Publications

During the period October 1988 through December 1988, a search was made for very high energy gamma rays from the direction of the Crab nebula using the atmospheric Cerenkov technique. The detector consisted of seven-fold arrays of photomultiplier tubes at the focii of two 11-meter diameter solar concentrators situated in Albuquerque, New Mexico. A DC signal was detected from the Crab nebula with a statistical significance of 5.8 sigma after the application of various cuts designed to suppress the background of hadronic showers. A search for a pulsed component failed to identify a significant signal in phase with the radio pulse from the Crab pulsar. These results with a threshold energy of 200 GeV are in substantial agreement with high energy results recently reported by the Mt. Hopkins group. 16 refs., 3 figs., 3 tabs.

The IAEA is increasingly confronted with decisions on how to use operator designed monitoring systems. A major question in the use of such systems focuses on how they may be authenticated. This report identifies four major areas of concern for authentication of an operator designed system. Generic methods to address these areas of concern are presented. Suggestions are also given on design features an operator can incorporate when designing a system which will aid in the application of authentication techniques.

A two-dimensional model of melt progression, oxidation and natural convection in reactor core debris beds has been developed. Three fields are considered in the model: vapor, melt and solid. Conservation equations are solved for the species of interest in each field. Momentum equations that are based on Darcy's law are solved for the vapor and the melt and a simplified model is used to calculate the motion of the solid as it settles downward. An energy equation is included that accounts for melting/freezing, convection, conduction, oxidation and decay heating. Key results from a sensitivity study include: (1) gas velocities increase rapidly at the onset of oxidation and subsequently decrease when the bed becomes steam-starved; (2) natural convection flows are sensitive to radial variations in the decay heat; (3) raising the pressure in the bed and the upper plenum increases the amount of steam that is available for oxidation and leads to much higher temperatures and gas velocities; (4) reducing the average particle diameter decreases the permeability and significantly lowers gas velocities; and (5) solutions are sensitive to conditions in the upper plenum and consequently, melt progression models discussed here must be coupled to a mechanistic code, such as MELPROG or SCDAP, in order to analyze specific accident sequences. 33 refs., 20 figs.

One critical issue to be addressed in the compact recirculating linac program concerns optimal beam injection into a racetrack-shaped accelerator. There are at least three candidates, axial beam injection, tangential beam injection, and laser-channel-assisted beam injection. In this report these three approaches are examined using computer simulation techniques. 3 refs., 27 figs., 2 tabs.

This report summarizes the current understanding of the expected long-term behavior of the Waste Isolation Pilot Plant (WIPP) repository and estimates long-term radionuclide doses in a series of six analyses investigating both undisturbed repository (Case I) and performance in response to a relatively high-consequence human intrusion (Case II). It is the result of an intensive effort over a short time. The US Department of Energy (DOE) decided to have Sandia National Laboratories prepare this report as a result of a meeting held January 5, 1989. The conceptual model of the expected long-term behavior of the WIPP repository used in this report was formulated in early to mid January 1989, drawing and understanding developed over the past decade. Numerical modeling of ground-water flow, radionuclide transport, and doses to humans began January 20, 1989 and was completed March 20, 1989. 332 refs., 98 figs., 69 tabs.

The particle code MAGIC and the trajectory code TRAJ were used to model diodes, gaps, and conditioning cells for several of Sandia's linear electron accelerators. In this report we summarize the main results obtained and discuss their significance. 29 refs., 50 figs., 10 tabs.

The US Department of Energy is planning to dispose of transuranic wastes at the Waste Isolation Pilot Plant (WIPP) near Carlsbad, New Mexico. Sandia National Laboratories is responsible for evaluating the compliance of the WIPP with the Environmental Protection Agency's Environmental Standards for the Management and Disposal of Spent Nuclear Fuel, High-Level and Transuranic Radioactive Wastes (40 CFR 191, Subpart B). This plan has been developed to present the issues that will be addressed before compliance can be evaluated. These issues examine the procedural nature of the Standard, and the technical requirements for further characterizing the behavior of the disposal system, including uncertainties, to support the compliance assessment. The plan briefly describes the activities that will be conducted prior to 1993 by Sandia to characterize the WIPP disposal system's behavior and predict its performance. 41 refs., 35 figs., 21 tabs.

