Publications

Gas generation from the microbial degradation of the organic constituents of transuranic waste under conditions expected at the Waste Isolation Pilot Plant (WIPP) repository was investigated at Brookhaven National Laboratory. The biodegradation of mixed cellulosics (various types of paper) and electron-beam irradiated plastic and rubber materials (polyethylene, polyvinylchloride, neoprene, hypalon, and leaded hypalon) was examined. The rate of gas production from cellulose biodegradation in inundated samples incubated for 1,228 days at 30 C was biphasic, with an initial rapid rate up to approximately 600 days incubation, followed by a slower rate. The rate of total gas production in anaerobic samples containing mixed inoculum was as follows: 0.002 mL/g cellulose/day without nutrients; 0.004 mL/g cellulose/day with nutrients; and 0.01 mL/g cellulose/day in the presence of excess nitrate. Carbon dioxide production proceeded at a rate of 0.009 {micro}mol/g cellulose/day in anaerobic samples without nutrients, 0.05 {micro}mol/g cellulose/day in the presence of nutrients, and 0.2 {micro}mol/g cellulose/day with excess nitrate. Adding nutrients and excess nitrate stimulated denitrification, as evidenced by the accumulation of N{sub 2}O in the headspace (200 {micro}mol/g cellulose). The addition of the potential backfill bentonite increased the rate of CO{sub 2} production to 0.3 {micro}mol/g cellulose/day in anaerobic samples with excess nitrate. Analysis of the solution showed that lactic, acetic, propionic, butyric, and valeric acids were produced due to cellulose degradation. Samples incubated under anaerobic humid conditions for 415 days produced CO{sub 2} at a rate of 0.2 {micro}mol/g cellulose/day in the absence of nutrients, and 1 {micro}mol/g cellulose/day in the presence of bentonite and nutrients. There was no evidence of biodegradation of electron-beam irradiated plastic and rubber.

This report describes a Strategic Environmental Research and Development Program (SERDP) project to field a dish/Stirling system at a southwestern US military facility. This project entitled ``Dish/Stirling for DoD Applications`` was started in August 1993 and was completed in September 1996. The project`s objective was to assist military facilities to field and evaluate emerging environmentally sound and potentially economical dish/Stirling technology. Dish/Stirling technology has the potential to produce electricity at competitive costs while at the same time providing a secure and environmentally benign source of power. In accordance with the SERDP charter, this project leveraged a US Department of Energy (DOE) cost-shared project between Sandia National Laboratories and Cummins Power Generation, Inc. (CPG). CPG is a wholly owned subsidiary of Cummins Engine Company, a leading manufacturer of diesel engines. To accomplish this objective, the project called for the installation of a dish/Stirling system at a military facility to establish first-hand experience in the operation of a dish/Stirling system. To scope the potential DoD market for dish/Stirling technology and to identify the site for the demonstration, a survey of southwestern US military facilities was also conducted. This report describes the project history, the Cummins dish/Stirling system, results from the military market survey, and the field test results.

Nuclear weapons have been produced in the US since the early 1950s by a network of contractor-operated Department of Energy (DOE) facilities collectively known as the Nuclear Weapon Complex (NWC). Recognizing that the failure of an essential process might stop weapon production for a substantial period of time, the DOE Albuquerque Operations office initiated the Production Risk Evaluation Program (PREP) at Sandia National Laboratories (SNL) to assess quantitatively the potential for serious disruptions in the NWC weapon production process. PREP was conducted from 1984-89. This document is an unclassified summary of the effort.

This report summarizes tests on five different foams. Two are manufactured at Allied Signal, two at North Carolina Foam Industries, and one at General Plastics. The tests conducted are: thermal conductivity at various temperatures, specific heat at 60{degrees}C, compressive strength at ambient and 60{degrees}C, thermogravimetric analysis to 800{degrees}C, intumescence, and char formation properties. A CHN analysis was also performed. Funding for the testing of rigid polyurethane foams originated from the AT-400A container program at Sandia National Laboratories. This testing supported the development of the AT-400A container. The AT-400A is a storage and transportation container that will be used initially at the Pantex Plant for storage of plutonium from dismantled nuclear weapons.

