Publications

Nuclear Thermal Propulsion (NTP) has been identified as a critical technology in support of the NASA Space Exploration Initiative (SEI). In order to safely develop a reliable, reusable, long-lived flight engine, facilities are required that will support ground tests to qualify the nuclear rocket engine design. Initial nuclear fuel element testing will need to be performed in a facility that supports a realistic thermal and neutronic environment in which the fuel elements will operate at a fraction of the power of a flight weight reactor/engine. Ground testing of nuclear rocket engines is not new. New restrictions mandated by the National Environmental Protection Act of 1970, however, now require major changes to be made in the manner in which reactor engines are now tested. These new restrictions now preclude the types of nuclear rocket engine tests that were performed in the past from being done today, A major attribute of a safely operating ground test facility is its ability to prevent fission products from being released in appreciable amounts to the environment. Details of the intricacies and complications involved with the design of a fuel element ground test facility are presented in this report with a strong emphasis on safety and economy.

Several new neutron cross section libraries, such as ENDF/ B-VI and IRDF-90, have recently been made available to the dosimetry community. Recommendations are made for the source selection of reaction cross sections that vary significantly among the libraries. In general, integral parameters from spectra obtained from unfold/adjustment codes using the new cross sections will not significantly change. A 61-reaction compendium of dosimetry cross sections drawn from existing evaluations has been compiled for use at the Sandia National Laboratories Radiation Metrology Laboratory. This dosimetry library (SNLRML) is recommended for use in spectrum determination with unfold/ adjustment methods. © 1992 IEEE

A rapid deployment access delay system (RAPADS) has been designed to provide high security protection of valued assets. The system or vault is transportable, modular, and utilizes a pin connection design. Individual panels are attached together to construct the vault. The pin connection allows for quick assembly and disassembly, and makes it possible to construct vaults of various sizes to meet a specific application. Because of the unique pin connection and overlapping joint arrangement, a sequence of assembly steps are required to assembly the vault. As a result, once the door is closed and locked, all pin connections are concealed and inaccessible. This provides a high level of protection in that no one panel or connection is vulnerable. This paper presents the RAPADS concept, design, fabrication, and construction.

There is an emerging interest in using thermal IR to automatically detect human intruders over wide areas. Such a capability could provide early warning beyond the perimeter at fixed sites, and could be used for portable security around mobile military assets. Sandia National Laboratories has been working on automatic detection systems based on the thermal contrast and motion of human intruders for several years, and has found that detection is sometimes difficult, depending on solar and other environmental conditions. Solar heating can dominate human thermal radiation by 100 fold, and dynamic background temperature changes can limit detector sensitivity. This paper explains those conditions and energy transfer mechanisms that lead to difficult thermal detection. We will not cover those adverse conditions that are more widely understood and previously reported on, such as fog, smoke, rain and falling snow. This work was sponsored by the Defense Nuclear Agency.

In the wavenumber-domain method of SAR imaging, frequencydomain radar data are used to reconstruct a portion of the 2-D Fourier transform of the scene, which is then inverted to create the image. The method suffers no inherent limits on aperture length or scene size. This paper extends the concept to the case where the synthetic aperture is not a straight line and the samples are unevenly spaced. An accumulation formula for wavenumberdomain reconstruction is derived and shown to be equivalent to earlier algorithms in the uniform-aperture case. It is then shown how data with three-dimensional irregularity in the aperture can be processed using height correction and mapping into the slant plane.

CIRCE2 is a cone-optics computer code for determining the flux distribution and total incident power upon a receiver, given concentrator and receiver geometries, sunshape (angular distribution of incident rays from the sun-disk), and concentrator imperfections such as surface roughness and random deviation in slope. Statistical methods are used to evaluate the directional distribution of reflected rays from any given point on the concentrator, whence the contribution to any point on the target can be obtained. DEKGEN2 is an interactive preprocessor which facilitates specification of geometry, sun models, and error distributions. The CIRCE2/DEKGEN2 package equips solar energy engineers with a quick, user-friendly design and analysis tool for study/optimization of dish-type distributed receiver systems. The package exhibits convenient features for analysis of 'conventional' concentrators, and has the generality required to investigate complex and unconventional designs. Among the more advanced features are the ability to model dish or faceted concentrators and stretched-membrane reflectors, and to analyze 3-D flux distributions on internal or external receivers with 3-D geometries. Facets of rectangular, triangular, or circular projected shape, with profiles of parabolic, spherical, flat, or custom curvature can be handled. Provisions for shading, blocking, and aperture specification are also included. This paper outlines the features and capabilities of the new package, as well as the theory and numerical models employed in CIRCE2.

