Publications

Most previous Probabilistic Risk Assessments have excluded consideration of accidents initiated in low power and shutdown modes of operation. A study of the risk associated with operation in low power and shutdown is being performed at Sandia National Laboratories for a US Boiling Water Reactor (BWR). This paper describes the proposed methodology for the analysis of the risk associated with the operation of a BWR during low power and shutdown modes and presents preliminary information resulting from the application of the methodology. 2 refs., 2 tabs.

In this paper we formulate a speech coding system that incorporates trellis coded vector quantization (TCVQ) and adaptive predictive coding (APC). A method for optimizing'' the TCVQ codebooks is presented and experimental results concerning survivor path mergings are reported. Simulation results are given for encoding rates of 16 and 9.6 kbps for a variety of coder parameters. The quality of the encoded speech is deemed excellent at an encoding rate of 16 kbps and very good at 9.6 kbps. 13 refs., 2 figs., 4 tabs.

The Institute of Certified Records Managers (ICRM) is a non-profit, certifying organization of professional records managers and administrators. ICRM members are experienced in information requirements, records and information systems, and the related office systems and technologies. All members have met certification requirements and have received the Certified Records Manager (CRM) designation. As the field of information and records management moves toward standardization, and as the application of new technologies and technicalities complicate the measurement and demonstration of professional competence, the need for a means of identifying persons who have basic competency increases. The ICRM is providing such a means by testing and certifying basic knowledge. More and more job announcements are requiring this evidence of competency. Unfortunately, as an organization, NIRMA has a relatively small number of CRMs. The goal of the ICRM Development Group is two-fold; (1) to encourage NIRMA members to obtain their certification by providing basic information and support and; (2) to develop the Nuclear Specialist test module which will demonstrate that bearers have demonstrated expertise in nuclear records management as well as basic competencies. This report covers the examination process.

The Nuclear Information and Records Management Association (NIRMA) Task Force on Requirements Identification is currently involved in a four part project. During the course of the next year the Task Force will: (1) identify the generic requirements documents which have common applicability to nuclear utilities and DOE organizations; (2) research the requirements documents to identify individual requirements; (3) develop and implement a PC based tracking system to present and maintain the research data; and (4) implement a process for ongoing review of requirements. This report discusses these issues.

Multiplexer and amplifier systems must be designed with transistors that can perform satisfactorily over ten years to a total gamma dose of 120E6 rads and a total neutron fluence of 1.6E15 nvt for the SP-100 reactor system. Series of gamma and neutron tests have been completed to measure transistor degradation as a function of total dose, fluence, and temperature. Test results indicate that modest increases in temperature result in substantial improvement of transistor performance at a neutron flux of 8E8 n/cm{sup 2}/s. 2 refs., 3 figs.

Critical Heat Flux (CHF), also called burnout, is one of the major design limits for water-cooled divertors in tokamaks. Another important design issue is the correct thermal modeling of the divertor plate geometry where heat is applied to only one side of the plate and highly subcooled flow boiling in internal passages is used for heat removal. This paper discusses analytical techniques developed to address these design issues, and the experimental evidence gathered in support of the approach. Typical water-cooled divertor designs for the International Thermonuclear Experimental Reactor (ITER) are analyzed, and design margins estimated. Peaking of the heat flux at the tube-water boundary is shown to be an important issue, and design concerns which could lead to imposing large design safety margins are identified. The use of flow enhancement techniques such as internal twisted tapes and fins are discussed, and some estimates of the gains in the design margin are presented. Finally, unresolved issues and concerns regarding hydraulic design of divertors are summarized, and some experiments which could help the ITER final design process identified. 23 refs., 10 figs.

Our previous calorimetric studies of weld melting efficiency and arc efficiency in the GTAW and PAW processes have naturally led us to speculate as to the magnitude of the efficiencies in the LBW process which to data have also not been adequately investigated. Most welding engineers that have had experience with the LBW process are acutely aware that the metals' absorptivity, the surface finish, and the laser wavelength, all play an important role in affecting the energy transfer efficiency, but the extent of their influence and our understanding of the influence of other process variables is not well understood. In addition, it is widely thought that only the LBW or EBW processes can be selected for applications where thermal damage and distortion from the welding process must be kept to a minimum. For these reasons, we have looked forward to performing these calorimetric experiments since they potentially can answer such important questions as: whether or not the melting efficiency of the LBW process is superior to that obtainable with conventional GTAW and PAW welding processes This study was prompted by poor production yields on switching device due to cracking of the ceramic header after final closure welding with the CO{sub 2} LBW process. This calorimetric study was begun in hopes of determining if allowed variations in production process control variables were responsible for increases in heat input and the resulting thermal stresses. By measuring the net heat input to the workpiece with the calorimeter and by measuring the laser output energy and the weld fusion zone size it was possible to determine the magnitudes of both the energy transfer efficiency and the melting efficiency as well as observe their dependence on the process variables. 3 refs.

