Publications

Aerodynamic force and moment measurements and flow visualization results are presented for a hypersonic vehicle configuration at Mach 8. The basic vehicle configuration is a spherically blunted 10{degree} half-angle cone with a slice parallel with the axis of the vehicle. On the slice portion of the vehicle, a flap could be attached so that deflection angles of 10{degree}, 20{degree} and 30{degree} could be obtained. All of the experimental results were obtained in the Sandia Mach 8 hypersonic wind tunnel for laminar boundary layer conditions. Flow visualization results include shear stress sensitive liquid crystal photographs, surface streak flow photographs (using liquid crystals), and spark schlieren photographs and video. The liquid crystals were used as an aid in verifying that a laminar boundary layer existed over the entire body. The surface flow photo-graphs show attached and separated flow on both the leeside of the vehicle and near the flap. A detailed uncertainty analysis was conducted to estimate the contributors to body force and moment measurement uncertainty. Comparisons are made with computational results to evaluate both the experimental and numerical results. This extensive set of high-quality experimental force and moment measurements is recommended for use in the calibration and validation of relevant computational aerodynamics codes.

Contact resistances of greater than 40 milliohms have been associated with hermetic connectors and lightning arrestor connectors (LAC) during routine testing. Empirical analysis demonstrated that the platings could be damaged within several mating cycles. The oxides that formed upon the exposed copper alloy had no significant impact upon contact resistance when the mated contacts were stationary, but effectively disrupted continuity when the mating interfaces were translated. The stiffness of the pin contact was determined to be about five times greater than the socket contact. As the pin contact engages the socket, therefore, the socket spring member deflects and the pin does not deflect. Hence, the pin contact could easily remain centered within the socket cavity in a mated condition, contacting the hemispherical spring at a localized point. Thus the only avenue for electrical conduction is between two contacting curved surfaces-the pin surface and the socket contact dimple surface. This scenario, coupled with the presence of corrosion products at the contacting interface, presents the opportunity for high contact resistances.

The author reports experimental measurements for the argon and oxygen permeability coefficients for the new EPDM material (SR793B-80) used for the environmental o-ring seals of the W88. The results allow the author to refine the argon gas analysis modeling predictions for W88 surveillance units. By comparing early surveillance results (up to four years in the field) with the modeling, the author shows that (1) up to this point in time, leakage past the seals is insignificant and (2) the argon approach should be able to inexpensively and easily monitor both integrated lifetime water leakage and the onset of any aging problems. Finally, the author provides a number of pieces of evidence indicating that aging of the SR793B-80 material will not be significant during the expected lifetime of the W88.

The image blur in a photograph is produced by the exposure of a moving object. Knowing the amount of image blur is important for recording useful data. If there is too much blur, it becomes hard to make quantitative measurements. This report discusses image blur, the parameters used to control it, and how to calculate it.

This report summarizes the purchasing and transportation activities of the Purchasing and Materials Management Organization for Fiscal Year 1992. Activities for both the New Mexico and California locations are included. Topics covered in this report include highlights for fiscal year 1992, personnel, procurements (small business procurements, disadvantaged business procurements, woman-owned business procurements, New Mexico commercial business procurements, Bay area commercial business procurements), commitments by states and foreign countries, and transportation activities. Also listed are the twenty-five commercial contractors receiving the largest dollar commitments, commercial contractors receiving commitments of $1,000 or more, integrated contractor and federal agency commitments of $1,000 or more from Sandia National Laboratories/New Mexico and California, and transportation commitments of $1,000 or more from Sandia National Laboratories/New Mexico and California.

This document is the Operations Manual for the Beneficial Uses Shipping System (BUSS) cask. These operating instructions address requirements; for loading, shipping, and unloading, supplementing general operational information found in the BUSS Safety Analysis Report for Packaging (SARP), SAND 83-0698. Use of the BUSS cask is authorized by Department of Energy (DOE) and Nuclear Regulatory Commission (NRC) for the shipment of special form cesium chloride or strontium flouride capsules.

