Publications

Sandia National Laboratories conducts the photovoltaic balance of systems (BOS) program, which is sponsored by the US Department of Energy`s Office of Energy Management. Under this program, SNL lets commercialization contracts and conducts a laboratory program designed to advance BOS technology, improve BOS component reliability, and reduce the BOS life-cycle-cost. This report details the testing of the first large US manufactured hybrid inverter and its associated maximum power tracker.

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 which 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 from the liner to the insert plate. 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 post-test examination of test specimens show 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. Further, it significantly increases the understanding of containment building response under severe conditions.

As part of an Environmentally Conscious Manufacturing (ECM) Program, a study was conducted at Sandia National Laboratories to identify an alternative cleaning process that would effectively replace trichloroethylene (TCE) for cleaning mechanical piece parts of Switch Tube assemblies. Eight aqueous alkaline cleaners, as well as an isopropyl alcohol and isopropyl alcohol/Cyclohexane cleaning process, were studied as potential replacements. Cleaning efficacy, materials compatibility, etch rate and corrosion studies were conducted and used to screen potential candidates. Cleaning efficacy was determined using visual examination, goniometer/contact angle measurements, Auger electron spectroscopy, X-ray Photoelectron spectroscopy and an evaporative rate analysis technique known as MESERAN Surface Analysis. Several cleaners were identified as potential replacements for TCE based solely on the cleaning efficacy results. Some of the cleaners, however, left undesirable residues studies were completed, Brulin 815GD (an aqueous alkaline cleaner) was selected as the replacement for TCE.

This paper describes the planning of evaluation for one large-scale national energy program with-scale, national energy program with international reporting requirements, US. Climate Change Action Plant. Referred to as Energy Partnerships for a Strong Economy, this program includes 19 DOE Office of Energy Efficiency and Renewable Energy (EE) initiatives and three other DOE projects. The evaluation strategy is to have a six year effort with ongoing performance measurement, market studies and process evaluations when deviations from targeted outcomes occur, and a final evaluation report that combines these results with other impact evaluations deemed necessary. The evaluation planning and implementation will use a collaborative approach involving program managers and stakeholders, including program partners and customers, to ensure that evaluation results are useful and utilized. Performance mapping will be used to describe the programs to be evaluated and determine data collection needs and key evaluation questions. The evaluation plan uses multiple evaluation methods, including model and engineering estimates, self-reporting by partners, case studies, surveys, and modified peer/expert review in order to accommodate the scope and diversity of programs and the need to measure progress as well as impact.

The part-load behavior of a typical 30-MWe SEGS (solar electric generating systems) plant was studied using a detailed thermodynamic model. As part of this analysis, a new solar field model was derived, based on measurement results of an LS-2 Collector and accounting for various conditions of receiver tubes, lost mirrors and measured reflectivity. A comparison was made of the model results to real plant conditions for a winter and summer day in order to test the accuracy of the model. The effects of bare tubes, different wind speeds, mirror reflectivity and other factors were studied showing, e.g., that heat losses due to wind are predicted to be very low. The comparison also shows that the model still lacks the capability to fully account for actual solar field conditions. The model was also compared to the SOLERGY model, showing differences between the assumptions used in both models. Finally different operating conditions of the plant were studied for a summer, fall, and winter day to provide a better understanding of how changing solar field outlet temperatures affect gross and net output of the plant. This clearly indicates that the lowest possible superheating temperature maximizes the gross electric output. On a net basis this conclusion is modified due to the high parasitics of the HTF (heat transfer fluid) pumps. It was found that the optimum operating strategy depends on the insolation conditions, e.g., different superheating temperatures should be chosen in summer, fall and winter. If the pressure drop in the solar field is reduced due to replacement of flex hoses with ball joints, increasing the HTF flow is more reasonable, so that at low isolation conditions the lowest possible superheating temperature also leads to the maximum net output.

The Energy Policy Act of 1992 required the DOE to develop recommendations and implement government programs to assist the domestic uranium industry in increasing export opportunities. In 1993, as part of that effort, the Office of Nuclear Energy identified several key factors that could (or have) significantly impact(ed) export opportunities for domestic uranium. This report addresses one of these factors: regulatory and policy impediments to the flow of uranium products between the US and other countries. It speaks primarily to the uranium market for civil nuclear power. Changes in the world political and economic order have changed US national security requirements, and the US uranium industry has found itself without the protected market it once enjoyed. An unlevel playing field for US uranium producers has resulted from a combination of geology, history, and a general US political philosophy of nonintervention that precludes the type of industrial policy practiced in other uranium-exporting countries. The US has also been hampered in its efforts to support the domestic uranium-producing industry by its own commitment to free and open global markets and by international agreements such as GATT and NAFTA. Several US policies, including the imposition of NRC fees and licensing costs and Harbor Maintenance fees, directly harm the competitiveness of the domestic uranium industry. Finally, requirements under US law, such as those in the 1979 Nuclear Nonproliferation Act, place very strict limits on the use of US-origin uranium, limitations not imposed by other uranium-producing countries. Export promotion and coordination are two areas in which the US can help the domestic uranium industry without violating existing trade agreements or other legal or policy constraints.

