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Resilient data staging through MxN distributed transactions

Lofstead, Gerald (Jay) F.; Oldfield, Ron

Scientific computing-driven discoveries are frequently driven from workflows that use persistent storage as a staging area for data between operations. With the bad and progressively worse bandwidth vs. data size issues as we continue towards exascale, eliminating persistent storage through techniques like data staging will both enable these workflows to continue online, but also enable more interactive workflows reducing the time to scientific discoveries. Data staging has shown to be an effective way for applications running on high-end computing platforms to offload expensive I/O operations and to manage the tremendous amounts of data they produce. This data staging approach, however, lacks the ACID style guarantees traditional straight-to-disk methods provide. Distributed transactions are a proven way to add ACID properties to data movements, however distributed transactions follow 1xN data movement semantics, where our highly parallel HPC environments employ MxN data movement semantics. In this paper we present a novel protocol that extends distributed transaction terminology to include MxN semantics which allows our data staging areas to benefit from ACID properties. We show that with our protocol we can provide resilient data staging with a limited performance penalty over current data staging implementations.

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TYPE SAND Report YEAR 2011
DOIOSTI

Efficient uncertainty quantification methodologies for high-dimensional climate land models

Sargsyan, Khachik; Safta, Cosmin; Berry, Robert D.; Ray, Jaideep; Debusschere, Bert J.; Najm, Habib N.

In this report, we proposed, examined and implemented approaches for performing efficient uncertainty quantification (UQ) in climate land models. Specifically, we applied Bayesian compressive sensing framework to a polynomial chaos spectral expansions, enhanced it with an iterative algorithm of basis reduction, and investigated the results on test models as well as on the community land model (CLM). Furthermore, we discussed construction of efficient quadrature rules for forward propagation of uncertainties from high-dimensional, constrained input space to output quantities of interest. The work lays grounds for efficient forward UQ for high-dimensional, strongly non-linear and computationally costly climate models. Moreover, to investigate parameter inference approaches, we have applied two variants of the Markov chain Monte Carlo (MCMC) method to a soil moisture dynamics submodel of the CLM. The evaluation of these algorithms gave us a good foundation for further building out the Bayesian calibration framework towards the goal of robust component-wise calibration.

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TYPE SAND Report YEAR 2011
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A general model of resource production and exchange in systems of interdependent specialists

Beyeler, Walter E.; Glass Jr., Robert J.; Finley, Patrick D.; Quach, Tu T.

Infrastructures are networks of dynamically interacting systems designed for the flow of information, energy, and materials. Under certain circumstances, disturbances from a targeted attack or natural disasters can cause cascading failures within and between infrastructures that result in significant service losses and long recovery times. Reliable interdependency models that can capture such multi-network cascading do not exist. The research reported here has extended Sandia's infrastructure modeling capabilities by: (1) addressing interdependencies among networks, (2) incorporating adaptive behavioral models into the network models, and (3) providing mechanisms for evaluating vulnerability to targeted attack and unforeseen disruptions. We have applied these capabilities to evaluate the robustness of various systems, and to identify factors that control the scale and duration of disruption. This capability lays the foundation for developing advanced system security solutions that encompass both external shocks and internal dynamics.

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TYPE SAND Report YEAR 2011
DOIOSTI

Conductive porous scaffolds as potential neural interface materials

Buerger, Stephen P.

Our overall intent is to develop improved prosthetic devices with the use of nerve interfaces through which transected nerves may grow, such that small groups of nerve fibers come into close contact with electrode sites, each of which is connected to electronics external to the interface. These interfaces must be physically structured to allow nerve fibers to grow through them, either by being porous or by including specific channels for the axons. They must be mechanically compatible with nerves such that they promote growth and do not harm the nervous system, and biocompatible to promote nerve fiber growth and to allow close integration with biological tissue. They must exhibit selective and structured conductivity to allow the connection of electrode sites with external circuitry, and electrical properties must be tuned to enable the transmission of neural signals. Finally, the interfaces must be capable of being physically connected to external circuitry, e.g. through attached wires. We have utilized electrospinning as a tool to create conductive, porous networks of non-woven biocompatible fibers in order to meet the materials requirements for the neural interface. The biocompatible fibers were based on the known biocompatible material poly(dimethyl siloxane) (PDMS) as well as a newer biomaterial developed in our laboratories, poly(butylene fumarate) (PBF). Both of the polymers cannot be electrospun using conventional electrospinning techniques due to their low glass transition temperatures, so in situ crosslinking methodologies were developed to facilitate micro- and nano-fiber formation during electrospinning. The conductivity of the electrospun fiber mats was controlled by controlling the loading with multi-walled carbon nanotubes (MWNTs). Fabrication, electrical and materials characterization will be discussed along with initial in vivo experimental results.

