Publications

Different insert (insulator) materials are undergoing evaluation to replace the Fiberite E-3938 BE96 material currently used. Also being evaluated is the reconfiguration of the insert and metal shell-edge geometries for the purpose of reducing the alleged interference principally responsible for insert damage.

The irradiation embrittlement of neutron shield tank (NST) material (A212 Grade B steel) from the Shippingport reactor has been characterized. Irradiation increases the Charpy transition temperature (CTT) by 23--28{degrees}C (41--50{degrees}F) and decreases the upper-shelf energy. The shift in CTT is not as severe as that observed in high-flux isotope reactor (HFIR) surveillance specimens. However, the actual value of the CTT is higher than that for the HFIR data. The increase in yield stress is 51 MPa (7.4 ksi), which is comparable to HFIR data. The NST material is weaker in the transverse orientation than in the longitudinal orientation. Some effects of position across the thickness of the wall are also observed; the CTT shift is slightly greater for specimens from the inner region of the wall. Annealing studies indicate complete recovery from embrittlement after 1 h at 400{degrees}C (752{degrees}F). Although the weld metal is significantly tougher than the base metal, the shifts in CTT are comparable. The shifts in CTT for the Shippingport NST are consistent with the test and Army reactor data for irradiations at <232{degrees}C (<450{degrees}F) and show very good agreement with the results for HFIR A212-B steel irradiated in the Oak Ridge Research Reactor (ORR). The effects of irradiation temperature, fluence rate, and neutron flux spectrum are discussed. The results indicate that fluence rate has no effect on radiation embrittlement at rates as low as 2 {times} 10{sup 8} n/cm{sup 2}{center dot}s and at the low operating temperatures of the Shippingport NST, i.e., 55{degrees}C (130{degrees}F). This suggests that the accelerated embrittlement of HFIR surveillance samples is most likely due to the relatively higher proportion of thermal neutrons in the HFIR spectrum compared to that for the test reactors. 28 refs., 25 figs.

An analysis of thermosyphoning in a stream generator model is presented. The model considers the transient development of buoyancy-driven steam flow in the steam generator tubing, secondary side heat transfer and an inlet plenum mixing model. Numerical solutions are obtained for conditions intended to simulate the natural circulation phenomena in a 3-Loop pressurized water reactor in a loss-of-coolant accident scenario. The relation between the circulation rate and the heating rate is determined. The sensitivity of the model to various key parameters is examined. 16 refs.

The drive designed and built by the Solar Power Engineering Company (SPECO) for its large area heliostat failed under high wind loads during a winter storm. This report details the testing and analysis done to verify the load capabilities of the rebuilt heliostat drive. Changes in design and improvements in fabrication resulted in a usable drive. 12 figs., 7 tabs.

Data are presented from the 18 W/m{sup 2} Mockup for Defense High-Level Waste, a very large scale in situ test fielded underground at the Waste Isolation Pilot Plant (WIPP). These data include selected fielding information, test configuration, instrumentation activities, and comprehensive results from a large number of gages. The results in this report give measured data from the mechanical response gages, i.e., room closure gages, extensometers, and stress meters emplaced in the test. Construction of the test began in June 1984; gage data in this report cover the complete test duration, that is, to June 1990.

Coaxial transmission cells have been developed for testing optical fiber current sensors. Three of these cells are airlines that provide transverse electromagnetic mode operation to 1.0, 2.3, and 13.7 GHz. Standing wave ratios are <1.5 for the unloaded airlines over their given frequency ranges. Solid and liquid dielectric coaxial cells use materials with high relative permittivities, >9.1. A ceramic test cell has a useful frequency range to 2.5 GHz; the liquid cells, filled with propanol, methanol, or water, are good to {approximately}500 MHz. The properties of the liquid cells are described using a model of a multilayer coaxial dielectric system with complex relative permittivities. 15 refs.