This paper presents two parallel implementations of a knowledge-based robotic grasp generator. The grasp generator, originally developed as a rule-based system, embodies a knowledge of the associations between the features of an object and the set of valid hand shapes/arm configurations which may be used to grasp it. Objects are assumed to be unknown, with no a priori models available. The first part of this paper presents a `parallelization' of this rule base using the connectionist paradigm. Rules are mapped into a set of nodes and connections which represent knowledge about object features, grasps, and the required conditions for a given grasp to be valid for a given set of features. Having shown that the object and knowledge representations lend themselves to this parallel recasting, the second part of the paper presents a back propagation neural net implementation of the system that allows the robot to learn the associations between object features and appropriate grasps.

The Capacitors Division at Sandia National Laboratories has for many years been actively involved in developing high reliability, low-inductance, energy-storage, pulse-discharge capacitors. Development has concentrated on two dielectric systems; mica-paper and Mylar (both dry wrap and fill and FC40 liquid impregnation). Continuous design improvements are constantly being sought. For pulse discharge usage lowering the capacitor inductance can improve circuit performance. This paper describes recent efforts to improve the efficiency of low-inductance, mica-paper capacitors by reducing the inductance through optimizing the component geometry. The study focused on a 0.2 {mu}F, 4000 V mica-paper extended-foil capacitor design. The experimental matrix was a two-level, three factor with center points design, and was replicated four times to give reasonable statistics. The factors were the capacitor width, capacitor length, and electrode width, and with response functions of capacitor inductance and circuit performance. The capacitor inductance was measured by the resonance technique, and the circuit performance was evaluated by peak (discharge) current and rise time. Results show that the inductance can be minimized by choice of geometry with accompanying improvements in circuit performance.

This paper describes the plan for a test to failure of a steel containment vessel model. The test specimen proposed for this test is a scale model representing certain features of an improved BWR MARK-2 containment vessel. The objective of this test is to investigate the ultimate structural behavior of the model by incrementally increasing the internal pressure, at ambient temperature, until failure occurs. Pre- and posttest analyses will be conducted to predict and evaluate the results of this test. The main objective of these analyses to validate, by comparisons with the experimental data, the analytical methods used to evaluate the structural behavior of an actual containment vessel under severe accident conditions. This experiment is part of a cooperative program between the Nuclear Power Engineering Corporation (NUPEC), the United States Nuclear Regulatory Commission (NRC), and Sandia National Laboratories (SNL).

Logging technologies developed hydrocarbon resource evaluation have not migrated into geothermal applications even though data so obtained would strengthen reservoir characterization efforts. Two causative issues have impeded progress: (i) there is a general lack of vetted, high-temperature instrumentation, and (ii) the interpretation of log data generated in a geothermal formation is in its infancy. Memory-logging tools provide a path around the first obstacle by providing quality data at a low cost. These tools feature on-board computers that process and store data, and newer systems may be programmed to make decisions.'' Since memory tools are completely self-contained, they are readily deployed using the slick line found on most drilling locations. They have proven to be rugged, and a minimum training program is required for operator personnel. Present tools measure properties such as temperature and pressure, and the development of noise, deviation, and fluid conductivity logs based on existing hardware is relatively easy. A more complex geochemical tool aimed at a quantitative analysis of potassium, uranium and thorium will be available in about on year, and it is expandable into all nuclear measurements common in the hydrocarbon industry. A second tool designed to sample fluids at conditions exceeding 400{degrees}C is in the proposal stage. Partnerships are being formed between the geothermal industry, scientific drilling programs, and the national laboratories to define and develop inversion algorithms relating raw tool data to more pertinent information. 8 refs.

