Publications

In this study, a discrete element technique was used to simulate drop breakup in two dimensions. A series of simulations in which the drop breakup occurred in the presence of a flow field was performed. The density ratio of the flow field to the drop in the simulations was comparable to many of the isothermal liquid/liquid drop breakup experiments performed to investigate hydrodynamic breakup during Fuel Coolant Interactions (FCIs). The randomly directed internal kinetic energy of the drop increased rapidly at the beginning of the interaction between the drop and the flow field due to momentum transfer from the flow field to the drop. After the initial increase in internal energy of the drop, the momentum transferred from the flow field to the drop in the form of translational kinetic energy of the center of mass of the drop. It was also observed that the drops simulated in the presence of a flow field required higher internal kinetic energies to fragment than did the drops observed in the simulations performed in the absence of a flow field.

Sandia National Laboratories is one of the nation's largest research and development (R and D) facilities and is responsible for national security programs in defense and energy with a primary emphasis on nuclear weapon R and D. However, Sandia also supports a wide variety of projects ranging from basic materials research to the design of specialized parachutes. As a multiprogram national laboratory, Sandia has much to offer both industrial and government customers in pursuing space nuclear technologies. A brief summary of Sandia's technical capabilities, test facilities, and example programs that relate to military and civilian objectives in space is presented.

Sandia National Laboratories is actively involved in testing coated particle nuclear fuels for the Space Nuclear Thermal Propulsion (SNTP) program managed by Phillips Laboratory. The testing program integrates the results of numerous in-pile and out-of-pile tests with modeling efforts to qualify fuel and fuel elements for the SNTP program. This paper briefly describes the capabilities of the Annular Core Research Reactor (in which the experiments are performed), the major in-pile tests, and the models used to determine the performance characteristics of the fuel and fuel elements. 6 refs.

The US Department of Energy's Slant Hole Completion Test Well, SHCT-1, was drilled in 1990 into gas-bearing, lenticular and blanket-shaped sandstones of the Mesaverde Formation, northwestern Colorado. The reservoirs are over-pressured, with sub-microdarcy, in situ, matrix-rock permeabilities. However, a set of sub-parallel natural fractures increases the whole-reservoir permeabilities, measured by well tests, to several tens of microdarcies. The slant hole azimuth was therefore oriented to cut across the dominant fracture strike, in order to access the natural-fracture permeability and increase drainage into the wellbore.

The intense radiation fields generated with useful uniformity over large volumes, using the novel compound-lens diode on Hermes III, are characterized. The measurements show that by changing the diode parameters, the peak dose, useful area, and useful volume of irradiation can be varied from ~100 krad(Si), ~600 cm2, and ~20×103 cm3 to 20 krad(Si), ~3400 cm2, and ~200×103 cm3, in a 19±2 ns radiation pulse. This versatility enables radiation fields to be tailored to a specified exposure requirement, significantly enhancing the capability of Hermes III to test radiation effects in systems. © 1992 IEEE

The well known Boltzmann-Matano analysis'' can be used in general to measure the diffusivity of binary and ternary alloys. However for alloys containing four or more components, the analysis requires making assumptions, for example that the diffusivity is constant. Conversely, it can be shown that the square root diffusivity analysis'' applies to measuring diffusivities that vary with concentration, as long as the variation is linear with concentration. Methods of designing samples and evaluating data for the square root diffusivity analysis are discussed.

A monolithic dose-rate nuclear event detector (NED) has been evaluated as a function of radiation pulse width. The dose-rate trip level of the NED was evaluated in "near" minimum and maximum sensitivity configurations for pulse widths from 20 to 250 ns and at dose rates from 106 to 109 rads(Si)/s. The trip level varied up to a factor of ∼16 with pulse width. At each pulse width the trip level can be varied intentionally by adding external resistors. Neutron irradiations caused an increase in the trip level, while electron irradiations, up to a total-dose of 50 krads(Si), had no measurable effect. This adjustable dose-rate-level detector should prove valuable to designers of radiation-hardened systems.

To assess the current capability for solving non-gray, anisotropically scattering multidimensional radiation problems, a specific problem was formulated for several participating authors to solve. They each applied their own methods to solve the problem, which was relevant to the modeling of heat transfer in coal-fired furnaces. This paper is a summary of the comparison of the results. Areas where future modeling efforts should address are identified.

The bonding configurations for simple phosphate glasses are quantitatively described by both the relative concentrations of different polyhedral phosphate sites (i.e., the Q{sup n} description) determined by {sup 31}p magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy and by the relative concentrations of bridging and nonbridging oxygen as measured by x-ray photoelectron spectroscopy (XPS). Both spectroscopies illustrate the depolymerizing effects of modifier additions in two series of Na{sub 2}O and ZnO-P{sub 2}0{sub 5} glasses.