Structural calculations were performed to evaluate the source-term nuclear fuels transport cask (ST Cask) under various hypothetical accident scenarios. (1) Three-dimensional transient dynamic analyses were performed to evaluate the strength of the cask`s end-closure clamp mechanism. The calculations were performed for two impact orientations: a side impact and a 20{degrees} corner impact. The calculations identified three weaknesses in the clamp design: a gap designed between the clamp and the cask provides a deformation mode which loosens the clamp, two unconstrained swing bolts used to fasten the clamp can lose preload and come free; and insufficient stiffness of the clamp in torsion. (2) An axisymmetric finite element model was used to evaluate the dynamics of end-drops from 5 and 10 ft. The calculations show that loads generated in the end-drops could break the payload support cable and damage the payload winch. Lead slump resulted in both end-drop calculations. The stresses generated in the cask wall during the end-drops was insufficient to cause buckling. (3) To determine the factor of safety to yield, calculations in which the cask was treated as a beam loaded under its own weight were performed for two support configurations: simply supported at both ends and simply supported at the center (trunnion loading). (4) The survival of the cask from a 1-m drop onto a mild steel punch was evaluated based on equations derived from empirical data. The calculations showed that the ST Cask could survive such an event. (5) Finally, the bolt configuration for the upper-closure was analyzed and determined to be inadequate because it does not prevent the closure from sliding relative to the cask body. Specific recommendations for design changes are made in the report to eliminate identified problems.

A major thrust of the Atmospheric Radiation Measurements (ARM) Program is the establishment of 5 primary and 4 supplementary Cloud and Radiation Testbed (CART) sites. The CART sites will provide the means to acquire the necessary data to test and further develop the components of GCMs (General Circulation Models) which describe the relationships between the characteristics of the atmosphere and the solar and thermal radiation which passes through it. The CART Locale Recommendation Team has presented a priority-ordered set of recommended locales for the primary and supplementary sites, along with alternatives for each. The selection was based primarily on the following criteria: geographical and climatological homogeneity; occurrence of climatologically important cloud types; seasonal change of surface properties; variability of radiatively-active atmospheric components; synergism with other programs; and manageable logistics. An additional criterion was that, taken together, the set of recommended locales must span a broad range of climate regimes. The recommended primary locales include two land and three ocean locales. The first CART Site will be established in the Southern Great Plains (SGP) of the US. The next CART site to be established on land is to be in the polar regions, on the North Slope of Alaska (NSA).

Thermal and mechanical models for intact and jointed rock mass behavior are being developed, verified, and validated at Sandia National Laboratories for the Yucca Mountain Site Characterization Project. Benchmarking is an essential part of this effort and is one of the tools used to demonstrate verification of engineering software used to solve thermomechanical problems. This report presents the results of the third (and final) phase of the first thermomechanical benchmark exercise. In the first phase of this exercise, nonlinear heat conduction code were used to solve the thermal portion of the benchmark problem. The results from the thermal analysis were then used as input to the second and third phases of the exercise, which consisted of solving the structural portion of the benchmark problem. In the second phase of the exercise, a linear elastic rock mass model was used. In the third phase of the exercise, two different nonlinear jointed rock mass models were used to solve the thermostructural problem. Both models, the Sandia compliant joint model and the RE/SPEC joint empirical model, explicitly incorporate the effect of the joints on the response of the continuum. Three different structural codes, JAC, SANCHO, and SPECTROM-31, were used with the above models in the third phase of the study. Each model was implemented in two different codes so that direct comparisons of results from each model could be made. The results submitted by the participants showed that the finite element solutions using each model were in reasonable agreement. Some consistent differences between the solutions using the two different models were noted but are not considered important to verification of the codes. 9 refs., 18 figs., 8 tabs.

