Publications

The Magma Energy Program is a speculative endeavor regarding practical utility of electrical power production from the thermal energy which reside in magma. The systematic investigation has identified an number of research areas which have application to the utilization of magma energy and to the field of geothermal energy. Eight topics were identified which involve thermal processes and which are areas for the application of the techniques of numerical simulation. These areas are: (1) two-phase flow of the working fluid in the wellbore, (2) thermodynamic cycles for the production of electrical power, (3) optimization of the entire system, (4) solidification and fracturing of the magma caused by the energy extraction process, (5) heat transfer and fluid flow within an open, direct-contact, heat-exchanger, (6) thermal convection in the overlying geothermal region, (7) thermal convection within the magma body, and (8) induced natural convection near the thermal energy extraction device. Modeling issues have been identified which will require systematic investigation in order to develop the most appropriate strategies for numerical simulation. It appears that numerical simulations will be of ever increasing importance to the study of geothermal processes as the size and complexity of the systems of interest increase. It is anticipated that, in the future, greater emphasis will be placed on the numerical simulation of large-scale, three-dimensional, transient, mixed convection in viscous flows and porous media. Increased computational capabilities, e.g.; massively parallel computers, will allow for the detailed study of specific processes in fractured media, non-Darcy effects in porous media, and non-Newtonian effects. 23 refs., 13 figs., 1 tab.

Sensitivity studies have been conducted for the gas release from the Waste Isolation Pilot Plant (WIPP) using the TOUGH2 computer code with performance measures of peak repository pressure and gas migration distance at 1000 years. The effect of formation permeabilities including impermeable halite, two-phase characteristic curves including different models and residual saturations, and other variations was studied to determine their impact on the performance of the WIPP repository. 15 refs., 7 figs., 2 tabs.

An important aspect of environmentally-conscious operations is adoption of an aggressive waste minimization program. This paper describes the waste minimization and pollution prevention program at Sandia National Laboratories. Although Sandia's approach is patterned after the generic waste minimization models proposed by the Environmental Protection Agency and the Department of Energy, the specifics of implementation, and the potential for payoff, are influenced by the R D nature of Sandia's work. Key aspects of the program are discussed, including why Sandia is developing and conducting the program; objectives; elements of the program; our approach to implementation; the magnitude of the undertaking; and the expected payoff. 3 refs., 2 figs.

The standard operating mode produces bremsstrahlung with an endpoint energy of about 18 MeV. This paper describes a new mode with a 8.5 MeV endpoint energy and the same standard mode pulse characteristics achieved by operating only half of the accelerator at full charge with the advantage of minimal setup time. An extension of the new half-voltage mode is to use the other half of the accelerator for delivering a second pulse at a later time with the same technique. The double pulse mode is ideal for beam generation which requires a long interpulse time in the millisecond regime. The beam characteristics of the two half-voltage pulses are nearly identical with the nominal radiation pulse full width at half maximum of 21 ns and 10--90 risetime of 11 ns recorded by the same Compton diode radiation monitors on instruments triggered 30 ms apart.

A series of shock-loading experiments on a nitrocellulose-based (NC-based) gun propellant was conducted using a light-gas gun. The intent of this work was to characterize the shock sensitivity of the gun propellant. The initial objectives were to obtained Hugoniot data and to investigate the pressure threshold at which a reaction initiates. For the Hugoniot/reaction threshold experiments, 1/4-length grains of propellant were mounted on the front of projectiles and were impacted onto either polymethylmethacrylate (PMMA), fused silica or sapphire targets at velocities as high as 1.4 mm/{mu}s, the upper limit of the gun. The particle velocity data obtained from the VISAR (Velocity Interferometer System for Any Reflector) records for the propellant fit a Hugoniot curve found in the Russian literature for a double-base, NC-nitroglycerine propellant. The density initial bulk sound velocity, and empirical parameter S values for the gun propellant were 1.63 g/cm{sup 3}, 1.70 mm/{mu}s and 1.85, respectively. VISAR data were also used to obtained the ignition threshold pressures of the gun propellant. Reactions were observed at impact pressures of 2.6 GPa and above. 5 refs., 6 figs., 1 tab.