Two separate Tiger Team assessments were conducted at Sandia National Laboratories (SNL). The first was conducted at the California site in Livermore between April 30, 1990, and May 18, 1990. A second Tiger Team assessment was conducted at the New Mexico site in Albuquerque between April 15 and May 24, 1991. This report is volume two, change one. One purpose of this Action Plan is to provide a formal written response to each of the findings and/or concerns cited in the SNL Tiger Team assessment reports. A second purpose is to present actions planned to be conducted to eliminate deficiencies identified by the Tiger Teams. A third purpose is to consolidate (group) related findings and to identify priorities assigned to the planned actions for improved efficiency and enhanced management of the tasks. A fourth and final purpose is to merge the two original SNL Action Plans for the New Mexico [Ref. a] and California [Ref. b] sites into a single Action Plan as a major step toward managing all SNL ES&H activities more similarly. Included in this combined SNL Action Plan are descriptions of the actions to be taken by SNL to liminate all problems identified in the Tiger Teams` findings/concerns, as well as estimated costs and schedules for planned actions.

Environmental monitoring, earth-resource mapping, and military systems require broad-area imaging at high resolutions. Many times the imagery must be acquired in inclement weather or during night as well as day. Synthetic aperture radar (SAR) provides such a capability. SAR systems take advantage of the long-range propagation characteristics of radar signals and the complex information processing capability of modern digital electronics to provide high resolution imagery. SAR complements photographic and other optical imaging capabilities because of the minimum constrains on time-of-day and atmospheric conditions and because of the unique responses of terrain and cultural targets to radar frequencies. Interferometry is a method for generating a three-dimensional image of terrain. The height projection is obtained by acquiring two SAR images from two slightly differing locations. It is different from the common method of stereoscopic imaging for topography. The latter relies on differing geometric projections for triangulation to define the surface geometry whereas interferometry relies on differences in radar propagation times between the two SAR locations. This paper presents the capabilities of SAR, explains how SAR works, describes a few SAR applications, provides an overview of SAR development at Sandia, and briefly describes the motion compensation subsystem.

Given a planar straight-line graph, we find a covering triangulation whose maximum angle is as small as possible. A covering triangulation is a triangulation whose vertex set contains the input vertex set and whose edge set contains the input edge set. Such a triangulation differs from the usual Steiner triangulation in that we may not add a Steiner vertex on any input edge. Covering triangulations provide a convenient method for triangulating multiple regions sharing a common boundary, as each region can be triangulated independently. As it is possible that no finite covering triangulation is optimal in terms of its maximum angle, we propose an approximation algorithm. Our algorithm produces a covering triangulation whose maximum angle {gamma} is probably close to {gamma}{sub opt}, a lower bound on the maximum angle in any covering triangulation of the input graph. Note that we must have {gamma} {le} 3{gamma}{sub opt}, since we always have {gamma}{sub opt} {ge} {pi}/3 and no triangulation can contain an angle of size greater than {pi}. We prove something significantly stronger. We show that {pi} {minus} {gamma} {ge} ({pi} {minus} {gamma}{sub opt})/6, i.e., our {gamma} is not much closer to {pi} than is {gamma}{sub opt}. This result represents the first nontrivial bound on a covering triangulation`s maximum angle. We require a subroutine for the following problem: Given a polygon with holes, find a Steiner triangulation whose maximum angle is bounded away from {pi}. No angle larger than 8{pi}/9 is sufficient for the bound on {gamma} claimed above. The number of Steiner vertices added by our algorithm and its running time are highly dependent on the corresponding bounds for the subroutine. Given an n-vertex planar straight-line graph, we require O(n + S(n)) Steiner vertices and O(n log n + T(n)) time, where S(n) is the number of Steiner vertices added by the subroutine and T(n) is its running time for an O(n)-vertex polygon with holes.

We have previously shown that charge carriers are generated by exciton-exciton annihilation in solid films of poly(di-n-hexylsilane). Using this phenomenon we show that the exciton-exciton annihilation rate constant γ at ambient temperature is not a function of the photon energy used to create the excitons even at energies well out into the long wavelength tail of the exciton absorption band. We also show that the excitons remain highly mobile throughout their 600 ps lifetime and that they diffuse distance comparable to the crystallite size in the film. The value of γ obtained in these studies is in excellent agreement with that obtained previously in fluorescence intensity studies. © 1993.