The fabrication of a prosthetic socket for a below-the-knee amputee requires knowledge of the underlying bone structure in order to provide pressure relief for sensitive areas and support for load bearing areas. The goal is to enable the residual limb to bear pressure with greater ease and utility. Conventional methods of prosthesis fabrication are based on limited knowledge about the patient`s underlying bone structure. A 3D ultrasound imaging system was developed at Sandia National Laboratories. The imaging system provides information about the location of the bones in the residual limb along with the shape of the skin surface. Computer assisted design (CAD) software can use this data to design prosthetic sockets for amputees. Ultrasound was selected as the imaging modality. A computer model was developed to analyze the effect of the various scanning parameters and to assist in the design of the overall system. The 3D ultrasound imaging system combines off-the-shelf technology for image capturing, custom hardware, and control and image processing software to generate two types of image data -- volumetric and planar. Both volumetric and planar images reveal definition of skin and bone geometry with planar images providing details on muscle fascial planes, muscle/fat interfaces, and blood vessel definition. The 3D ultrasound imaging system was tested on 9 unilateral below-the- knee amputees. Image data was acquired from both the sound limb and the residual limb. The imaging system was operated in both volumetric and planar formats. An x-ray CT (Computed Tomography) scan was performed on each amputee for comparison. Results of the test indicate beneficial use of ultrasound to generate databases for fabrication of prostheses at a lower cost and with better initial fit as compared to manually fabricated prostheses.

Combination glass electrodes were tested for determining H{sup +} concentrations in concentrated pure and mixed NaCl and Na{sub 2}SO{sub 4} solutions, as well as natural brine systems. NaCl, Na{sub 2}SO{sub 4}, and mixtures of NaCl and Na{sub 2}SO{sub 4} solutions were analyzed. Correction factors for estimating pC{sub H}{sup +} (negative logarithm of H{sup +} concentration) were determined from measured/observed pH values. Required Gran-type titrations were done with HCl and/or NaOH. The titration method is described and a step-by-step procedure provided; it has been used previously for determining pC{sub H}{sup +} values of synthetic chloride-dominated brines. Precautions are required to determine correction factors for electrolytes that react with H{sup +} or OH{sup {minus}} [sulfate brines for titration with acid; magnesium brines for titration with base because of precipitation of Mg(OH)2]. Correction factors A (pC{sub H}{sup +} = pH{sub ob} + A) from HCl titrations were similar to those from NaOH titrations where the concentration of free H{sup +} was calculated using a thermodynamic model. These values should be applicable to solns with a very large range in measured pH values (2 to 12). Because a large number of solns were titrated with HCl and the A values are similar for HCl and NaOH titrations, the A values for NaCl and Na2SO4 solns were fit as a function of molality to allow extrapolation. For NaCl solns 0 to 6.0 M, A can be obtained by multiplying the molality by 0.159. For Na2SO4 solns 0 to 2.0 M, the values of A can be obtained from (0.221 {minus} 0.549X + 0.201X{sup 2}), where X is the molality of Na{sub 2}SO{sub 4}. Orion-Ross electrode evaluations indicated that the A values did not differ significantly for different electrodes. Results suggest that the data in this report can be used to estimate A values for different NaCl and Na{sub 2}SO{sub 4} solns even for noncalibrated electrodes.

