Publications

Concern for the environment and cost reduction are the driving forces for a broad effort in government and the private sector to develop new, more cost-effective technologies for characterizing, monitoring and remediating environmental sites. Secondary goals of the characterization, monitoring and remediation (CMR) activity are: minimize secondary waste generation, minimize site impact, protect water tables, and develop methods/strategies to apply new technologies. The Sandia National Laboratories (SNL) project in directional boring for CMR of waste sites with enhanced machinery from the underground utility installation industry was initiated in 1990. Preliminary activities included surveying the directional drilling access needs of various DOE sites, identifying an existing class of machinery that could be enhanced for environmental work through development, and establishing a mutually beneficial working relationship with an industry partner. Since that time the project has tested a variety of prototype machinery and hardware built by the industrial partner, and SNL. The project continues to test and develop the machinery and technique refinements needed for future applications at DOE, DOD, and private sector sites. The original goal of cost-effectiveness is being met through innovation, adaptation, and application of fundamental concepts. Secondary goals are being met via a basic philosophy of ``cut/thrust and compact cuttings without adding large quantities of fluid`` to an environmental problem site. Technology transfer to the private sector is ongoing and ultimately should result in commercial availability of the machinery. Education of regulatory agencies resulting in restructuring appropriate regulatory standards for specification of the horizontal drilling techniques will be a final project goal.

The Beneficial Uses Shipping System cask is a Type B packaging developed by Sandia National Laboratories for the U.S. Department of Energy. The cask is designed to transport special form radioactive source capsules (cesium chloride and strontium fluoride) produced by the Department of Energy`s Hanford Waste Encapsulation and Storage Facility. This paper describes the cask system and the analyses performed to predict the response of the cask in impact, puncture, and fire accident conditions as specified in the regulations. The cask prototype has been fabricated and Certificates of Compliance have been obtained.

L-{alpha}-alanine, a nontoxic polycrystalline amino acid, has been investigated for use in high-precision, high-level absorbed-dose measurements in mixed neutron/photon environments such as research and test reactors. The technique is based on the use of electron paramagnetic resonance spectroscopy to determine the extent of free radical production in a sample exposed to ionizing radiation, and has been successfully used for photon absorbed-dose measurements at levels exceeding 10{sup 5} Gy with high measurement precision. Application of the technique to mixed environments requires knowledge of the energy-dependent response of the dosimeter for both photons and neutrons. Determination of the dosimeter response to photons is accomplished by irradiations in {sup 60}Co and bremsstrahlung sources and by calculations of energy-dependent photon kerma. Neutron response is determined by irradiations in conjunction with CaF{sub 2}:Mn thermoluminescence dosimeters and by calculations of energy-dependent neutron kerma. Several neutron environments are used, including those provided by the Annular Core Research Reactor and Sandia Pulsed Reactor.

The RADTRAN 4 computer code for transportation risk assessment is the central code in a system that contains both other codes and data libraries. Some of these codes and data libraries supply input data for RADTRAN; others perform supplemental calculations. RADTRAN 4 will be released by the IAEA in an international version known as INTERTRAN 2 in 1995. In the United States, RADTRAN 4 and its supporting system may be accessed via the INTERNET, a precursor to the Information Superhighway. Similar networks are being contemplated elsewhere in the world, and the RADTRAN System may serve as a prototype for systems on these networks. A system is desirable for the following reasons. Some classes of data and data-handling methods are country-specific and some are not -- ancillary codes and data libraries that provide the latter are not affected by national and regional borders while the former must be provided on a country-by-country basis. Making the invariant portions available to all users in an international system would simplify quality assurance (QA) and, therefore, the reliability and consistency of risk results. Among the classes of data used in RADTRAN 4 (and INTERTRAN 2) and the supplemental calculational capabilities that are essentially invariant for all countries and regions are: (1) radionuclide characteristics such as half-life, photon energy, and dose-conversion factors; (2) characteristics of radioactive-material packages found in international commerce; (3) features of highly standardized international transportation modes (primarily sea and air); and (4) uncertainty analysis. These features and their related QA benefits are discussed.

