Publications

A hardness assurance test approach has been developed for bipolar linear circuits and devices in space. It consists of a screen for dose rate sensitivity and a characterization test method to develop the conditions for a lot acceptance test at high dose rate.

Virtual reality concepts are changing the way one thinks about and with computers. The concepts have already proven their potential usefulness in a broad range of applications. This research was concerned with exploring and demonstrating the utility of virtual reality in robotics and satellite command and control applications. The robotics work addressed the need to quickly build accurate graphical models of physical environments by allowing a user to interactively build a model of a remote environment by superimposing stereo graphics onto live stereo video. The satellite work addressed the fusion of multiple data sets or models into one synergistic display for more effective training, design, and command and control of satellite systems.

The US Department of Energy (DOE) has stored or expects to generate over the next five years more than 130,000 m{sup 3} of mixed low-level waste (MLLW). Before disposal, MLLW is usually treated to comply with the land disposal restrictions of the Resource Conservation and Recovery Act. Depending on the type of treatment, the original volume of MLLW and the radionuclide concentrations in the waste streams may change. These changes must be taken into account in determining the necessary disposal capacity at a site. Treatment may remove the characteristic in some waste that caused it to be classified as mixed. Treatment of some waste may, by reduction of the mass, increase the concentrations of some transuranic radionuclides sufficiently so that it becomes transuranic waste. In this report, the DOE MLLW streams were analyzed to determine after-treatment volumes and radionuclide concentrations. The waste streams were reclassified as residual MLLW or low-level or transuranic waste resulting from treatment. The volume analysis indicated that about 89,000 m{sup 3} of waste will require disposal as residual MLLW. Fifteen DOE sites were then evaluated to determine their capabilities for hosting disposal facilities for some or all of the residual MLLW. Waste streams associated with about 90% of the total residual MLLW volume are likely to present no significant issues for disposal and require little additional analysis. Future studies should focus on the remaining waste streams that are potentially problematic by examining site-specific waste acceptance criteria, alternative treatment processes, alternative waste forms for disposal, and pending changes in regulatory requirements.

Static overpressurization tests of two scale models of nuclear containment structures - a steel containment vessel (SCV) representative of an improved, boiling water reactor (BWR) Mark II design and a prestressed concrete containment vessel (PCCV) for pressurized water reactors (PWR) - are being conducted by Sandia National Laboratories for the Nuclear Power Engineering Corporation of Japan and the U.S. Nuclear Regulatory Commission. This paper discusses plans for instrumentation and testing of the PCCV model. 6 refs., 2 figs., 2 tabs.

A mixed-scale containment vessel model, with 1:10 in containment geometry and 1:4 in shell thickness, was fabricated to represent an improved, boiling water reactor (BWR) Mark II containment vessel. A contact structure, installed over the model and separated at a nominally uniform distance from it, provided a simplified representation of a reactor shield building in the actual plant. This paper describes the pretest preparations and the conduct of the high pressure test of the model performed on December 11-12, 1996. 4 refs., 2 figs.

A high pressure test of a mixed-scaled model (1:10 in geometry and 1:4 in shell thickness) of a steel containment vessel (SCV), representing an improved boiling water reactor (BWR) Mark II containment, was conducted on December 11-12, 1996 at Sandia National Laboratories. This paper describes the preliminary results of the high pressure test. In addition, the preliminary post-test measurement data and the preliminary comparison of test data with pretest analysis predictions are also presented.

Sandia National Laboratories/New Mexico (SNL/NM) is located in Albuquerque, New Mexico. The SNL/NM Environmental Restoration (ER) Project is tasked with performing the assessment and remediation of environmental releases resulting from the almost 50 years of engineering development and testing activities. Operable Unit 1295, Septic Tanks and Drainfields, includes inactive septic and drain systems at 23 separate ER sites that were listed as Solid Waste Management Units (SWMUs) in the SNL/NM Resource Conservation and Recovery Act (RCRA) Hazardous and Solid Waste Amendments (HSWA) Module Permit. These sites were identified, based on process histories and interviews with facility personnel, as the subset of all SNL/NM septic and drain systems that had the highest potential for releases of hazardous and radioactive wastes into the environment. An additional 101 septic and drain systems not currently classified as SWMUs also have been identified as needing future characterization.

Asynchronous Transfer Mode (ATM) users often open multiple ATM Virtual Circuits (VCs) to multiple ATM users on multiple ATM networks. Each network and user may implement a different encryption policy. Hence ATM users may need shared, flexible hardware-based 3encryption that supports multiple encryption algorithms for multiple concurrent ATM users and VCs. An algorithm-agile encryption architecture, that uses multiple, parallel encryption-pipelines, is proposed. That algorithm-agile encryptor`s effect on the ATM Quality of Service (QoS) metrics, such as Cell Transfer Delay (CTD) and Cell Delay Variation (CDV), is analyzed. Bounds on the maximum CDV and the CDV`s probability density are derived.

