Detailed simulations have been performed for the TEVES (Thermal Enhanced Vapor Extraction System) Project using the TOUGH2 code considering air, water, and a single-component NAPL. A critical parameter varied in the simulations is the borehole vacuum which directly affects air flow through the system and indirectly influences soil temperatures and water and NAPL fluid masses. Contaminant migration from the heated zone into the unheated soil can occur if the borehole vacuum, or borehole flow rate, is not sufficient. Under these conditions, evaporation of liquids (water and NAPL) due to the heating can cause flow from the heated zone into the unheated soil. Insufficient air sweep may be indicated by a vapor dominated mass flow rate into the borehole, at least for the present configuration. Sufficient air flow through the heated zone must be provided to contain the contaminants within the heated zone.
The DOE requires that sensitive unclassified data be protected while being transmitted electronically. On most large networks it is difficult and expensive to provide the required level of physical protection. At Sandia National Laboratories, we are assembling the structure necessary to protect sensitive unclassified data using software-based encryption. This approach has the advantage that the data can be protected after arrival at its destination without additional investment While Sandia has expertise in cryptography, we had not used cryptography in this field. This discussion deals with the client-server model of file-based data exchange and interactive access to on-line data bases using Unix workstations, Macs and PCs.
The goal of the Offsite Demonstration Project for Mixed Waste Landfill Integrated Demonstration (MWLID)-developed environmental site characterization and remediation technologies is to facilitate the transfer, use, and commercialization of these technologies to the public and private sector. The meet this goal, the project identified environmental restoration needs of mixed waste and/or hazardous waste landfill owners (Native American, municipal, DOE, and DoD); documenting potential demonstration sites and the contaminants present at each site; assessing the environmental regulations that would effect demonstration activities; and evaluating site suitability for demonstrating MWLID technologies at the tribal and municipal sites identified. Eighteen landfill sites within a 40.2-km radius of Sandia National Laboratories are listed on the CERCLIS Site/Event Listing for the state of New Mexico. Seventeen are not located within DOE or DoD facilities and are potential offsite MWLID technology demonstration sites. Two of the seventeen CERCLIS sites, one on Native American land and one on municipal land, were evaluated and identified as potential candidates for off-site demonstrations of MWLID-developed technologies. Contaminants potentially present on site include chromium waste, household/commercial hazardous waste, volatile organic compounds, and petroleum products. MWLID characterization technologies applicable to these sites include Magnetometer Towed Array, Cross-borehole Electromagnetic Imaging, SitePlanner {trademark}/PLUME, Hybrid Directional Drilling, Seamist{trademark}/Vadose Zone Monitoring, Stripping Analyses, and x-ray Fluorescence Spectroscopy for Heavy Metals.
The industrial sector is the most complex and diverse segment of the US economy. There are more than 360,000 industrial facilities in the US, using tens of thousands of processes with millions of different pieces of equipment and employing nearly 30 million people to make hundreds of thousands of products. These facilities consume large quantities of raw materials and energy resources every year. Their waste streams, as well as the technology options for preventing them, are very specific not only to individual industries, but even to plants within the same industry that produce similar products. On October 24, 1992, President Bush signed the Energy Policy Act of 1992 (EPAct) into law as Public Law 102-486. Section 2108 of the Act requires the DOE to identify opportunities to demonstrate energy efficient pollution prevention technologies and processes. As a first step in DOE`s response to congress, Sandia National Laboratories lead a fast tracked project to compile information from the open literature, and pilot a process for identifying and prioritizing opportunity areas from industrial and federal experts. Approximately 300 documents were collected and reviewed, and knowledgeable individuals in government, universities, and trade associations were interviewed. A panel of experts from petroleum industry was assembled for the future opportunity assessments pilot These activities were conducted between May and August, 1993. Project background and results are summarized.
Human intrusion scenarios at the Waste Isolation Pilot Plant (WIPP) involve penetration of the repository and an underlying brine reservoir by a future borehole. Brine and gas from the brine reservoir and the repository may flow up the borehole and into the overlying Culebra formation, which is saturated with water containing different amounts of dissolved `solids resulting in a spatially varying density. Current modeling approaches involve perturbing a steady-state Culebra flow field by inflow of gas and/or brine from a breach borehole that has passed through the repository. Previous studies simulating steady-state flow in the Culebra have been done. One specific study by LaVenue et al. (1990) used the SWIFT 2 code, a single-phase flow and transport code, to develop the steady-state flow field. Because gas may also be present in the fluids from the intrusion borehole, a two-phase code such as TOUGH2 can be used to determine the effect that emitted fluids may have on the steady-state Culebra flow field. Thus a comparison between TOUGH2 and SWIFT2 was prompted. In order to compare the two codes and to evaluate the influence of gas on flow in the Culebra, modifications were made to TOUGH2. Modifications were performed by the authors to allow for element-specific values of permeability, porosity, and elevation. The analysis also used a new equation of state module for a water-brine-air mixture, EOS7 (Pruess, 1991), which was developed to simulate variable water densities by assuming a miscible mixture of water and brine phases and allows for element-specific brine concentration in the INCON file.
