Publications

Silicon power diodes, transistors, thyristors and other devices can be damaged by elevated temperatures, temperature cycling, and radiation. In this paper we discuss the vulnerability of devices that integrate bipolar and MOSFET (metal-oxide-semiconductor-field-effect transistor) devices onto a single chip. Such devices offer the advantages of good current carrying capability that is characteristic of bipolar structures and high impedance control nodes that are characteristic of MOSFET devices. Devices located near a space-based fission power source will be subjected to high temperatures, temperature cycling, naturally occurring radiation, radiation from the reactor; and these devices may be subjected to radiation from or caused by weapons used to attack the power source. Damaging radiation includes electrons and protons trapped in naturally occurring radiation belts, electrons pumped into these belts as a result of nuclear explosions, cosmic rays, neutrons from the reactor, and high energy photons (gamma rays and x-rays). 3 refs., 2 figs.

The DOE/Sandia 34-m diameter Vertical-Axis Wind turbine (VAWT) utilizes a step-tapered, multiple-airfoil section blade. One of the airfoil sections is a natural laminar flow profile, the SAND 0018/50, designed specifically for use on VAWTs. The turbine has now been fully operational for more than a year, and extensive turbine aerodynamic performance data have been obtained. This paper reviews the design and fabrication of the rotor blade, with emphasis on the SAND 0018/50 airfoil, and compares the performance measurements to date with the performance predictions. Possible sources of the discrepancies between measured and predicted performance are identified, and plans for additional aerodynamic testing on the turbine are briefly discussed. 12 refs., 10 figs.

The utility of the magnetically insulated transmission line oscillator (MILO) as a high power microwave source depends on how efficiently power can be extracted from it. We have designed a slow-wave stepped transformer for the purpose of axially extracting microwave power from a 3.6 GHz coaxial MILO. The slow-wave transformer design was optimized using particle-in-cell simulation, and tested in experiments performed on the HPM Simulation Division's GEMINI and GYPSY water Blumlein pulse power sources. In this paper we summarize the slow-wave stepped transformer design, and describe MILO axial power extraction experiments which yielded up to 300 MW of radiated power. 10 refs., 4 figs., 2 tabs.

This presentation is a case study of the system that was developed to move data between our mainframe HRIS and the REGISTRAR. It not only contains a description of the system itself but of the factors that come into play in deciding whether to implement a system at all and in deciding what kind of system to implement.

Heavy particle radiation can produce upsets in digital circuits as well as trigger burn out or breakdown in power MOSFETs and MNOS nonvolatile memories. Latch-up may also be stimulated by heavy ions. This report covers work done on the effects of heavy particle radiation on PN junctions, CMOS inverters, CMOS latch, MOSFET and non-volatile memories. 15 refs., 3 figs.

In this study, we explored several ways of extending SP-100 reactor technology to higher power levels. One approach was to use the reference SP-100 pin design and increase the fuel pin length and the number of fuel pins as needed to provide higher capability. The impact on scaling of a modified and advanced SP-100 reactor technology was also explored. Finally, the effect of using alternative power conversion subsystems, with SP-100 reactor technology was investigated. One of the principal concerns for any space-based system is mass; consequently, this study focused on estimating reactor, shield, and total system mass. The RSMASS code (Marshall 1986) was used to estimate reactor and shield mass. Simple algorithms developed at NASA Lewis Research Center were used to estimate the balance of system mass. Power ranges from 100 kWe to 10 MWe were explored assuming both one year and seven years of operation. Thermoelectric, Stirling, Rankine, and Brayton power conversion systems were investigated. The impact on safety, reliability, and other system attributes, caused by extending the technology to higher power levels, was also investigated. 6 refs., 4 figs., 3 tabs.

Outlier samples can have very detrimental effects on the performances of multivariate calibration methods, as these methods are generally not very robust. Often, the software implementations of these methods do not check for outliers. If outliers are not detected, invalid predictions may result. This paper illustrates some simple exploratory procedures for detecting outliers with examples from near-infrared and mid-infrared spectroscopy using partial least-squares regression as the calibration method. 8 refs., 9 figs., 1 tab.

