtual reality system provides a means by which operators can operate, and be trained to operate, complex robotic systems in an intuitive, cost-effective way. Operator interaction with the robotic system is at a high, task-oriented, level. Continuous state monitoring prevents illegal robot actions and provides interactive feedback to the operator and real-time training for novice users.

A sensor-based control approach for real-time seam tracking of rocket thrust chamber assemblies has been developed to enable automation of a braze paste dispensing process. This approach utilizes a non-contact Multi-Axis Seam Tracking (MAST) sensor to track the seams. Thee MAST sensor measures capacitance variations between the sensor and the workpiece and produces four varying voltages which are read directly into the robot controller. A PID control algorithm which runs at the application program level has been designed based upon a simple dynamic model of the combined robot and sensor plant. The control algorithm acts on the incoming sensor signals in real-time to guide the robot motion along the seam path. Experiments demonstrate that seams can be tracked at 100 mm/sec within the accuracy required for braze paste dispensing.

Probabilistic risk assessment (PRA) is a process for evaluating hazardous operations by considering what can go wrong, the likelihood of these undesired events, and the resultant consequences. Techniques used in PRA originated in the 1960s. Although there were early exploratory applications to nuclear weapons and other technologies, the first major application of these techniques was in the Reactor Safety Study, WASH-1400, {sup 1} in which the risks of nuclear power accidents were thoroughly investigated for the first time. Recently, these techniques have begun to be adapted to nuclear weapon system applications. This report discusses this application to nuclear weapon systems.

In this paper, we present a new hybrid motion planner than is capable of exploiting previous planning episodes when confronted with new planning problems. Our approach is applicable when several (similar) problems are successively posed for the same static environment, or when the environment changes incrementally between planning episodes. At the heart of our system lie two low-level motion planners: a fast, but incomplete planner (which we call LOCAL), and a computationally costly (possibly resolution) complete planner (which we call GLOBAL). When a new planning problem is presented to our planner, a meta-level planner (which we call MANAGER) decomposes the problem into segments that are amenable to solution by LOCAL. This decomposition is made by exploiting a task graph, in which successful planning episodes have been recorded. In cases where the decomposition fails, GLOBAL is invoked. The key to our planner`s success is a novel representation of solution trajectories, in which segments of collision-free paths are associated with the boundary of nearby obstacles.

Sandia has been studying automatic assembly planning of electromechanical devices for some years, based on an implemented system called Archimedes. Work done to date has focussed on automatic generation of high-level plans, and translation of these plans into robotic control code and workcell layout. More recently, the importance of an assembly planning capability as a design aid has been emphasized, as it could potentially provide early feedback to a designer on the manufacturability of the design. This paper describes the work done on assembly planning to date, plans for extending it, and its applications to agile manufacturing. In particular, we describe an agile manufacturing demonstration project underway at Sandia, and the role the Archimedes assembly planning system will play in it.

Today, 109 nuclear power plants provide over 20 percent of the electrical energy generated in the US The operating license of the first of these plants will expire in the year 2000; one-third of the operating licenses will expire by 2010 and the remaining plant licenses are scheduled to expire by 2033. The National Energy Strategy assumes that 70 percent of these plants will continue to operate beyond their current license expiration to assist in ensuring an adequate, diverse, and environmentally acceptable energy supply for economic growth. In order to preserve this energy resource in the US three major tasks must be successfully completed: establishment of regulations, technical standards, and procedures for the preparation and review of a license renewal application; development, verification, and validation of technical criteria and bases for monitoring, refurbishing, and/or replacing plant equipment; and demonstration of the regulatory process. Since 1985, the US Department of Energy (DOE) has been working with the nuclear industry and the US Nuclear Regulatory Commission (NRC) to establish and demonstrate the option to extend the life of nuclear power plants through the renewal of operating licenses. This paper focuses primarily on DOE`s Plant Lifetime Improvement (PLIM) Program efforts to develop the technical criteria and bases for effective aging management and lifetime improvement for continued operation of nuclear power plants. This paper describes current projects to resolve generic technical issues in the principal areas of reactor pressure vessel (RPV) integrity, fatigue, and environmental qualification (EQ).