The Waste Isolation Pilot Plant (WIPP) is a US Department of Energy (DOE) research and development facility for the underground disposal of transuranic waste in southeastern New Mexico. The WIPP repository is located 655 m below the land surface in the lower portion of the Salado Formation, which is comprised of beds of pure and impure halite with thin interbeds of anhydrite and related clay seams. The regional dip of the Salado Formation is approximately 1{degree} southeast in the vicinity of the repository. The proposed waste storage area has eight waste disposal panels, each of which will contain seven rooms. The repository is designed to follow a single stratigraphic horizon. Due to the dip, the north end of the repository will be about 10 meters higher than the south end. Waste that is emplaced in the disposal rooms will generate gas due to microbial degradation, anoxic corrosion, and radiolysis. Brine inflow to the rooms from the surrounding Salado Formation may significantly influence the gas generation rate and the total amount of gas generated. The salt surrounding the repository will creep in response to the excavation, reducing the room volume. Gas generation in the room may increase the pressure sufficiently to drive brine and gas into the surrounding Salado Formation. Migration of gas and brine in the Salado is an important factor in evaluating the performance of the repository. The studies summarized in this paper have. been performed to evaluate brine and gas flow processes in the WIPP disposal system and to identify some of the important processes. These studies are done in support of, but are not part of, the formal Performance Assessment (PA) effort. Because of probabilistic and system-scale requirements, the PA effort uses the Sandia-developed BRAGFLO (BRine And Gas FLOw) code for multiphase flow calculations.
The Waste Isolation Pilot Plant (WIPP) is a US Department of Energy facility designed to demonstrate the safe underground disposal of transuranic waste. Following waste emplacement, each room will be backfilled with crushed salt. Due to deviatoric stress introduced by excavation, the walls of the waste disposal rooms in the repository will deform over time, consolidating waste containers and salt backfill, thereby decreasing the void volume of the repository. Long-term repository assessment must consider the processes of gas generation, room closure and expansion due to salt creep, and multiphase (brine and gas) fluid flow, as well as the complex coupling between these three processes. Stone (1992) used the mechanical creep closure code SANCHO to simulate the closure of a single, perfectly sealed disposal room filled with waste and backfill. The results of the SANCHO f-series simulations provide a relationship between gas generation, room closure, and room pressure. Several methods for coupling this relationship with multiphase fluid flow into and out of a room were examined by Freeze et al. TOUGH2 was employed to couple the processes of gas generation, room closure/consolidation, and multiphase brine and gas flow. Two empirically-based methods for approximating salt creep and room consolidation were implemented in TOUGH2: the pressure-time-porosity line interpolation approach and the fluid-phase-salt approach. Both approaches utilized links to the SANCHO f-series simulation results to calculate room-void-volume changes with time during a simulation.
The Waste Isolation Pilot Plant (WIPP) is a US Department of Energy research and development facility for the underground disposal of transuranic waste from US defense-related activities. The WIPP repository is located within the Salado Formation, which is comprised of beds of pure and impure halite with thin interbeds of anhydrite and related clay seams. This formation is brine saturated with a pore pressure of approximately 12.5 MPa at the repository horizon. The Salado Formation dips gently southeast, on the average approximately 1{degree}, with steeper dips locally. Elevated repository pressures, caused by gas generated as emplaced waste corrodes and degrades, may drive brine and gas out of the repository into the surrounding formation. Stratigraphic dip may cause increased brine inflow to the repository through countercurrent flow in the interbeds and enhanced gas migration distances in the updip direction due to buoyancy. Two-dimensional simulations of isolated WIPP repository room have been performed using TOUGH2 for horizontal and 1{degree} dipping stratigraphy. The impact of dip on multiphase flow at the WIPP may be significant. With dip, an additional mechanism for brine inflow may occur, namely the formation of a cell of countercurrent brine and gas flow in the interbeds. The additional volume of brine inflow resulting from the countercurrent flow cell may be of similar magnitude to brine inflow without dip. Therefore, dip must be included in any repository model to include the countercurrent brine inflow mechanism. Gas migration may also be significantly influenced due to dip. Gas migration distances may increase dramatically with preferential migration updip.