The overpressurization of a 1:6 scale reinforced concrete containment building demonstrated that liner tearing is a plausible failure mode in such structures under severe accident conditions. A combined experimental and analytical program was developed to determine the important parameters that affect liner tearing and to develop reasonably simple analytical methods for predicting when tearing will occur. Three sets of test specimens were designed to allow individual control over and investigation of the mechanisms believed to be important in causing failure of the liner plate. The series of tests investigated the effect on liner tearing produced by the anchorage system, the loading conditions, and the transition in thickness of the liner. Before testing, the specimens were analyzed using two- and three-dimensional finite element models. Based on the analysis, the failure mode and corresponding load conditions were predicted for each specimen. Test data and posttest examination of test specimens shows mixed agreement with the analytical predictions with regard to failure mode and specimen response for most tests. Many similarities were also observed between the response of the liner in the 1:6 scale reinforced concrete containment model and the response of the test specimens. This work illustrates the fact that the failure mechanism of a reinforced concrete containment building can be greatly influenced by details of liner and anchorage system design. Furthermore, it significantly increases the understanding of containment building response under severe accident conditions.

Acoustic telemetry has been a dream of the drilling industry for the past 50 years. It offers the promise of data rates which are one-hundred times greater than existing technology. Such a system would open the door to true logging-while-drilling technology and bring enormous profits to its developers. The basic idea is to produce an encoded sound wave at the bottom of the well, let it propagate up the steel drillpipe, and extract the data from the signal at the surface. Unfortunately, substantial difficulties arise. The first difficult problem is to produce the sound wave. Since the most promising transmission wavelengths are about 20 feet, normal transducer efficiencies are quire low. Compounding this problem is the structural complexity of the bottomhole assembly and drillstring. For example, the acoustic impedance of the drillstring changes every 30 feet and produces an unusual scattering pattern in the acoustic transmission. This scattering pattern causes distortion of the signal and is often confused with signal attenuation. These problems are not intractable. Recent work has demonstrated that broad frequency bands exist which are capable of transmitting data at rates up to 100 bits per second. Our work has also identified the mechanism which is responsible for the observed anomalies in the patterns of signal attenuation. Furthermore in the past few years a body of experience has been developed in designing more efficient transducers for application to metal waveguides. The direction of future work is clear. New transducer designs which are more efficient and compatible with existing downhole power supplies need to be built and tested; existing field test data need to be analyzed for transmission bandwidth and attenuation; and the new and less expensive methods of collecting data on transmission path quality need to be incorporated into this effort. 11 refs.

An effort has been undertaken to develop a brittle fracture acceptance criterion for structural components of nuclear material transportation casks. The need for such a criterion was twofold. First, new generation cask designs have proposed the use of ferritic steels and other materials to replace the austenitic stainless steel commonly used for structural components in transport casks. Unlike austenitic stainless steel which fails in a high-energy absorbing, ductile tearing mode, it is possible for these candidate materials to fail via brittle fracture when subjected to certain combinations of elevated loading rates and low temperatures. Second, there is no established brittle fracture criterion accepted by the regulatory community that covers a broad range of structural materials. Although the existing IAEA Safety Series {number sign}37 addressed brittle fracture, its the guidance was dated and pertained only to ferritic steels. Consultant's Services Meetings held under the auspices of the IAEA have resulted in a recommended brittle fracture criterion. The brittle fracture criterion is based on linear elastic fracture mechanics, and is the result of a consensus of experts from six participating IAEA-member countries. The brittle fracture criterion allows three approaches to determine the fracture toughness of the structural material. The three approaches present the opportunity to balance material testing requirements and the conservatism of the material's fracture toughness which must be used to demonstrate resistance to brittle fracture. This work has resulted in a revised Appendix IX to Safety Series {number sign}37 which will be released as an IAEA Technical Document within the coming year.

We show experimentally and theoretically that the generation of the 13-TW Hermes III electron beam can be accurately monitored, and that the beam can be accurately directed onto a high-Z target to produce a wide variety of bremsstrahlung patterns. This control allows the study of radiation effects induced by gamma rays to be extended into new parameters regimes. Finally, we show that the beam can be stably transported in low-pressure gas cells.

This paper presents the groundwork for a completely automatic 3-D hexahedral mesh generation algorithm called plastering. It is an extension of the paving algorithm developed by Blacker, where paving is a completely automatic 2-D quadrilateral meshing technique.