One proven method of evading the detection of a nuclear test is to decouple the explosion with a large air-filled cavity. Past tests have shown it is possible to substantially reduce the seismic energy emanating from a nuclear explosion by as much as two, orders of magnitude. The problem is not whether it can be done; the problem is the expense involved in mining a large cavity to fully decouple any reasonable size test. It has been suggested that partial decoupling may exist so some fraction of decoupling may be attained between factors of 1 to 100. MISTY ECHO and MINERAL QUARRY are two nuclear tests which were instrumented to look at this concept. MISTY ECHO was a nuclear explosion conducted in an 11 m hemispherical cavity such that the walls were over driven and reacted in a non-linear manner. MINERAL QUARRY was a nearby tamped event that is used as a reference to compare with MISTY ECHO. The scaled cavity radius of MISTY ECHO was greater than 2m/kt[sup l/3]. Both of these tests had free-field accelerometers located within 400 m of their respective sources. Analysis of surface ground motion is inconclusive on the question of partial decoupling. This is due to the difference in medium properties that the ray paths take to the surface. The free-field configuration alleviates this concern. The analysis consists of cube-root signal MINERAL QUARRYs signal to MISTY ECHO's yield and calculating the ratio of the Fourier amplitudes of both the acceleration and the reduced displacement potentials. The results do not indicate the presence of partial decoupling. In fact, there is a coupling enhancement factor of 2.

Hazardous operations which involve the dextrous manipulation of dangerous materials in the field have, in the past, been completed by technicians. Use of humans in such hazardous operations is under increased scrutiny due to high costs and low productivity associated with providing protective clothing and environments. Remote systems are needed to accomplish many tasks such as the clean up of waste sites in which the exposure of personnel to radiation, chemical, explosive, and other hazardous constituents is unacceptable. Traditional remote manual field operations have, unfortunately, proven to have very low productivity when compared with unencumbered human operators. Recent advances in the integration of wars and computing into the control of remotely operated equipment have shown great promise for reducing the cost of remote systems while providing faster and safer remote systems. This paper discusses applications of such advances to remote field operations.

Multiple tracer techniques were used to estimate recharge rates through unsaturated alluvium beneath the Greater Confinement Disposal site, a waste disposal site located in Frenchman Flat, on the Nevada Test Site. Three tracers of soil water movement -- meteoric chloride, stable isotopes of water, and cosmogenic chlorine-36 -- yielded consistent results indicating that recharge rates were negligible for the purpose of performance assessment at the site.

This report describes work performed for the development of a fiber-optic shock position sensor used to measure the location of a shock front in the neighborhood of a nuclear explosion. Such a measurement would provide a hydrodynamic determination of nuclear yield. The original proposal was prompted by the Defense Nuclear Agency`s interest in replacing as many electrical sensors as possible with their optical counterparts for the verification of a treaty limiting the yield of a nuclear device used in underground testing. Immunity to electromagnetic pulse is the reason for the agency`s interest; unlike electrical sensors and their associated cabling, fiber-optic systems do not transmit to the outside world noise pulses from the device containing secret information.

This paper describes the connection between mechanical degradation of common cable materials in radiation and elevated temperature environments and density increases caused by the oxidation which leads to this degradation. Two techniques based on density changes are suggested as potential non-destructive evaluation (NDE) procedures which may be applicable to monitoring the mechanical condition of cable materials in power plant environments. The first technique is direct measurement of density changes, via a density gradient column, using small shavings removed from the surface of cable jackets at selected locations. The second technique is computed X-ray tomography, utilizing a portable scanning device.

We technologists generally only address risk magnitudes in our analyses, although other studies have found nineteen additional dimensions for the way the public perceives risk. These include controllability, voluntariness, catastrophic potential, and trust in the institution putting forth the risk. We and the geneml public use two different languages, and to understand what their concerns are, we need to realize that the culture surrounding nuclear weapons is completely alien to the general public. Ultimately, the acceptability of a risk is a values question, not a technical question. For most of the risk dimensions, the public would perceive no significant difference between using oralloy and plutonium. This does not mean that the suggested design change should not be proposed, only that the case for, or against, it be made comprehensively using the best information available today. The world has changed: the ending of the cold war has decreased the benefit of nuclear weapons in the minds of the public and the specter of Chernobyl has increased the perceived risks of processes that use radioactive materials. Our analyses need to incorporate the lessons pertinent to this newer world.

This is the final report for a study performed for the 1992 LDRD spaceborne SAR (Synthetic Aperture Radar) study. This report presents an overview of some of the issues that must be considered for design and implementation of a SAR on a spaceborne platform. The issues addressed in this report include: a survey of past, present, and future spaceborne SARs; pulse-repetition frequency (PRF); general image processing issues; transmitter power requirements; the ionosphere; antennas; two case studies; and an appendix with a simplified presentation on geometry and orbits.

Damage induced during electron-beam metallization results in a three-order-of-magnitude increase in the generation rate of bulk GaAs. The damage appears to be radiation induced, with low-energy electrons being the most likely from p{sup +}-i-n-i-p{sup +}-GaAs layers damaging mechanism.