Even if software code is fault-free, hardware failures can alter a value in memory, possibly where the code itself is stored, causing a computer system to reach an unacceptable state. Microprocessor systems are used to perform many safety and security functions where a design goal is to eliminate single-point failures such as these. One design approach is to use multiple processors, compare the outputs, and assume a failure has occurred if the outputs don`t agree. In systems where the design is constrained to a single processor, however, analytical methods are needed to identify potential single-point failures at the bit level so that an effective fault-tolerant strategy can be employed. This paper describes a top-down methodology, based upon Fault Tree Analysis, that has been used to identify potential high-consequence faults in microprocessor-based systems. The key to making the Fault Tree Analysis tractable is to effectively incorporate appropriate design features such as software path control and checksums so that complicated branches of the fault tree can be terminated early. The analysis uses simplified software flow diagrams depicting relevant code elements. Pertinent sections of machine language are then examined to identify suspect hardware. A comparison of this methodology with approaches based upon Failure Modes and Effects Analysis is made. The methodology is demonstrated through a simple example. Use of fault trees to show that software code is free of safety or security faults is also demonstrated.

A variety of geophysical methods including the spectrum of seismic, electrical, electromagnetic and potential field techniques have supported characterization, monitoring and experimental studies at the Waste Isolation Pilot Plant (WIPP). The geophysical studies have provided significant understanding of the nature of site deformation, tectonics and stability. Geophysical methods have delineated possible brine reservoirs beneath the underground facility and have defined the disturbed rock zone that forms around underground excavations. The role of geophysics in the WIPP project has evolved with the project. The early uses were for site characterization to satisfy site selection criteria or factors. As the regulatory framework for WIPP grew since 1980, the geophysics program supported experimental and field programs such as Salado hydrogeology and underground room systems and excavations. In summary, the major types of issues that geophysical studies addressed for WIPP are: Site Characterization; Castile Brine Reservoirs; Rustler/Dewey Lake Hydrogeology; Salado Hydrogeology; and Excavation Effects. The nature of geophysics programs for WIPP has been to support investigation rather than being the principal investigation itself. The geophysics program has been used to define conceptual models (e.g., the Disturbed Rock Zone-DRZ) or to test conceptual models (e.g., high transmissivity zones in the Rustler Formation). The geophysics program primarily supported larger characterization and experimental programs. Funding was not available for the complete documentation and interpretation. Therefore, a great deal of the geophysics survey information resides in contractor reports.

For FY97, the LDRD National Grand Challenges Investment Area initiated three new projects with the goal of developing an integrated approach to chemical microsystems. Collectively, these projects promise to deliver a distributed system of fully integrated, autonomous chemical sensor microsystems (e.g., a handheld or smaller device to detect explosives in airports or chemical warfare agents in the battle field) and the microscience foundation to extend this concept to a wide range of applications. Reaching this goal will require research, development and integration over a wide range of technologies; some that have already been demonstrated and others that do not yet existence. This report documents the completion of the first project task: an assessment of the science and technology base needed to achieve the overall goals. The report is comprised of ten separate assessments, each focused on specific technology areas that were identified as having critical impact on the development of integrated chemical microsystems. Technical staff throughout SNL contributed to these assessments. Each section addresses the state of current technological developments in that technical area and forecasts the future science and technology needed to drive toward higher levels of miniaturization and integration in these systems. This report provides an important guide to the technical investments needed to achieve the National Grand Challenge goals in addition to clearly identifying valuable partnering opportunities with industry, university and other national laboratories. The ten areas of evaluation are: sampling, preconcentration, and separation; pumps, valves, plumbing; optical detection; acoustic detection; other detection approaches; power sources; data analysis; packaging and assembly; analog/digital microelectronics; and mobile platforms.

No abstract available.

Recently, the authors have demonstrated that annealing Si/SiO{sub 2}/Si structures in a hydrogen containing ambient introduces mobile H{sup +} ions into the buried SiO{sub 2} layer. Changes in the H{sup +} spatial distribution within the SiO{sub 2} layer were electrically monitored by current-voltage (I-V) measurements. The ability to directly probe reversible protonic motion in Si/SiO{sub 2}/Si structures makes this an exemplar system to explore the physics and chemistry of hydrogen in the technologically relevant Si/SiO{sub 2} structure. In this work, they illustrate that this effect can be used as the basis for a programmable nonvolatile field effect transistor (NVFET) memory that may compete with other Si-based memory devices. The power of this novel device is its simplicity; it is based upon standard Si/SiO{sub 2}/Si technology and forming gas annealing, a common treatment used in integrated circuit processing. They also briefly discuss the effects of radiation on its retention properties.