The transport of a chemically reactive fluid through a permeable medium is governed by many classes of chemical interactions. Dissolution/precipitation (D/P) reactions are among the interactions of primary importance because of their significant influence on the mobility of aqueous ions. In general, D/P reactions lead to the propagation of coherent waves. This paper provides an overview of the types of wave phenomena observed in one-dimensional (1D) and two-dimensional (2D) porous media for systems in which mineral D/P is the dominant type of chemical reaction. It is demonstrated that minerals dissolve in sharp waves in 1D advection-dominated transport, and that these waves separate zones of constant chemical compositions in the aqueous and mineral phases. Analytical solutions based on coherence methods are presented for solving 1D advection-dominated transport problems with constant and variable boundary conditions. Numerical solutions of diffusion-dominated transport in porous media show that sharp D/P fronts occur in this system as well. A final example presents a simple dual-porosity system with advection in an idealized fracture and solute diffusion into an adjacent porous matrix. The example illustrates the delay of contaminant release from the 2D domain due to a combination of physical retardation and chemical retardation.

A closely coupled computational and experimental aerodynamics research program was conducted on a hypersonic vehicle configuration at Mach 8. Aerodynamic force and moment measurements and flow visualization results were obtained in the Sandia National Laboratories hypersonic wind tunnel for laminar boundary layer conditions. Parabolized and iterative Navier-Stokes simulations were used to predict flow fields and forces and moments on the hypersonic configuration. The basic vehicle configuration is a spherically blunted 10{degrees} cone with a slice parallel with the axis of the vehicle. On the slice portion of the vehicle, a flap can be attached so that deflection angles of 10{degrees}, 20{degrees}, and 30{degrees} can be obtained. Comparisons are made between experimental and computational results to evaluate quality of each and to identify areas where improvements are needed. This extensive set of high-quality experimental force and moment measurements is recommended for use in the calibration and validation of computational aerodynamics codes. 22 refs.

Microstructural models of deformation of polycrystalline materials suggest that inelastic deformation leads to the formation of a corner or vertex at the current load point. This vertex can cause the response to non-proportional loading to be more compliant than predicted by the smooth yield-surface idealization. Combined compression-torsion experiments on Tennessee marble indicate that a vertex forms during inelastic flow. An important implication is that strain localization by bifurcation occurs earlier than predicted by bifurcation analysis using isotropic hardening.

Acoustic emissions and conventional strain measurements were used to follow the evolution of the damage surface and plastic potential in a limestone under triaxial compression. Confining pressures were chosen such that macroscopically, the limestone exhibited both brittle and ductile behavior. The parameters derived are useful for modeling the deformation of a pressure-dependent material and for computing when localization would occur. For modeling, simple approximations are adequate, but a more complete understanding of the evolution of the various parameters is necessary in order to calculate when localization can be expected. 11 refs., 6 figs.

Light emission microscopy is now currently used in most integrated circuit (IC) failure analysis laboratories. This tutorial is designed to benefit both novice and experienced failure analysts by providing an introduction to light emission microscopy as well as information on new techniques, such as the use of spectral signatures. The use of light emission for accurate identification and spatial localization of physical defects and failure mechanisms is presented. This includes the analysis of defects such as short circuits which do not themselves emit light. The importance of understanding the particular IC design and applying the correct electrical stimulus is stressed. A video tape is used to show light emission from pn junctions, MOS transistors, test structures, and CMOS ICs in static and dynamic electrical stimulus conditions. 27 refs.

The Thermionic System Evaluation Test (TSET) is a ground test of an unfueled Russian TOPAZ-II in-core thermionic space reactor powered by electric heaters. The facility that will be used for testing of the TOPAZ-II systems is located at the New Mexico Engineering Research Institute (NMERI) complex in Albuquerque, NM. The reassembly of the Russian test equipment is the responsibility of International Scientific Products (ISP), a San Jose, CA, company and Inertek, a Russian corporation, with support provided by engineers and technicians from Phillips Laboratory (PL), Sandia National Laboratories (SNL), Los Alamos National Laboratory (LANL), and the University of New Mexico (UNM). This test is the first test to be performed under the New Mexico Strategic Alliance agreement. This alliance consist of the PL, SNL, LANL, and UNM. The testing is being funded by the Strategic Defense Initiative Organization (SDIO) with the PL responsible for project execution.

