Publications

Current computer network protocols are very robust and capable of being used in a variety of different environments. Typically, the implementations of these protocols come to the user with preset parameters that provide reasonable performance for low delay- bandwidth product environments with low error rates, but these defaults do not necessarily provide optimal performance for high delay-bandwidth, high error rate environments. To provide optimal performance from the user's perspective, which is application to application, all equivalent layers of the protocol must be tuned. The key to tuning protocols is reducing idle time on the links caused by various protocol layers waiting for acknowledgments. The circuit bandwidth, propagation delay, error rate, number of outstanding packets, buffer length, number of buffers, and buffer size can all affect the observed idle time. Experiments have been conducted on test bed systems, and on live satellite and terrestrial circuits. Observations from these experiments led the authors to draw conclusions about the locations of common bottlenecks. Various aspects of network tuning and certain specific issues relating to the tuning of three protocols (DECnet, TCP/IP, NETEX) over various media types (point-to-point and broadcast) under several different conditions (terrestrial and satellite) are examined in this paper. Also described are the lessons learned about protocol and network tuning. 3 refs., 2 tabs.

A comparison of the short-transverse SCC behavior of 2090 in pH 5.5 Cl{sup {minus}} and alkaline CO{sub 3}{sup 2 {minus}}/Cl{sup {minus}} solutions using a static load smooth bar SCC technique was made. In the alkaline CO{sub 3}{sup 2 {minus}}/Cl{sup {minus}} solutions, E{sub br} for the {alpha}-Al matrix phase was 0.130 V more positive than the E{sub br} of the subgrain boundary T{sub 1} phase. In this environment, stress corrosion cracking test specimens subjected to potentials in the window defined by the two breakaway potentials failed along an intersubgranular path in less than an hour. In the Cl{sup {minus}} environment, the E{sub br} values for the two phases were nearly equal and this rapid SCC condition could not be satisfied; accordingly SCC failures were not observed. Rapid SCC failure of 2090 in CO{sub 3}{sup 2 {minus}}/Cl{sup {minus}} in our static load, constant immersion experiments appear to be related to recently reported pre-exposure embrittlement'' failures induced by immersing stressed specimens removed into ambient laboratory air after immersion in aerated NaCl solution for 7 days. In those experiments, specimens failed in less than 24 hours after removal from solution. Our polarization experiments have shown that the corrosion behavior of T{sub 1}, CO{sub 3}{sup 2 {minus}}/Cl{sup {minus}} environments, but the {alpha}-Al phase crack walls, is rapidly passivated. X-ray diffraction of the films which formed in simulated crevices suggests that this passivating film belongs to a class of compounds known as hydrotalcites.

Vertical axis wind turbine (VAWT) technology in the United States started in the early 1970s directly from the original work in Canada. The close, and very productive relationships among laboratories, universities and industry have continued since that time. This paper briefly discusses the significant technical progress and rather dramatic programmatic changes that have occurred in the past 18 to 24 months on the US side of the border. 20 refs., 14 figs.

Numerous small-scale in situ seal experiments have been emplaced in boreholes up to 38 in. in diameter at the WIPP. Seal materials include expansive salt concrete, bentonite, and crushed salt. Emplacement techniques stressed conventional technology and the use of available site personnel. Preliminary evaluation of the performance of these seals has been completed by using structural data from embedded instrumentation and fluid flow data from gas and brine flow measurements. Preliminary results suggest that submicrodarcy permeabilities can be obtained using these materials and that structural performance is satisfactory. 17 refs., 3 figs., 1 tab.

This paper describes a formal process for selecting, from a diverse set of proposed waste minimization activities, those activities that provide the greatest benefit to DOE. A methodology for evaluating and prioritizing proposals was developed to illustrate how the selection process works and what types of data are required to characterize waste minimization activities. It is clearly impossible to remove all aspects of subjective judgment from the proposal selection process. With this important consideration in mind, the methodology presented is put forth to enhance, not replace, the traditional DOE decision-making process. With relatively minor refinements, this methodology can be immediately useful to DOE Environmental Restoration and Waste Management and Defense Program organizations in preparing, evaluating, and prioritizing waste minimization proposals. 7 refs., 1 tab., 2 figs.

Our primary purpose in this test is to provide a brief general description of a few applications of various electrophoretic systems which have been investigated and have found use in various coating applications at Sandia National Laboratories. Both organic and inorganic suspensions in aqueous and non-aqueous media have been considered in these studies. Applications include high voltage insulating dielectrics, thermally conductive/electrically insulating films, adherent lubricating films, uniform photoresist films, glass coatings, and fissile uranium oxide/carbon composite films for studies of nuclear powered lasers. More recently, we have become interested in the beneficial environmental aspects of being able to provide protective polymer coatings which reduce or minimize the use of organic solvents required by traditional spray coat processes. Important practical factors which relate to film uniformity, adhesion, and composition are related to unique coating or plating capabilities and applications. 6 refs., 2 figs., 1 tab.