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TYPE Conference YEAR 2011
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High-Density Nanopore Array for Selective Biomolecule Transport

Patel, Kamlesh D.

Development of sophisticated tools capable of manipulating molecules at their own length scale enables new methods for chemical synthesis and detection. Although nanoscale devices have been developed to perform individual tasks, little work has been done on developing a truly scalable platform: a system that combines multiple components for sequential processing, as well as simultaneously processing and identifying the millions of potential species that may be present in a biological sample. The development of a scalable micro-nanofluidic device is limited in part by the ability to combine different materials (polymers, metals, semiconductors) onto a single chip, and the challenges with locally controlling the chemical, electrical, and mechanical properties within a micro or nanochannel. We have developed a unique construct known as a molecular gate: a multilayered polymer based device that combines microscale fluid channels with nanofluidic interconnects. Molecular gates have been demonstrated to selectively transport molecules between channels based on size or charge. In order to fully utilize these structures, we need to develop methods to actively control transport and identify species inside a nanopore. While previous work has been limited to creating electrical connections off-channel or metallizing the entire nanopore wall, we now have the ability to create multiple, separate conductive connections at the interior surface of a nanopore. These interior electrodes will be used for direct sensing of biological molecules, probing the electrical potential and charge distribution at the surface, and to actively turn on and off electrically driven transport of molecules through nanopores.

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TYPE SAND Report YEAR 2011
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Ota City: Characterizing Output Variability from 553 Homes with Residential PV Systems on a Distribution Feeder

Ellis, Abraham; Lave, Matt; Stein, Joshua; Hansen, Clifford

This report describes in-depth analysis of photovoltaic (PV) output variability in a high-penetration residential PV installation in the Pal Town neighborhood of Ota City, Japan. Pal Town is a unique test bed of high-penetration PV deployment. A total of 553 homes (approximately 80% of the neighborhood) have grid-connected PV totaling over 2 MW, and all are on a common distribution line. Power output at each house and irradiance at several locations were measured once per second in 2006 and 2007. Analysis of the Ota City data allowed for detailed characterization of distributed PV output variability and a better understanding of how variability scales spatially and temporally. For a highly variable test day, extreme power ramp rates (defined as the 99th percentile) were found to initially decrease with an increase in the number of houses at all timescales, but the reduction became negligible after a certain number of houses. Wavelet analysis resolved the variability reduction due to geographic diversity at various timescales, and the effect of geographic smoothing was found to be much more significant at shorter timescales.

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TYPE SAND Report YEAR 2011
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Nanotexturing of Surfaces to Reduce Melting Point

Garcia, Ernest J.

This investigation examined the use of nano-patterned structures on Silicon-on-Insulator (SOI) material to reduce the bulk material melting point (1414 °C). It has been found that sharp-tipped and other similar structures have a propensity to move to the lower energy states of spherical structures and as a result exhibit lower melting points than the bulk material. Such a reduction of the melting point would offer a number of interesting opportunities for bonding in microsystems packaging applications. Nano patterning process capabilities were developed to create the required structures for the investigation. One of the technical challenges of the project was understanding and creating the specialized conditions required to observe the melting and reshaping phenomena. Through systematic experimentation and review of the literature these conditions were determined and used to conduct phase change experiments. Melting temperatures as low as 1030 C were observed.

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TYPE SAND Report YEAR 2011
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Observation of instability growth in a copper Z-pinch target using two-color monochromatic X-ray backlighting

IEEE Transactions on Plasma Science

Sinars, Daniel; Wenger, D.F.; Peterson, K.J.; Slutz, Stephen A.; Herrmann, Mark H.; Yu, Edmund; Cuneo, Michael E.; Smith, Ian C.; Atherton, B.; Porter, John L.