The experiments described here indicate when one of Nature's best fractals -- the Brownian trail -- becomes nonfractal. In most ambient fluids, the trail of a Brownian particle is self-similar over many decades of length. For example, the trail of a submicron particle suspended in an ordinary liquid, recorded at equal time intervals, exhibits apparently discontinuous changes in velocity from macroscopic lengths down to molecular lengths: the trail is a random walk with no velocity memory'' from one step to the next. In ideal Brownian motion, the kinks in the trail persist to infinitesimal time intervals, i.e., it is a curve without tangents. Even in real Brownian motion in a liquid, the time interval must be shortened to {approximately}10{sup {minus}8}s before the velocity appears continuous. In sufficiently rarefied environments, this time resolution at which a Brownian trail is rectified from a curve without tangents to a smoothly varying trajectory is greatly lengthened, making it possible to study the kinetic regime by dynamic light scattering. Our recent experiments with particles in a plasma have demonstrated this capability. In this regime, the particle velocity persists over a finite step length'' allowing an analogy to an ideal gas with Maxwell-Boltzmann velocities; the particle mass could be obtained from equipartition. The crossover from ballistic flight to hydrodynamic diffusion was also seen. 8 refs., 1 fig.

The MELCOR computer code, which has been developed at Sandia National Laboratories for the US Nuclear Regulatory Commission as a tool for calculating realistic estimates of severe accident consequences and source terms, has been used to analyze a series of containment issues for station blackout sequences for the Grand Gulf Nuclear Power Plant. The results indicate that there is a limited time interval in which the drywell atmosphere would be flammable, and that this would only occur if the vacuum breaker were to stick open within a narrow time window. If burning does occur during this time, it appears quite likely that it would not pose a threat to the drywell wall. The main conclusion from this study is that the drywell atmosphere is not very likely to be flammable for a station blackout sequence. 1 ref. (S.J.)

The influence of postweld heat treatment (PWHT) on the structure, mechanical properties and fracture characteristics of pulsed, Nd: YAG laser welds in a Ti-14.8 wt % Al-21.3 wt % Nb titanium aluminide has been investigated. Significant microstructure variations within the fusion zone (FZ) of all heat-treated welds were attributed primarily to the influence of local compositional fluctuations on decomposition of the metastable-{beta} microstructure present in the as-welded FZ. An increase in PWHT temperature promoted a decrease in the maximum FZ hardness and an increase in the longitudinal-weld bend ductility. Correspondingly, the proportion of ductile tearing to cleavage fracture within the FZ increased with an increase in PWHT temperature. 8 refs., 6 figs.

A matched chirp transform (MCT) method for detecting a dispersive electromagnetic pulse is described. The unique feature of this transform is that it gives a distribution of signal amplitude over time rather than frequency, and thereby simplifies signal detection and identification in the case described here. In the MCT method, the incoming signal is matched to a set of signal segments that chirp in accordance with an expected model of the dispersive medium. The performance of the MCT method is compared with that of a standard periodogram method of frequency measurement. 6 refs., 5 figs.

In this paper we have studied the stochasticity of the triple-channel configuration. Further studies on the evolution of the ion-hose instability are under way but incomplete at present. 3 refs., 6 figs.

In previous RADLAC-II beam propagation experiments, stable propagation over a Nordsieck length, in full pressure Albuquerque air (p {approximately}640 Torr) was observed. In these experiments, high transverse momentum resulted in a large equilibrium radius and thus a long betatron wavelength. Following the completion of the RADLAC-II upgrade, a new set of experiments with a small diameter (d {approximately}2 cm), high current (I {approximately}40 kA), low transverse momentum ({beta}{perpendicular} {approximately}0.2) should be possible. The development of time-resolved diagnostics, data analysis codes, and the formulation of output from theoretical calculations in a format as seen by these diagnostics in the lab continues to be a major source of effort in the program. 2 figs.

The final link in the High-Power Microwave (HPM) coupling chain is the distribution of energy on printed-circuit (pc) boards. This distribution is a critical part of the total problem, because the bottom line for damage or upset is what occurs at the component level. Like ports-of-entry (POE's), board coupling paths have their own transfer functions. Since most pc boards are not designed to operate at microwave frequencies, these transfer functions can be very complicated. In addition, active elements on the board are likely to make this part of the problem non-linear. 3 refs., 5 figs.