This paper describes results from efforts to develop VOC sensing systems based on two complementary techniques. The first technique used a gated channeltron detector for resonant laser-induced multiphoton photoionization detection of trace organic vapors in a supersonic molecular beam. The channeltron was gated using a relatively simple circuit to generate a negative gate pulse with a width of 400 ns (FWHM), a 50 ns turn-on (rise) time, a 1.5 {mu}s turn-off (decay) time, a pulse amplitude of {minus}1000 Volts, and a DC offset adjustable from zero to {minus}1500 Volts. The gated channeltron allows rejection of spurious responses to UV laser light scattered directly into the channeltron and time-delayed ionization signals induced by photoionization of residual gas in the vacuum chamber. Detection limits in the part-per-trillion range have been demonstrated with the gated detector. The second technique used arrays of surface acoustic wave (SAW) devices coated with various chemically selective materials (e.g., polymers, self assembled monolayers) to provide unique response patterns to various chemical analytes. This work focused on polymers, formed by spin casting from solution or by plasma polymerization, as well as on self assembled monolayers. Response from coated SAWs to various concentrations of water, volatile organics, and organophosphonates (chemical warfare agent simulants) were used to provide calibration data. A novel visual empirical region of influence (VIERI) pattern recognition technique was used to evaluate the ability to use these response patterns to correctly identify chemical species. This investigation shows how the VERI technique can be used to determine the best set of coatings for an array, to predict the performance of the array even if sensor responses change due to aging of the coating materials, and to identify unknown analytes based on previous calibration data.

Paving is an automated mesh generation algorithm which produces all-quadrilateral elements. It can additionally generate these elements in varying sizes such that the resulting mesh adapts to a function distribution, such as an error function. While powerful, conventional paving is a very serial algorithm in its operation. Parallel paving is the extension of serial paving into parallel environments to perform the same meshing functions as conventional paving only on distributed, discretized models. This extension allows large, adaptive, parallel finite element simulations to take advantage of paving`s meshing capabilities for h-remap remeshing. A significantly modified version of the CUBIT mesh generation code has been developed to host the parallel paving algorithm and demonstrate its capabilities on both two dimensional and three dimensional surface geometries and compare the resulting parallel produced meshes to conventionally paved meshes for mesh quality and algorithm performance. Sandia`s {open_quotes}tiling{close_quotes} dynamic load balancing code has also been extended to work with the paving algorithm to retain parallel efficiency as subdomains undergo iterative mesh refinement.

Advanced reactor systems are likely to use protection systems with digital electronics that ideally should be resistant to environmental hazards, including smoke from possible cable fires. Previous smoke tests have shown that digital safety systems can fail even at relatively low levels of smoke density and that short-term failures are likely to be caused by circuit bridging. Experiments were performed to examine these failures, with a focus on component packaging and protection schemes. Circuit bridging, which causes increased leakage currents and arcs, was gauged by measuring leakage currents among the leads of component packages. The resistance among circuit leads typically varies over a wide range, depending on the nature of the circuitry between the pins, bias conditions, circuit board material, etc. Resistance between leads can be as low as 20 k{Omega} and still be good, depending on the component. For these tests, the authors chose a printed circuit board and components that normally have an interlead resistance above 10{sup 12} {Omega}, but if the circuit is exposed to smoke, circuit bridging causes the resistance to fall below 10{sup 3} {Omega}. Plated-through-hole (PTH) and surface-mounted (SMT) packages were exposed to a series of different smoke environments using a mixture of environmentally qualified cables for fuel. Conformal coatings and enclosures were tested as circuit protection methods. High fuel levels, high humidity, and high flaming burns were the conditions most likely to cause circuit bridging. The inexpensive conformal coating that was tested - an acrylic spray - reduced leakage currents, but enclosure in a chassis with a fan did not. PTH packages were more resistant to smoke-induced circuit bridging than SMT packages. Active components failed most often in tests where the leakage currents were high, but failure did not always accompany high leakage currents.