Licensing of the potential nuclear-waste repository at Yucca Mountain by the Nuclear Regulatory Commission would require, among other things, demonstrations of the long term usability of the underground facilities. Such a demonstration involves analysis of the mechanical response of the rock to the presence of underground openings and heat-producing waste, which in turn requires data on the mechanical properties of the rock. This document describes the experimental results from a scoping study which led to the development of procedures for performing quality-affecting rock-mechanics experiments on intact rock. The future experiments performed with these procedures will produce information on the time-dependent deformation of welded tuff and represent one aspect of the overall effort to characterize the rheology of the rock mass. 3 refs., 42 figs., 6 tabs.

This report describes a joint shear model used in conjunction with a computational model for jointed media with orthogonal joint sets. The joint shear model allows nonlinear behavior for both joint sets. Because nonlinear behavior is allowed for both joint sets, a great many cases must be considered to fully describe the joint shear behavior of the jointed medium. An extensive set of equations is required to describe the joint shear stress and slip displacements that can occur for all the various cases. This report examines possible methods for simplifying this set of equations so that the model can be implemented efficiently form a computational standpoint. The shear model must be examined carefully to obtain a computationally efficient implementation that does not lead to numerical problems. The application to fractures in rock is discussed. 5 refs., 4 figs.

Sandia National Laboratories has completed a requirements study for a networked mass storage system. The areas of user functionality, network connectivity, and performance were analyzed to determine specifications for a Network Storage Service to operate in supercomputer environment. 4 refs.

The Network File System (NFS) is used in UNIX-based networks to provide transparent file sharing between heterogeneous systems. Although NFS is well-known for being weak in security, it is widely used and has become a de facto standard. This paper examines the user authentication shortcomings of NFS and the approach Sandia National Laboratories has taken to strengthen it with Kerberos. The implementation on a Cray Y-MP8/864 running UNICOS is described and resource/performance issues are discussed. 4 refs., 4 figs.

Ground water flow in unsaturated, fractured rock is often assumed to be dominated by the porous matrix component. This is frequently based on the argument that water flowing in the fractures is rapidly imbibed into the rock matrix by capillary suction forces with negligible resistance to uptake at the matrix-fracture interface. However, the existence of a low-permeability mineralized layer or coating at this interface may substantially reduce matrix imbibition and consequently result in fracture-dominated flow. To test this concept, four tuff samples containing natural fractures were obtained from tuff formations in southern Nevada. By performing imbibition experiments into the matrix rock, across a mineralized fracture face and then across a fresh uncoated fracture face, water uptake as a function of time and coating was measured. A relatively simple model has been developed to describe the imbibition behavior. 6 refs.

An important aspect of environmentally-conscious operations is adoption of an aggressive waste minimization program. This paper describes the waste minimization and pollution prevention program at Sandia National Laboratories. Although Sandia's approach is patterned after the generic waste minimization models proposed by the Environmental Protection Agency and the Department of Energy, the specifics of implementation, and the potential for payoff, are influenced by the R&D nature of Sandia's work. Key aspects of the program are discussed, including why Sandia is developing and conducting the program; objectives; elements of the program; our approach to implementation; the magnitude of the undertaking; and the expected payoff.

The distribution of copper in aluminum thin films is examined with respect to how the copper can influence electromigration behavior. Al-Cu thin films annealed in the single-phase region, to just below the solvus temperature, have θ-phase Al₂Cu precipitates at the aluminum grain boundaries. The grain boundaries between precipitates are depleted in copper. Al-Cu thin films heat treated at lower temperatures, within the two-phase region, also have θ-phase precipitates at the grain boundaries but the aluminum grain boundaries continuously become enriched in copper, perhaps due to the formation of a thin coating of θ-phase at the grain boundary. Here, it is proposed that electromigration behavior of aluminum is improved by adding copper because the θ-phase precipitates may hinder aluminum diffusion along the grain boundaries. It was also found that resistivity of Al-Cu thin films decrease during accelerated electromigration testing prior to failure. Pure Al films did not exhibit this behavior. The decrease in resistivity is attributed to there distribution of copper from the aluminum grain matrix to the θ-phase precipitates growing at the grain boundaries thereby reducing the number of defects in the microstructure.