We report on the use of a deposition/etch approach to the loss of selectivity problem, using high activity fluorine chemistries in the etch step. Proof-of-concept experiments were initially performed in a hot wall system, the excellent results obtained lead us to prove out the concept in a commercially available cold wall Genus reactor. We observed that WF{sub 6} is ineffective as an etchant of W. The technique has been able to produce perfectly selective depositions 1 micron thick in both hot wall, and cold wall, systems. Sheet resistivity values and film morphology are good. 9 refs., 4 figs., 1 tab.

This paper's main result is an O(({radical}{bar m}lgm)(n lg n) + mlg n)-time algorithm for computing the kth smallest entry in each row of an m {times} n totally monotone array. (A two-dimensional A = a(i,j) is totally monotone if for all i{sub 1} < i{sub 2} and j{sub 1} < j{sup 2}, < a(i{sub 1},j{sub 2}) implies a(i{sub 2},j{sub 1})). For large values of k (in particular, for k=(n/2)), this algorithm is significantly faster than the O(k(m+n))-time algorithm for the same problem due to Kravets and Park. An immediate consequence of this result is an O(n{sup 3/2} lg{sup 2}n)-time algorithm for computing the kth nearest neighbor of each vertex of a convex n-gon. In addition to the main result, we also give an O(n lg m)-time algorithm for computing an approximate median in each row of an m {times} n totally monotone array; this approximate median is an entry whose rank in its row lies between (n/4) and (3n/4) {minus} 1. 20 refs., 3 figs.

Presents a practical algorithm for partitioning a program into sequential threads. A thread is a sequence of instructions, possibly including branches, that can be scheduled as an indivisible unit on a von Neumann-like processor. The primary target of the proposed compilation strategy is large-scale parallel systems that rely on multithreading at the processor level to tolerate long communication latencies. As such, the algorithm incorporates a mechanism to balance the desire to maximize thread length with the desire to expose useful high-level parallelism. It can also exploit known dependency information (gathered through subscript analysis, for example). Although this paper focuses on non-strict (but not lazy) language semantics, the partitioning analysis is equally well suited to a non-strict language on a sequential machine or a strict language on a parallel multithreaded machine.

The Silver Bullet Skunk Works, and experimental product realization team at AT T Consumer Products, designed and shipped a new telephone answering system to market in eight months, approximately one year faster than previous AT T products of similar complexity. This paper outlines the Design for X'' (DFX) philosophies and the team structure that enabled the group to accelerate the Product Realization Process. The Answering System 1300, developed in record time, was a successful product that met its schedule and cost objectives, and sold out its entire high-volume manufacturing run. Lessons learned from the Skunk Works experience have since been applied to other development activities in AT T Consumer Products. 3 figs.

The refractory metals of Groups 5B and 6B and their alloys display a variety of unique physical and mechanical characteristics in addition to their high melting points. In turn, these characteristics make these materials strong candidates for severe service and specialized applications. However, these materials also present a variety of challenges with respect to both fabrication weldability and the in-service behavior of weldments, many of which are related to the dominant effects of interstitial impurities. This work reviews current understanding of the physical and joining metallurgy of these metals and their alloys with emphasis on fusion welding. Of specific interest are the role of impurities and alloy chemistry in fabrication and service weldability, the material processing route, eg. vacuum melting vs. powder metallurgy, the importance of welding process procedures and variables, weldment mechanical properties, and fracture behavior. Specific examples from the various alloy systems are used to illustrate general metallurgical and joining characteristics of this class of materials. 34 refs., 14 figs., 3 tabs.

Resistance Welding (RW) has been known for about a century and in common use for much of that time. Much knowledge has been accumulated concerning many aspects of the process. However, upon examining contemporary RW handbooks, a few subjects that have been overlooked'' were found. Usually, this oversight will not be important; however, when the RW process is being applied at its limits, these factors may become critical. In this paper we will discuss such overlooked'' factors as the Peltier and Thomson effects, and the dynamics of welding head motions and how they are affected by the current pulse. Examples taken from sheet metal and microwelding applications will be given as examples. 12 refs., 7 figs., 4 tabs.

Short communication.

Increasingly stringent air emission standards in various states has dictated the elimination of engineering finishes which are derived from high volatile organic compound (VOC) paint chemistries. In July 1989, Allied-Signal, Inc., Kansas City Division, Kansas City, Missouri, voluntarily closed its paint facility, due to non-compliance with local air emission standards. The following details the materials selection and evaluations which led to current processing using low VOC paints, which permitted the Allied Signal, Inc., paint facility to achieve compliance and resume operations. 1 tab.