A robotic rover vehicle designed for use in the exploration of the Lunar surface is described. The Robotic All-Terrain Lunar Exploration Rover (R.A.T.L.E.R.) is a four wheeled all-wheel-drive dual-body vehicle. A uniquely simple method of chassis articulation is employed which allows all four wheels to remain in contact with the ground, even while climbing over step-like obstacles as large as 1.3 wheel diameters. Skid steering and modular construction are used to produce a simple, rugged, highly agile mobility chassis with a reduction in the number of parts required when compared to current designs being considered for planetary exploration missions. The design configuration, mobility parameters, and performance of several existing R.A.T.L.E.R. prototypes are discussed.

Particulate contamination during IC fabrication is generally acknowledged as a major contributor to yield loss. In particular, plasma processes have the potential for generating copious quantities of process induced particulates. Ideally, in order to effectively control process generated particulate contamination, a fundamental understanding of the particulate generation and transport is essential. Although a considerable amount of effort has been expended to study particles in laboratory apparatus, only a limited amount of work has been performed in production line equipment with production processes. In these experiments, a Drytek Quad Model 480 single wafer etcher was used to etch blanket thermal SiO{sub 2} films on 150 mm substrates in fluorocarbon discharges. The effects of rf power, reactor pressure, and feed gas composition on particle production rates were evaluated. Particles were measured using an HYT downstream particle flux monitor. Surface particle deposition was measured using a Tencor Surfscan 4500, as well as advanced ex situ techniques. Particle morphology and composition were also determined ex situ. Response surface methodology was utilized to determine the process conditions under which particle generation was most pronounced. The use of in situ and ex situ techniques has provided some insight into the mechanisms involved for particle generation and particle dynamics within the plasma during oxide etching.

Nitronic 60 is a nitrogen-strengthened austenitic stainless steel used for applications where metal-to-metal wear and galling resistance are required. In addition, it does not transfer to martensite with strain or upon cooling to cryogenic temperatures. In comparison to type 304 stainless steel, the nickel content is similar, chromium content is slightly reduced and manganese, silicon, and nitrogen are all increased in Nitronic 60. Although studies have shown that it can be joined with arc welding, it fabrication weldability is limited by heat-affected zone (HAZ) cracking. This study examined the HAZ cracking behavior of this alloy during autogenous gas tungsten arc welding and pulsed autogenous Nd:YAG welding.

The conclusions of the vulnerability test on VOPAN (verification of Operator's Analysis) as conducted at Safeguards Analytical Laboratory (ASA) at Seibersdorf, Austria in October 1990 and documented in STR-266, indicate that whenever samples are taken for safeguards purposes extreme care must be taken to ensure that they have not been interfered with during the sample taking, transportation, storage or sample preparation process.'' Indeed there exist a number of possibilities to alter the content of a safeguards sample vial from the moment of sampling up to the arrival of the treated (or untreated) sample at SAL. The time lapse between these two events can range from a few days up to months. The sample history over this period can be subdivided into three main sub-periods: (1) the period from when the sampling activities are commenced up to the treatment in the operator's laboratory, (2) during treatment of samples in the operator's laboratory, and finally, (3) the period between that treatment and the arrival of the sample at SAL. A combined effort between the Agency and the United States Support Program to the Agency (POTAS) has resulted in two active tasks and one proposed task to investigate improving the maintenance of continuity of knowledge on safeguards samples during the entire period of their existence. This paper describes the use of the Sample Vial Secure Container (SVSC), of the Authenticated Secure Container System (ASCS), and of the Secure Container for Storage and Transportation of samples (SCST) to guarantee that a representative portion of the solution sample will be received at SAL.

Three methods of evaluating accelerated battery test data are described. Criteria for each method are used to determine the minimum test matrix required for accurate predictions. Other test methods involving high current discharge and real time techniques are discussed.

Neutron spin-echo spectroscopy is used to study the topology of aerogels. Topology or connectivity is varied through precursor chemistry and thermal annealing. Topology is characterized using the concept of fractons (the vibrational excitations of a fractal network). A qualitative difference is observed in the spectrum of polymeric vs. colloidal aerogels, the latter showing a peak in the density of vibrational states. For colloidal aerogels whose structure appears to arise from phase separation in the solution precursor, low-energy excitations were only observed in the lowest density material studied. Finally, a transition from fractal to colloidal microstructure was observed during the sintering of polymeric aerogels. This transformation revealed itself as a transition from a fracton-like to a peaked density of states function. © 1992 Elsevier Science Publishers B.V. All rights reserved.

This document presents recent accomplishments in engineering and science at Sandia National Laboratories. Commercial-scale parabolic troughs at the National Solar Thermal Test Facility are used for such applications as heating water, producing steam for industrial processes, and driving absorption air conditioning systems. Computerized-aided design, superconductor technology, radar imaging, soldering technology, software development breakthroughs are made known. Defense programs are exhibited. And microchip engineering applications in test chips, flow sensors, miniature computers, integrated circuits, and microsensors are presented.