Asynchronous Transfer Mode (ATM) technology is currently receiving extensive attention in the computer networking arena. Many experts predict that ATM will be the future networking technology for both the Local Area Network (LAN) and the Wide Area Network (WAN). This paper presents the results of a collaboration between Sandia National Laboratories` Advanced Networking Department and Engineering Sciences Center to study the implementation of ATM in one of Sandia`s most heavily loaded production networks. The network consists of over 120 Sun Sparc 10s and 20s, two SparcCenter 2000s, a 12 node parallel IBM SP-2, and several other miscellaneous high-end workstations. The existing network was first characterized through extensive traffic measurements to better understand the capabilities and limitations of the existing network technologies and to provide a baseline for comparison to an ATM network. This characterization was used to select a subset of the network elements which would benefit most from conversion to the ATM technology. This subset was then converted to equipment based on the latest ATM standards. With direct OC-3c (155 Mbps) host connections for the workstations and the file and compute servers, we demonstrated as much as 122 Mbps throughput (memory-to-memory TCP/IP transfers) between endpoints. Flow control in the classical many-to-one client server environment was also investigated. Throughout all of our tests, the interaction of the user applications with the network technologies was documented and possible improvements were tested. The performance and reliability of the ATM network was compared to the original network to determine the benefits and liabilities of the ATM technology.

No abstract available.

Models for direct containment heating (DCH) in the CONTAIN code for severe accident analysis have been reviewed and a standard input prescription for their use has been defined. The code has been exercised against a large subset of the available DCH data base. Generally good agreement with the experimental results for containment pressurization ({Delta}P) and hydrogen generation has been obtained. Extensive sensitivity studies have been performed which permit assessment of many of the strengths and weaknesses of specific model features. These include models for debris transport and trapping, DCH heat transfer and chemistry, atmosphere-structure heat transfer, interactions between nonairborne debris and blowdown steam, potential effects of debris-water interactions, and hydrogen combustion under DCH conditions. Containment compartmentalization is an important DCH mitigator in the calculations, in agreement with experimental results. The CONTAIN model includes partially parametric treatments for some processes that are not well understood. The importance of the associated uncertainties depends upon the details of the DCH scenario being analyzed. Recommended sensitivity studies are summarized that allow the user to obtain a reasonable estimate of the uncertainties in the calculated results.

In this paper we study the question: How useful is randomization in speeding up Exclusive Write PRAM computations? Our results give further evidence that randomization is of limited use in these types of computations. First we examine a compaction problem on both the CREW and EREW PRAM models, and we present randomized lower bounds which match the best deterministic lower bounds known. (For the CREW PRAM model, the lower bound is asymptotically optimal.) These are the first non-trivial randomized lower bounds known for the compaction problem on these models. We show that our lower bounds also apply to the problem of approximate compaction. Next we examine the problem of computing boolean functions on the CREW PRAM model, and we present a randomized lower bound, which improves on the previous best randomized lower bound for many boolean functions, including the OR function. (The previous lower bounds for these functions were asymptotically optimal, but we improve the constant multiplicative factor.) We also give an alternate proof for the randomized lower bound on PARITY, which was already optimal to within a constant additive factor. Lastly, we give a randomized lower bound for integer merging on an EREW PRAM which matches the best deterministic lower bound known. In all our proofs, we use the Random Adversary method, which has previously only been used for proving lower bounds on models with Concurrent Write capabilities. Thus this paper also serves to illustrate the power and generality of this method for proving parallel randomized lower bounds.

The queue-read, queue-write (QRQW) parallel random access machine (PRAM) model is a shared memory model which allows concurrent reading and writing with a time cost proportional to the contention. This is designed to model currently available parallel machines more accurately than either the CRCW PRAM or EREW PRAM models. Many algorithmic results have been developed for the QRQW PRAM. However, the only lower bound results have been fairly simple reductions from lower bounds for other models, such as the EREW PRAM or the ``few-write`` CREW PRAM. Here we present a lower bound specific to the QRQW PRAM. This lower bound is on the problem of Linear Approximate Compaction (LAC), whose input consists of at most m marked items in an array of size n, and whose output consists of the rn marked items in an array of size 0(m). There is an O({radical}log n), expected time randomized algorithm for LAC on the QRQW PRAM. We prove a lower bound of {Omega}(log log log n) expected time for any randomized algorithm for LAC. This bound applies regardless of the number of processors and memory cells of the QRQW PRAM. The previous best lower bound was {Omega}(log* n) time, taken from the known lower bound for LAC on the CRCW PRAM.

SPH (Smoothed Particle Hydrodynamics) is a gridless Lagrangian technique which is appealing as a possible alternative to numerical techniques currently used to analyze high deformation impulsive loading events. In the present study, the SPH algorithm has been subjected to detailed testing and analysis to determine the feasibility of using PRONTO/SPH for the analysis of various types of underwater explosion problems involving fluid-structure and shock-structure interactions. Of particular interest are effects of bubble formation and collapse and the permanent deformation of thin walled structures due to these loadings. These are exceptionally difficult problems to model. Past attempts with various types of codes have not been satisfactory. Coupling SPH into the finite element code PRONTO represents a new approach to the problem. Results show that the method is well-suited for transmission of loads from underwater explosions to nearby structures, but the calculation of late time effects due to acceleration of gravity and bubble buoyancy will require additional development, and possibly coupling with implicit or incompressible methods. © 1995 Springer-Verlag.