The thermo-hydrologic behavior of the potential repository at Yucca Mountain, Nevada, has been simulated to investigate the effects of infiltration. Transient temperatures, liquid saturations, and liquid mass flow rates through the fractures and matrix were simulated using several different steady infiltration rates ranging from 0.3 to 30 min./year. The lower infiltration rates resulted in higher temperatures near the repository element, but the overall transient temperature profiles were similar. The hydrologic response near the repository (liquid saturations and fluxes) was found to be very sensitive to the infiltration rate. Increased infiltration rates reduced the time to re-wet the simulated repository during cooling, and an infiltration rate of 10 mm/year was sufficient to completely eliminate the dry-out zone around the repository.

In March 1994, the US Department of Energy Carlsbad Area Office (DOE/CAO) implemented a performance based decision-aiding method to assist in programmatic prioritization within the Waste Isolation Pilot Plant (WIPP) project. The prioritization was with respect to 40 CFR Part 191.13(a) and 40 CFR part 268.6. U.S. Environmental Protection Agency (EPA) requirements for long-term isolation of radioactive and hazardous wastes. The Systems Prioritization Method (SPM), was designed by Sandia National Laboratories to: (1) identify programmatic options (activities), their costs and durations; (2) analyze combinations of activities in terms of their predicted contribution to long-term performance of the WIPP disposal system; and (3) analyze cost, duration, and performance tradeoffs. SPM results were the basis for activities recommended to DOE/CAO in May 1995. SPM identified eight activities (less than 15% of the 58 proposed for consideration) predicted to be essential in addressing key regulatory issues. The SPM method proved useful for risk or performance-based prioritization in which options are interdependent and system behavior is nonlinear. 10 refs., 2 figs., 1 tab.

A series of eight fire tests with simulated radioactive material shipping containers aboard the test ship Mayo Lykes, a break-bulk freighter, is described. The tests simulate three basic types of fires: engine room fires, cargo fires and open pool fires. Detailed results from the tests include temperatures, heat fluxes and air flows measured during the fires. The first examination of the results indicates that shipboard fires are not significantly different from fires encountered in land transport. 13 refs., 15 figs., 11 tabs.

A series of hydraulic-fracture experiments using a downhole tiltmeter array, called an inclinometer array, was conducted at the Department of Energy (DOE)/Gas Research Institute (GRI) Multi-Site facility in Colorado. The inclinometer array was used to measure the deformation of the reservoir rock in response to hydraulic fracture opening and confirm microseismically measured results. In addition, the inclinometer array was found to be a useful tool for accurately measuring closure stress, measuring residual widths of both propped and unpropped fractures, estimating proppant distribution, and evaluating values of in situ moduli.

An extension to classical covariance control methods, introduced by Skelton and co-workers, is proposed specifically for application to the control of civil engineering structures subjected to random dynamic excitations. The covariance structure of the system is developed directly from specification of its reliability via the assumption of independent (Poisson) outcrossings of its stationary response process from a polyhedral safe region. This leads to a set of state covariance controllers, each of which guarantees that the closed-loop system will possess the specified level of reliability. An example civil engineering structure is considered.

The simultaneous formation of a filler phase and a polymer matrix via in situ sol-gel techniques provides silica-siloxane nanocomposite materials of high strength. This study concentrates on the effects of temperature and relative humidity on a trimodal polymer system in an attempt to accelerate the reaction as well as evaluate subtle process- structure-property relations. It was found that successful process acceleration is only viable for high humidity systems when using the tin(IV) catalyst dibutyltin dilaurate. Processes involving low humidity were found to be very temperature and time dependent. Bimodal systems were investigated and demonstrated that the presence of a short-chain component led to enhanced material strength. This part of the study also revealed a link between the particle size and population density and the optimization of material properties.