As the United States embarks upon a major effort to cleanup its nuclear defense facilities, a large quantity of low-level waste (LLW) will be generated. This LLW must be managed and ultimately placed into final disposal. Much of this waste is expected to exceed certain limits defined in U.S. regulations (Title 10, U.S. Code of Federal Regulations, part 61) called Class C. The waste which exceeds Class C, called Greater-than-Class-C (GTCC), poses a major challenge to waste managers. Each GTCC waste form must be placed into costly geologic disposal unless separate approval is obtained from the United States regulator to place it into less costly {open_quotes}near-surface{close_quotes} land burial. Management of GTCC will also require, to some extent, storage and transport prior to its final disposal. A further LLW stream exists in the United States also stemming from the prior operations of United States defense facilities, viz., radioactively contaminated and irradiated scrap metal which has been accumulating over the past forty years. Similarly, as cleanup, decontamination, and decommissioning proceeds, this contaminated scrap metal inventory is expected to grow rapidly. This paper explores the notion of the authors that an opportunity for a synergistic solution to two difficult waste management problems may be available in the United States today, and perhaps may similarly be available in other nuclear countries as well. The possibility exists for fabricating packagings from contaminated scrap metal (which would otherwise be part of the waste inventory) and for using these packaging for storage, transport and disposal of GTCC in near-surface burial facilities without reopening or repacking. This approach is appealing and should lead to major safety and cost benefits. An examination of existing regulations with the intent to propose additions, changes, or clarifications that would effectively and beneficially regulate such combined activity is proposed.

No abstract available.

A tunable, high-accelerating-gradient cavity has been designed for use in the rf system of the Low Energy Booster (LEB) at the Superconducting Super Collider (SSC). Details of the cavity design are discussed along with low level, swept frequency, and high pwoer test results.

The Robotic All-Terrain Lunar Exploration Rover (RATLER) is a four wheeled all-wheel-drive dual-body vehicle. A uniquely simple method of chassis articulation is employed which allows all four wheels to remain in contact with the ground, even while climbing over step-like obstacles as large as 1.3 wheel diameters. The RATLER design concept began at Sandia National Laboratories in late 1991 with a series of small, proof-of-principle, working scale models. The models proved the viability of the concept for high mobility through mechanical simplicity, and eventually received internal funding at Sandia National Laboratories for full scale, proof-of-concept prototype development. Whereas the proof-of-principle models demonstrated the mechanical design's capabilities for mobility, the full scale proof-of-concept design currently under development is intended to support field operations for experiments in telerobotics, autonomous robotic operations, telerobotic field geology, and advanced man-machine interface concepts. The development program's current status is described, including an outline of the program's work over the past year, recent accomplishments, and plans for follow-on development work.

This paper describes a collision avoidance system using Whole Arm Proximity (WHAP) sensors on a PUMA 560 robot arm. The capacitance-based sensors generate electric fields which can completely encompass the robot arm and detect obstacles as they approach from any direction. The directional obstacle information gathered by the WHAP sensors together with the sensor geometry and robot configuration is used to scale the commanded joint velocities of the robot. A linearized relationship between the WHAP sensor reading and the distance from the obstacle allows direct transformation of perturbations in WHAP readings to perturbations in joint velocities. The WHAP reading is used to directly reduce the component of the command input velocity along the normal axis of the sensor, allowing graceful reductions in speed as the arm approaches the obstacle. By scaling only the component of the velocity vector in the direction of the nearest obstacles, the control system restricts motion in the direction of obstacles while permitting unconstrained motion in other directions.

The computational fluid dynamics code FIDAP (Fluid Dynamics International) is used to perform simulations of the steady laminar flow of an incompressible fluid in a three-dimensional rectangular cavity. Although most previous studies have considered a 'lid-driven' cavity, where a uniform horizontal velocity is imposed on the cavity lid, the flow in the channel above the cavity is explicitly included in the computational domain in these simulations. Simulations are performed for various Reynolds numbers in the range 0 ≤ Re ≤ 1000 and are compared to corresponding two-dimensional results. The three-dimensional flows are seen to exhibit a smooth topology change around Re ≈ 35.

Detection of air-borne environmental contaminants, such as organic solvents, requires unambiguous compound identification and sensitivity to concentrations below those permitted by regulating agencies. One promising detection approach uses a pulsed supersonic molecular beam vacuum expansion in combination with fluorescence signal spectral analysis to identify species in a chemical mixture. This report describes the use and performance of the ultraviolet excitation molecular beam fluorometer.