This paper reports the changes caused by fast neutrons and 200 MeV protons in the electrical properties of high electron mobility transistors (HEMT). A larger gate voltage was required after irradiation with neutron fluences in the 1E14 to 2E15 n/cm{sup 2} range and 200 MeV proton fluences in the 1E14 to 1E15 p/cm{sup 2} range than was required prior to irradiation to obtain the same value of I{sub ds}. The increase in gate voltage required to compensate for a fluence of 1E15 protons/cm{sup 2} was up to four times as great as that required to compensate for the same fluence of neutrons. All devices showed microwave gain (s21) after exposure to 6E14 particles/cm{sup 2} if the gate bias was adjusted to maintain the pre-irradiation value of I{sub ds}. Gamma irradiation at 5E7 rads(GaAs) had no detectable effect on the devices. 8 refs., 6 figs., 1 tab.

Concerns about low-{gamma} relativistic electron beams (REB) being initially injected into the RLA and about energy spreads due to degradation of the accelerating cavity repeating pulse shapes have resulted in our designing a new 4-MV, 20-kA injector, improving the 24-switch trigger system for the ET-2 cavity, and identifying critical factors in the cavity design that affect the pulse shape. We summarize the Metglas inductively isolated, stacked cavity injector design and report on the improvements (completed and proposed) for the ET-2 cavity pulsed power. 7 refs., 6 figs.

Three prototype zinc/bromine batteries were evaluated a Sandia during the last year. The objectives of these tests were to determine performance, cycle life, durability of the auxiliary components, and failure mechanisms. All three were deliverables from a Sandia development contract with Energy Research Corporation (ERC). The test results were communicated to ERC along with suggestions for improving battery design and reliability. 3 figs., 2 tabs.

Zinc/bromine flow batteries are being developed for vehicular and utility load leveling applications by Johnson Controls Co. and Energy Research Corp. under DOE sponsorship. Problems that have been encountered with the zinc/bromine battery are loss of coulombic efficiency brought about by permeation of bromine through the separator and limited life caused by attack of the bromine-containing electrolyte on plastic parts, particularly the flow frame. In this paper, we show that large decreases in the bromine transport rates through microporous separators can be achieved with only a minimal loss of conductivity and identify a chemically stable replacement for PVC, a flowframe material. 4 figs., 1 tab.

The working group on electrical breakdown in vacuum was charged with considering all possible mechanisms by which electrical breakdown might occur either through the vacuum or along insulator bushings in large area electron beam emitter assemblies. It was understood that present systems need to be scaled up, by an order of magnitude or more in both beam area and total energy, to meet demands for higher power and larger size machines, and that increases in the e-beam current density and transport efficiency are also sought. A consideration of the consequences of such a scale-up was pertinent to many of the topics listed in the working-group agenda. Our group attempted to address each of these topics. 18 refs.

Whenever a new elastomer is formulated or an old formulation is modified, it is important to estimate the material's anticipated lifetime in various use environments. For extended lifetimes (years) this often requires the application of accelerated aging techniques which typically involve the modelling of results obtained at higher-than-ambient environmental stress levels. For many practical applications of elastomers, air is present during environmental exposures -- this usually implies that important oxidation effects underly the degradation of the material. Unfortunately, exposure of elastomers to air during aging often results in inhomogeneously oxidized samples, a complication which impacts attempts both to understand the oxidation process and to extrapolate accelerated exposures to long-term conditions. As has been clear for many years, in order to confidently extrapolate shorter-term accelerated simulations to long-term, air-aging conditions, one must be able to monitor and quantitatively understand diffusion-limited oxidation effects. In this review we will highlight some of the recent developments in both experimental techniques and theoretical modelling of relevance to this goal. 28 refs., 12 figs.

