Publications

Results are presented of a detailed survey of the present state of scientific understanding of cloud electrification processes and lightning warning technology. A review is given of the principles of operation and demonstrated performance factors of lightning strike location technologies and associated commercial products. Emphasis is given to the local lightning warning problem, which is divided into two categories: detection and tracking of active storms that originate outside of and move into the declared safety zone, and early detection of cloud electrification that initiates within the zone. A prototype single-station warning system design is presented that is intended to accumulate data simultaneously from a complement of different types of sensors during intervals immediately preceding the onset of lightning conditions within the area of coverage. The resultant data base will be analyzed statistically to identify the most promising combinations of early warning indicators and to quantify their reliability as a function of the warning intervals they provide.

Multiple sources of variation will often affect the stability of a manufacturing process. Items from different batches may vary because of variation both within a batch and among different batches. Potential sources of variation include within run, run-to-run and week-to-week differences in a manufacturing process. If multiple sources of variation are present, traditional control chart methods may not be appropriate. In this report we develop control charts for monitoring these sources of variation as well as the process average. An example of how to use the control charts is given, using Field 89 data from functional testing of the MC3854 neutron tube.

We have determined the effects that orientation and stress have on chemically prepared Pb(Zr,Ti)0{sub 3} (PZT) film properties. Systematic modification of the underlying substrate technology has permitted us to fabricate suites of films that have various degrees of orientation at a constant stress level, and to also fabricate films that are in different states of stress, but have similar orientation. We have fabricated highly oriented films of the following compositions: PZT 60/40, PZT 40/60 and PZT 20/80. Remanent polarizations ({approx}60 {mu}C/cm{sup 2}) greater than the best bulk polycrystalline ferroelectrics were obtained for PZT 40/60 films that were under compression and highly (001) oriented. While we show that systematically varying orientation influences ferroelectric properties, film stress also has a considerable effect. Perhaps the most important concept presented in this paper is that the sign of the film stress at the Curie point controls the type of ferroelectric behavior exhibited by PZT thin films. Further, our stress measurements as a function of thermal history indicate that the coefficient of thermal expansion of the paraelectric state is critical in determining the type of film ferroelectric behavior.

GROPE is a program that examines the input to a finite element analysis (which is in the GENESIS database format) or the output from an analysis (in the EXODUS database format). GROPE allows the user to examine any value in the database. The display can be directed to the user`s terminal or to a print file.

A Quality Management System was defined by Sub-Process teams within Data Analysis Department 2722. Each of the processes is concerned with a different phase of work for intemal customers (members of the Department) and for external customers (Sandians external to the Department, or agencies outside of Sandia). This report identifies and defines the crucial Work Processes of the Department, where each Process is documented in a separate ``Chapter.`` This report documents the effort of the Data Analysis Department to effectively provide services to its customers and to assess/improve these services. Thus this report is intended to be a ``living document`` for the Department and each member of the Department is expected to follow its guidelines.

Solar heat gain inside a radiation-shielded forklift operator compartment can be a significant problem due to the ``greenhouse effect``. Battery power prohibits the use of a refrigerant type of air-conditioning system, which limits the interior temperature to be approximately equal to the outside ambient temperature through alternative cooling methods. A heat transfer analysis is performed to determine the amount of solar heat gain in this type of mobile vehicle shelter. Various results are presented that depend on exterior surface finish and temperature difference between inside and outside ambient. An amount of forced air flow along with several design recommendations are then specified to rid the compartment of this excess heat.

Sandia National Laboratories operates the Primary Standards Laboratory for the Department of Energy, Albuquerque Operations Office (DOE/AL). This report summarizes metrology activities that received emphasis in the first half of 1992 and provides information pertinent to the operation of the DOE/AL system wide Standards and Calibration Program.

Aprepro is an algebraic preprocessor that reads a file containing both general text and algebraic, string, or conditional expressions. It interprets the expressions and outputs them to the output file along with the general text. The syntax used in Aprepro is such that all expressions between the delimiters and are evaluated and all other text is simply echoed to the output file. Aprepro contains several mathematical functions, string functions, and flow control constructs. In addition, functions are included that, with some additional files, implement a units conversion system and a material database lookup system. Aprepro was written primarily to simplify the preparation of parameterized input files for finite element analyses at Sandia National Laboratories; however, it can process any text file that does not use the characters.