MELCOR models the progression of severe accidents in light water reactor nuclear power plants. Recent efforts in MELCOR development to incorporate CORCON-Mod3 models for core-concrete interactions, new models for advanced reactors, and improvements to several other existing models have resulted in release of MELCOR 1.8.3. In addition, continuing efforts to expand the code assessment database have filled in many of the gaps in phenomenological coverage. Efforts are now under way to develop models for chemical interactions of fission products with structural surfaces and for reactions of iodine in the presence of water, and work is also in progress to improve models for the scrubbing of fission products by water pools, the chemical reactions of boron carbide with steam, and the coupling of flow blockages with the hydrodynamics. Several code assessment analyses are in progress, and more are planned.
Sandia National Laboratories performs R and D in structural dynamics and vibration suppression for precision applications in weapon systems, space, underwater, transportation and civil structures. Over the last decade these efforts have expanded into the areas of active vibration control and ``smart`` structures and material systems. In addition, Sandia has focused major resources towards technology to support weapon product development and agile manufacturing capability for defense and industrial applications. This paper will briefly describe the structural dynamics modeling and verification process currently in place at Sandia that supports vibration control and some specific applications of these techniques to manufacturing in the areas of lithography, machine tools and flexible robotics.
To improve process reliability and deposition methods, it is essential to identify the rate-limiting step in TEOS-based SiO{sub 2} CVD and its dependence on process conditions. For this purpose, experiments designed to evaluate by-product inhibition effects and to identify the rate-limiting step in TEOS decomposition have been carried out in a research reactor using GCMS and FTIR. By repetitively sampling a series of reactions in which TEOS was first mixed with ethylene, ethanol, and water in the gas-phase, GCMS was used to show clearly that these reaction by-products do not inhibit the heterogeneous reaction step on SiO{sub 2} at 1,000K. FTIR was used to determine that ethoxy groups from TEOS dissociative chemisorption have a significant lifetime on the SiO{sub 2} surface at CVD temperatures and have an activation energy for decomposition of 16kcal/mol{+-}4kcal/mol. This is much higher than the activation energy of 6 kcal/mol reported for the initial chemisorption step and is near the 22 kcal/mol reported for the overall activation energy for SiO{sub 2} deposition in a cold-wall reactor. These results suggest that, whether or not surface ethoxy groups inhibit TEOS reactions, their decomposition may be directly related to the rate-limiting step in SiO{sub 2} deposition.
If current plans are realized, within the next few years, an extraordinary set of coordinated research efforts focusing on energy flows in the Arctic will be implemented. All are motivated by the prospect of global climate change. SHEBA (Surface Energy Budget of the Arctic Ocean), led by the National Science Foundation (NSF) and the Office of Naval Research (ONR), involves instrumenting an ice camp in the perennial Arctic ice pack, and taking data for 12--18 months. The ARM (Atmospheric Radiation Measurement) North Slope of Alaska and Adjacent Arctic Ocean (NSA/AAO) Cloud and Radiation Testbed (CART) focuses on atmospheric radiative transport, especially in the presence of clouds. The NSA/AAO CART involves instrumenting a sizeable area on the North Slope of Alaska and adjacent waters in the vicinity of Barrow, and acquiring data over a period of about 10 years. FIRE (First ISCCP [International Satellite Cloud Climatology Program] Regional Experiment) Phase 3 is a program led by the National Aeronautics and Space Administration (NASA) which focuses on Arctic clouds, and which is coordinated with SHEBA and ARM. FIRE has historically emphasized data from airborne and satellite platforms. All three program anticipate initiating Arctic data acquisition during spring, 1997. In light of his historic opportunity, the authors discuss a strawman atmospheric radiative transfer experimental plan that identifies which features of the radiative transport models they think should be tested, what experimental data are required for each type of test, the platforms and instrumentation necessary to acquire those data, and in general terms, how the experiments could be conducted. Aspects of the plan are applicable to all three programs.
This paper describes an application of Sandia`s non-contact capacitive sensing technology for collision avoidance during the manufacturing of rocket engine thrust chambers. The collision avoidance system consists of an octagon shaped collar with a capacitive proximity sensor mounted on each face. The sensors produced electric fields which extend several inches from the face of the collar and detect potential collisions between the robot and the workpiece. A signal conditioning system processes the sensor output and provides varying voltage signals to the robot controller for stopping the robot.