We have developed a model which utilizes a probabilistic failure criterion to describe intergranular stress corrosion cracking (IGSCC). A two-dimensional array of elements representing a section of a pipe wall is analyzed, with each element in the array representing a segment of grain boundary. The failure criterion is applied repetitively to each element of the array that is exposed to the interior of the pipe (i.e. the corrosive fluid) until that element dissolves, thereby exposing the next element. A number of environmental, mechanical, and materials factors have been incorporated into the model, including: (1) the macroscopic applied stress profile, (2) the stress history, (3) the extent and grain-to- grain distribution of carbide sensitization levels, which can be applied to a subset of elements comprising a grain boundary, and (4) a data set containing IGSCC crack growth rates as function of applied stress intensity and sensitization level averaged over a large population of grains. The latter information was obtained from the literature for AISI 304 stainless steel under light water nuclear reactor primary coolant environmental conditions. The resulting crack growth simulations are presented and discussed. 14 refs., 10 figs.

Edge finishing and deburring of parts is a tedious operation that should be automated. This paper describes the use of direct-drive XY table in the automated edge finishing of machined parts. The table is faster and more accurate than an articulated robot, thus where planar motion in a small work area is sufficient it is preferable. Hybrid force/position control is used to guide the table (with mounted workpiece) past the tool and maintain the contact force at the desired level. A six-axis force sensor on the tool spindle is used to measure contact force. We identified a dynamic model for the table from experimental measurements and used this model to design a force/position controller for the table. An example application of the table in the deburring of an actual jet engine turbine hub is presented. 5 refs., 12 figs.

This paper justifies the need for and describes studies of brine chemistry under way for German and American high- and intermediate-level radioactive waste repositories in domal and bedded salt formation. In particular, it discusses the origin and composition of fluids that could enter these repositories and some sampling, modeling, and statistical techniques used to characterize them. 24 refs., 4 figs., 5 tabs.

Historically, characterization of fluid flow and transport of soluble elements in the unsaturated, or vadose, zone has been limited. Until recently, most of the interest in transport of water-soluble pollutants has been focused on aquifer contamination, i.e. saturated conditions. Vadose zone investigations are hampered by a lack of appropriate technology for the necessary measurements; little work has been done to relate laboratory measurements to field-scale effects; and development and validation of computational models has been limited, in part through lack of data. We describe here results of a small-scale field experiment in which existing technology is used to quantify fluid movement following controlled infiltration. 6 refs., 2 figs.

Sandia National Laboratories has considerable experience with video systems used for alarm assessment. Until recently the camera of choice for lighted security applications was the monochrome vacuum tube video camera. However, with recent advancements in the solid state imager technology, the integration of tube cameras in security systems may soon become obsolete. The sensitivity and resolution of solid state imagers is approaching that of vacuum tube imagers. In addition, solid state cameras have a relatively long lifetime and require little maintenance. Initial equipment costs are similar. Due to the increased performance of solid state imagers, Sandia has established an ongoing program to evaluate these cameras. The evaluations are performed mainly to verify manufacturers' specifications for resolution, sensitivity, and signal to noise ratio, which are the critical camera parameters that should be considered when designing video systems. This report defines these parameters, describes the test procedures, and provides test results. 1 figs., 2 tabs.

Analysis of an intermittent failure to write the 1'' state to a particular memory location at low temperature ({minus}55{degree}C) in a 16K {times} 1 CMOS SRAM is presented. The failure was found to be due to an open metallization at a metal-to-silicon contact. The root cause of the failure was poor step coverage of the metallization over an oxide step. A variety of failure analysis techniques including dynamic electron beam analysis at low temperature using a Peltier cold stage were employed to study the intermittently failing SRAM. The failure site was located by using capacitive coupling voltage contrast analysis. PSPICE simulation, light emission microscopy, scanning electron microscopy, and focused-ion beam techniques were used to confirm the failure mechanism and location. The write cycle time of the failed IC was abnormally long, but within the allowable tester limit. The vulnerability of other ICs to failure by open metallization in metal-to-silicon contacts is reviewed. 8 refs., 10 figs., 2 tabs.