The authors have characterized the pyrochlore-to-perovskite crystallization process in solution-derived Pb(Zr{sub 0.20}Ti{sub 0.80})O{sub 3} thin films on (100) MgO single crystal substrates. It has been determined that the perovskite phase nucleated preferentially at the film/MgO interface out of a nanocrystalline ({approx}100{angstrom} grains) pyrochlore matrix. During the early stages of the pyrochlore-to-perovskite conversion process, perovskite growth proceeded nearly isotropically from the substrate to form hemispherically shaped grains. Deviations from isotropic growth were shown to result from a growth dependence based on the crystallographic orientation of a growing perovskite grain relative to the orientations of pyrochlore grains being transformed. The volume change that occurs during the pyrochlore-to-perovskite transformation along with two-dimensional grain growth has been used to develop a mechanism for formation of porosity that commonly is concentrated in grain boundary regions.

Sandia National Laboratories has established a Cooperative Research and Development Agreement with consortium members of the National Center for Manufacturing Sciences (NCMS) to develop fundamental generic technology in the area of printed wiring board materials and surface finishes. Improved solderability of copper substrates is an important component of the Sandia-NCMS program. The authors are investigating the effects of surface roughness on the wettability and solderability behavior of several different types of copper board finishes. In this paper, the authors present roughness and solderability characterizations for a variety of chemically-etched copper substrates. Initial testing on six chemical etches demonstrate that surface roughness can be greatly enhanced through chemical etching. Noticeable improvements in solder wettability were observed to accompany increases in roughness. A number of different algorithms and measures of roughness were used to gain insight into surface morphologies that lead to improved solderability.

This report describes the results of experiments performed to determine the viability of titanium dioxide photocatalysis towards the treatment of water contaminated with different metal-EDTA complexes. Both the PB-EDTA and Ni-EDTA complexes were chosen for study, as they represent respectively metals that are and are not capable of photodeposition onto the TiO{sub 2} catalyst during the photoreaction. Batch reactions were carried out in a jacketed glass pot reactor using 300 ml of 50m g/l metal chelated with an equimolar amount of EDTA and 0.1wt% of TiO{sub 2} in the solution. The UV source used was a 100 W low-pressure Hg spot lamp. The two systems were studied using Degussa P-25 titanium dioxide, and Aldrich titanium dioxide loaded with Pt and Au. Around 80% removal of the Ni-EDTA complex was attained after 120 min using both catalysts with no photodeposition of Ni onto the catalyst. However, pH precipitation treatment of the reacted solutions indicated that the Ni was still complexed, probably to complexing agents that were EDTA oxidation products. Apparent zero-order kinetics was observed in the P-25 catalyst reaction, whereas apparent first-order kinetics was observed in the metal-loaded TiO{sub 2} catalyst. In contrast the Pb-EDTA complex was completely removed in 10 min using both catalysts. Also, complete Pb deposition onto the catalyst was attained in 30 min for both catalysts. The Pb deposition seemed to first require the degradation of the complex. Total organic carbon was reduced in the Ni-EDTA system 15--21% using both catalysts, and about 33% in the Pb-EDTA system using both catalysts. No reduction of either metal or metal complex was observed when no catalyst was present and the other conditions held constant.

Borehole-to-surface electromagnetic (EM) methods are an attractive alternative to Surface-based EM methods for a variety of environmental and engineering applications. They have improved sensitivity to the subsurface resistivity distribution because of the closer proximity to the area of interest offered by the borehole for the source or the receiver. For the borehole-to-surface measurements the source is in the borehole and the receivers are on the surface. On the other hand, for the surface-to-borehole methods, the source is on the surface and the receiver is in a borehole. The surface-to-borehole method has an added advantage since measurements are often more accurate due to the lower noise environment for the receiver. For these methods, the source can be a grounded electric dipole or a vertical magnetic dipole source. An added benefit of these techniques is field measurements are made using a variety of arrays where the system is tailored to the application and where one can take advantage of some new imaging methods. In this short paper the authors describe the application of the borehole-to-surface method, discuss benefits and shortcomings, and give two field examples where they have been used for underground imaging. The examples were the monitoring of a salt water flooding of an oil well and the characterization of a fuel oil spill.