GJOIN is a two- or three-dimensional mesh combination program. GJOIN combines two or more meshes written in the GENESIS mesh database format into a single GENESIS mesh. Selected nodes in the two meshes that are closer than a specified distance can be combined The geometry of the mesh databases can be modified by scaling, offsetting, revolving, and mirroring. The combined meshes can be further modified by deleting, renaming, or combining material blocks, sideset identifications, or nodeset identifications. GJOIN is one of the mesh generation tools in the Sandia National Laboratories Engineering Analysis Code Access System (SEACAS). GJOIN is typically used with the other SEACAS mesh generation codes GEN3D, GENSHELL, GREPOS, and Aprepro.

This report describes preliminary probabilistic sensitivity analyses of long term gas and brine migration at the Waste Isolation Pilot Plant (WIPP). Because gas and brine are potential transport media for organic compounds and heavy metals, understanding two-phase flow in the repository and the surrounding Salado Formation is essential to evaluating long-term compliance with 40 CFR 268.6, which is the portion of the Land Disposal Restrictions of the Hazardous and Solid Waste Amendments to the Resource Conservation and Recovery Act that states the conditions for disposal of specified hazardous wastes. Calculations described here are designed to provide guidance to the WIPP Project by identifying important parameters and helping to recognize processes not yet modeled that may affect compliance. Based on these analyses, performance is sensitive to shaft-seal permeabilities, parameters affecting gas generation, and the conceptual model used for the disturbed rock zone surrounding the excavation. Brine migration is less likely to affect compliance with 40 CFR 268.6 than gas migration. However, results are preliminary, and additional iterations of uncertainty and sensitivity analyses will be required to provide the confidence needed for a defensible compliance evaluation. Specifically, subsequent analyses will explicitly include effects of salt creep and, when conceptual and computational models are available, pressure-dependent fracturing of anhydrite marker beds.

Iterative, annual performance-assessment calculations are being performed for the Waste Isolation Pilot Plant (WIPP), which is a planned underground repository in southeastern New Mexico for the disposal of transuranic radioactive waste. The performance-assessment calculations estimate long-term (10,000-year) radionuclide releases from the disposal system to the accessible environment. The estimation of the releases is probabilistic in nature, requiring system parameters to be described with probability distributions. Because direct experimental data in some areas are presently insufficient or unavailable to form the required distributions, researchers at Sandia National Laboratories have used a formalized expert-judgment elicitation procedure to determine the state of knowledge in these areas. Expert judgment was used to estimate the concentrations of specific radionuclides in a repository brine that might be forced up an intruding borehole, and also to estimate the distribution coefficients to determine the retardation of radionuclides in the overlying Culebra Dolomite. The variables representing these concentrations and coefficients have been shown by 1990 sensitivity analyses to be among the set of parameters making the greatest contribution to the uncertainty in WIPP performance assessment predictions. Using available information, the experts (one expert panel addressed concentrations and a second panel addressed retardation) were briefed on the problem of insufficient experimental data and were formally elicited to obtain probability distributions that characterize the uncertainty in fixed, but unknown, quantities. The probability distributions developed by the experts were incorporated into the 1991 and 1992 performance-assessment calculations.

Using concepts of decision analysis, this paper examines how government policy makers might consider and evaluate the contribution of additional inspection, openness, and confidence-building measures to diplomatic questions involving compliance with arms control agreements. During the current debate among parties to the Biological Weapons Convention as to what constitutes effective verification of compliance with that Convention, these analytical concepts were employed to evaluate some proposed inspection or confidence-building measures. Some of the salient points not bound up in the confidentiality of on-going negotiations will be summarized here.

This paper describes a current research program at Sandia National Laboratories whereby magnetic stripes are produced through the use of a new particle rotation technology. This new process allows the stripes to be produced in bulk and then held in a latent state so that they may be encoded at a later date. Since particle rotation is less dependent on the type of magnetic particle used, very high coercivity particles could provide a way to increase both magnetic tamper-resistance and accidental erasure protection. This research was initially funded by the Department of Energy, Office of Safeguard and Security as a portion of their Science and Technology Base Development, Advanced Security Concepts program. Current program funding is being provided by Sandia National Laboratories as part of their Laboratory Directed Research and Development program.

The remand of the US Environmental Protection Agency`s long-term performance standards for radioactive-waste disposal provides an opportunity to suggest modifications that would make the regulation more defensible and remove inconsistencies yet retain the basic structure of the original rule. Proposed modifications are in three specific areas: release and dose limits, probabilistic containment requirements, and transuranic-waste disposal criteria. Examination of the modifications includes discussion of the alternatives, demonstration of methods of development and implementation, comparison of the characteristics, attributes, and deficiencies of possible options within each area, and analysis of the implications for performance assessments. An additional consideration is the impact on the entire regulation when developing or modifying the individual components of the radiological standards.