Component test plans are often designed by allocating a system's reliability goal among the system's components, then designing individual component test plans suitable for demonstrating achievement of each component's reliability goal. One use of the resulting component test data is the calculation of estimated system reliability, based on a model linking the component reliabilities to system reliability. The statistical precision of this system estimate depends on the component test plans (numbers of each component tested and the type of tests, e.g., variables or attributes) and, hence, is determined by the component test planners. Because system reliability may be of considerable interest, we feel an integrated view of component testing is required to assure that the ensemble of component tests will provide an adequate system reliability estimate. This paper considers the case of a series system of different components and binomial component data. For the case of equal numbers of units tested of each component (which can be shown to minimize total cost, subject to the risk constraints) the O.C. envelope is readily derived and from this envelope component test plans that satisfy the specified risks can be derived from equations that involve the cumulative binomial distribution function. Existing tables pertaining to acceptance sampling plans based on the binomial distribution can be used to determine the required number of component tests. 10 refs., 2 figs.

Weak formulations in Analytical Dynamics are developed, paralleling the variational methods in elastostatics, and including a fundamental yet novel approach for treating constraints (both holonomic and nonholonomic). A general three field approach is presented, in which the momentum balance conditions, the compatibility conditions between displacement and velocity, the constitutive relations and the displacement and momentum boundary conditions are all enforced in weak form. A primal, or kinematic formulation is developed from the general form by enforcing the compatibility conditions and displacement boundary conditions a priori. The conditional stability of the kinematic formulation is the counterpart of the locking phenomenon in elastostatics and may be avoided, either by reduced order integration, or by utilizing a mixed formulation. Toward this end, a two field mixed formulation is presented, which follows from the general form, when the constitutive relations are satisfied a priori. A general set of the constraint equations are introduced into the kinematic and mixed formulations, using a specific choice of multipliers, which results in modified variational principles. Several simple examples concerning rigid body dynamics are presented. 15 refs., 18 figs.

This paper describes arc discharge tests conducted in a prepressurized, constant-volume pressure vessel to study arc behavior over a wide range of current densities, discharge durations and initial vessel pressures. This method allows controlled access to a wider range of conditions than those previously studied in capillary tests. We have investigated aspects of the radiative heat transfer by calculating the material opacity and mean free paths of photons for conditions typical of arc diagnostics. We also performed one-dimensional Eulerian hydrodynamic calculations of the boundary layer behavior in the radiative diffusion approximation. These calculations, which describe the radial mass flow and heat transfer in the absence of turbulent flow effects, show the characteristic times for equilibrium of the high-pressure arc. Finally, we describe progress on a promising means for increasing the mass flux from the capillary discharge through the use of chemically reactive media on the capillary walls. 20 refs., 7 figs.

Integrated circuit logic states are maintained by virtue of specific transistor combinations being either on'' (conducting) or off'' (nonconducting). High energy ion strikes on the microcircuit generate photocurrents whose primary detrimental effect is to make off'' transistors appear on,'' confusing the logic state and leading to single event upset (SEU). Protection against these soft errors is accomplished using either technology or circuit techniques, actions that generally impact yield and performance relative to unhardened circuits. We describe, and using circuit simulations analyze, a technique for hardening latches which requires combinations of technology and circuit modifications, but which provides SEU immunity without loss of speed. Specifically, a single logic state is hardened against SEU using technology methods and the information concerning valid states is then used to simplify hardened circuit design. The technique emphasizes some basic hardening concepts, ideas for which will be reviewed. 3 refs., 2 figs.

Particle Impact Noise Detection (PIND) testing is widely used to test electronic devices for the presence of conductive particles which can cause catastrophic failure. This paper develops a statistical model based on the rate of particles contaminating the part, the rate of particles induced by the test vibration, the escape rate, and the false alarm rate. Based on data from a large number of PIND tests for a canned transistor, the model is shown to fit the observed results closely. Knowledge of the parameters for which this fit is made is important in evaluating the effectiveness of the PIND test procedure and for developing background judgment about the performance of the PIND test. Furthermore, by varying the input parameters to the model, the resulting yield, failure rate and percent fallout can be examined and used to plan and implement PIND test programs.

Fabrication of high-efficiency silicon solar cells requires processing technology capable of maintaining long bulk carrier lifetime and low surface recombination. Development of long-lifetime processing techniques using experimental designs based on statistical methods is described. The first three experiments investigated pre-oxidation cleans, phosphorus gettering, and a comparison of different phosphorus diffusion sources. Optimal processing parameters were found to depend on type of silicon material. 2 refs., 2 figs., 2 tabs.