Much controversy surrounds the dependence of stress intensity factor of glassy thermosets, epoxies in particular, with crosslink density. One could scan the literature and find references that claim K{sub Ic} increases with crosslink density, decreases with crosslink density, or is independent of crosslink density. The authors feel that two factors contribute to this confusion. First, a typical method for assessing this dependence relies on modifying the crosslink density by changing the precursor epoxy molecular weight. On the other hand, one could change stoichiometry or quench the reaction at intermediate extents of reaction to obtain large changes in crosslink density. However, most studies have not measured the resulting stress intensity factor of these partially cured systems at constant T-T{sub g}, where T{sub g} is the glass transition temperature of the epoxy. Since T{sub g} can change significantly with cure and since fracture processes at the crack tip are dissipative, they must work at constant T-T{sub g} to ensure that the nonlinear viscoelastic mechanisms are fairly compared. In this study, they quenched the reaction of the diglycidyl ether of bisphenol A (DGEBA) and diethanolamine (DEA) at various stages past the gel point and measured the three-point-bend stress intensity factor at a constant T-T{sub g} = {minus}50 C. The trend is clear and significant; increasing crosslink density directly increases the load-to-fail.

Microfabricated chip technologies offer researchers novel types of analysis of human clinical samples. Current examples of such technology include DNA amplification and analysis,and fluorescent cell analysis by flow cytometry. Potential applications include the development of rapid techniques for examining large numbers of cells in tissue or blood. This paper will outline criteria that successful devices must satisfy.

High speed modulation and pulsing are reported for oxide-confined vertical cavity surface emitting laser diodes (VCSELs) with inverted doping and proton implantation to reduce the extrinsic limitations.

This paper presents a method for Critical Software Event Execution Reliability (Critical SEER). The Critical SEER method is intended for high assurance software that operates in an environment where transient upsets could occur, causing a disturbance of the critical software event execution order, which could cause safety or security hazards. The method has a finite automata based module that watches (hence SEER) and tracks the critical events and ensures they occur in the proper order or else a fail safe state is forced. This method is applied during the analysis, design and implementation phases of software engineering.

EIGER (Electromagnetic Interactions GEneRalized), a single integrated software tool set, brings together a variety of spectral domain analysis methods. These include moment method solutions of integral equation formulations and finite elements solutions of partial differential equations. New software engineering methods, specifically, object oriented design, are being used to implement abstractions of key components of spectral analysis methods so that the tools can be easily modified and extended to treat new classes of problems. The key components of the numerical analysis tool, and their roles, are: elements - to describe the geometry, basis (expansion) functions - to interpolate the unknowns (e.g., fields) locally, and operators - to express the underlying physics formulations used to propagate the energy or enforce fundamental principals. The development of EMPACK provided the fundamental impetus for these abstractions which are discussed more fully in subsequent sections. This design approach is in contrast to standard design procedures where entire codes are developed around a particular element type with a specific basis function for a single operator. Although such tools can be effectively used to model large classes of problems, it is often very difficult, if not intractable, to extend the tools beyond their initial design. Overcoming this limitation is one of the most compelling goals of this project. We have successfully overcome roadblocks encountered in extension of past development efforts, such as the extension of Patch to treat wires and wire-surface junctions in the presence of non-homogeneous media. Moreover, the application base for EIGER grows as we cast a variety of Green`s functions into a form compatible with the numerical procedures in EIGER.

This report describes work conducted under the Laboratory Directed Research and Development (LDRD) Project entitled {open_quotes}Cooperating Robot Arms,{close_quotes} which was conducted from October 1, 1994, to September 30, 1996. Multiple cooperating robot arms are necessary for handling large ungainly objects, for achieving greater rigidity through mutual bracing, and for transferring and fixturing parts in a flexible fashion. There has been significant research in the area of robot arms, and yet there has been little commercial acceptance of these approaches. There are three primary reasons for this lack of success, the inability to deal with different kinematic modes of the system in a simple fashion, the difficulty in programming multi-robot behaviors, and a failure to apply this technology to realistic problems. The LDRD research described in this document addresses these critical areas. The report is divided into two primary sections, representing the thrusts of each year of research. First, the theoretical feasibility of building a modular control system for multiple robots which allows rapid reconfiguration of control system parameters for multi-arm modes of operation is demonstrated. Second, a high-level graphical programming environment which makes programming complex multi-robot tasks simpler is described.