Existing monochromatic X-ray backlighting diagnostics at 1.865 and 6.151 keV have been combined to create a two-color monochromatic X-ray backlighting diagnostic. The use of different photon energies can allow a much broader range of areal densities to be observed in a single experiment. Here, we apply the two-color backlighter to the study of instability growth on the outside edge of an initially solid copper rod target driven by a 100-ns rise-time current pulse with a peak value of 20 MA. The different opacity of Cu at these two photon energies allows a dynamic range of ∼1600x to be surveyed instead of ∼60x (assuming a useful transmission range of 5%-95%). © 2006 IEEE.

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TYPE Journal Article YEAR 2011
OSTIScopusOSTIScopus

Stagnation and disruption of wire array Z-pinch radiation sources on the Z pulsed power generator

IEEE Transactions on Plasma Science

Jones, Brent M.; Ampleford, David; Nielsen, D.S.; Coverdale, Christine A.; Jennings, Christopher A.; Cuneo, Michael E.

Magnetic implosions provide extremely intense soft X-ray radiation on the Z accelerator. Shock heating at stagnation provides temperatures that are capable of producing K-shell radiation from stainless steel plasma. Time-gated multicolor X-ray pinhole imaging is used to study stagnation and disruption in fast Z pinches. Magnetohydrodynamic instabilities are observed to grow, following peak X-ray power until the Z-pinch column disrupts well after the main power pulse. © 2006 IEEE.

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TYPE Journal Article YEAR 2011
OSTIOSTIScopusScopus

Plasma expansion in a negative-polarity rod-pinch diode

IEEE Transactions on Plasma Science

Leckbee, Joshua; Johnston, Mark D.; Oliver, Bryan V.

The negative-polarity rod-pinch diode is being developed and tested on the RITS-6 accelerator to expand radiographic capabilities. High current densities at the tip of the rod anode generate a plasma which expands at a rate of 2-4 cm μs. Images of visible light captured with a high-speed intensified charge-coupled device camera show the development and expansion of the plasma. © 2006 IEEE.

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TYPE Journal Article YEAR 2011
OSTIScopusOSTIScopus

A negative-index metamaterial design based on metal-core, dielectric shell resonators

IEEE Antennas and Propagation Society, AP-S International Symposium (Digest)

Basilio, L.I.; Warne, Larry K.; Langston, William L.; Johnson, William A.; Sinclair, M.B.

In this paper a simple effective-media analysis (including higher-order multipoles) is used to design a single-resonator, negative-index design based on a metal-core, dielectric-shell (MCDS) unit cell. In addition to comparing the performance of the MCDS design to other core-shell negative-index designs, performance trade-offs resulting from the relative positioning of the electric and magnetic modal resonances in the MCDS design are also discussed. © 2011 IEEE.

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TYPE Conference YEAR 2011
ScopusOSTI

High/Ultra-high speed imaging as a diagnostic tool

Applied Mechanics and Materials

Reu, P.L.

The ability to see what is happening during an experiment is often critical to human understanding. High and ultra-high speed cameras have for decades allowed scientists to see these extremely short time-scale events; starting with film cameras and now with digital versions of these cameras. The move to digital cameras has invited the use of computer analysis of the images for obtaining quantitative information well beyond the qualitative usefulness of merely being able to see the event. Digital image correlation (DIC) is one of these powerful and popular quantitative techniques, but by no means the only possible image analysis method. All of these analysis techniques ask more of the camera technology than simply providing images. They require highquality images that are amenable to analysis and do not introduce error sources that compromise the data. Possible error sources include image noise, image distortions, synchronization and spatial sampling issues. As a minimal starting point, the introduced errors must be well understood in order to put error bounds on the results. This is because in many experiments some result is better than no result; with the caveat that the error sources and the relative confidence of the data are understood. The concepts will be framed in relation to ongoing ultra-high speed work being done at Sandia. A call and challenge will be given to begin thinking in more detail about how to successfully turn these cameras into diagnostic instruments. © (2011) Trans tech publications Switzerland.