Given a graph G = (V, E) where each vertex v {element_of} V is assigned a weight w(v) and each edge e {element_of} E is assigned a cost c(e), the quotient of a cut partitioning the vertices of V into sets S and {bar S} is c(S, {bar S})/min{l_brace}w(S), w(S){r_brace}, where c(S, {bar S}) is the sum of the costs of the edges crossing the cut and w(S) and w({bar S}) are the sum of the weights of the vertices in S and {bar S}, respectively. The problem of finding a cut whose quotient is minimum for a graph has in recent years attracted considerable attention, due in large part to the work of Rao and Leighton and Rao. They have shown that an algorithm (exact or approximation) for the minimum-quotient-cut problem can be used to obtain an approximation algorithm for the more famous minimumb-balanced-cut problem, which requires finding a cut (S,{bar S}) minimizing c(S,{bar S}) subject to the constraint bW {le} w(S) {le} (1 {minus} b)W, where W is the total vertex weight and b is some fixed balance in the range 0 < b {le} {1/2}. Unfortunately, the minimum-quotient-cut problem is strongly NP-hard for general graphs, and the best polynomial-time approximation algorithm known for the general problem guarantees only a cut whose quotient is at mostO(lg n) times optimal, where n is the size of the graph. However, for planar graphs, the minimum-quotient-cut problem appears more tractable, as Rao has developed several efficient approximation algorithms for the planar version of the problem capable of finding a cut whose quotient is at most some constant times optimal. In this paper, we improve Rao`s algorithms, both in terms of accuracy and speed. As our first result, we present two pseudopolynomial-time exact algorithms for the planar minimum-quotient-cut problem. As Rao`s most accurate approximation algorithm for the problem -- also a pseudopolynomial-time algorithm -- guarantees only a 1.5-times-optimal cut, our algorithms represent a significant advance.

The ability to design gating systems that reliably feed and support investment castings is often the result of ``cut-and-try`` methodology. Factors such as hot tearing, porosity, cold shuts, misruns, and shrink are defects often corrected by several empirical gating design iterations. Sandia National Laboratories is developing rules that aid in removing the uncertainty involved in the design of gating systems for investment castings. In this work, gating geometries used for filling of thin walled investment cast 17-4PH stainless steel flat plates were investigated. A full factorial experiment evaluating the influence of metal pour temperature, mold preheat temperature, and mold channel thickness were conducted for orientations that filled a horizontal flat plate from the edge. A single wedge gate geometry was used for the edge-gated configuration. Thermocouples placed along the top of the mold recorded metal front temperatures, and a real-time x-ray imaging system tracked the fluid flow behavior during filling of the casting. Data from these experiments were used to determine the terminal fill volumes and terminal fill times for each gate design.

This paper studied the behavior of retained system poles and transmission zeros in a control design model when the model is truncated. The sensitivity of the transmission zeros due to the tuncation of system dynamics was analytically obtained. The sensitivity of system poles to the truncation of system dynamics was shown to be zero as expected. The effects of actuator-sensor type and location was also studied. The results were illustrated with two example problems. The effect of transmission zero shifts in control design models and the controllers designed from them was illustrated with an example.

A telerobotic system demonstration was developed for the Department of Energy`s Accident Response group to highlight the applications of telerobotic vehicles to accident site inspection. The proof-of- principle system employs two mobile robots, Dixie and RAYBOT, to inspect a simulated accident site. Both robots are controlled serially from a single driving station, allowing an operator to take advantage of having multiple robots at the scene. The telerobotic system is described and some of the advantages of having more than one robot present are discussed. Future plans for the system are also presented.

This report will present a brief overview of the transient dynamics capabilities at Sandia National Laboratories, with an emphasis on recent new developments and current research. In addition, the Sandia National Laboratories (SNL) Engineering Analysis Code Access System (SEACAS), which is a collection of structural and thermal codes and utilities used by analysts at SNL, will be described. The SEACAS system includes pre- and post-processing codes, analysis codes, database translation codes, support libraries, Unix shell scripts for execution, and an installation system. SEACAS is used at SNL on a daily basis as a production, research, and development system for the engineering analysts and code developers. Over the past year, approximately 190 days of CPU time have been used by SEACAS codes on jobs running from a few seconds up to two and one-half days of CPU time. SEACAS is running on several different systems at SNL including Cray Unicos, Hewlett Packard HP-UX, Digital Equipment Ultrix, and Sun SunOS. An overview of SEACAS, including a short description of the codes in the system, will be presented. Abstracts and references for the codes are listed at the end of the report.