This paper describes experiments on the wettability of tin on oxygen free, high conductivity (OFHC) copper using a ″point source″ ultrasonic horn. Ultrasonics are used on such metals as aluminum or stainless steel which are difficult to wet without the use of very strong corrosives. These experiments explore the behavior of acoustic energy transmission in the horn-solder-substrate systems indicated by the solder film generated and explore the use of ultrasonics in actual electronic systems component fabrication and assembly processes.

An evaluation of substitutes for tin-lead alloy solders is discribed. The first part of the evaluation studies the wettability of tin-based, lead free solders. The second part evaluates the solderability. The solders evaluated were commercially available.

We present calculations which show the radial dependence of the KVV and L12VV Auger matrix elements of silicon. We find greatly differing dependences, converging within ~ 1 a.u. of the nucleus in the case of the KVV, but not until — 4 a.u. in the case of the L23VV, well beyond the bond midpoint of — 2.2 a.u. We also find quite different dependences for the various elements within a particular CVV transition. Because the local density of states (LDOS) is dependent on the radius of the sphere of integration, our results suggest that different CVV Auger processes on the same atom in fact probe different LDOSs, as do even different contributions within the same transition. (This effect is separate from the well-known matrix element property which weights angular-momentum components differently.) These results call into question both the single-site LDOS approximation when used in the interpretation of low-energy ( < 100 eV) Auger spectra, and the application to high-energy spectra of local densities of states obtained by integration over muffin-tin or Wigner-Seitz spheres which have a large radius compared to the region probed by the Auger process. © 1992, American Vacuum Society. All rights reserved.

This paper presents the results of a set of structural analyses performed to investigate the effects of internal gas generation on the extension of pre-existing fractures around disposal rooms at the Waste Isolation Pilot Plant. The response of a room and its contents is computed for this scenario to establish the condition of the room at any point in time. The development of the capability to perform these analyses represents an additional step in the development of an overall model for the disposal room.

Acid vapors have been used to fluxlessly reduce metal oxides and enhance wetting of solder on metallizations. Dilute solutions of hydrogen, acetic acid and formic acid in an inert carrier gas of nitrogen or argon were used with the sessile drop technique for 60Sn-40Pb solder on Cu and Au/Ni metallizations. The time to reduce metal oxides and degree of wetting as a function of acid vapor concentration were characterized. Acetic and formic acids reduce the surface metal oxides sufficiently to form metallurgically sound solder joints. Hydrogen did not reduce oxides rapidly enough at 220°C to be suitable for soldering applications. The optimum conditions for oxide reduction with formic acid was with an acid vapor concentration in nitrogen carrier gas of 4% for Cu metallizations and 1.6% on Au/Ni. The acetic acid vapor concentration, also in nitrogen, was optimized at 1.5% for both metallizations. Above a vapor concentration of 1.5%, the acetic acid combined with the bare metal to form acetates which increased the wetting time. These results indicate that acid vapor fluxless soldering is a viable alternative to traditional flux soldering.

The measurement of surface pressures on a body which is submerged in flowing water involves several problems which are not encountered when the test medium is air. Many of these problems exist even if the water velocity is low, and become more severe at higher velocitics (45-65 ft/sec) where the surface pressure may be low enough for cavitation to occur. Problem areas which are discussed include:hydrostatic pressure, surface tension, orifice errors, thermal effects on surface-mounted transducers, electrical fields, two-phase phenomena and air content.

Nuclear weapons system designers and safety analysts are contemplating broader use of probabilistic risk assessment techniques. As an aid to their understanding, this document summarizes the development and use of probabilistic risk assessment (PRA) techniques in the nuclear power industry. This report emphasizes the use of PRA in decision making with the use of case studies. Nuclear weapon system designers and safety analysts, contemplating the broader use of PRA techniques, will find this document useful.

This document contains implementation details for the Quality Information Management System (QIMS) Pilot Project, which has been released for VAX/VMS systems using the INGRES RDBMS. The INGRES Applications-By-Forms (ABF) software development tool was used to define the modules and screens which comprise the QIMS Pilot application. These specifications together with the QIMS information model and corresponding database definition constitute the QIMS technical specification and implementation description presented herein. The QIMS Pilot Project represents a completed software product which has been released for production use. Further extension projects are planned which will release new versions for QIMS. These versions will offer expanded and enhanced functionality to meet further customer requirements not accommodated by the QIMS Pilot Project.

Deconing controllers are developed for a spinning spacecraft, where the control mechanism is that of axial or radial moving masses that are used to produce intentional, transient principal axis misalignments. A single mass axial controller is used to motivate the concept, and then axial and radial dual mass controllers are described. The two mass problem is of particular interest since spacecraft imbalances can be simultaneously removed with the same control logic. Each controller is tested via simulation for its ability to eliminate existing coning motion for a range of spin rates. Both controllers are developed via a linear-quadratic-regulator synthesis procedure, which is motivated by their multi-input/multi-output nature. The dynamic coupling in the radial two mass control problem introduces some particularly interesting design complications.