The introduction of alternative, non-lead bearing solders into electronic assemblies requires a thorough investigation of product manufacturability and reliability. Both of these attributes can be impacted by the excessive growth of intermetallic compound (IMC) layers at the solder/substrate interface. An extensive study has documented the stoichiometry and solid state growth kinetics of IMC layers formed between copper and the lead-free solders: 96.5Sn-3.5Ag (wt.%), 95Sn-5Sb, 100Sn, and 58Bi-42Sn. Aging temperatures were 70--205 C for the Sn-based solders and 55--120 C for the Bi-rich solder. Time periods were 1--400 days for all of the alloys. The Sn/Cu, Sn-Ag/Cu, and Sn-Sb/Cu IMC layers exhibited sub-layers of Cu{sub 6}Sn{sub 5} and Cu{sub 3}Sn; the latter composition was present only following prolonged aging times or higher temperatures. The total layer growth exhibited a time exponent of n = 0.5 at low temperatures and a value of n = 0.42 at higher temperatures in each of the solder/Cu systems. Similar growth kinetics were observed with the low temperature 58Bi-42Sn solder; however, a considerably more complex sub-layer structure was observed. The kinetic data will be discussed with respect to predicting IMC layer growth based upon solder composition.
Optoelectronic and photonic devices hold great promise for high data-rate communication and computing. Their wide implementation was limited first by the device technologies and now suffers due to the need for high-precision packaging that is mass-produced. The use of photons as a medium of communication and control implies a unique set of packaging constraints that are highly driven by the need for micron and even sub-micron alignments between photonic devices and their transmission media. Current trends in optoelectronic device packaging are reviewed and future directions are identified both for free-space (3-dimensional) and guided-wave (2-dimensional) photonics. Emphasis will be placed on the special needs generated by increasing levels of device integration.
Sandia Labs` mobile tracking systems have only one moving part. The double gimballed 18 inch diameter beryllium mirror is capable of constant tracking velocities up to 5 rads/sec in both axes, and accelerations to 150 rads/sec/sec in both axes. Orthogonality is <10 microradians. The mirror directs the 488 and 514 nm wavelength CW laser beams to adhesive-backed reflective material applied to the test unit. The mirror catches the return beam and visual image, directing the visual image to three camera bays, and the return beam to an image dissector behind an 80 inch gathering telescope. The image dissector or image position sensor is a photomultiplier with amplifying drift tube and electron aperture and its associated electronics. During the test, the image dissector scan senses the change in position of the reflective material and produces signals to operate the azimuth and elevation torque motors in the gimbal assembly. With the help of 1 1/8 inch diameter azimuth and elevation galvonometer steering mirrors in the optical path, the laser beam is kept on the target at extremely high velocities. To maintain a constant return signal strength, the outgoing beam is run through a microprocessor controlled beam focusing telescope.
Geologic Site Characterization should be a dynamic, continuing process, not an event. Its successes and failures are legion and can make or break an operator. A balanced approach must be sought to provide adequate information for safety of operations, neither slighting nor overdoing the effort. The evolving nature of study methods and geologic knowledge essentially mandates that characterization efforts be reviewed periodically. However, indifference, nonchallance, and even outright disdain describe attitudes witnessed in some circles regarding this subject. Unawareness may also be a factor. Unfortunately, several unanticipated events have led to severe economic consequences for the operators. The hard-learned lessons involving several unanticipated geotechnical occurrences at several Gulf Coast salt domes are discussed. The ultimate benefit of valuing site characterization efforts may be more than just enhanced safety and health--costs not expended in lost facilities and litigation can become profit.
In order to provide needed security assurances for traffic carried in Asynchronous Transfer Mode (ATM) networks, methods of protecting the integrity and privacy of traffic must be employed. Cryptographic methods can be used to assure authenticity and privacy, but are hard to scale and the incorporation of these methods into computer networks can severely impact functionality, reliability, and performance. To study these trade-offs, a research prototype encryptor/decryptor is under development. This prototype is to demonstrate the viability of implementing certain encryption techniques in high speed networks by processing Asynchronous Transfer Mode (ATM) cells in a SONET OC-3 payload. This paper describes the objectives and design trade-offs intended to be investigated with the prototype. User requirements for high performance computing and communication have driven Sandia to do work in the areas of functionality, reliability, security, and performance of high speed communication networks. Adherence to standards (including emerging standards) achieves greater functionality of high speed computer networks by providing wide interoperability of applications, network hardware, and network software.