A simple, approximate model of parachute inflation is described. The model is based on the traditional, practical treatment of the fluid resistance of rigid bodies in nonsteady flow, with appropriate extensions to accommodate the change in canopy inflated shape. Correlations for the steady drag and steady radial force as functions of the inflated radius are required as input to the dynamic model. In a novel approach, the radial force is expressed in terms of easily obtainable drag and reefing fine tension measurements. A series of wind tunnel experiments provides the needed correlations. Coefficients associated with the added mass of fluid are evaluated by calibrating the model against an extensive and reliable set of flight data. A parameter is introduced which appears to universally govern the strong dependence of the axial added mass coefficient on motion history. Through comparisons with flight data, the model is shown to realistically predict inflation forces for ribbon and ringslot canopies over a wide range of sizes and deployment conditions.

This document presents the quality assurance (QA) procedures for Parameter Selection and Expert Judgment Panels used by the performance Assessment Department of Sandia National Laboratories, which directly supports the Waste Isolation Pilot Plant (WIPP). Parameter Selection QA procedures described herein will be incorporated into the general Performance Assessment Quality Assurance Procedures, QAP 2-3; the Expert Judgment Panel procedures will be incorporated into QAP 2-6. Both sets of procedures will apply to all Sandia and Sandia contractor activities related to performance assessment (except where the contractor has its own approved QA procedures). This report presents the philosophy behind the QA procedures, provides the standards adopted for performance assessment Parameter Selection and Expert Judgment Panels, and discusses the implementation of these standards.

This 1991 report contains monitoring data from routine radiological and nonradiological environmental surveillance activities. Summaries of significant environmental compliance programs in progress such as National Environmental Policy Act (NEPA) documentation, environmental permits, environmental restoration (ER), and various waste management programs for Sandia National Laboratories in Albuquerque (SNL, Albuquerque) are included. The maximum offsite dose impact was calculated to be 1.3 {times} 10{sup {minus}3} mrem. The total population within a 50-mile radius of SNL, Albuquerque, received a collective dose of 0.53 person-rem during 1991 from SNL, Albuquerque, operations. As in the previous year, the 1991 operations at SNL, Albuquerque, had no discernible impact on the general public or on the environment.

This preliminary study analyzes the atmospheric entry of a solid core nuclear thermal rocket (NTR) engine under three accidental entry scenarios. Depending on the scenario, results of the analysis showed that, without external thermal protection, an aluminum pressure vessel will fail at altitudes ranging 25 to 73 km. subsequent release the core materials occurs. The graphitic based core materials will undergo partial ablation, with the percent mass loss depending on the geometry of the fuel elements. A carbon-phenolic thermal protection system was sized to prevent pressure vessel aerothermal failure. It was found to increase the mass of the NTR by approximately 15 percent.

This report examines containment requirements for spent-fuel transport containers that are transported under normal and hypothetical accident conditions. A methodology is described that estimates the probability of rod failure and the quantity of radioactive material released from breached rods. This methodology characterizes the dynamic environment of the cask and its contents and deterministically models the peak stresses that are induced in spent-fuel cladding by the mechanical and thermal dynamic environments. The peak stresses are evaluated in relation to probabilistic failure criteria for generated or preexisting ductile tearing and material fractures at cracks partially through the wall in fuel rods. Activity concentrations in the cask cavity are predicted from estimates of the fraction of gases, volatiles, and fuel fines that are released when the rod cladding is breached. Containment requirements based on the source term are calculated in terms of maximum permissible volumetric leak rates from the cask. Calculations are included for representative cask designs.

This report describes a mechanism for compiling the functional language SISAL for Sandia`s Epsilon-2 hybrid dataflow machine. The strategy couples the front-end of the standard SISAL compiler (which generates a data dependence graph intermediate form called IF1) with an optimizing code-generator for Epsilon-2. The Epsilon-2 code-generator is the back-end of a compiler for the functional language Id. It translates a data dependence graph intermediate form called Program Graphs into Epsilon-2 machine code. This report describes a translation path from IF1 graphs to Program Graphs. This report also comments on the relative merits of the IF1 and Program Graph representations.