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TYPE Conference YEAR 2011
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Modeling excitation-dependent bandstructure effects on InGaN light-emitting diode efficiency

Optics Express

Chow, Weng W.

Bandstructure properties in wurtzite quantum wells can change appreciably with changing carrier density because of screening of quantumconfined Stark effect. An approach for incorporating these changes in an InGaN light-emitting-diode model is described. Bandstructure is computed for different carrier densities by solving Poisson and k·p equations in the envelop approximation. The information is used as input in a dynamical model for populations in momentum-resolved electron and hole states. Application of the approach is illustrated by modeling device internal quantum efficiency as a function of excitation. © 2011 Optical Society of America.

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TYPE Journal Article YEAR 2011
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Pore networks in continental and marine mudstones: Characteristics and controls on sealing behavior

Geosphere

Heath, Jason E.; Dewers, Thomas; McPherson, Brian J.O.L.; Petrusak, Robin; Chidsey, Thomas C.; Rinehart, Alex J.; Mozley, Peter S.

Mudstone pore networks are strong modifiers of sedimentary basin fluid dynamics and have a critical role in the distribution of hydrocarbons and containment of injected fluids. Using core samples from continental and marine mudstones, we investigate properties of pore types and networks from a variety of geologic environments, together with estimates of capillary beam- scanning electron microscopy, suggest seven dominant mudstone pore types distinguished by geometry and connectivity. A dominant planar pore type occurs in all investigated mudstones and generally has high coordination numbers (i.e., number of neighboring connected pores). Connected networks of pores of this type contribute to high mercury capillary pressures due to small pore throats at the junctions of connected pores and likely control most matrix transport in these mudstones. Other pore types are related to authigenic (e.g., replacement or pore-lining precipitation) clay minerals and pyrite nodules; pores in clay packets adjacent to larger, more competent clastic grains; pores in organic phases; and stylolitic and microfracture-related pores. Pores within regions of authigenic clay minerals often form small isolated networks (<3 μm). Pores in stringers of organic phases occur as tubular pores or slit- and/or sheet-like pores. These form short, connected lengths in 3D reconstructions, but appear to form networks no larger than a few microns in size. Sealing efficiency of the studied mudstones increases with greater distal depositional environments and greater maximum depth of burial. © 2011 Geological Society of America.

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TYPE Journal Article YEAR 2011
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Carrier leakage in Ge/Si core-shell nanocrystals for lasers: Core size and strain effects

Proceedings of SPIE - The International Society for Optical Engineering

Neupane, Mahesh R.; Rahman, Rajib; Lake, Roger K.

The electronic structure and optical properties of Ge-core/Si-shell nanocrystal or quantum dot (QD) are investigated using the atomistic tight binding method as implemented in NEMO3D. The thermionic lifetime that governs the hole leakage mechanism in the Ge/Si QD based laser, as a function of the Ge core size and strain, is also calculated by capturing the bound and extended eigenstates, well below the band edges. We also analyzed the effect of core size and strain on optical properties such as transition energies and transition rates between electron and hole states. Finally, a quantitative and qualitative analysis of the leakage current due to the hole leakage through the Ge-core/Si-shell QD laser, at different temperatures and Ge core sizes, is presented. © 2011 SPIE.

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TYPE Conference YEAR 2011
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Thermal and mechanical aging of self-assembled monolayers as studied by near edge X-ray absorption fine structure

Langmuir

Klein, Robert J.; Fischer, Daniel A.; Lenhart, Joseph L.