Many advanced light water reactor (ALWR) concepts proposed for the next generation of nuclear power plants rely on passive systems to perform safety functions, rather than active systems as in current reactor designs. These passive systems depend to a great extent on physical processes such as natural circulation for their driving force, and not on active components, such as pumps. An NRC-sponsored study was begun at Sandia National Laboratories to develop and implement a methodology for evaluating ALWR passive system reliability in the context of probabilistic risk assessment (PRA). This report documents the first of three phases of this study, including methodology development, system-level qualitative analysis, and sequence-level component failure quantification. The methodology developed addresses both the component (e.g. valve) failure aspect of passive system failure, and uncertainties in system success criteria arising from uncertainties in the system`s underlying physical processes. Traditional PRA methods, such as fault and event tree modeling, are applied to the component failure aspect. Thermal-hydraulic calculations are incorporated into a formal expert judgment process to address uncertainties in selected natural processes and success criteria. The first phase of the program has emphasized the component failure element of passive system reliability, rather than the natural process uncertainties. Although cursory evaluation of the natural processes has been performed as part of Phase 1, detailed assessment of these processes will take place during Phases 2 and 3 of the program.
Full-scale fire characterization tests are becoming less frequent due to cost restrictions and environmental concerns. This trend, combined with significant advances in fire field modeling, has resulted in an increased effort to perform well-designed experiments which support the development and validation of numerical tools. In pursuit of improved fire characterization, large-fire measurement techniques in large-scale (D > 2m) fires are reviewed in this work. Primary attention is focused on the measurement of temperature and heat flux. Additional measurements of quantities such as soot volume fraction, soot emission temperature, and gas species are also addressed. Issues relating to the use of existing techniques, and methods for improving and interpreting the results from existing measurement techniques are presented. Alternate techniques for fire characterization and needs for development of advanced measurement technology are also briefly discussed.
A series of tests investigating dynamic pulse buckling of a cylindrical shell under axial impact is compared to several 2D and 3D finite element simulations of the event. The purpose of the work is to investigate the performance of various analysis codes and element types on a problem which is applicable to radioactive material transport packages, and ultimately to develop a benchmark problem to qualify finite element analysis codes for the transport package design industry. During the pulse buckling tests, a buckle formed at each end of the cylinder, and one of the two buckles became unstable and collapsed. Numerical simulations of the test were performed using PRONTO, a Sandia developed transient dynamics analysis code, and ABAQUS/Explicit with both shell and continuum elements. The calculations are compared to the tests with respect to deformed shape and impact load history.
This paper presents an analysis of the Chemical Vapor Deposition of diamond thin films in a direct-current (dc) arc-jet reactor. The analysis discussed here includes a model of the performance of the arc-jet hydrogen excitation source, chemistry in the free-stream region, diffusive transport and chemistry in the boundary layer and at the surface. The surface chemistry model includes pathways for deposition of diamond, as well as creation of defects in the diamond lattice.
An overview is presented of work on strained InAsSb heterostructures and infrared emitters. InAsSb/InGaAs strained-layer superlattices (SLS) and InAsSb quantum wells were grown by metal-organic chemical vapor deposition and characterized using magneto-photoluminescence. LEDs and lasers with InAsSb heterostructure active regions are described.
When a system is being designed, one of the system requirements will specify the intended life for the system, which is called the design life, the system life, the expected operational lifetime, or the service life. This specification is an important driver of the total life cycle cost. This paper suggests how specifying this design life affects the design and the cost of the system.
Over the next decade, the US Department of Energy (DOE) must retire and dismantle many nuclear weapon systems. In support of this effort, Sandia National Laboratories (SNL) has developed the Hazard Separation System (HSS). The HSS combines abrasive waterjet cutting technology and real-time radiography. Using the HSS, operators determine the exact location of interior, hazardous sub-components and remove them through precision cutting. The system minimizes waste and maximizes the recovery of recyclable materials. During 1994, the HSS was completed and demonstrated. Weapon components processed during the demonstration period included arming, fusing, and firing units; preflight control units; neutron generator subassemblies; and x-units. Hazards removed included radioactive krytron tubes and gap tubes, thermal batteries, neutron generator tubes, and oil-filled capacitors. Currently, the HSS is being operated at SNL in a research and development mode to facilitate the transfer of the technology to other DOE facilities for support of their dismantlement operations.