The discrete ordinates (S{sub N}) method, first developed for stellar atmospheres, has been used extensively on various other radiation transport problems. In reactor analysis the method is generally used to generate parameters for design models based on more approximate but less expensive methods (such as diffusion theory) so that the spatial-spectrum coupling is represented accurately on a microscopic reaction rate level. It has a decisive advantage over Monte Carlo methods in computing the pin and assembly power profiles. In shielding problems where the penetration of the radiation can be deep, the method is used widely in design calculations. In oil-well logging problems which also involve deep penetration and have a stringent accuracy requirement on the detector responses, the method complements the Monte Carlo techniques. Recently, the discrete ordinates method with appropriate cross sections has been used in coupled photon-electron transport problems. In this paper the basic method is briefly reviewed, its applications illustrated, its merits and pitfalls discussed, and the recent advances in the attendant numerical techniques which have enhanced the capabilities of the method are enumerated. 28 refs., 1 fig.

During severe light water reactor accidents like Three-Mile Island (TMI-2), the reactor core can suffer considerable damage. Of interest here are melt progression, oxidation and gas phase natural convection in the reactor core after the fuel rods suffer a significant loss of geometry. This study describes a two-dimensional porous medium model that considers the motion of three fields: vapor, melt, and solid. A base case solution is described and the effects of oxidation, melt relocation, and Fe-Zr interactions are discussed. 16 refs., 7 figs.

Materials Control techniques are utilized to provide assurance that nuclear materials are being handled properly. In the event that materials are improperly handled or potentially malevolent activities utilizing nuclear materials are initiated, the materials control approach should provide a real-time indication to allow a rapid mitigating response. The appropriate response can range from correcting an inadvertent error to preventing an intentional insider-perpetrated incident. This paper is directed at the use of materials control techniques to deter and detect insider malevolence. 1 fig.

A two-part polyurethane foam has been tested in the laboratory and in the field to assess its utility in controlling lost circulation encountered when drilling geothermal wells. A field test was conducted in The Geysers in January, 1988, to evaluate the chemical formulation and downhole tool used to deploy the chemicals. Although the tool apparently functioned properly in the field test, the chemicals failed to expand sufficiently downhole, instead forming a dense polymer that may be ineffective in sealing loss zones. Subsequent laboratory tests conducted under simulated downhole conditions indicate that the foam chemical undergo sever mixing with water in the wellbore, which disturbs the kinetics of the chemical reaction more than was previously contemplated. The results indicate that without significant changes in the foam chemical formulation or delivery technique, the foam system will be ineffective in lost circulation control except under very favorable conditions. 4 refs., 6 figs., 2 tabs.

Results of fixed-bed hydropyrolysis and low temperature hydrogenation tests with a selection of coals and dispersed catalysts are described. Tar yields greater than 60% have been achieved in hydropyrolysis using sulphided molybdenum (Mo) with Mo concentrations as low as 0.1% daf coal for a number of bituminous coals. The hydrogenation tests indicated that the threshold temperature with these catalysts for oil generation from bituminous coals is 350{degree}C. 16 refs., 2 figs., 2 tabs.

We have developed a fast parallel version of an existing synthetic aperture radar (SAR) simulation program, SRIM. On a 1024-processor NCUBE hypercube it runs an order of magnitude faster than on a CRAY X-MP or CRAY Y-MP processor. This speed advantage is coupled with an order of magnitude advantage in machine acquisition cost. SRIM is a somewhat large (30,000 lines of Fortran 77) program designed for uniprocessors; its restructuring for hypercube provides new lessons in the task of altering older serial programs to run well on modern parallel architectures. We describe the techniques used for parallelization, and the performance obtained. Several novel parallel approaches to problems of task distribution, and direct output were required. These techniques increase performance and appear to have general applicability for massive parallelism. We describe the hierarchy necessary to dynamically manage (i.e., load balance) a large ensemble. The ensemble is used in a heterogeneous manner, with different programs on different parts of the hypercube. The heterogeneous approach takes advantage of the independent instruction streams possible on MIMD machines. 18 refs., 7 figs., 4 tabs.