We have studied a singly-resonant KTP ring OPO pumped by nanosecond pulses from a frequency-doubled NdYAG laser. We present measurements of the temporal and spatial intensity profiles of the incident pump beam and OPO output beams, including the depleted pump, as well as the output energy as a function of pump laser energy. These measurements have been carried out for both injection-seeded and unseeded operation of the OPO The results of these measurements have been compared to the output of a computer model.

The Telemanaged Mobile Security Station (TMSS) was developed at Sandia National Laboratories to investigate the role of mobile robotics in exterior perimeter security systems. A major feature of the system is its capability to perform autonomous patrols of the security site's network of roads. Perimeter security sites are well known, structured environments; the locations of the roads, buildings, and fences are relatively static. A security robot has the advantage of being able to learn its new environment prior to autonomous travel. The TMSS robot combines information from a microwave beacon system and on-board dead reckoning sensors to determine its location within the site. The operator is required to teleoperate the robot in a teach mode over all desired paths before autonomous operations can commence. During this teach phase, TMSS stores points from its position location system at two meter intervals. This map data base is used for planning paths and for reference during path following. Details of the position location and path following systems will be described along with system performance and recommendations for future enhancements.

Fluorescence depolarization studies of polysilane chains in solution have shown that energy transfer along the polymer chains occurs for only a very short time relative to the excited state lifetime and only over short distances before the excited states become trapped in long, low-energy segments. However, in solid films we have shown in previous work that excitons are highly mobile throughout their 600 ps lifetime at room temperature, presumably because energy transfer among neighboring, parallel chain segments becomes possible. In this paper we report that the exciton-exciton annihilation rate constant decreases by only a factor of five between room temperature and 12 K, showing that the excitons do not become trapped even at low temperatures.

Many safety analyses depend on uncertain inputs and on mathematical models chosen from various alternatives, but give fixed results (implying no uncertainty). Conventional uncertainty analyses help, but are also based on assumptions and models, the accuracy of which may be difficult to assure. Some of the models and assumptions that on cursory examination seem reasonable can be misleading. As a result, quantitative assessments, even those accompanied by uncertainty measures, can give unwarranted impressions of accuracy. Because analysis results can be a major contributor to a safety-measure decision process, risk management depends on relating uncertainty to only the information available. The uncertainties due to abnormal environments are even more challenging than those in normal-environment safety assessments, and therefore require an even more cautious approach. A fuzzy-algebra analysis is proposed in this article that has the potential to appropriately reflect the information available and portray uncertainties well, especially for abnormal environments. © 1994 John Wiley & Sons, Inc.

The blast-induced movement and final location of geologic layers that may cause environmental problems can be predicted using discrete element methods. This prediction capability can be used by mine operators to locate the material in the muck pile during excavation which would allow encapsulation to prevent groundwater infiltration.

Time-resolved velocity interferometry measurements have been made on boron carbide and silicon carbide ceramics to assess dynamic equation-of-state and strength properties of these materials. Hugoniot precursor characteristics, and post-yield shock and release wave properties, indicated markedly different dynamic strength and flow behavior for the two carbides.

This study is a comparison of hydraulic fracture models run using test data from the GRI Staged Field Experiment No. 3. Models compared include 2D, pseudo-3D, and 3D codes, run on up to eight different cases. Documented in this comparison are the differences in length, height, width, pressure, and efficiency. The purpose of this study is to provide the completions engineer with a practical comparison of the available models so that rational decisions can be made as to which model is optimal for a given application.

The excess base current in an irradiated BJT increases superlinearly with total dose at low-total-dose levels. In this regime, the excess base current depends on the particular charge-trapping properties of the oxide that covers the emitter base junction. The device response is dose-rate-, irradiation-bias-, and technology-dependent in this regime. However, once a critical amount of charge has accumulated in the oxide, the excess base current saturates at a value that is independent of how the charge accumulated. This saturated excess base current depends on the device layout, bulk lifetime in the base region, and the measurement bias. In addition to providing important insight into the physics of bipolar-transistor total-dose response, these results have significant circuit-level implications. For example, in some circuits, the transistor gain that corresponds to the saturated excess base current is sufficient to allow reliable circuit operation. For cases in which the saturated value of current gain is acceptable, and where other circuit elements permit such over-testing, this can greatly simplify hardness assurance for space applications. © 1994 IEEE