System dynamicists frequently encounter signals they interpret as realizations of normal random processes. To simulate these analytically and in the laboratory they use methods that yield approximately normal random signals. The traditional digital methods for generating such signals have been developed during the past 25 years. During the same period of time much development has been done in the theory of chaotic processes. The conditions under which chaos occurs have been studied, and several measures of the nature of chaotic processes have been developed. Some of the measures used to characterize the nature of dynamic system motions are common to the study of both random vibrations and chaotic processes. This paper considers chaotic processes and random vibrations. It shows contrasts between the two and situations where they are indistinguishable. The applicability of the Central Limit Theorem to chaotic processes is demonstrated. 12 refs., 8 figs.

A knowledge of the short term creep rupture behavior of Tantalum alloy T-111 is necessary to predict device integrity in the heat source section of Radioisotope Thermoelectric Generators (RTG's) at the end of service life, in the event of a fuel fire. High pressures exist in RTG's near the end of service life, these are caused by gas generation resulting from radioactive decay of the nuclear fuel. The internal pressure exerts a significant hoop stress on the T-111 alloy structural containment member. This paper analyses the short term creep behavior (rupture times up to {approximately}2 {times} 10{sup 3} hrs.) of cold worked (CW) T-111 alloy, using the existing data of Stephenson (1967). Corellations for the time to rupture, time to 1% strain and minimum creep rate have been obtained from this data using multivariable linear regression analysis. These results are compared to other short term rupture data for T-111 alloy. Finally, at the stress/temperature levels relevant to the RTG fuel fire scenario near the end of service life, the rupture time correlation for T-111 alloy predicts a rupture time of approximately 100 hrs. 10 refs., 3 figs., 1 tab.

Before the Waste Isolation Pilot Plant (WIPP) may begin service as the United States' first repository for the permanent disposal of transuranic (TRU) radioactive waste, the Department of Energy (DOE) must establish compliance with applicable environmental and safety regulations. This paper addresses one major regulation, the United States Environmental Protection Agency's (EPA) Environmental Radiation Protection Standards for Management and Disposal of Spent Nuclear Fuel, High-Level and Transuranic Radioactive Wastes, hereafter referred to as the Standard. The paper does not address compliance with other regulations. This paper summarizes Sandia National Laboratories' (SNL) early-1990 understanding of the WIPP Project's ability to comply with the long-term performance requirements set by Subpart B of the Standard, the Environmental Standards for Disposal. It also reviews the current understanding of questions critically affecting compliance and outlines the options available to assure that radionuclide releases will remain within regulatory limits. 10 refs., 3 figs.

An advanced Synthetic Aperture Radar Motion Compensation System has been developed by Sandia National Laboratories (SNL). The system includes a miniaturized high accuracy ring laser gyro inertial measurement unit, a three axis gimbal pointing and stabilization assembly, a differential Global Positioning System (GPS) navigation aiding system, and a pilot guidance system. The system provides several improvements over previous SNL motion compensation systems and is capable of antenna stabilization to less than 0.01 degrees RMS and absolute position measurement to less than 5.0 meters RMS. These accuracies have been demonstrated in recent flight testing aboard a DHC-6-300 Twin Otter'' aircraft.

We are studying the kinetics of singlet oxygen ({sup 1}{Delta}{sub g}O{sub 2}) in solid polymers by monitoring its phosphorescence in time-resolved experiments. In macromolecular matrices where {sup 1}{Delta}{sub g}O{sub 2} is produced by energy transfer from a photosensitizer, {sup 1}{Delta}{sub g}O{sub 2} lifetimes can be obtained by deconvoluting the {sup 1}{Delta}{sub g}O{sub 2} sensitizer kinetics from the {sup 1}{Delta}{sub g}O{sub 2} phosphorescence signal. The sensitizer kinetics can be obtained in a flash absorption experiment. These time-resolved techniques have been utilized to examine the interaction of {sup 1}{Delta}{sub g}O{sub 2} in polymers with two types of additives: (1) molecules capable of undergoing chemical reactions with {sup 1}{Delta}{sub g}O{sub 2} (reactive quenchers) and (2) molecules capable of quenching {sup 1}{Delta}{sub g}O{sub 2} to its ground triplet state (physical quenchers). From this study we have determined directly that significant reactive and physical quenching of {sup 1}{Delta}{sub g}O{sub 2} are possible in a solid polymer. The polymer matrix greatly reduces the quenching rate of a very efficient quencher and slightly elevates the quenching rate of inefficient quenchers, as compared with rates determined in analogous liquids. This compressed range of quenching efficiencies has implications for understanding photodegradation and stabilization of polymers. 12 refs., 3 figs., 1 tab.