Zeolite-based tritium lamps are a possible alternative to traditional tritium gas tube light sources. Rare earth luminescing centers may be ion-exchanged into zeolite matrices. Close proximity of tritium atoms to the rare earths can be provided by highly tritiated water sorbed within the pore structure of the zeolite aluminosilicate matrix. Zeolites are optically clear and radiation stable. Light outputs from tritium-loaded zeolites are shown here to exceed 2{mu}W/cm{sup 2}, with good stability. Procedures for obtaining light sources are presented and results are discussed. The possible use of these luminescent materials as process monitors for zeolite absorption columns in tritium service is also discussed. 13 refs., 3 figs.

The electron photo-excitation from the K- state and its subsequent trapping by K+ state is probably at the origin of the silicon dangling bonds (K0) formation during broad-band UV illumination of the N-rich amorphous silicon nitride films. Because the photo-excited electron will move towards the metal electrode the positive charge is expected to accumulate near the nitride-silicon interface with illumination time. Our data also suggest that the N-H group may be at the origin of the nitrogen dangling bonds creation in N-rich films. © 1991 Elsevier Science Publishers B.V. All rights reserved.

For 15 years, the United States Department of Energy has worked with industry, both utilities and manufacturers, to develop the technology of solar central receiver power plants. In this type of plant, sunlight is concentrated by a field of sun-tracking mirrors, called heliostats, onto a centrally located receiver. The solar energy is collected in the form of a heated fluid, which is used to generate steam to power a conventional turbine generator. For a number of reasons, molten nitrate salt is now the preferred heat transfer fluid. Commercial plants will be sized between 100 and 200 MW. The impetus for developing central receivers comes from their unique advantages: (1) They produce clean, reliable, low-cost electricity; (2) they have practical energy storage that provides a high degree of dispatchability (annually up to 60%) -- without fossil fuels; and, (3) they are environmentally benign. Development efforts around the world have brought the technology to the brink of commercialization: The technical feasibility has been proven, and cost, performance, and reliability can be confidently predicted. Plans are currently being developed for the final steps toward commercial central receiver power plants. 24 refs., 7 figs.

To provide a method for addressing the uncertainty associated with conceptual models developed for performance assessment of waste management sites, probabilistic networks have been applied to the conceptual model development process. The application of probabilistic networks provides a graphical representation of the reasoning process that goes into developing conceptual models. Probability tables associated with decision points in the process provide a quantification of the uncertainty that is associated with the resulting conceptual models. To support the development of this probabilistic network, a formal process is being designed and implemented to elicit expert information about the conceptual model development process. This paper discusses the approach to designing this expert judgment elicitation process. 10 refs.

Engineers invest several years becoming skilled in the many disciplines necessary to effectively carry out analysis, design and development. This typically includes math, physics, computer science, and special study in their core area of expertise. However, once promoted into management, engineers use less and less of these hard-earned technical skills and find themselves operating in nontechnical arenas in which they have little or no formal training. (The formal training that they do get is often through company-sponsored courses, lacking both the rigor and cohesiveness that they have grown accustomed to in their engineering curriculum.) Often, what they are exposed to are continually varying management doctrines that resemble the flavor of the month, each laying claim to the true secrets of motivation, productivity, and organizational competitiveness. Under such circumstances, it is difficult for the neophyte manager to sort out fact from fancy, and help from hype. It therefore would be helpful to put such theories in perspective and present them in a form most easily digested by technical managers, i.e., from an analytical point of view. This paper attempts to do just that. There are many factors that influence a manager's career progression. One of the most rational factors is how the manager's actions affect the productivity of his or her group. This paper focuses on principles and techniques that a manager can, and should, employ to improve group productivity and enhance his or her opportunities for further advancement. 9 refs.

The short-transverse (S-T) stress corrosion cracking (SCC) behavior of Al-Li-CU alloy 2090 was studied using a static load SCC test technique. Time to failure was measured as a function of applied potential in several different environments. Rapid SCC failures (< 10 hours) were observed only when the following criteria were satisfied: E{sub br, T1} < E{sub applied} < E{sub br, matrix} where potentials refer to the breakaway potentials of the subgrain boundary T{sub 1} (Al{sub 2}CuLi) phase and the {alpha}-Al matrix phase. E{sub br} values were measured using potentiodynamic polarization of bulk materials intended to simulate the individual phases found in the subgrain boundary region. Results strongly suggest an anodic dissolution based SCC mechanism for this alloy where selective dissolution of T{sub 1} on the subgrain boundary is a critical step. The unusual pre-exposure embrittlement phenomenon demonstrated by Al- Li alloys is also shown to be consistent with these simple SCC criteria. 21 refs., 9 figs., 6 tabs.