The authors performed an X-ray diffraction study of tetrahedral-coordinated-amorphous carbon (a-tC) films prepared by pulsed laser deposition (PLD). Samples properties were analyzed as a function of laser energy and thickness. For all thicknesses and laser energies, films were made up of clusters with a basic unit size of 7 - 11 nm. Thicker films, as well as films prepared at higher laser densities exhibit larger clusters, in the tens of nanometers. The clusters are not readily observable by AFM, which may indicate the presence of a flat (graphitized) top film surface.

The structural evaluation test unit is roughly equivalent to a 1/3 scale model of a high level waste rail cask. The test unit was designed to just meet the requirements of NRC Regulatory Guide 7.6 when subjected to a 9 m (30 ft) free drop resulting in an impact velocity of 13.4 m/s (30 mph) onto an unyielding target in the end-on orientation. The test unit was then subjected to impacts with higher velocities to determine the amount of built-in conservatism in this design approach. Test impacts of 13.4, 20.1 and 26.8 m/s (30, 45, and 60 mph) were performed. This paper will describe the design, testing, and comparison of measured strains and deformations to the equivalent analytical predictions.

A Discrete element computer program named DMC (Distinct Motion Code) has been developed for modeling rock blasting. This program employs explicit time integration and uses spherical or cylindrical elements which are represented as circles in 2-D. DMC calculations have been compared with measurements on bench blasts in the field with relatively good comparison. Structural rock mass characteristics have a significant impact on any blast and DMC has not, until now, included these effects. This paper discusses a recently added DMC capability for treating joints and bedding planes in bench blast simulations. Material strength is treated in DMC by creating links between spheres to hold them together. The links can be broken based on any criterion; simple tension, compression and shear are currently employed. Joint sets are treated in DMC by defining the dip of each set toward or away from the bench face along with the joint spacing. Strength links that cross joint planes can have their strength properties modified or they can be deleted. Modification of the link patterns based on joint sets creates distinct blocks of spheres outlined by the intersecting joints. These blocks of spheres move together as a solid unit unless stress and strain conditions within the block indicate that links should be broken. Simulations using this capability show some blocks remaining intact throughout the blast and some being partially or completely broken. When this occurs, the joint pattern is shown to influence the characteristics of the blast. Upon completion of this capability both rock breakage and motion will be modeled during the same simulation. Much work remains to be done on this concept making this paper a progress report on the development of this new capability.

Hydrogen is found to readily diffuse into InGaN, InAlN and InGaAlN epitaxial layers during plasma exposures at 170-250{degree}C for 40 sec-30 min. The diffusivity of hydrogen is > 10{sup -11} cm{sup 2} {center_dot} s{sup -1} at 170{degree}C, and the native donor species are passivated by association with the hydrogen. Reactivation of these species occurs at 450-500{degree}C, but the hydrogen remains in the material until {ge} 800{degree}C.

Pb(Zr,Ti)O{sub 3} (PZT) thin films are being developed for use in optical and electronic memory devices. To study ferroelectric switching behavior, the authors have produced relatively untextured PZT thin films on Si substrates. They have developed a method for using X-ray diffraction to observe domain switching in situ. This study involved the use of a micro-diffractometer to monitor the switching behavior in relatively small (0.7 mm diameter) electroded areas. Diffraction analyses were done while DC voltages were applied and removed, representing several places in the hysteresis loop. In particular, the authors were looking for relative intensity changes in the [h00],[00l] diffraction peaks as a function of position in the hysteresis loop. This study indicates that the 90{degrees} domain switching exhibited by bulk ferroelectrics, is very limited in films on Si when grain sizes are less than about 1{mu}m.

Increasingly constrained budgets in the defense community, both DoD and DOE, have created a need to emphasize affordability in the development of future weapons systems and components. Increased use of commercially compatible components will play an important role, but there will always remain a need for specialized production, especially at the system level. We will present on-going work at Sandia National Laboratories (referred to from here as Sandia) aimed at insuring the affordability of low-volume, defence-specific systems.

The 6.4 MeV p({sup l5}N,{alpha}{gamma}){sup 12}C resonant nuclear reaction has been used to investigate the role of hydrogen as a contributing factor in the formation of stress-induced voids in very large scale integrated circuit metallizations. Hydrogen profiles were measured from a series of layered structures consisting of aluminum-copper alloy metallizations deposited on borophosphosilicate glass and capped with a variety of commercial passivation materials in order to examine differences in the concentrations and depth distributions of hydrogen within the layered structures.