Neutron spin-echo spectroscopy is used to study the topology of aerogels. Topology or connectivity is varied through precursor chemistry and thermal annealing. Topology is characterized using the concept of fractons (the vibrational excitations of a fractal network). A qualitative difference is observed in the spectrum of polymeric vs colloidal aerogels, the latter showing a peak in the density of vibrational states. For colloidal aerogels whose structure appears to arise from phase separation in the solution precursor, low-energy excitations were only observed in the lowest density material studied. Finally, a transition from fractal to colloidal microstructure was observed during the sintering of polymeric aerogels. This transformation revealed itself as a transition from a fracton-like to a peaked density of states function. 23 refs., 7 figs.

Detailed geometric models have been used within a graphical simulation environment to study transportation cask facility design and to perform design and analyses of robotic systems for handling of nuclear waste. The models form the basis for a robot control environment which provides safety, flexibility, and reliability for operations which span the spectrum from autonomous control to tasks requiring direct human intervention.

This paper provides a summary and status report for two ongoing experimental programs. The purpose of each program is to determine the behavior of certain components of the containment pressure boundary when subjected to severe accident conditions. The first program is investigating the effect of various parameters on tearing of the steel liner in reinforced concrete containments. The second will attempt to determine if worst-case containment loading conditions are capable of causing leakage through piping penetration bellows. The liner test program is almost complete; however, the bellows tests have not yet begun. Therefore, the emphasis of the paper is on the liner experiments. The research activities described herein are a part of the Containment Integrity Programs, which are managed by Sandia National Laboratories for the US Nuclear Regulatory Commission.

A Science Advisor Program has been established at Sandia National Laboratories (SNL) for the long term augmentation of math and science instruction in New Mexico schools. Volunteer SNL engineers and scientists team with the faculty of participating schools to enhance the teachers' abilities to capture and hold the student's scientific imagination and develop their scientific skills. This is done primarily through providing laboratory resources, training the teachers how to use those resources, and advising how to obtain them in the future. In its first year, over 140 advisors teamed with 132 schools, for average weekly contact with 500 teachers and 10,000 students. Surveys indicate a general rise in frequency and quality of hands-on science instruction, as well as teacher and student attitudes. An expanded evaluation is planned for subsequent years.

The mechanical strength of silicon, in combination with the sophisticated silicon wafer processing techniques developed to produce silicon integrated circuits, makes it an ideal candidate for the development of a microelectromechanical device technology. We describe a new electrochemical processing technique based on porous silicon that can produce surface and buried insulators, conductors, and sacrificial layers required for sensor, micromotor, and membrane fabrication. 4 refs., 2 figs.

This paper discusses the development of the software for Source Term Analyses for Containment Evaluations (STACE). This software is being developed for the Source Term Technical Issue Resolution Program at Sandia National Laboratories (SNL) in support of the Cask Systems Development Program (CSDP) that is sponsored by the US Department of Energy's Office of Civilian Radioactive Waste Management (OCRWM). STACE is a system of computer codes operating under a graphics-based controller that performs source term analysis of spent fuel transport casks. Output from STACE includes the cladding breach probability, the releasable radionuclide concentrations, and maximum permissible gas flow rates past the closure seals. STACE is anticipated being used for on- and off-site situations related to the handling and transport of spent fuel casks.

A methodology for determining the probability spent-fuel cladding breach due to normal and accident class B cask transport conditions is introduced. This technique uses deterministic stress analysis results as well as probabilistic cladding material properties, initial flaws, and breach criteria. Best estimates are presented for the probability distributions of irradiated Zircaloy properties such as ductility and fracture toughness, and for fuel rod initial conditions such as manufacturing flaws and PCI part-wall cracks. Example analyses are used to illustrate the implementation of this methodology for a BWR (GE 7 {times} 7) and a PWR (B W 15 {times} 15) assembly. The cladding breach probabilities for each assembly are tabulated for regulatory normal and accident transport conditions including fire.