The Buckshot code is a gridless particle simulation code which is used extensively at Sandia to study relativistic electron beam propagation in the ion-focused regime. The present version of the code evaluates the force on a particle by summing over all the other particles, thus the execution time is proportional to N{sup 2} where N is the number of simulation particles. A new gridless field solver has been developed with time scaling of N log N and the breakeven point between the old and new code is around N = 64 on the Cray X-MP computer. For N = 1000, the new solver is about nine times faster than the old version. The new solver is based on a solution of the two-dimensional Poisson equation which if Fourier decomposed in the azimuthal direction and the solution of the radial equation is represented by integrals over the charge density. These integrals are then replaced by sums over the simulation particles which are assumed to be point particles. The near-field singularity is removed by the Fourier decomposition so long as the number of Fourier modes is much less than the number of simulation particles. The algorithm is written in such a way that the field due to a given species is Fourier decomposed with respect to the center of mass of that species, thus it is possible to study linear and nonlinear ion hose physics with a very small number of azimuthal modes. Typically M = 2 is found to be sufficient for most IFR problems. The old and new solvers have been compared and the agreement is excellent. 2 refs., 3 figs.

It has been shown that a constant axial magnetic field does not affect the growth rate of the ion hose instability. However, if the field is allowed to vary in time, on the ion motion time scale, it is expected that particle orbits will be affected in a way that will result in a time varying beam wavelength. This can lead to detuning of the instability. Results of the rigid model with a time varying field of strength similar to the channel strength, show a significant decrease in the growth of the instability. Also, simulations using the BUCKSHOT code confirm the small effect of a steady magnetic field on hose growth and show a significant decrease in growth with a time varying field. 3 figs.

Sandia National Laboratories (SNL) has been involved in the evaluation of the sodium/sulfur technology for several years. Until recently, the effort concentrated on the performance of single cells. Recently, the evaluation of 4-cell string was initiated. The majority of the activity during the past two years has focused on cells from Chloride Silent Power, Limited (CSPL). To date, four groups of PB cells and 4-cell strings, which consisted of PB cells, have been evaluated. The first group of ten cells delivered to Sandia were on test for approximately one year. The majority of these cells failed due to corrosion problems in the sulfur seal. However, two cells completed over 800 cycles, and one of these cells completed nearly 1600 cycles. 4 figs., 1 tab.

A high detectivity infrared photodiode was constructed using an InAs{sub 0.15}Sb{sub 0.85}/InSb strained-layer superlattice (SLS). The surface passivated device exhibited detectivities {ge} 1 {times} 10{sup 10} cm{radical}Hz/W at wavelengths {le} 10 {mu}m. This device demonstrates the feasibility of a long wavelength, photovoltaic infrared detector technology based on InAsSb SLSs. 8 refs., 4 figs.

The Borehole Directional Radar System is a high-power, high- resolution tool that is being developed to locate lithologic layers of fractures away from a wellbore. The prototype is a 50-kW peak- power pulsed directional radar system that determines fracture location by transmitting powerful radar pulses, 8 nanoseconds in length, in a known direction from a borehole. The frequency spectrum of the pulses ranges up to the VHF band, which is between 30 and 300 MHz. The transmitter and receiver rotate in place, permitting the tool to scan for fractures in all directions from the borehole. Because discontinuities in the rock interrupt and reflect radar signals, signals that return to the tool's receiving antenna indicate fractures. The distance of the fracture from the borehole is determined by the time delay of the return signal. The radio frequency signal is sampled and transmitted to the surface by wireline at audio frequencies, and then reconstructed at the surface using a personal computer. The key to the tool's potential is its ability to accurately measure distance and direction of a lithologic discontinuity underground. This paper presents field test results that show the capabilities of the tool for locating lithological discontinuities up to 10.5 m (34.5 ft) away from a wellbore. Unique features of the system are discussed. Potential applications of the system are described, such as locating gas and oil reservoirs below a salt dome and possibly detecting a blow-out well with or without casing. 10 refs., 8 figs.

An empirical scaling relationship between the mean electric field and the breakdown time has been found. Many divergent sets of data were used from breakdown experiments on power lines, laser-triggered switches, trigatrons, e-beam triggered gaps, sharp-point electrode to plane gaps, and uniform field gaps. This relationship builds on the Felsenthal and Proud data and extends their breakdown time delay (formative time) data by three orders of magnitude and into the region of interest for triggered gas switching. The data indicates that electrically triggered gaps, laser-triggered gaps, and untriggered gaps are governed by the same time-delay processes. Predictions can be made of trigger gap geometry, trigger delays, and trigger polarity effects. Breakdown delays of sub-centimeter-long to at least 8-meter-long gaps in air with either high or low field-enhanced electrodes are described by this equation. In addition, this relationship appears to be valid for a variety of gases and even accurately predicts the breakdown delay of mixtures of air and SF/sub 6/. 13 refs., 12 figs., 1 tab.