Computer simulations, using the hydrocode HULL, were performed to analyze a method to discard the sabot and the effectiveness of several designs in reducing the kinetic energy of pusher plates for Davis Gun systems. This study assumed an axisymmetric impact of the pusher plate on one metal and multi-metal annual plates. Based on these simulations, a four petal sabot that is mechanically attached to the penetrator and an aluminum-steel composite target plate are recommended. 12 refs., 27 figs.

Over 4100 ft (1100 ft oriented) of Mesaverde core was taken during the drilling of the three Multiwell Experiment (MWX) wells, for study in a comprehensive core analysis program. This core traversed five separate depositional environments (shoreline/marine, coastal, paludal, fluvial, and paralic), and almost every major sand in the Mesaverde at the site was sampled. This paper summarizes MWX core analysis and describes the petrophysical properties at the MWX site; reservoir parameters, including permeabilities of naturally fractured core; and mechanical rock properties including stress-related measurements. Some correlations are made between reservoir properties and mineralogy/petrology data. Comparisons are made between the properties of lenticular and blanket sandstone morphologies existing at the site. This paper provides an overview of a complete core analysis in a low-permeability sandstone reservoir. 66 refs., 17 figs. , 9 tabs.

A very simple algorithm is presented that allows particles to be loaded or initialized in a particle simulation code. The algorithm can load particle positions or velocities according to any well- behaved density or distribution function. Sample codes are given in 1, 2, and 3 dimensions. The technique is highly efficient. 2 refs., 9 figs., 3 tabs.

Experiments were run using a PC-100 ion mobility spectrometer and TNT explosive vapor source to evaluate the adsorb-desorb characteristics of select 6.2 mm O.D. by 4.0 mm I.D. by 76.2 mm long glass preconcentrator tubes. This study was done to aid in the continuing search for an efficient preconcentrating device to be used with explosive vapor detecting instruments. These tubes were tested at various sampling rates ranging from 60 to 510 ml/min and the samples were thermally desorbed to provide the maximum output signal. Data showed the tubes with the greatest internal surface area for the explosive molecules to stick to produced the best desorption results, namely the glass wool packed tubes. Correlation between tube type and sampling flows with respect to maximum output signal proved to be significant, along with the individual tube desorption profiles. 23 figs.

Hermes III is a 20-megavolt, 15-terawatt, pulsed accelerator which is available for gamma-ray testing. The purpose of this guide is to serve as a basic source of information for prospective users of Hermes III. Included is a brief discussion of the design and operation of the accelerator and a summary of gamma-ray environmental data. The guide also contains a description of experimental support facilities, data acquisition and analysis systems and general information for users. 6 refs., 16 figs.

Characterizing the explosive dispersal of inert solid particles is of interest in a number of applications. A mixture theory approach is used to calculate the radial motion of the gas-solid mixture as it expands into an infinite atmosphere. Two initial gas-solid configurations are considered. In the first, a core of high pressure gas initially at rest is surrounded by a porous shell of the solid. The other configuration considered is a uniform mixture of solid and gas throughout the sphere. An adaptive finite element method is used to solve the set of partial differential equations for mass, momentum and energy conservation in each phase as well as the compaction equation for the time evolution of solid volume fraction. An adaptive grid scheme is used to refine the mesh to limit discretization errors. This places a fine mesh near the porosity and pressure fronts and greatly reduces the spatial resolution in areas of relatively constant pressure and volume fraction. The dispersal of the solid for the two initial configurations shows quite different behavior. For the gas core and porous shell, the solids are initially compacted to a maximum density of /approximately/80--90% in a very thin region before rapidly dispersing to a broad concentration distribution. For the homogeneous gas-solid sphere, however, there is only a slight compaction region at the leading edge of the expanding gas, and the concentration of solid decays rapidly. 25 refs., 32 figs., 5 tabs.

