Publications

Sandia National Laboratories (SNL) is conducting several research programs to help develop validated methods for the prediction of the ultimate pressure capacity, at elevated temperatures, of light water reactor (LWR) containment structures. To help understand the ultimate pressure of the entire containment pressure boundary, each component must be evaluated. The containment pressure boundary consists of the containment shell and many access, piping, and electrical penetrations. The focus of the current research program is to study the ultimate behavior of flexible metal bellows that are used at piping penetrations. Bellows are commonly used at piping penetrations in steel containments; however, they have very few applications in concrete (reinforced or prestressed) containments. The purpose of piping bellows is to provide a soft connection between the containment shell and the pipe are attached while maintaining the containment pressure boundary. In this way, piping loads caused by differential movement between the piping and the containment shell are minimized. SNL is conducting a test program to determine the leaktight capacity of containment bellows when subjected to postulated severe accident conditions. If the test results indicate that containment bellows could be a possible failure mode of the containment pressure boundary, then methods will be developed to predict the deformation, pressure, and temperature conditions that would likely cause a bellows failure. Results from the test program would be used to validate the prediction methods. This paper provides a description of the use and design of bellows in containment piping penetrations, the types of possible bellows loadings during a severe accident, and an overview of the test program, including available test results at the time of writing.

The Department of Energy`s Nevada Field Office has disposed of a small quantity of high activity and special case wastes using Greater Confinement Disposal facilities in Area 5 of the Nevada Test Site. Because some of these wastes are transuranic radioactive wastes, the Environmental Protection Agency standards for their disposal under 40 CFR Part 191 which requires a compliance assessment. In conducting the 40 CFR Part 191 compliance assessment, review of the Greater Confinement Disposal inventory revealed potentially land disposal restricted hazardous wastes. The regulatory options for disposing of land disposal restricted wastes consist of (1) treatment and monitoring, or (2) developing a no-migration petition. Given that the waste is already buried without treatment, a no-migration petition becomes the primary option. Based on a desire to minimize costs associated with site characterization and performance assessment, a single approach has been developed for assessing compliance with 40 CFR Part 191, DOE Order 5820.2A (which regulates low-level radioactive wastes contained in Greater Confinement Disposal facilities) and developing a no-migration petition. The approach consists of common points of compliance, common time frame for analysis, and common treatment of uncertainty. The procedure calls for conservative bias of modeling assumptions, including model input parameter distributions and adverse processes and events that can occur over the regulatory time frame, coupled with a quantitative treatment of data and parameter uncertainty. This approach provides a basis for a defensible regulatory decision. In addition, the process is iterative between modeling and site characterization activities, where the need for site characterization activities is based on a quantitative definition of the most important and uncertain parameters or assumptions.

An element based finite control volume procedure is applied to the solution of ablation problems for 2-D axisymmetric geometries. A mesh consisting of four node quadrilateral elements was used. The nodes are allowed to move in response to the surface recession rate. The computational domain is divided into a region with a structured mesh with moving nodes and a region with an unstructured mesh with stationary nodes. The mesh is costrained to move along spines associated with the original mesh. Example problems are presented for the ablation of a realistic nose tip geometry exposed to aerodynamic heating from a uniform free stream environment.

The paper gives some of the highlights of a panel discussion on surface diffusion held Monday, November 30, 1992 at the Fall MRS Meeting in Boston, Massachusetts. Four invited speakers discussed computer modeling techniques and scanning tunneling microscopy experiments that have been used to provide new understanding of the atomistic processes that occur at surfaces. We present a summary of each of the invited talks, indicate other presentations on surface diffusion in this proceedings, and provide a transcript of the two discussion sessions.

Sandia has developed an advanced operational control system approach, caged Graphical Programming, to design and operate robotic waste cleanup and other hazardous duty robotic systems. The Graphical Programming approach produces robot systems that are faster to develop and use, safer in operation, and cheaper overall than altemative teleoperation or autonomous robot control systems. The Graphical Programming approach uses 3-D visualization and simulation software with intuitive operator interfaces for the programming and control of complex robotic systems. Graphical Programming Supervisor software modules allow an operator to command and simulate complex tasks in a graphic preview mode and, when acceptable, command the actual robots and monitor their motions with the graphic system. Graphical Progranuning Supervisors maintain registration with the real world and allow the robot to perform tasks that cannot be accurately represented with models alone by using a combination of model and sensor-based control. This paper describes the Graphical Programming approach, several example control systems that use Graphical Programming, and key features necessary for implementing successful Graphical Programming systems.