The effect of dose rate on radiation-induced gain degradation is compared for verticle npn and lateral pnp bipolar transistors. High dose rate irradiations at elevated temperatures are more effective at simulating low dose rate degradation in the lateral pnp transistors.

Effects of irradiation and annealing temperature on radiation-induced charge densities are explored for MOS transistors. Both interface- and border-trap density increase with increasing radiation temperature, while the net oxide-trap charge density decreases.

The ionizing radiation response of several semiconductor process technologies has been shown to be enhanced by plastic packaging and/or pre-conditioning (burn-in). Potential mechanisms for this effect are discussed and data on bipolar linear circuits are presented.

Windows NT desktop and server systems are becoming increasingly important to Sandia. These systems are capable of network performance considerably in excess of the 10 Mbps Ethernet data rate. As alternatives to conventional Ethernet, 155 Mbps Asynchronous Transfer Mode, ATM, and 100 Mbps Ethernet network interface cards were tested and compared to conventional 10 Mbps Ethernet cards in a typical Windows NT system. The results of the tests were analyzed and compared to show the advantages of the alternative technologies. Both 155 Mbps ATM and 100 Mbps Ethernet offer significant performance improvements over conventional 10 Mbps shared media Ethernet.

Thin metal films (∼ 100 nm thick) of Be, W, V and Mo, were deposited on a Si depth-marked graphite sample and exposed to the steady-state outer strike point on DIII-D in order to measure their respective erosion rates. Gross erosion rates and redeposition lengths are found to decrease with the atomic number of the metallic species, as expected. The maximum net erosion rate for carbon, which occurs near the separatrix, increased from 4 to 16 nm/s when the incident heat flux was increased from 0.7 to 2 MW/m2. Comparisons of the measured carbon erosion with REDEP code calculations show good agreement for both the absolute net erosion rate and its spatial variation. Visible spectroscopic measurements of singly ionized Be (BeII 4674 Å) have determined that the erosion process reaches steady-state during the exposure.

Measurements of the deuterium particle flux and energy to the divertor of the DIII-D tokamak during a series of plasmas that terminated in disruptions have been made using a silicon collector probe installed on the DiMES (divertor materials exposure system) mechanism. During the steady state portion of each discharge, the probe was located in the private flux region, but immediately before disrupting the plasma, by injecting either Ar or D2 gas, the strike point of the outer divertor leg was positioned over the probe. Comparison of the amount of retained D in the probe for the two types of disruptions indicates that much of the trapped D could have resulted from exposure in the private flux zone prior to the disruption. Measurements of the depth distribution of the trapped D in the Si imply that the incident ion energy was approximately 100 eV at normal incidence and decreased slightly at oblique angles. The measurements give an upper bound to the energy of deuterons striking the divertor floor in the vicinity of the strikepoint during disruptions.

The ability to image complex geologies such as salt domes in the Gulf of Mexico and thrusts in mountainous regions is a key to reducing the risk and cost associated with oil and gas exploration. Imaging these structures, however, is computationally expensive. Datasets can be terabytes in size, and the processing time required for the multiple iterations needed to produce a velocity model can take months, even with the massively parallel computers available today. Some algorithms, such as 3D, finite-difference, prestack, depth migration remain beyond the capacity of production seismic processing. Massively parallel processors (MPPs) and algorithms research are the tools that will enable this project to provide new seismic processing capabilities to the oil and gas industry. The goals of this work are to (1) develop finite-difference algorithms for 3D, prestack, depth migration; (2) develop efficient computational approaches for seismic imaging and for processing terabyte datasets on massively parallel computers; and (3) develop a modular, portable, seismic imaging code.