The purpose of this report is to provide some basic information to beginning users of Department 9140's Computer-Aided Engineering (CAE) workstations. These workstations are all Digital Equipment Corporation (DEC) color VAXstations, and they use the VAX/VMS operating system. This manual shows users how to boot the workstations, login, use the window interface, and use some basic VMS commands. It also discusses some of the CAE software available on the workstations, such as ANVIL-5000. References are given so users can get additional information. 25 refs., 27 figs.

The difficulty of detecting, locating and identifying low-magnitude seismic events has been an ongoing problem. In this note, we describe processing methods that help us to find low-magnitude seismic events. A series of algorithms with beamforming has been developed and has proven effective in helping to discover very low yield events. The beamforming technique consists of determining the array element time delays for the specific source region using previously established events. This allows us to concentrate the array to look at the specified source location. Examples of this type of analysis are provided. In the analysis of seismic data one may be in possession of other information, e.g., newspaper reports of an earthquake. Using this information to concentrate the search for an event will often identify an otherwise overlooked signal. The algorithms for this type of search are incorporated into computer software that includes capabilities for plotting, spectral and signal-to-noise estimation, direction finding, and other functions. 2 refs., 25 figs.

The LeCroy 6880 uses 32 interleaved linear CCD arrays to digitize data up to 250 MHz. Each CCD array has different offset, droop, and gain characteristics. To obtain usable data once the outputs from the CCDs are interleaved, the raw data must be ''corrected'' to account for these different characteristics. This report describes the DC corrections used on raw data to compensate for the differences in CCD characteristics. 5 refs., 12 figs.

An electron moving in the magnetic field generated by a current-carrying rod will drift in the direction defined by the rod. The motion can be characterized by two dimensionless parameters,/var epsilon/ = 2eI/mc/sup 3/..gamma beta.. and xi = (v/sub /phi///v)exp(v/sub z///var epsilon/v). The drift velocity can be computed by numerical integration for arbitrary values of /var epsilon/ and xi. Analytic solutions are derived for the limiting cases xi = 0 and /vert bar/xi/vert bar/ = xi/sub MAX/. Series solutions are derived that are accurate in the limit /vert bar/xi//var epsilon//vert bar/ << 1. A simple algorithm is developed that has an error of less than +- 0.08% for /var epsilon/ greater than or equal to 2. 14 refs., 18 figs.

A new program, ELLIPSE, for the analysis of ellipsometric data is described. The program is interactive and includes on-line help, performs explicit error analysis for single-angle-of-incidence measurements, allows the input of four-zone null data, and performs least-squares analysis of multiple-angle-of-incidence data. Solutions for the transparent-film-on-substrate model are obtained using decoupled equations for film thickness and index. No initial guess is required for thickness, and the algorithm is insensitive to the initial guess for film index. This document combines the user's manual and program description for ELLIPSE, and includes several examples of its use. 11 refs.

One of the factors considered in the design of critical concrete structures is the estimation of the global elasto-plastic structural response caused by the accidental impact of an aircraft. To estimate the response of the structure, the impact force (the force versus time relationship) must be known. Previous analytical studies have derived the forcing function using the impact velocity of the aircraft and the calculated mass and strength distribution of the aircraft. This paper describes a test conducted on April 19, 1988, at an existing rocket sled facility at Sandia National Laboratories in Albuquerque, New Mexico, USA, in which an actual F-4 Phantom aircraft was impacted at a nominal velocity of 215 m/s into an essentially rigid block of concrete. This was accomplished by supporting the F-4 on four struts that were attached to the sled track by carriage shoes to direct the path of the aircraft. Propulsion was accomplished by two stages of rockets. The concrete target was 'floated' on a set of air bearings. Data acquisition consisted of measurements of the acceleration of the fuselage and engines of the F-4, and measurements of the displacement, velocity and acceleration of the concrete target. High-speed photography recorded the impact process and also permitted the determination of the impact velocity. This paper describes the test plan, method and results, while a companion paper discusses the analyses of the results. 6 refs., 11 figs.