We have designed and manufactured a test chip devoted to the study of interconnect voiding. The test chip is suitable for evaluating theoretical models, acceleration recipes, and the effects of process variations. We describe the chip and a simple, stress-free packaging technique that eliminates any stress to the chip from die bonding or packaging thermal cycles. With this test chip, we can perform many necessary and desirable experiments: determining stress, observing or stimulating void growth, profiling hydrogen concentrations, and measuring excess current noise. We report here preliminary measurements of residual stress, observations of voids, and determinations of hydrogen concentrations of hydrogen concentration under variations in aluminum annealing and passivation. In agreement with observations elsewhere, we find that passivations which differ greatly in intrinsic stress do not differ much in the stress they impart to patterned metal; some workers have suggested instead that excess hydrogen in the aluminum contributes to voiding. Following this lead, we have used nuclear reaction analysis to profile the hydrogen concentration in passivation, metallization, barrier metal, and interlevel dielectric and present some preliminary measurements here. We conclude that passivated metallization may contain as much as 0.1 atomic % hydrogen.

The current status of lifetime prediction under conditions of thermomechanical creep/fatigue is reviewed. Each method is summarized and the results of the application to solder joints is shown. While each method has been applied with some success, a predictive, phenomenological approach has not been developed and validated. A method which captures the response of a crack to steady-state and cycling environments appears to hold most the most promise to provide a useful design tool.

We present a simple and effective path planning algorithm, an essential component in facilitating robot programming, based on a series of plausible task restriction. It is designed to solve realistic'' problems very quickly, at the expense of not being able to solve every problem. First, the notion of realistic'' problems is motivated with heuristic arguments and formalized through task restrictions. Next, an algorithm solving the resulting tasks of interest is provided. We prove its corrections and theoretical efficiency, and demonstrate empirically its effectiveness and speed. We expect our algorithm to be of practical significance based on its simplicity and predicted performance. 9 refs., 7 figs.

To address the need of a practical motion planner for manipulators, we present an efficient and resolution-complete algorithm that has performance commensurate with task difficulty. The algorithm uses SANDROS, a new search strategy that combines hierarchical, nonuniform-multi-resolution, and best-fit search to find a near-optimal solution in the configuration space. This algorithm can be applied to any manipulator, and has been tested with 5 and 6-degree-of-freedom robots, with execution time ranging from 20 seconds to 10 minutes on a 16 MIPS workstation. 14 refs., 3 figs., 1 tab.

Activation procedures can have a dramatic effect on the activity of iron-based catalysts for Fischer-Tropsch (F-T) synthesis. CO conversion over a 100 Fe/3 Cu/0.2 K catalyst (parts by weight) can vary by nearly a factor of 3, depending on activation treatment. In contrast, a 100 Fe/5 Cu/4.2 K/25 SiO₂ catalyst displays little dependence of F-T activity on activation treatment. An ultra-high vacuum surface analysis chamber coupled to an atmospheric reactor has been used to measure the surface composition of these catalysts following activation in carbon monoxide at 280°C, while transmission electron microscopy (TEM) and BET surface area measurements have been used to investigate catalyst morphology. CO activation of the 100 Fe/5 Cu/4.2 K/25 SiO₂ catalyst at 280°C results in partial reduction of iron to a mixture of Fe_xO and Fe₃O₄, and an overall surface composition very similar to that obtained following hydrogen activation at 220 or 280°C, consistent with the invariance of F-T activity with activation treatment for this catalyst. Activation of the 100 Fe/3 Cu/0.2 K catalyst in CO at 280°C results in the formation of iron carbide particles, growth of graphitic carbon (C_g) filaments, and formation of a thick, porous, Cg layer covering the carbide particles. Differences in F-T activity between the hydrogen- and CO-activated 100 Fe/3 Cu/O.2 K catalyst are discussed in terms of surface composition and catalyst morphology. The difference in sensitivity of the two catalysts to activation conditions is related to differences in the extent of reduction of the catalysts.