This report describes the design, development, manufacturing processes, acceptance equipment, test results, and conclusions for the SA3581/MC4196 LAC program. Four development groups (Identified as Groups 1 through 3 and a Proof of Development Build) provided the evaluation criteria for the PPI/TMS production units.

An ever increasing demand for highly rugged, miniature AT strip resonators prompted the development of a resonator package for use in high-g shock applications. This package, designed and developed by Statek Corporation, is based on the package configuration currently being used by Statek for commercial devices. This report describes the design intent, component characteristics, and evaluation test results for this device.

A temperature between 400 and 500 and a pressure between 40 MPa and 160 MPa were indicated by a two-factor, three-level factorial experiment for diffusion bonding of molybdenum sheet substrates. These substrates were sputter ion plated with palladium (0.5 {mu}m) and silver (10 {mu}m) films on the mating surfaces, with the silver used as a bonding interlayer. The palladium acted as an adhesive layer between the silver film and molybdenum substrate. The silver diffusion bonds that resulted were qualitatively characterized at the interfacial regions, and bonds with no visible interface were obtained at 750OX magnification. Correlations were obtained for voids found optically at the silver/silver bonding interface and colored image maps, illustrating bond quality, produced by nondestructive ultrasonic imaging. Above 160 MPa, the bonding process produces samples with a nonuniform load distribution. These samples contained regions with gaps and well-bonded regions at the silver/silver interface, and all had macroscopic deformation of the silver films.

Salford Electrical Instruments, Ltd., and the General Electric Company`s Hirst Research Centre, under contract to the United Kingdom`s (UK) Ministry of Defence, developed a radiation-hard, leadless chip-carrier-packaged oscillator/divider. Two preproduction clocks brought to Sandia National Laboratories (SNL) by a potential SNL customer underwent mechanical and thermal environmental evaluation. Because of the subsequent failure of one device and the deteriorating condition of another device, the devices were not subjected to radiation tests. This report describes the specifics of the environmental evaluation performed on these two clocks and the postmortem analysis of one unit, which ultimately failed. Clock startup time versus temperature studies were also performed and compared to an SNL-designed clock having the same fundamental frequency.

High speed flash radiography has been used to record phenomena that occur during rapid dynamic events. The events are difficult, if not impossible, to record by other means due to the speed of the event or the obscuration associated with it. To eliminate the motion blur of objects moving at high speeds it is necessary to have extremely short exposure times. This short exposure time requires the use of high speed intensifying screens and high speed x-ray film to record the radiographic image. Technicians who use flash x-rays have to depend on recommendations from present and former flash x-ray users for film and screen selection. The film and screen industry has made many changes in the last few years. It is not uncommon to find that the particular film or screen used in the past is no longer manufactured. This paper will describe some of the films and screens that are currently used for testing. It will also describe the optimum experimental setup used to obtain the best images.

The Modal Group at Sandia National Laboratories performs a variety of tests on structures ranging from weapons systems to wind turbines. The desired number of data channels for these tests has increased significantly over the past several years. Tests requiring large numbers of data channels makes roving, accelerometers impractical and inefficient. The Modal Lab has implemented a method in which the test unit is fully instrumented before any data measurements are taken. This method uses a 16 channel data acquisition system and a mechanical switching setup to access each bank of accelerometers. A data base containing all transducer sensitivities, location numbers, and coordinate information is resident on the system enabling quick updates for each data set as it is patched into the system. Ibis method has reduced test time considerably and is easily customized to accommodate data acquisition systems with larger channel capabilities.

A new class of inorganic ion exchange materials that can separate low parts per million level concentrations of Cs{sup +} from molar concentrations of Na{sup +} has recently been developed as a result of a collaborative effort between Sandia National Laboratories and Texas A&M University. The materials, called crystalline silicotitanates, show significant potential for application to the treatment of aqueous nuclear waste solutions, especially neutralized defense wastes that contain molar concentrations of Na{sup +} in highly alkaline solutions. In experiments with alkaline solutions that simulate defense waste compositions, the crystalline silicotitanates exhibit distribution coefficients for Cs{sup +} of greater than 2,000 ml/g, and distribution coefficients greater than 10,000 for solutions adjusted to a pH between 1 and 10. Additionally, the crystalline silicotitanates were found to exhibit distribution coefficients for Pu and Sr{sup 2+} of greater than 2,000 and 100,000 respectively. Development of these materials for use in processes to treat defense waste streams is currently being pursued.