Radioactive material transport casks use either lead or depleted uranium (DU) as gamma-ray shielding material. Stainless steel is conventionally used for structural containment. If a DU alloy had sufficient properties to guarantee resistance to failure during both nominal use and accident conditions to serve the dual-role of shielding and containment, the use of other structure materials (i.e., stainless steel) could be reduced. (It is recognized that lead can play no structural role.) Significant reductions in cask weight and dimensions could then be achieved perhaps allowing an increase in payload. The mechanical response of depleted uranium has previously not been included in calculations intended to show that DU-shielded transport casks will maintain their containment function during all conditions. This paper describesa two-part study of depleted uranium alloys: First, the mechanical behavior of DU alloys was determined in order to extend the limited set of mechanical properties reported in the literature. The mechanical properties measured include the tensile behavior the impact energy. Fracture toughness testing was also performed to determine the sensitivity of DU alloys to brittle fracture. Fracture toughness is the inherent material property which quantifies the fracmm resistance of a material. Tensile strength and ductility are significant in terms of other failure modes, however, as win be discussed. These mechanical properties were then input into finite element calculations of cask response to loading conditions to quantify the potential for claiming structural credit for DU. (The term structural credit'' describes whether a material has adequate properties to allow it to assume a positive role in withstanding structural loadings.)

Interfacial microchemical characterization is required in all aspects of surface processing as applied to transportation and utility technologies. Corrosion protection, fuel cells and batteries, wear surfaces, polymers and polymer-oxide interfaces, thin film multilayers, photoelectrochemical systems, and organized molecular assemblies are just a few examples of interfacial systems of interest to these industries. A number of materials and processing problems, both related to fundamental understanding and to monitoring manufacturing operations, have been identified where our microchemical characterization abilities need improving. Over twenty areas for research are identified where progress will contribute to improved understanding of materials and processes, improved problem-solving abilities, improved manufacturing consistency, and lower costs. Some of the highest priority areas for research include (1) developing techniques and methods with improved chemical specificity at interfaces, (2) developing fast, real-time surface and interface probes and (3) improving the cost and reliability of manufacturing monitors. Increased collaboration among University, Industry, and Government laboratories will be a prerequisite to making the required progress in a timely fashion.

A parallel processor that is optimized for real-time linear control has been developed. This modular system consists of A/D modules, D/A modules, and floating-point processor modules. The scalable processor uses up to 1,000 Motorola DSP96002 floating-point processors for a peak computational rate of 60 GFLOPS. Sampling rates up to 625 kHz are supported by this analog-in to analog-out controller. The high processing rate and parallel architecture make this processor suitable for computing state-space equations and other multiply/accumulate-intensive digital filters. Processor features include 14-bit conversion devices, low input-output latency, 240 Mbyte/s synchronous backplane bus, low-skew clock distribution circuit, VME connection to host computer, parallelizing code generator, and look-up-tables for actuator linearization. This processor was designed primarily for experiments in structural control. The A/D modules sample sensors mounted on the structure and the floating-point processor modules compute the outputs using the programmed control equations. The outputs are sent through the D/A module to the power amps used to drive the structure's actuators. The host computer is a Sun workstation. An Open Windows-based control panel is provided to facilitate data transfer to and from the processor, as well as to control the operating mode of the processor. A diagnostic mode is provided to allow stimulation of the structure and acquisition of the structural response via sensor inputs.

International Atomic Energy Agency (IAEA) inspectors must maintain continuity of knowledge on all safeguard samples, and in particular on those samples drawn from plutonium product and spent fuel input tanks at a nuclear reprocessing plant's blister sampling station. Integrity of safeguard samples must be guaranteed from the sampling point to the moment of sample analysis at the IAEA's Safeguards Analytical Laboratory (SAL Seibersdorf) or at an accepted local laboratory. These safeguard samples are drawn at a blister sampling station with inspector participation, and then transferred via a pneumatic post system to the facility's analytical laboratory. The transfer of the sample by the pneumatic post system, the arrival of the sample in the operator's analytical laboratory, and the storage of the sample awaiting analysis is very time consuming for the inspector, particularly if continuous human surveillance is required for all these activities. This process might be observed by ordinary surveillance methods, such as a video monitoring system, but again this would be cumbersome and time consuming for both the inspector and operator. This paper will describe a secure container designed to assure sample vial integrity from the point the sample is drawn to the treatment of the sample at the facility's analytical laboratory.