During the past few years, methods have been developed for quantifying and analyzing common cause failures (CCFs). These methods have outpaced current data collection activities. This document discusses the collection and documentation of failure events at nuclear power plants with respect to these new CCFs methods. The report concentrates on the information necessary to improve the parameter estimates for both independent and dependent events in probabilistic risk assessments (PRAS) and alludes to the fact that the same information can be used to enhance other nuclear power plant activities. Several existing data bases are reviewed as to their adequacy for these new CCF methods, and areas where information is lacking, either because certain information is simply not required to be reported or because required information was simply not reported, are identified. Finally, data needs identified from recent PRAs are discussed.

Hazardous operations which in the past have been completed by technicians are under increased scrutiny due to high costs and low productivity associated with providing protective clothing and environments. As a result, remote systems are needed to accomplish many hazardous materials handling tasks such as the clean up of waste sites in which the exposure of personnel to radiation, chemical, explosive, and other hazardous constituents is unacceptable. Traditional remote manual operations have proven to have very low productivity when compared with unencumbered humans. Computer models augmented by sensing and structured, modular computing environments are proving to be effective in automating many unstructured hazardous tasks.

A panel discussion on interface roughness was held at the Fall 1992 Materials Research Society meeting. We present a of results presented by the invited speakers on the application and interpretation of X-ray reflectivity, atomic force microscopy (AFM), scanning tunneling microscopy (STM), photoluminescence and transmission electron microscopy.

Testing and analysis of shock wave characteristics such as produced by detonators and ground shock propagation frequently require a method of measuring velocity and displacement of the surface of interest. One method of measurement is doppler interferometry. The VISAR (Velocity Interferometer System for Any Reflector) uses doppler interferometry and has pined wide acceptance as the preferred tool for shock measurement. An important asset of VISAR is that it measures velocity and displacement non intrusively. The conventional VISAR is not well suited for portability because of its sensitive components, large power and cooling requirements, and hazardous laser beam. A new VISAR using the latest technology in solid state lasers and detectors has been developed and tested. To further enhance this system`s versatility, the unit is fiber optic coupled which allows remote testing, permitting the VISAR to be placed over a kilometer away from the target being measured. Because the laser light is contained in the fiber optic, operation of the system around personnel is far less hazardous. A software package for data reduction has also been developed for use with a personal computer. These new advances have produced a very versatile system with full portability which can be totally powered by batteries or a small generator. This paper describes the solid state VISAR and its peripheral components, fiber optic coupling methods and the fiber optic coupled sensors used for sending and receiving laser radiation.

A safety system has been designed and constructed to mitigate the asphyxiation and low temperature hazards presented by the distribution and usage of cryogenic liquids in work spaces at Sandia National Laboratories. After identifying common accident scenarios, the CRYOFACS (Cryogenic Fail-Safe Control System) unit was designed, employing microprocessor technology and software that can be easily modified to accommodate varying laboratory requirements. Sensors have been incorporated in the unit for the early detection of accidental releases or overflows of cryogenic liquids. The CRYOFACS design includes control (and shutdown) of the cryogen source upon error detection, and interfaces with existing oxygen monitors, in common use at Sandia Labs, to provide comprehensive protection for both personnel and property.

The Greater Confinement Disposal (GCD) facility was established by the Nevada office of the Department of Energy (DOE) in Area 5 at the Nevada Test Site for containment of waste inappropriate for shallow land burial. Some transuranic (TRU) waste has been disposed of at the GCD facility, and compliance of this disposal system with Environmental Protection Agency (EPA) regulations 40 CFR 191 must be evaluated by performance assessment calculations. We have adopted an iterative approach where performance assessment results guide site data collection which in turn influences the parameters and models used in performance assessment. The first iteration was based upon readily available data. The first iteration indicated that the GCD facility would likely comply with 40 CFR 191 and that the downward recharge rate had a major influence on the results. As a result, a site characterization project was initiated to study recharge in Area 5 by use of three environmental tracers. This study resulted in the conclusion that recharge was extremely small, if not negligible. Thus, downward advection to the water table is no longer considered a viable release pathway, leaving upward liquid diffusion as the sole release pathway. This second performance assessment iteration refined the upward pathway models and parameters. The results of the performance assessment using these models still indicate that the GCD site is likely to comply with all sections of 40 CFR 191.

Thick film Au metallizations are commonly used as conductors in hybrid microelectronics that operate at high frequencies. Discrete components are attached to these conductors with 5OPb/5OIn solder. Intermetallic compounds form and grow in the solid state with time; AuIn{sub 2} is the primary compound formed in the Au-5OPb/50In system. A hybrid failed after being artificially aged to consume all of the Au and then subjected to normal thermal cycle and vibration testing. Postmortem analysis revealed that three capacitors had debonded. The failed parts were studied to determine the failure mechanism(s) and define a parametric study to characterize the mechanisms that bond the Au thick film to the ceramic substrate.