Residual stress states that are a direct result of fabrication and processing are known to exist inside wound capacitors. Considerable insights into the nature of these mechanical and thermomechanical stress states have been gained through the application of analytical prediction capabilities that have been developed for that purpose. For example, analysis shows where roll slip may occur in the capacitor due to steep wound tension gradients or low radial pressures, and how the tension loss of individual plies is distributed throughout the capacitor. Significant tension loss differences between dielectric and conducting plies has also been predicted, with conducting plies not only losing their initial winding tension, but actually experiencing a net compressive value of wound tension. While the results of these predictions are both quantitative and qualitative, only qualitative verification has been obtained thus far, such as visual observation of wrinkled conducting plies discovered in unwrapped capacitors. The purpose of this paper is to describe two experimental activities that were undertaken to support the analytical modeling effort and provide quantitative, experimental verification of some of the analysis predictions.

Fourier transform-infrared spectroscopy (FT-IR) was used to investigate the adsorption and thermally-induced decomposition of copper (I) {beta}-diketonate precursors of the type (hfac)CuL, where hfac is the hexafluoroacetylacetonate bidentate ligand and L is trimethylphosphine or 1,5-cyclooctadiene. The (hfac)CuPMe{sub 3} precursor desorbs from the surface at very low temperatures whereas the (hfac)Cu(1,5-COD) dissociates on adsorption, liberating 1,5-COD and leaving a surface(hfac)Cu complex which can subsequently disproportionate. Evidence is provided for hydrogen-bonding between the hfac ligand and the surface silanols for (hfac)CuPMe{sub 3}, but not for (hfac)Cu(1,5-COD). These results are consistent with the selective behavior of these precursors for copper deposition and suggest that the selectivity of the (hfac)CuPMe{sub 3} and (hfac)Cu(1, 5-COD) precursors may be due to the ability of the hfac ligand to hydrogen bond to the surface silanol groups.

The concept of allowing reactivity credit for the transmuted state of spent fuel offers both economic and risk incentives. This paper presents a general overview of the technical work being performed in support of the US Department of Energy (DOE) program to resolve issues related to the implementation of burnup credit. An analysis methodology is presented along with information representing the validation of the method against available experimental data. The experimental data that are applicable to burnup credit include chemical assay data for the validation of the isotopic prediction models, fresh fuel critical experiments for the validation of criticality calculations for various casks geometries, and reactor restart critical data to validate criticality calculations with spent fuel. The methodology has been specifically developed to be simple and generally applicable, therefore giving rise to uncertainties or sensitivities which are identified and quantified in terms of a percent bias in k{sub eff}. Implementation issues affecting licensing requirements and operational procedures are discussed briefly.

The US Department of Energy is sponsoring a research effort through Sandia National Laboratories and the University of Missour-Rolla to test a correlation for the upper shelf energy (USE) values obtained from the impact testing of subsize Charpy V-notch specimens to those obtained from the testing of full size samples. The program involves the impact testing of unirradiated and irradiated full, half, and third size Charpy V-notch specimens. To verify the applicability of the correlation on LWR materials unirradiated and irradiated full, half, and third size Charpy V-notch specimens of a commercial pressure vessel steel (ASTM A533 Grade B) will be tested. This paper will provide details of the program and present results obtained from the application of the developed correlation methodology to the impact testing of the unirradiated full, half, and third size A533 Grade B Charpy V-notch specimens.

Two controllers are developed to provide attitude control of a spinning rocket that has a thrust vectoring capability. The first controller has a single-input/single-output design that ignores the gyroscopic coupling between the control channels. The second controller has a multi-input/multi-output structure that is specifically intended to account for the gyroscopic coupling effects. A performance comparison between the two approached is conducted for a range of roll rates. Each controller is tested for the ability to track step commands, and for the amount of coupling impurity. Both controllers are developed via a linear-quadratic-regulator synthesis procedure, which is motivated by the multi-input/multi-output nature of second controller. Time responses and a singular value analysis are used to evaluate controller performance. This paper describes the development and comparison of two controllers that are designed to provide attitude control of a spinning rocket that is equipped with thrust vector control. 12 refs., 13 figs., 2 tabs.

The theoretical basis for the relationship between moisture content and light transmission (FFM) is developed, and shown to correspond well to the observed behavior. A calibration procedure for FFM based on the relationship between moisture content and matric potential is presented and tested. Means of expanding the range of sensitivity of the FFM are discussed.

We report dramatic improvements to the implanted-planar buried-heterostructure graded-index separate confinement heterostructure (IPBH-GRINSCH) laser in (AlGa)As/GaAs which produces low threshold current, continuous-wave operation. Our process features significantly reduced fabrication complexity of high quality, index-guided laser diodes compared to regrowth techniques and, in contrast to diffusion-induced disordering, allows creation of self-aligned, buried, blocking junctions by ion implantation. The improved single-stripe IPBH-GRINSCH lasers exhibit 39 mA threshold current, cw operation.