Recovery of impact loaded samples is extremely difficult owing to the highly destructive post-shock environment. A variety of techniques have been introduced to accomplish this task for both organic and inorganic samples. The design principles underlying these techniques and the practical limitations encountered in applications are described. 3 figs.

Over the past several decades, many researchers have contributed to present understanding of the flashover of electrically stressed insulators in vacuum, and a wealth of theories have been proposed to explain the many surprising attributes of this complex breakdown mechanism. Surface flashover appears to comprise at least two distinct phenomena which can be distinguished as being cathode-initiated or anode-initiated, with the former having received by far the most attention. Several models describing cathode-initiated flashover have been built on the pioneering work of Boersch and coworkers, published in 1963, and credit the breakdown mechanism to the action of an intense secondary-electron-emission avalanche on the insulator surface. Other researchers consider the electron avalanche to be only partially, if at all, responsible, and invoke various hot-carrier effects in the insulator bulk, the surface interfacial region, or in a layer of gas adsorbed on the insulator surface. Anode-initiated flashover, which contends with the cathode-initiated variety for the breakdown of insulators of conventional design, is thought to involve bulk breakdown in a way related to treeing failure. In spite of the considerable effort applied to understanding vacuum surface flashover, no single theory appears capable of explaining all the data, and new and often unexpected observations continue to be made. 42 refs., 6 figs.

The need for ever-increasing miniaturization of airborne instrumentation through the use of surface mounted components closely placed on printed circuit boards highlights problems with traditional board cleaning methods. The reliability of assemblies which have been cleaned with vapor degreasing and spray cleaning can be seriously compromised by residual contaminants leading to solder joint failure, board corrosion, and even electrical failure of the mounted parts. In addition, recent government actions to eliminate fully halogenated chlorofluorocarbons (CFC) and chlorinated hydrocarbons from the industrial environment require the development of new cleaning materials and techniques. This paper will discuss alternative cleaning materials and techniques and results that can be expected with them. Particular emphasis will be placed on problems related to surface-mounted parts. These new techniques may lead to improved circuit reliability and, at the same time, be less expensive and less environmentally hazardous than the traditional systems. 5 refs.

The Recirculating Linear Accelerator (RLA) uses ion-focusing to provide the radial confinement of the beam. At the ends of the ion- channel racetrack, a ramped vertical magnetic field will be required to keep the beam in the channel. A sector field, whose strength increases with distance from the channel axis, has been proposed to provide an energy bandwidth for the transport system. This manuscript reports on design studies for coil systems that produce the required fields. It also describes particle simulations in the combined IFR-B-field transport system to address the issues of energy bandwidth and emittance growth. 4 refs., 6 figs.

Are single event upsets an important vulnerability or lethality issue for strategic systems Neutron-induced single events have become a part of the vulnerability analysis for nuclear weapon environments, but there has been no serious consideration of proton-induced single events from neutron particle beam environments. Is this appropriate This paper examines this concept.

As a result of the popularity of using HyperCard to rapidly prototype equipment and computer interfaces on Macintosh personal computers, the need ensued to evaluate prototype usability by collecting subjects' interactive performance data in real-time. Sandia National Laboratories, in collaboration with Stone Design Software, has developed ProtoTymer, a HyperCard stack that can time and record users' interactive sessions with prototypes developed using HyperCard. While operating in the background, ProtoTymer records the times, locations, and targets (objects clicked) of a subject's inputs during an interactive session. At the conclusion of the session, the resultant data file can be reviewed, summarized, printed, or transferred to a spreadsheet for statistical or graphical analysis. This paper describes ProtoTymer's design approach, features, limitations, and considerations for future versions. 2 refs., 4 figs.

TORE SUPRA is a fairly large supra conducting Tokamak (R = 2.350 m and r = 0.800 m) and has an original goal to withstand a large power removal (25 MW) during a 30 second long pulse. The monitoring of the plasma density and of the particle balance will be partially controlled by the pump limiter system. Depending on the amount of convected plasma power on these limiter and of the upgrading of the total injected power, the limiters are designed to remove in excess of 8 MW at steady state. 3 refs., 4 figs.