Low energy Ar and Xe ion bombardment of Ge (001) produces large numbers of point defects on the Ge surface and in the near-surface regions. Defect concentrations on the surface are detected and quantified in real time during bombardment using in situ Reflection High Energy Electron Diffraction (RHEED). We report the energy dependence of the defect yield for 70-500 eV Ar and Xe ion bombardment, and the temperature dependence of the defect yield (defects/ion) during 200 eV ion bombardment. The defect yield drops rapidly as the substrate temperature during bombardment is varied from 175 K to 400 K. We attribute the yield reduction to surface recombination of adatoms and vacancies produced in the same collision cascade.

Least-squares sine-fit algorithms are used extensively in signal processing applications. The parameter estimates produced by such algorithms are subject to both random and systematic errors when the record of input samples consists of a fundamental sine wave corrupted by harmonic distortion or noise. The errors occur because, in general, such sine-fits will incorporate a portion of the harmonic distortion or noise into their estimate of the fundamental. Bounds are developed for these errors for least-squares four-parameter (amplitude, frequency, phase, and offset) sine-fit algorithms. The errors are functions of the number of periods in the record, the number of samples in the record, the harmonic order, and fundamental and harmonic amplitudes and phases. The bounds do not apply to cases in which harmonic components become aliased.

We demonstrate the use of HAST and Assembly Test Chips to evaluate the susceptability of epoxy molding compounds to moisture induced corrosion of Al conductors. We show that the procedure is sufficiently sensitive to discriminate between assembly processes used by different molding facilities. Our data show that the location in time of the 'knee' in the failure distribution is dependent on material properties of the epoxy. Reducing the failure rate in the early or 'extrinsic' region of the time-failure distribution is key to achieving high reliability. We examine the failure modes in the extrinsic region for test chips encapsulated with a number of high quality molding compounds in an attempt to better understand this region.

We are studying carbon thin films by using a pulsed excimer laser to ablate pyrolytic graphite targets to form highly tetrahedral coordinated amorphous carbon (at-C) films. These films have been grown on room temperature p-type Si (100) substrates without the intentional incorporation of hydrogen. In order to understand and optimize the growth of at-C films, parametric studies of the growth parameters have been performed. We have also introduced various background gases (H2, N2 and Ar) and varied the background gas pressure during deposition. The residual compressive stress levels in the films have been measured and correlated to changes in the Raman spectra of the at-C band near 1565 cm-1. The residual compressive stress falls with gas pressure, indicating a decreasing atomic sp3-bonded carbon fraction. We find that reactive gases such as hydrogen and nitrogen significantly alter the Raman spectra at higher pressures. These effects are due to a combination of chemical incorporation of nitrogen and hydrogen into the film as well as collisional cooling of the ablation plume. In contrast, films grown in non-reactive Ar background gases show much less dramatic changes in the Raman spectra at similar pressures.

Granular salt can be used to construct high performance permanent seals in boreholes which penetrate rock salt formations. These seals are described as seal systems comprised of the host rock, the seal material, and the seal rock interface. The performance of these seal systems is defined by the complex interactions between these seal system components through time. The interactions are largely driven by the creep of the host formation applying boundary stress on the seal forcing consolidation of the granular salt. The permeability of well constructed granular salt seal systems is expected to approach the host rock permeability (<10-21 m2 (10"9 darcy)) with time. The immediate permeability of these seals is dependent on the emplaced density. Laboratory test results suggest that careful emplacement techniques could result in immediate seal system permeability on the order of 10'16 m2 to 10*1* m2 (10*4 darcy to 10"^ darcy). The visco-plastic behavior of the host rock coupled with the granular salts ability to "heal" or consolidate make granular salt an ideal sealing material for boreholes whose permanent sealing is required.

The Department of Energy’s Solar Thermal Electric Program is managed by the Solar Thermal and Biomass Power Division, which is part of the Office of Utility Technologies. The focus of the Program is to commercialize solar electric technologies. In this regard, three major projects are currently being pursued in trough, central receiver, and dish/Stirling electric power generation. This paper describes these three projects and the activities at the National Laboratories that support them.