The effects of the midgap-level interface trap density and net oxide charge on the total-dose gain degradation of a bipolar transistor are separately identified. The superlinear dose dependence of the excess base current is explained.

MOS total-dose response is shown to depend strongly on transistor gate length. Simple scaling models cannot predict short-channel device response from long-channel results. Hardness assurance implications are discussed for weapon and space environments.

We have studied intrinsic free-carrier recombination in a variety of GaAs structures, including: OMVPE- and MBE-prepared GaAs/Al{sub x}Ga{sub 1-x}As double heterostructures, Na{sub 2}S passivated GaAs structures and bare GaAs structures. We find OMVPE prepared structures are superior to all of these other structures with 300 K lifetimes of {approximately} 2.5 {mu}s and negligible nonradiative interface and bulkrecombination, and thus are truly surface-free (S < 40 cm/s). Moreover, we observe systematic trends in optical properties versus growth conditions. Lastly, we find that the presence of free-exciton recombination in the low-temperature photoluminescence spectra is a necessary but not sufficient condition for optimal optical properties (i.e. long minority-carrier lifetimes).

Sandia National Laboratories (SNL) is conducting several research programs to help develop validated methods for the prediction of the ultimate pressure capacity, at elevated temperatures, of light water reactor (LWR) containment structures. To help understand the ultimate pressure of the entire containment pressure boundary, each component must be evaluated. The containment pressure boundary consists of the containment shell and many access, piping, and electrical penetrations. The focus of the current research program is to study the ultimate behavior of flexible metal bellows that are used at piping penetrations. Bellows are commonly used at piping penetrations in steel containments; however, they have very few applications in concrete (reinforced or prestressed) containments. The purpose of piping bellows is to provide a soft connection between the containment shell and the pipe are attached while maintaining the containment pressure boundary. In this way, piping loads caused by differential movement between the piping and the containment shell are minimized. SNL is conducting a test program to determine the leaktight capacity of containment bellows when subjected to postulated severe accident conditions. If the test results indicate that containment bellows could be a possible failure mode of the containment pressure boundary, then methods will be developed to predict the deformation, pressure, and temperature conditions that would likely cause a bellows failure. Results from the test program would be used to validate the prediction methods. This paper provides a description of the use and design of bellows in containment piping penetrations, the types of possible bellows loadings during a severe accident, and an overview of the test program, including available test results at the time of writing.

The Department of Energy`s Nevada Field Office has disposed of a small quantity of high activity and special case wastes using Greater Confinement Disposal facilities in Area 5 of the Nevada Test Site. Because some of these wastes are transuranic radioactive wastes, the Environmental Protection Agency standards for their disposal under 40 CFR Part 191 which requires a compliance assessment. In conducting the 40 CFR Part 191 compliance assessment, review of the Greater Confinement Disposal inventory revealed potentially land disposal restricted hazardous wastes. The regulatory options for disposing of land disposal restricted wastes consist of (1) treatment and monitoring, or (2) developing a no-migration petition. Given that the waste is already buried without treatment, a no-migration petition becomes the primary option. Based on a desire to minimize costs associated with site characterization and performance assessment, a single approach has been developed for assessing compliance with 40 CFR Part 191, DOE Order 5820.2A (which regulates low-level radioactive wastes contained in Greater Confinement Disposal facilities) and developing a no-migration petition. The approach consists of common points of compliance, common time frame for analysis, and common treatment of uncertainty. The procedure calls for conservative bias of modeling assumptions, including model input parameter distributions and adverse processes and events that can occur over the regulatory time frame, coupled with a quantitative treatment of data and parameter uncertainty. This approach provides a basis for a defensible regulatory decision. In addition, the process is iterative between modeling and site characterization activities, where the need for site characterization activities is based on a quantitative definition of the most important and uncertain parameters or assumptions.

The first portion of this paper proposes a method of fabricating a material whose modulus can be changed substantially through the application of a specified stimulus. The particular implementation presented here indirectly exploits the large deformation associated with shape memory alloys to achieve the desired modulation of stiffness. The next portion of this paper discusses a class of vibration problems for which such materials have a serious potential for vibration suppression. These are problems, such as the spinning up of rotating machinery, in which the excitation at any time lies within a narrow frequency band, and that band moves through the frequency spectrum in a predictable manner. Finally, an example problem is examined and the utility of this approach is discussed.