We compare the hydrogen assisted cracking resistance of wrought PH 13-8 Mo stainless steel alloyed with 0.4 to 1.0 wt.% palladium to the conventional alloy when aged to yield strengths of 1170--1250 MPa. Pd is found both in solid solution in the martensitic phase and also in the form of randomly distributed, incoherent PdAl precipitates in the modified alloy. Interfacial segregation of Pd to grain boundaries and lath boundaries is not observed. Intergranular hydrogen cracking is suppressed with Pd in slow strain rate tests conducted during electrochemical hydrogen charging of precharged samples. Hydrogen permeation analyses indicate that hydrogen ingress is not inhibited by Pd but that bulk diffusion rates are lowered relative to the conventional alloy. These results are consistent with the creation of a strong hydrogen trap, most likely the uniformly distributed PdAl phase, which lowers the levels of interfacially segregated hydrogen. 15 refs.

From an interplay between theory based on the effective-medium scheme and experiments, an extremely simple picture has evolved which is capable of describing a vast number of experimental quantities related to interaction of hydrogen with metals, especially the trapping of hydrogen at defects. It is shown that the trap strengths are determined mainly by the interstitial electron density, and any open structures in the lattice leads to a trap, with the vacancies and voids being the strongest traps. It is also found theoretically and experimentally that up to six hydrogen atoms can be accommodated in a vacancy, and the change in trap strengths with occupancy has been determined. Recent results for the trapping of deuterium to defects in Pd are discussed. 29 refs., 5 figs.

Recent experimental works on the effect of dose rate on the total dose failure threshold of MOS devices have shown that the failure level is strategic environments may be less than the failure level measured in the laboratory by a factor of 3 to 10. This difference in dose rate response raises concerns about using laboratory sources to predict the radiation hardness in strategic environments. A solution to the problem of determining the total dose hardness of piece parts is to perform lot acceptance testing at relevant dose rates such that the time dependent effects can be directly observed. A low cost method of measuring the total dose hardness of piece parts in the laboratory at requisite dose rates is presented. 11 refs., 5 figs.

The propulsion working fluid for the containment closure used at the Nevada Test Site consists of a mixture of a driver gas and the hot detonation products from the shaped charge that cuts the wall of the storage vessel. Nitrogen had always been used as the driver gas. However, helium gas, because of its superior propulsion characteristics, has enabled us to design considerably heavier and stronger gates. Operational times can be equal to or less than operational times when nitrogen gas was used. Assume, maintaining the same functional time, that an appreciably stronger steel/aluminum composite gate is designed and developed. The gate consists of two 3/4-in.-thick, high-strength 4340 circular steel plates imbedded in the two sides of the 7075-T73 aluminum forging. Mechanical circular keys are used to ensure the effective transfer of horizontal shear loads from aluminum to steel. Three point bending experiments on small composite beams were conducted to determine the effectiveness of the mechanical keying system. Also explored was structural adhesive used as a bonding and shear transfer mechanism. 4 refs., 8 figs., 1 tab.

The Seismic Verification Program at Sandia focuses on designing and building seismic monitoring systems which could be deployed within the Soviet Union. To support this effort, Sandia also is involved in developing and testing seismic components, and in evaluating system performance and new monitoring techniques. Seismic studies conducted under the latter task concentrate on analyzing regional seismic signals, recorded within 2000 km of the source. In-country monitoring stations would be able to exploit these regional signals to improve on the capabilities of external stations at teleseismic ranges. The principal advantages which regional signals offer are greater amplitudes and broader frequency bands. However, such signals are more complex and less well understood than teleseismic records. Ongoing studies at Sandia will help define the performance which can be expected from an in-country network. Other studies are testing new monitoring concepts which may further improve in-country capabilities. This presentation gives a brief overview of some of these projects.