Thin film ferroelectric materials are the basis for a new, promising IC nonvolatile memory technology. The primary material being studied for ferroelectric memories is PZT. One of the key factors in determining the feasibility of PZT ferroelectric memories for weapon or space applications is whether PZT ferroelectric technology can be integrated into a radiation-hardened CMOS or bipolar process. Sandia National Laboratories has a program to study ferroelectric/CMOS process integration issues. The primary goal of this program is to determine if radiation-hardened reliable ferroelectric/CMOS IC memories can be fabricated. This program includes both the fabrication and characterization of ferroelectric test capacitors. In this paper we will give a brief overview of the program, discuss techniques developed to characterize ferroelectric devices for retention and endurance, and give results on studies of fatigue and retention of capacitors.

A travelling wave Faraday effect fiber current sensor, consisting of a helical optical fiber coil immersed in a dielectric medium, has been demonstrated. Improved phase matching conditions have led to measured bandwidth enhancements of greater than a factor of four. Sensitive devices with multi-gigahertz bandwidths are possible using this technique. 7 refs., 3 figs.

The deformation and crack initiation behavior of Ti-24Al-11Nb has been examined over a temperature range of 298 to 923 K and for strain rates from 10{sup {minus}4}/s to 10{sup 2}/s. Tests performed in compression indicate much lower strain hardening at 10{sup 2}/s than at either 10{sup {minus}1}/s or 10{sup {minus}4}/s at all temperatures. Associated with this behavior is the occurrence of non-uniform, localized deformation bands at 10{sup 2}/s. An analysis indicates that adiabatic deformation conditions predominate at 10{sup 2}/s and that these result in adiabatic softening. Furthermore, as a result of non-uniform deformation and adiabatic heating, this Ti{sub 3}-Al-based alloy is actually more resistant to strain-induced microcrack initiation at 10{sup 2}/s than at 10{sup {minus}4}/s during room temperature testing. 16 refs., 7 figs.

This paper attempts to give an elementary review of the kinematics of large deformations with a view to illustrating some of the underlying geometric concepts, and then goes on to review some basic features of elastic, hypoelastic, and rate type constitutive equations relevant to their use in numerical methods. Since some recent work has emphasized working in a rotated'' intermediate configuration, one in which the rigid body rotation has been backed out, results relating to this configuration are included, otherwise all of the results have been read off directly from Truesdell and Toupin ( ) or Truesdell and Noll ( ). Finally, results given by Nemat-Nasser ( ) are quoted which reconcile some generalizations of infinitesimal plasticity and some remarks are made relevant to the introduction of tensor internal state variables. Thermodynamic effects, although important in calculations, are omitted to emphasize kinematical effects. Because recent authors have used different names and symbols for stress and strain tensors, it has been found necessary to give a self contained if abbreviated development of the kinematics, which, however, allows a compact discussion of constitutive equations.

We report formation of several small colloidal metal catatlysts in inverted micelle (oil-continuous) systems. These materials have demonstrated catalytic activity in situ (i.e. unsupported). The range of solvents possible in this process is large, including all saturated hydrocarbons, cyclic hydrocarbons (e.g. cyclohexane) and aromatics (e.g. toluene, xylene). Three classes of micelle system were investigated, nonionic, anionic, and cationic. Nonionic types allow precise size control but in general do not act as strong stabilizing agents at high temperatures. Cationics can be chosen to provide this permanent stability, providing both charge and steric stabilization. Metal systems formed include Rh, Ni, NiB, MoO{sub 2}, Pd, Au and Ag and alloys. Selected examples are given. 4 figs.

This paper presents an analytical and numerical analysis which evaluates the core-structure heat-up and subsequent relocation of molten core materials during a NWR short-term station blackout accident with ADS. A simplified one-dimensional approach coupled with bounding arguments is first presented to establish an estimate of the temperature differences within a BWR assembly at the point when structural material first begins to melt. This analysis leads to the conclusions that the control blade will be the first structure to melt and that at this point in time, overall temperature differences across the canister-blade region will not be more than 200 K. Next, a three-dimensional heat-transfer model of the canister-blade region within the core is presented that uses a diffusion approximation for the radiation heat transfer. This is compared to the one-dimensional analysis to establish its compatibility. Finally, the extension of the three-dimensional model to include melt relocation using a porous media type approximation is described. The results of this analysis suggest that under these conditions significant amounts of material will relocate to the core plate region and refreeze, potentially forming a significant blockage. The results also indicate that a large amount of lateral spreading of the melted blade and canister material into the fuel rod regions will occur during the melt progression process. 22 refs., 18 figs., 1 tab.