An element based finite control volume procedure is applied to the solution of ablation problems for 2-D axisymmetric geometries. A mesh consisting of four node quadrilateral elements was used. The nodes are allowed to move in response to the surface recession rate. The computational domain is divided into a region with a structured mesh with moving nodes and a region with an unstructured mesh with stationary nodes. The mesh is costrained to move along spines associated with the original mesh. Example problems are presented for the ablation of a realistic nose tip geometry exposed to aerodynamic heating from a uniform free stream environment.

The paper gives some of the highlights of a panel discussion on surface diffusion held Monday, November 30, 1992 at the Fall MRS Meeting in Boston, Massachusetts. Four invited speakers discussed computer modeling techniques and scanning tunneling microscopy experiments that have been used to provide new understanding of the atomistic processes that occur at surfaces. We present a summary of each of the invited talks, indicate other presentations on surface diffusion in this proceedings, and provide a transcript of the two discussion sessions.

During the past few years, methods have been developed for quantifying and analyzing common cause failures (CCFs). These methods have outpaced current data collection activities. This document discusses the collection and documentation of failure events at nuclear power plants with respect to these new CCFs methods. The report concentrates on the information necessary to improve the parameter estimates for both independent and dependent events in probabilistic risk assessments (PRAS) and alludes to the fact that the same information can be used to enhance other nuclear power plant activities. Several existing data bases are reviewed as to their adequacy for these new CCF methods, and areas where information is lacking, either because certain information is simply not required to be reported or because required information was simply not reported, are identified. Finally, data needs identified from recent PRAs are discussed.

Lighting protection systems (LPSs) for explosives handling and storage facilities have long been designed similarly to those will for more conventional facilities, but their overall effectiveness in controlling interior electromagnetic (EM) environments has still not been rigorously assessed. Frequent lightning-caused failures of a security system installed in earth-covered explosives storage structures prompted the U.& Army and Sandia National Laboratories to conduct a program to determine quantitatively the EM environments inside an explosives storage structure that is struck by lightning. These environments were measured directly during rocket-triggered lightning (RTL) tests in the summer of 1991 and were computed using linear finite-difference, time-domain (FDTD) EM solvers. The experimental and computational results were first compared in order to validate the code and were also used to construct bounds for interior environments corresponding to seven incident lightning flashes. The code insults were also used to develop simple circuit models for the EM field behavior-a process that insulted in a very simple and somewhat surprising physical interpretation of the structure`s response that has significant practical and economic implications for design, construction, and maintenance of such facilities.

A panel discussion on interface roughness was held at the Fall 1992 Materials Research Society meeting. We present a of results presented by the invited speakers on the application and interpretation of X-ray reflectivity, atomic force microscopy (AFM), scanning tunneling microscopy (STM), photoluminescence and transmission electron microscopy.

A safety system has been designed and constructed to mitigate the asphyxiation and low temperature hazards presented by the distribution and usage of cryogenic liquids in work spaces at Sandia National Laboratories. After identifying common accident scenarios, the CRYOFACS (Cryogenic Fail-Safe Control System) unit was designed, employing microprocessor technology and software that can be easily modified to accommodate varying laboratory requirements. Sensors have been incorporated in the unit for the early detection of accidental releases or overflows of cryogenic liquids. The CRYOFACS design includes control (and shutdown) of the cryogen source upon error detection, and interfaces with existing oxygen monitors, in common use at Sandia Labs, to provide comprehensive protection for both personnel and property.

The Greater Confinement Disposal (GCD) facility was established by the Nevada office of the Department of Energy (DOE) in Area 5 at the Nevada Test Site for containment of waste inappropriate for shallow land burial. Some transuranic (TRU) waste has been disposed of at the GCD facility, and compliance of this disposal system with Environmental Protection Agency (EPA) regulations 40 CFR 191 must be evaluated by performance assessment calculations. We have adopted an iterative approach where performance assessment results guide site data collection which in turn influences the parameters and models used in performance assessment. The first iteration was based upon readily available data. The first iteration indicated that the GCD facility would likely comply with 40 CFR 191 and that the downward recharge rate had a major influence on the results. As a result, a site characterization project was initiated to study recharge in Area 5 by use of three environmental tracers. This study resulted in the conclusion that recharge was extremely small, if not negligible. Thus, downward advection to the water table is no longer considered a viable release pathway, leaving upward liquid diffusion as the sole release pathway. This second performance assessment iteration refined the upward pathway models and parameters. The results of the performance assessment using these models still indicate that the GCD site is likely to comply with all sections of 40 CFR 191.