HISPLT is a graphics postprocessor designed to plot time histories for wave propagation codes. HISPLT is available for CRAY UNICOS, CRAY CTSS, VAX VMS computer systems, and a variety of UNIX workstations. The original HISPLT code employs a database structure that allows the program to be used without modification to process data generated by many wave propagation codes. HISPLT has recently been modified to process time histories for the reactor safety analysis code, MELCOR. This report provides a complete set of input instructions for HISPLT and provides examples of the types of plotted output that can be generated using HISPLT. 6 refs., 8 figs., 5 tabs.

The purpose of this NUREG is to present technical information that should be useful to NRC licensees in designing closed-circuit television systems for video alarm assessment. There is a section on each of the major components in a video system: camera, lens, lighting, transmission, synchronization, switcher, monitor, and recorder. Each section includes information on component selection, procurement, installation, test, and maintenance. Considerations for system integration of the components are contained in each section. System emphasis is focused on perimeter intrusion detection and assessment systems. A glossary of video terms is included. 13 figs., 9 tabs.

Blade fatigue life is an important element in determining the economic viability of the Vertical-Axis Wind Turbine (VAWT). A principal source of blade fatigue is thought to be the stochastic (i.e., random) aerodynamic loads created by atmospheric turbulence. This report describes the theoretical background of the VAWT Stochastic Aerodynamic Loads (VAWT-SAL) computer code, whose purpose is to numerically simulate these random loads, given the rotor geometry, operating conditions, and assumed turbulence properties. A Double-Multiple-Stream Tube (DMST) analysis is employed to model the rotor's aerodynamic response. The analysis includes the effects of Reynolds number variations, different airfoil sections and chord lengths along the blade span, and an empirical model for dynamic stall effects. The mean ambient wind is assumed to have a shear profile which is described by either a power law or a logarithmic variation with height above ground. Superimposed on this is a full 3-D field of turbulence: i.e., in addition to random fluctuations in time, the turbulence is allowed to vary randomly in planes perpendicular to the mean wind. The influence of flow retardation on the convection of turbulence through the turbine is also modeled. Calculations are presented for the VAWT 34-m Test Bed currently in operation at Bushland, Texas. Predicted time histories of the loads, as well as their Fourier spectra, are presented and discussed. Particular emphasis is placed on the differences between so-called steady-state'' (mean wind only) predictions, and those produced with turbulence present. Somewhat surprisingly, turbulence is found to be capable of either increasing or decreasing the average output power, depending on the turbine's tip-speed ratio. A heuristic explanation for such behavior is postulated, and a simple formula is derived for predicting the magnitude of this effect without the need for a full stochastic simulation. 41 refs., 32 figs., 1 tab.

Division 2525 Battery Test Laboratory is a fully automated battery testing facility used in evaluating various battery technologies. The results of these tests are used to verify developers' claims, characterize prototypes, and assist in identifying the strengths and weaknesses of each technology. The Test Facility consists of a central computer and nine remote computer controlled battery test systems. Data acquired during the battery testing process is sent to the central computer system. The test data is then stored in a large database for future analysis. The central computer system is also used in configuring battery tests. These test configurations are then sent to their appropriate remote battery test sites. The Battery Test Facility can perform a variety of battery tests, which include the following: Life Cycle Testing; Parametric Testing at various temperature levels, cutoff parameters, charge rates, and discharge rates; Constant Power Testing at various power levels; Peak Power Testing at various State-of-Charge levels; Simplified Federal Urban Driving Schedule Tests (SFUDS79). The Battery Test Facility is capable of charging a battery either by constant current, constant voltage, step current levels, or any combination of them. Discharge cycles can be by constant current, constant resistance, constant power, step current levels, or also any combination of them. The Battery Test Facility has been configured to provide the flexibility to evaluate a large variety of battery technologies. These technologies include Lead-Acid, Sodium/Sulfur, Zinc/Bromine, Nickel/Hydrogen, Aluminum/Air, and Nickel/Cadmium batteries.