Fatigue life estimates for wind turbine components can be extremely variable due to both inherently random and uncertain parameters. A structural reliability analysis is used to qualify the probability that the fatigue life will fall short of a selected target. Reliability analysis also produces measures of the relative importance of the various sources of uncertainty and the sensitivity of the reliability to each input parameter. The process of obtaining reliability estimates is briefly outlined. An example fatigue reliability calculation for a blade joint is formulated; reliability estimates, importance factors, and sensitivities are produced. Guidance in selecting distribution functions for the random variables used to model the random and uncertain parameters is also provided. 5 refs., 9 figs., 1 tab.

Photovoltaic concentrator collectors are an attractive option for utility-scale photovoltaic power plants. This paper reviews the current status of photovoltaic concentrator collector and cell development. Included in the review is a discussion of the economic motivation for concentrators, a summary of recent concentrator collector and cell development, and a description of a major new program to accelerate development and commercial introduction of concentrator collectors. 21 refs., 1 fig., 3 tabs.

Physical security specialists have been attracted to the concept of video motion detection for several years. Claimed potential advantages included additional benefit from existing video surveillance systems, automatic detection, improved performance compared to human observers, and cost effectiveness. In recent years significant advances in image processing dedicated hardware and image analysis algorithms and software have accelerated the successful application of video motion detection systems to a variety of physical security applications. Currently Sandia is developing several advanced systems that employ image processing techniques for a broader set of safeguards and security applications. TCATS (Target Cueing and Tracking System) uses a set of powerful, flexible, modular algorithms and software to alarm on purposeful target motion. Custom TCATS hardware optimized for perimeter security applications is currently being evaluated with video input. VISDTA (Video Imaging System for Detection, Tracking, and Assessment) uses some of the same TCATS algorithms and operates with a thermal imager input. In the scan mode, VISDTA detects changes in a scene from the previous image at a given scan point; in the stare mode, VISDTA detects purposeful motion similar to TCATS.

Many of the properties associated with ceramic materials such as high hardness, high dielectric constant, refractoriness, and good optical properties will play a critical role in the development of devices for new and emerging technologies. In many cases, the combination of properties that is required demands that a composite material be designed to fulfill these complex materials needs. The increasing emphasis upon composite materials design and performance necessarily focuses greater attention upon the structure and properties of interfaces in ceramic materials. One on the most important aspects of interfacial behavior is the adhesive stability. As an example, high hardness ceramic coatings for tribological applications require a high degree of interfacial adhesion with the underlying substate material. Alternatively it has been shown that fiber reinforced ceramic composites that are designed for high fracture toughness must contain weak interfaces that allow for fiber pull-out to toughen the instrinsically brittle ceramic matrix. Our ability to design ceramic interfaces for specific interfacial adhesive behavior dictates that we develop a full understanding of the factors that control the adhesive bond in these systems. We report on the use of continuum fracture mechanics techniques to identify the molecular source of adhesion between oxide surfaces and introduce a new approach to measuring interfacial adhesive forces using an Interfacial Force Microscope.

Although computational aerodynamics simulation has been taking more responsibility during recent years, wind tunnel experimentation has continued to play the major role in flight vehicle analysis and design.This role, however, is changing because of the great strides in the capability and confidence in numerical simulations. For a small, well defined, class of supersonic and hypersonic flow problems, high quality numerical solutions are now believed to represent the physics of the problem more accurately than a wind tunnel experimental can simulate the free flight conditions. An example of this is the supersonic or hypersonic, laminar, perfect gas flow over a spherically blunted cone at low angle of attack. In this paper, aerodynamic force and moment measurements and flow visualization results are presented for a reentry vehicle configuration at Mach 8. All of the results were obtained in the Sandia Mach 8 long duration, blow-down, hypersonic wind tunnel. The basic vehicle configuration is a spherically blunted cone with a slice parallel with the axis of the vehicle. Onto the slice portion of the vehicle can be attached flaps with three different deflection angles, 10, 20 and 30 deg. Flow visualization results include surface oil flow, spark Schlieren, and liquid crystal photographs. 1 ref., 7 figs.

An AlGaAs window layer is used in high-efficiency GaAs solar cells to reduce carrier recombination at the front surface. Free surfaces of III-V semiconductors have a high density of surface states that serve as recombination sites and create a depletion region at the front surface. We have performed a theoretical investigation of front-surface recombination that includes the effect of a surface space-charge layer. It was found that the surface space-charge layer can have a profound effect on front-surface recombination for thin or lightly doped window layers. 15 refs., 5 figs., 1 tab.