We have developed a method for generating chromate-free corrosion resistant coatings on aluminum alloys using a process procedurally similar to standard chromate conversion. These coatings provide good corrosion resistance on 6061-T6 and 1100 A1 under salt spray testing conditions. The resistance of the new coating is comparable to that of chromate conversion coatings in four point probe tests, but higher when a mercury probe technique is used. Initial tests of paint adhesion, and under paint corrosion resistance are promising. Primary advantage of this new process is that no hazardous chemicals are used or produced during the coating operation.

A method is described to characterize shocks (transient time histories) in terms of the Fourier energy spectrum and the temporal moments of the shock passed through a contiguous set of bandpass filters. This method is compared for two transient time histories with the more conventional methods of shock response spectra (SRS) and a nonstationary random characteristic.

Qualitatively different trends in postirradiation electrical response are observed in MOS devices after very long (up to 2.75-year) switched-bias bakes. A revised defect nomenclature is introduced, and implications for MOS defect models are discussed.

La{sub 2-x}Sr{sub x}CuO{sub 4+{delta}} with x = 0.01, 0.025, 0.050, 0.10 and 0.16 and excess oxygen {delta} incorporated by high-pressure O{sub 2} anneals. These compounds were examined using time-of-flight neutron diffraction data. Various models were fit by Rietveld least-squares refinement, with the maximum amount of {delta} being only of the order of 10 standard deviations. {delta} is largest for x near 0, is zero for x = 0.10 and is intermediate for x = 0.16. Only the sample with x = 0.01 is found to phase separate distinctly into a nearly stoichiometric phase with {delta} {approx} 0 and an oxygen-rich superconducting phase as the temperature is lowered. Coincidence of phase separation and Neel temperature strongly suggests that the phase separation is driven by free energy provided by long-range antiferromagnetic ordering in the nearly stoichiometric, weakly Sr-doped La{sub 2-x}Sr{sub x}CuO{sub 4}. The excess oxygen stoichiometry shows that at low values of x, hole doping is provided primarily by the excess oxygen, and is enhanced substantially by phase separation. At larger values of x, excess oxygen is no longer incorporated, and hole doping is provided by the substitution of Sr{sup +2} for La{sup +3}.

The US Nuclear Regulatory Commission (NRC) is investigating the performance of containments subject to severe accidents. This work is being performed by Sandia National Laboratories (SNL). In 1987, a 1:6-scale Reinforced Concrete Containment (RCC) model was tested to failure. The failure mode was a liner tear. As a result, a separate effects test program has been conducted to investigate liner tearing. This paper discusses the design of test specimens and the results of the testing. The post-test examination of the 1:6-scale RCC model revealed that the large tear was not an isolated event. Other small tears in similar locations were also discovered. All tears occurred near the insert-to-liner transition which is also the region of closest stud spacing. Also, all tears propagated vertically, in response to the hoop strain. Finally, all tears were adjacent to a row of studs. The tears point to a mechanism which could involve the liner/insert transition, the liner anchorage, and the material properties. The separate effects tests investigated these effects. The program included the design of three types of specimens with each simulating some features of the 1:6-scale RCC model. The specimens were instrumented using strain gages and photoelastic materials.

The problem of constructing trees given a matrix of interleaf distances is motivated by applications in computational evolutionary biology and linguistics. The general problem is to find an edge-weighted tree which most closely approximates the distance matrix. Although the construction problem is easy when the tree exactly fits the distance matrix, optimization problems under all popular criteria are either known or conjectured to be NP-complete. In this paper we consider the related problem where we are given a partial order on the pairwise distances, and wish to construct (if possible) an edge-weighted tree realizing the partial order. In particular we are interested in partial orders which arise from experiments on triples of species, which determine either a linear ordering of the three pairwise distances (called Total Order Model or TOM experiments) or only the pair(s) of minimum distance apart (called Partial Order Model or POM experiments). The POM and TOM experimental model is inspired by the model proposed by Kannan, Lawler, and Warnow for constructing trees from experiments which determine the rooted topology for any triple of species. We examine issues of construction of trees and consistency of TOM and POM experiments, where the trees may either be weighted or unweighted. Using these experiments to construct unweighted trees without nodes of degree two is motivated by a similar problem studied by Winkler, called the Discrete Metric Realization problem, which he showed to be strongly NP-hard. We have the following results: Determining consistency of a set of TOM or POM experiments is NP-Complete whether the tree is weighted or constrained to be unweighted and without degree two nodes. We can construct unweighted trees without degree two nodes from TOM experiments in optimal O(n{sup 3}) time and from POM experiments in O(n{sup 4}) time.