Trapping of mobile protons is observed in various SOI materials, but only upon irradiating under a positive top Si bias. Thermal detrapping shows that the proton traps are shallow and located near the substrate Si/SiO{sub 2} interface.

The AQUASCAN, a commercially available, fully automated purge-and-trap gas chromatograph from Sentex Systems Inc., was implemented and evaluated as an in-field, automated monitoring system of contaminated groundwater at an active DOE remediation site in Pinellas, FL. Though the AQUASCAN is designed as a stand alone process analytical unit, implementation at this site required additional hardware. The hardware included a sample dilution system and a method for delivering standard solution to the gas chromatograph for automated calibration. As a result of the evaluation the system was determined to be a reliable and accurate instrument. The AQUASCAN reported concentration values for methylene chloride, trichloroethylene, and toluene in the Pinellas ground water were within 20% of reference laboratory values.

Interconnect delays, arising in part from intralevel capacitance, are one of the factors limiting the performance of advanced circuits. In addition, the problem of filling the spaces between neighboring metal lines with an insulator is becoming increasingly acute as aspect ratios increase. We address these problems simultaneously by intentionally creating an air gap between closely spaced metal lines. Undesirable topography is eliminated using a spin-on dielectric. We then cap the wafers with silicon dioxide and planarize using chemical mechanical polishing. Simple modeling of test structures predicts an equivalent dielectric constant of 1.9 on features similar to those expected for 0.25 micron technologies. Two level metal test structures fabricated in a 0.5 micron CMOS technology show that the process can be readily integrated with current standard CMOS processes. The potential problems of via misalignment, overall dielectric stack height, and the relative difficulty of ensuring void formation compared to that of ensuring a void-free fill are considered.

During the qualification of Low Temperature Cofire Ceramic (LTCC) as an enabling WR packaging technology for manufacturing the MC4352 (MET), issues pertaining to the mechanical performance of the DuPont 951 ``Green Tape{trademark}`` tape were investigated. Understanding the fundamental mechanical performance of the DuPont 951 substrate material, including the effect of surface metallization in STS environments, is required to determine MC4352 survivability. Both fast fracture and slow crack growth behavior were characterized for the MET configuration. A minimum stress threshold of 6.5 Kpsi for slow crack growth was established for substrates containing surface conductors, resistors, and resistor glaze. Finite element analysis was used to optimize the MET substrate thickness and to design the supporting structures to limit mechanical loading of the populated substrate below the slow crack growth threshold. Additionally, test coupons that failed during environmental testing are discussed. The root cause of electrical failures was attributed to solder leaching of the thick film metallization. Changes to solder pad configuration were incorporated to reduce the solder-metallization intermetallic from reaching the substrate interface. Finally, four-point bend tests revealed that the YAG laser approach for sizing LTCC substrates induced flaws, which substantially reduced the overall strength of the test samples as compared to samples sized using a diamond saw.

The Fork measurement system has been used to examine spent-fuel assemblies at the two reactors of Arkansas Nuclear One, operated by Entergy Operations, Inc. The Unit 1 reactor is a Babcock and Wilcox (B and W) design, and the Unit 2 reactor is a Combustion Engineering (CE) design. The neutron and gamma-ray emissions from individual spent-fuel assemblies were measured in the storage pools by raising each assembly pathway out of the storage rack and performing a measurement near the center of the assembly. The overall accuracy of the measurements after corrections is about 2%. Thirty-four assemblies were examined at Unit 1, and forty-one assemblies at Unit 2. The average deviation of the burnup measurements from the calibration was 3.0% at Unit 1 and 3.5% at Unit 2, indicating 2 to 3% random variation among the reactor records. There was no indication of clearly anomalous assemblies. Axial Scans of the variation in neutron and gamma ray emission were obtained by collecting data at several locations along the length of three assemblies at Unit 2. Two of these assemblies were nonstandard in that each contained a small neutron source. The sources were detected by the axial scans. The test program was a cooperative effort involving Sandia National Laboratories, Los Alamos National Laboratory, Entergy Operations, Inc., the Electric Power Research Institute, and the Office of Civilian Radioactive Waste Management of the US Department of Energy.

The development and initial evaluation of a prototype boring bar featuring active vibration control for increased chatter immunity is described. The significance of active damping both normal and tangential to the workpiece surface is evaluated, indicating the need for two axis control to ensure adequate performance over expected variations in tool mounting procedures. The prototype tool features a commercially available boring bar modified to accommodate four PZT stack actuators for two axis bending control. Measured closed-loop dynamics are combined with a computer model of the boring process to simulate increased metal removal rate and improved workpiece surface finish through active control.