Two important areas of hydrogen combustion with uncertainties are identified: (1) high-temperature combustion and (2) flame acceleration and deflagration-to-detonation transition (DDT). The uncertainties associated with high-temperature combustion may affect phenomena in a least four different accident scenarios: the in-cavity oxidation of combustible gases produced by core-concrete interactions, the combustion of hydrogen following high pressure melt ejection, the possibility of local detonations, and combustion in the BWR Mark I and Mark II secondary containments. The uncertainty in the area of DDT has increased importance due to recent experimental results that show that the detonability limit is nominally at or near the flammability limit for some mixture conditions. How these uncertainties may affect various accident scenarios is discussed and recommendations are made to reduce these uncertainties. 35 refs., 8 figs., 2 tabs.

In this work high frequency SPICE models were developed to simulate the hysteresis and saturation effects of toroidal shaped ferrite core inductors and transformers. The models include the nonlinear, multi-valued B-H characteristic of the core material, leakage flux, stray capacitances, and core losses. The saturation effects were modeled using two diode clamping arrangements in conjunction with nonlinear dependent sources. Two possible controlling schemes were developed for the saturation switch. One of the arrangements used the current flowing through a series RC branch to control the switch, while the other used a NAND gate. The NAND gate implementation of the switch proved to be simpler and the parameters associated with it were easier to determine from the measurements and the B-H characteristics of the material. Lumped parameters were used to simulate the parasitic effects. Techniques for measuring these parasitic are described. The models were verified using manganese-zinc ferrite-type toroidal cores and they have general applicability to all circuit analysis codes equivalent function blocks such as multipliers, adders, and logic components. 7 refs., 22 figs.

Knowledge of coal molecular structure is important in the understanding of coal reactivity. Computer-aided Molecular Design (CAMD) has been used to create and study three-dimensional models of several postulated coal structures (Given, Wiser, Solomon, and Shinn). Using molecular dynamics calculations, the minimum-energy conformations for each structural model have been compared. The physical densities of the minimum-energy conformations have been calculated, and are in agreement with experimental evidence. The frequencies of cross-linking hydrogen bonds have been evaluated for these structures. Finally, we have also begun to use CAMD to study model polymeric compounds, whose structure and reactivity may give new insights into coal conversion processes. 15 refs., 5 figs., 2 tabs.

Transient burning of TiH/sub X//KClO/sub 4/ in a closed system is formulated including the effect of condensed species. Thermodynamic properties are evaluated using both BLAKE and TIGER computer codes. Three different equations of state for gaseous species are used and their effect on the burning rate is evaluated. For more accurate transient burning analysis, a pressure dependent covolume for gaseous species is generated. The effect of pressure dependent covolume as well as the condensed species on transient burning is evaluated. Both parameters are found to be important when the burning rate at high loading densities in a closed system is considered. At high loading densities, condensed species become important not only because of the their effect on thermodynamic properties but also due to the volume occupied by these species. 11 refs., 2 figs., 2 tabs.

The influence of coal structure on primary conversions and oil yields in thermolytic extraction with different H-donor and non-H-donor solvents and in dry catalytic hydrogenation has been investigated. Pre-soaking of coal/H-donor solvent slurries at 250/degree/C increased conversions and the level of hydrogen transfer at short contact times (SCT, /le/ 10 min) with 9,10-dihydrophenanthrene demonstrating the importance of solvent accessibility. However, contrary to other studies, prior removal of THF-extractable material (mobile phase) from one bituminous coal actually gave rise to higher conversions to pyridine - solubles for non-donor polynuclear aromatic compounds (PAC), such as naphthalene, phenanthrene and pyrene. These findings highlight the difficulties in relating primary conversions to coal characteristics. In contrast, oil yields have been found to broadly increase with decreasing rank on both H-donor solvent extraction with a process solvent and dry catalytic hydrogenation. However, in SCT tetralin extraction where poor physical contact between coal and solvent exists, neither total conversion nor oil yield correlated with rank. 27 refs., 6 figs., 4 tabs.

After a decade of photovoltaic system research, most system related issues have been successfully resolved. Current system research activities are now oriented toward maintaining and updating the comprehensive database on system performance established by previous research efforts, integrating new components into system designs, and transferring the accumulated information to industry and users of the technology. This paper presents a brief overview of the status of system research in the United States, emphasizing three key activities - field evaluation, balance-of-system hardware development, and technology transfer. 5 refs., 2 tabs.