A related function takes place in situations where an intermediate memory device may be used to store the unique signal information. In this case, ''verification patterns'' are communicated back to the source as status of the memory in which the unique signal is stored. If properly used, unique signals and verification patterns can support acceptable abnormal-environment nuclear detonation safety. If improperly used, there is danger of a false sense of complacency. In this report, the potential danger of misunderstanding the implications of abnormal environments is described. Unfortunately, a number of common normal-environment assumptions and analytical techniques are sometimes applied to abnormal environment situations. Several of these are shown to be misleading for assessing unique signal performance in abnormal environments. Misapplied approaches can encourage communication system design features that may seriously degrade nuclear detonation safety. 8 refs., 10 figs.

To analytically model soldering and welding processes it is necessary to track the deformation of a material as it changes from a solid to a liquid and then back again to a solid. Because it is the residual stress state in the solid that is of primary interest, the most suitable tools for studying this class of problems appear to be Lagrangian finite element codes that are typically used in the analysis of solids. It is possible to obtain solutions to hydrostatic fluids problems using a Lagrangian finite element code by allowing the ''fluid'' phase of the material to sustain a deviatoric stress component that is very small in magnitude relative to the hydrostatic pressure that exists in the material. The capability to model surface tension phenomena was added to the finite element code SANCHO. SANCHO is a Lagrangian finite element code that uses a dynamic relaxation scheme to solve nonlinear problems involving quasistatic loading of two-dimensional solids. SANCHO is formulated so that it properly accounts for large deformations. This report details the theory and implementation of the method used to model surface tension. With this new capability, SANCHO can be used to solve surface tension problems that are more complex than the problems that can be treated with other more tradition methods of surface tension analysis. 3 refs., 10 figs.

GEN3D is a three-dimensional mesh generation program. The three- dimensional mesh is generated by mapping a two-dimensional mesh into three dimensions according to one of four types of transformations: translating, rotating, mapping onto a spherical surface, and mapping onto a cylindrical surface. The generated three-dimensional mesh can then be reoriented by offsetting, reflecting about an axis, and revolving about an axis. GEN3D can be used to mesh geometries that are axisymmetric or planar, but, due to three-dimensional loading or boundary conditions, require a three-dimensional finite element mesh and analysis. More importantly, it can be used to mesh complex three-dimensional geometries composed of several sections when the sections can be defined in terms of transformations of two-dimensional geometries. The code GJOIN is then used to join the separate sections into a single body. GEN3D reads and writes two-dimensional and three- dimensional mesh databases in the GENESIS database format; therefore, it is compatible with the preprocessing, postprocessing,and analysis codes used by the Engineering Analysis Department at Sandia National Laboratories, Albuquerque, NM. 19 refs., 7 figs.

This report discusses the application of finite-element methods to the solution of magnetostatic field problems. A brief description is given of the finite-element representation of the magnetostatic field. Two computer codes which solve this problem are described. The code MAGNUM is commercially available and the code ISO is a Sandia in-house product. Both codes are currently available on the Sandia CRAY. Some general remarks are presented on modeling techniques and boundary conditions. A new method for estimating solenoid magnetic forces and dynamic response is described. A suite of codes for generating various electromagnetic devices is briefly discussed. Finally, some numerical results are presented. 6 refs., 10 figs.

Sandia National Laboratories operates the Primary Standards Laboratory (PSL) for the Department of Energy, Albuquerque Operations Office (DOE/AL). This report summarizes metrology activities that received emphasis in the second half of 1988 and provides information pertinent to the operation of the DOE/AL system-wide Standards and Calibration Program. 8 refs.

The FAC-SIM factory simulation environment provides systems analysis capabilities during the natural top-down design process for industrial facilities. Models can be constructed and simulations run for coarse descriptions of facility systems and process operations. Detail can be added incrementally to the models as the design progresses. Simulations run with FAC-SIM can identify critical subsystems and determine the impacts of variations in system design and operations. The graphical and hierarchical representations of both physical objects and operations are the unique features of FAC-SIM that permit ease of top-down simulations. This paper describes the FAC-SIM environment and its use in the ongoing development of the Repository Simulation System, REPSIMS, for the analysis of surface facilities at geological repositories for radioactive waste. 13 refs., 5 figs., 5 tabs.