This document specifies signaling procedures required to support security services in the Phase I ATM Security Specification. These signaling procedures are in addition to those described in UNI 4.0 Signaling. When establishing point-to-point and point-to-multipoint calls, the call control procedures described in the ATM Forum UNI 4.0 Signaling apply. This document describes the additional information elements and procedures necessary to support security services. This description is in an incremental form with differences from the point-to-point and point-to-multipoint calls with respect to messages, information elements, and signaling procedures.

Germanosilicate glasses exhibit a significant photosensitive response which has been linked to the presence of oxygen-deficient germanium point defects in the glass structure. Based on this correlation, highly photosensitive thin films have been engineered which demonstrate the largest reported ultraviolet-induced refractive index perturbations (An) in an as-synthesized material. Our thin-film fabrication process avoids the use of hydrogen sensitizing treatments and, thus, yields stable films which retain their predisposition for large photosensitivity for over one year of storage. Understanding the nature of the defects in such films and their relationship to charge trapping and enhanced photosensitivity is of paramount importance in designing and optimizing the materials. Toward this end, our films have been studied using electron paramagnetic resonance (EPR), capacitance-voltage, and optical bleaching and absorption spectroscopies. We find experimental evidence suggesting a model in which a change in spin state and charge state of isolated paramagnetic neutral Ge dangling bonds form either diamagnetic positively or negatively charged Ge sites which are largely responsible for the charge trapping and photosensitivity in these thin films. We present experimental data and theoretical modeling to support our defect model and to show the relevance of the work.

The optical performance of refractive index structures induced in photosensitive (PS) glasses ultimately depends on the index modulation depth attainable. In germanosilicate materials, the photosensitive response is linked to the presence of oxygen-deficient germanium point defect centers. Prior efforts to increase PS in these materials, e.g., hydrogen loading, rely on a chemical reduction of the glass structure to enhance the population of oxygen deficient centers and thus increase the saturated refractive index change. We have previously reported the development of highly photosensitive, as-deposited germanosilicate glass films through reactive atmosphere (O{sub 2}/Ar) sputtering from a Ge/Si alloy target. The present work details our investigation of the effect of substrate temperature during deposition on the material structure and propensity for photosensitivity. Using optical absorption/bleaching, Raman, electron paramagnetic resonance (EPR) and selective charge injection techniques we show that the predominate defect states responsible for the PS response can be varied through substrate temperature control. We find that two regimes of photosensitive behavior can be accessed which exhibit dramatically different uv-bleaching characteristics. Thus, the corresponding dispersion of the refractive index change as well as its magnitude can be controlled using our synthesis technique. Tentative defect models for the photosensitive process in materials deposited at both ambient temperature and at elevated substrate temperatures will be presented.

If photonic data and power transfer links are constructed in a modular fashion, they can be easily adapted into various forms to meet a wide range of needs for aerospace and military applications. The performance specifications associated with these needs can vary widely according to application. Alignment tolerance needs also tend to vary greatly, as can requirements on power consumption. An example of a modular photonic data and/or power transfer link that can be applied to military and aerospace needs is presented. In this approach, a link is designed for low (<10 kb/s) data rates, ultra-low electrical power consumption, large alignment tolerance, and power transfer to provide complete electrical shielding in a remote module that might be found in a military or aerospace application.

The effects of heterogeneities on the performance of capillary barriers is investigated by simulating three systems comprised of a fine soil layer overlying a coarse gravel layer with homogeneous, layered heterogeneous, and random heterogeneous property fields. The amount of lateral diversion above the coarse layer under steady-state infiltration conditions is compared between the simulations. Results indicate that the performance of capillary barriers may be significantly influenced by the spatial variability of the properties. The layered heterogeneous system performed best as a result of horizontal features within the fine layer that acted as additional local capillary barriers that delayed breakthrough into the coarse layer. The random heterogeneous system performed worst because of channeled flow that produced localized regions of water breakthrough into the coarse layer. These results indicate that engineered capillary barriers may be improved through emplacement and packing methods that induce a layered system similar to the layered heterogeneous field simulated in this study.