We have developed a method for generating chromate-free corrosion resistant coatings on aluminum alloys using a process procedurally similar to standard chromate conversion. These coatings provide good corrosion resistance on 6061-T6 and 1100 A1 under salt spray testing conditions. The resistance of the new coating is comparable to that of chromate conversion coatings in four point probe tests, but higher when a mercury probe technique is used. Initial tests of paint adhesion, and under paint corrosion resistance are promising. Primary advantage of this new process is that no hazardous chemicals are used or produced during the coating operation.

A method is described to characterize shocks (transient time histories) in terms of the Fourier energy spectrum and the temporal moments of the shock passed through a contiguous set of bandpass filters. This method is compared for two transient time histories with the more conventional methods of shock response spectra (SRS) and a nonstationary random characteristic.

This is a peer review report of the Environmental and Molecule Sciences Laboratory. Although the Pretreatment, Treatment, and Waste Forms comments are focused specifically on pretreatment treatment, and waste forms, the group recognizes that the life cycle designation is a somewhat arbitrary breakdown of a series of activities that form a continuum in the environmental restoration and waste management program. Consequently, some of the comments made here are relevant in a broader context or even for EM as a whole. particular, characterization activities pervade all life cycles in environmental restoration/waste management. As we use the term in this section, ``characterization`` refers to the process monitoring and control that are required during pretreatment and treatment. Most of the technology presentations during the review identified links to support this area and delineated to varying degrees the specific ties to the Hanford Site cleanup requirements. Overall, the EMSL especially its planned facilities, are most impressive, and DOE and PNL are urged to proceed with all due haste toward its completion. Specific issues or concerns identified during the review are included in the following section.

Qualitatively different trends in postirradiation electrical response are observed in MOS devices after very long (up to 2.75-year) switched-bias bakes. A revised defect nomenclature is introduced, and implications for MOS defect models are discussed.

La{sub 2-x}Sr{sub x}CuO{sub 4+{delta}} with x = 0.01, 0.025, 0.050, 0.10 and 0.16 and excess oxygen {delta} incorporated by high-pressure O{sub 2} anneals. These compounds were examined using time-of-flight neutron diffraction data. Various models were fit by Rietveld least-squares refinement, with the maximum amount of {delta} being only of the order of 10 standard deviations. {delta} is largest for x near 0, is zero for x = 0.10 and is intermediate for x = 0.16. Only the sample with x = 0.01 is found to phase separate distinctly into a nearly stoichiometric phase with {delta} {approx} 0 and an oxygen-rich superconducting phase as the temperature is lowered. Coincidence of phase separation and Neel temperature strongly suggests that the phase separation is driven by free energy provided by long-range antiferromagnetic ordering in the nearly stoichiometric, weakly Sr-doped La{sub 2-x}Sr{sub x}CuO{sub 4}. The excess oxygen stoichiometry shows that at low values of x, hole doping is provided primarily by the excess oxygen, and is enhanced substantially by phase separation. At larger values of x, excess oxygen is no longer incorporated, and hole doping is provided by the substitution of Sr{sup +2} for La{sup +3}.

The US Nuclear Regulatory Commission (NRC) is investigating the performance of containments subject to severe accidents. This work is being performed by Sandia National Laboratories (SNL). In 1987, a 1:6-scale Reinforced Concrete Containment (RCC) model was tested to failure. The failure mode was a liner tear. As a result, a separate effects test program has been conducted to investigate liner tearing. This paper discusses the design of test specimens and the results of the testing. The post-test examination of the 1:6-scale RCC model revealed that the large tear was not an isolated event. Other small tears in similar locations were also discovered. All tears occurred near the insert-to-liner transition which is also the region of closest stud spacing. Also, all tears propagated vertically, in response to the hoop strain. Finally, all tears were adjacent to a row of studs. The tears point to a mechanism which could involve the liner/insert transition, the liner anchorage, and the material properties. The separate effects tests investigated these effects. The program included the design of three types of specimens with each simulating some features of the 1:6-scale RCC model. The specimens were instrumented using strain gages and photoelastic materials.

Scientific visualization is playing an increasingly important role in the analysis and interpretation of massively parallel CFD simulations due to the enormous volume of data that can be generated on these machines. In this paper we will describe the development of a visualization technique based on a parallel analogue to the Marching Cubes algorithm. The algorithm has been developed for Multiple-Instruction, Multiple-Data (MIMD) massively parallel computers and is designed to take advantage of the heterogeneous programming capabilities of the MIMD architecture. We examine several different configurations and conclude that for producing animations the best one, in terms of both frame generation time and disk usage, is to run the two applications heterogeneously and send the resulting geometry description directly to a workstation for rendering, thereby totally eliminating the use of files from the animation process.