Semiconductor ring lasers are being developed for use as direct-waveguide-coupled sources for photonic integrated circuits. This report describes the results of our research and development of this new class of diode lasers. We have fabricated and characterized semiconductor ring lasers which operate continuous-wave at room temperature with a single-frequency output of several milliwatts. Our work has led to an increased understanding of the operating behavior of these lasers and to the development of two new types of advanced devices. The interferometric ring diode laser uses a coupled-cavity structure to improve the level of single-frequency performance. And, the unidirectional ring diode laser uses an active crossover waveguide to promote lasing in a single ring direction with up to 96% of the output emitted in the preferred lasing direction.

Results from fundamental investigations of low-temperature plasma systems were used to improve chamber-to-chamber reproducibility and reliability in commercial plasma-etching equipment. The fundamental studies were performed with a GEC RF Reference Cell, a laboratory research system designed to facilitate experimental and theoretical studies of plasma systems. Results and diagnostics from the Reference Cell studies were then applied to analysis and rectification of chamber-to-chamber variability on a commercial, multichamber, plasma reactor. Pertinent results were transferred to industry.

Compression seals are commonly used in electronic components. Because glass has such a low fracture toughness, tensile residual stresses must be kept low to avoid crackS. N. Burchett analyzed a variety of compression pin seals to identify mechanically optimal configurations when work hardened Alloy 52 conductor pins are sealed in a 304 stainless steel housing with a Kimble TM-9 glass insulator. Mechanical property tests on Alloy 52, have shown that the heat treatments encountered in a typical glass sealing cycle are capable of annealing the Alloy 52 pins, increasing ductility and lowering the yield strength. Since most seal analyses are routinely based on unannealed Alloy 52 properties, a limited study has been performed to determine the design impact of lowering the yield strength of the pins in a typical compression seal. Thermal residual stresses were computed in coaxial compression seals with annealed pins and the results then were used to reconstruct design guidelines following the procedures employed by Miller and Burchett. Annealing was found to significantly narrow the optimal design range (as defined by a dimensionless geometric parameter). The Miller-Burchett analyses which were based on very coarse finite element meshes and a 50 ksi yield strength fortuitously predicted an overly conservative design range that is a subset of the narrow design window prevalent when the yield strength is assumed to be 34 ksi. This may not remain true for lower yield strengths. The presence of pin wetting was shown to exacerbate the glass stress state. The time is right to develop a modern and enhanced set of design guidelines which could address new material systems, three dimensional geometries, and viscoelastic effects.

With ever increasing processor and memory speeds, new methods to overcome the ``I/O bottleneck`` need to be found. This is especially true for massively parallel computers that need to store and retrieve large amounts of data fast and reliably, to fully utilize the available processing power. We have designed and implemented a parallel file system, that distributes the work of transferring data to and from mass storage, across several I/O nodes and communication channels. The prototype parallel file system makes use of the existing single threaded file system of the Sandia/University of New Mexico Operating System (SUNMOS). SUNMOS is a joint project between Sandia National Laboratory and the University of New Mexico to create a small and efficient OS for Massively Parallel (MP) Multiple Instruction, Multiple Data (MIMD) machines. We chose file striping to interleave files across sixteen disks. By using source-routing of messages we were able to increase throughput beyond the maximum single channel bandwidth the default routing algorithm of the nCUBE 2 hypercube allows. We describe our implementation, the results of our experiments, and the influence this work has had on the design of the Performance-oriented, User-managed, Messaging Architecture (PUMA) operating system, the successor to SUNMOS.

An automatic phase identification system that employs a neural network approach to classifying seismic event phases is described. Extraction of feature vectors used to distinguish the different classes is explained, and the design and training of the neural networks in the system are detailed. Criteria used to evaluate the performance of the neural network approach are provided.

Satellite electronics may be subjected to a large fluence of protons from the Van Allen belt and from solar flares. To determine if unhardened electronics will survive a radiation environment, the total ionizing dose and displacement damage to the electronics must be determined. Several computer codes are available for modeling proton transport, ranging in complexity for a very-efficient straight-line approximation to general-geometry time-dependent Monte Carlo transport, with corresponding increase in computer run time. For most satellite applications, neutrons can be neglected in the analysis. However, neutrons may be important for modeling heavily shielded compartments for personnel and electronics.