Semiconductor ring lasers are being developed for use as direct-waveguide-coupled sources for photonic integrated circuits. This report describes the results of our research and development of this new class of diode lasers. We have fabricated and characterized semiconductor ring lasers which operate continuous-wave at room temperature with a single-frequency output of several milliwatts. Our work has led to an increased understanding of the operating behavior of these lasers and to the development of two new types of advanced devices. The interferometric ring diode laser uses a coupled-cavity structure to improve the level of single-frequency performance. And, the unidirectional ring diode laser uses an active crossover waveguide to promote lasing in a single ring direction with up to 96% of the output emitted in the preferred lasing direction.

Results from fundamental investigations of low-temperature plasma systems were used to improve chamber-to-chamber reproducibility and reliability in commercial plasma-etching equipment. The fundamental studies were performed with a GEC RF Reference Cell, a laboratory research system designed to facilitate experimental and theoretical studies of plasma systems. Results and diagnostics from the Reference Cell studies were then applied to analysis and rectification of chamber-to-chamber variability on a commercial, multichamber, plasma reactor. Pertinent results were transferred to industry.

Compression seals are commonly used in electronic components. Because glass has such a low fracture toughness, tensile residual stresses must be kept low to avoid crackS. N. Burchett analyzed a variety of compression pin seals to identify mechanically optimal configurations when work hardened Alloy 52 conductor pins are sealed in a 304 stainless steel housing with a Kimble TM-9 glass insulator. Mechanical property tests on Alloy 52, have shown that the heat treatments encountered in a typical glass sealing cycle are capable of annealing the Alloy 52 pins, increasing ductility and lowering the yield strength. Since most seal analyses are routinely based on unannealed Alloy 52 properties, a limited study has been performed to determine the design impact of lowering the yield strength of the pins in a typical compression seal. Thermal residual stresses were computed in coaxial compression seals with annealed pins and the results then were used to reconstruct design guidelines following the procedures employed by Miller and Burchett. Annealing was found to significantly narrow the optimal design range (as defined by a dimensionless geometric parameter). The Miller-Burchett analyses which were based on very coarse finite element meshes and a 50 ksi yield strength fortuitously predicted an overly conservative design range that is a subset of the narrow design window prevalent when the yield strength is assumed to be 34 ksi. This may not remain true for lower yield strengths. The presence of pin wetting was shown to exacerbate the glass stress state. The time is right to develop a modern and enhanced set of design guidelines which could address new material systems, three dimensional geometries, and viscoelastic effects.

With ever increasing processor and memory speeds, new methods to overcome the ``I/O bottleneck`` need to be found. This is especially true for massively parallel computers that need to store and retrieve large amounts of data fast and reliably, to fully utilize the available processing power. We have designed and implemented a parallel file system, that distributes the work of transferring data to and from mass storage, across several I/O nodes and communication channels. The prototype parallel file system makes use of the existing single threaded file system of the Sandia/University of New Mexico Operating System (SUNMOS). SUNMOS is a joint project between Sandia National Laboratory and the University of New Mexico to create a small and efficient OS for Massively Parallel (MP) Multiple Instruction, Multiple Data (MIMD) machines. We chose file striping to interleave files across sixteen disks. By using source-routing of messages we were able to increase throughput beyond the maximum single channel bandwidth the default routing algorithm of the nCUBE 2 hypercube allows. We describe our implementation, the results of our experiments, and the influence this work has had on the design of the Performance-oriented, User-managed, Messaging Architecture (PUMA) operating system, the successor to SUNMOS.

An automatic phase identification system that employs a neural network approach to classifying seismic event phases is described. Extraction of feature vectors used to distinguish the different classes is explained, and the design and training of the neural networks in the system are detailed. Criteria used to evaluate the performance of the neural network approach are provided.

Satellite electronics may be subjected to a large fluence of protons from the Van Allen belt and from solar flares. To determine if unhardened electronics will survive a radiation environment, the total ionizing dose and displacement damage to the electronics must be determined. Several computer codes are available for modeling proton transport, ranging in complexity for a very-efficient straight-line approximation to general-geometry time-dependent Monte Carlo transport, with corresponding increase in computer run time. For most satellite applications, neutrons can be neglected in the analysis. However, neutrons may be important for modeling heavily shielded compartments for personnel and electronics.