Self-assembled monolayers (SAMs) enable significant changes in the surface energy and/or specific interactions of surfaces, which are desirable for microelectromechanical systems (MEMS), superhydrophobic coatings, sensors, and other applications. However, SAMs often exhibit poor durability and rapid degradation upon mechanical, thermal, or moisture exposure. The chemical and orientational changes in SAMs due to mechanical and thermal degradation were investigated using near-edge X-ray absorption fine structure (NEXAFS) and the water contact angle. SAMs were based on unfluorinated or fluorinated linear hydrocarbons that form highly oriented and densely packed structures on silicon substrates. Complex chemical and orientational changes were observed via NEXAFS following degradation. Under heating in a dry, oxygen-rich environment, unfluorinated SAMs tended to cleave at C-C bonds on the main chain; below 250 °C, CH3 groups were sequentially cleaved toward the surface, whereas above 250 °C, remaining hydrocarbon groups were converted to a graphitic coating dominated by C=C bonds. Under similar conditions, fluorinated SAMs began their chemical degradation at 350 °C and above, although the orientation decreased steadily from 150 to 300 °C; at and above 350 °C, the preferential removal of F occurred and the SAM was slowly converted to a graphitic layer. By contrast, under vacuum the fluorinated molecules were very thermally stable, showing good stability up to 550 °C; when degradation occurred, entire molecules were removed. Mechanical degradation followed two routes; both unfluorinated and fluorinated SAMs that were mechanically rubbed with smooth surfaces exhibited severe chemical degradation of the molecules, leading to an amorphous and poorly defined layer with C=C, C-C, C-H, and C-F bonds. Unfluorinated and fluorinated surfaces that were mechanically rubbed in the presence of free silicon particulates showed the rapid and complete destruction of both the molecular orientation and the protective SAM layer, even for short exposure periods. The resulting NEXAFS spectra were very similar to those produced by heating to 550 °C, suggesting that the friction created by granular particles may lead to extreme local heating. © 2011 American Chemical Society.

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TYPE Journal Article YEAR 2011
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Low-cost mitigation of privacy loss due to radiometric identification

Proceedings of the Annual International Conference on Mobile Computing and Networking, MOBICOM

Haas, Jason J.; Hu, Yih C.; Laurenti, Nicola

Recently, there has been much interest in using radiometric identification (also known as wireless fingerprinting) for the purposes of authentication. Previous work has shown that using radiometric identification can discriminate among devices with a high degree of accuracy when simultaneously using multiple radiometric characteristics. Additionally, researchers have noted the potential for wireless fingerprinting to be used for more devious purposes, specifically that of privacy invasion or compromise. In fact, any such radiometric characteristic that is useful for authentication is useful for privacy compromise. To date, there has not been any proposal of how to mitigate such privacy loss for many of these radiometric characteristics, and specifically no such proposal for how to mitigate such privacy loss in a low-cost manner. In this paper, we investigate some limits of an attacker's ability to compromise privacy, specifically an attacker that uses a transmitter's carrier frequency. We propose low-cost mechanisms for mitigating privacy loss for various radiometric characteristics. In our development and evaluation, we specifically consider a vehicular network (VANET) environment. We consider this environment in particular because VANETs will have the potential to leak significant, longterm information that could be used to compromise drivers' personal information such as home address, work address, and the locations of any businesses the driver frequents. While tracking a vehicle using visually observable information (e.g., license plates) to obtain personal information is possible, such means require line-of-sight, whereas radiometric identification would not. Finally, we evaluate one of our proposed mechanisms via simulation. Specifically, we evaluate our carrier frequency switching mechanism, comparing it to the theory we develop, and we show the precision with which vehicles will need to switch their physical layer identities given our parameterization for VANETs. © 2011 ACM.

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TYPE Conference YEAR 2011
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DSMC moving-boundary algorithms for simulating mems geometries with opening and closing gaps

AIP Conference Proceedings

Rader, Daniel J.; Gallis, Michael A.; Torczynski, John R.

Moving-boundary algorithms for the Direct Simulation Monte Carlo (DSMC) method are investigated for a microbeam that moves toward and away from a parallel substrate. The simpler but analogous one-dimensional situation of a piston moving between two parallel walls is investigated using two moving-boundary algorithms. In the first, molecules are reflected rigorously from the moving piston by performing the reflections in the piston frame of reference. In the second, molecules are reflected approximately from the moving piston by moving the piston and subsequently moving all molecules and reflecting them from the moving piston at its new or old position. © 2011 American Institute of Physics.

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TYPE Conference YEAR 2011
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Simulation of ion beam induced current in radiation detectors and microelectronic devices

Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms

Vizkelethy, Gyorgy

Ion Beam Induced Charge (IBIC) is the basic mechanism of the operation of semiconductor detectors and it can lead to Single Event Effects (SEEs) in microelectronic devices. To be able to predict SEEs in ICs and detector responses one needs to be able to simulate the radiation-induced current as the function of time on the electrodes of the devices and detectors. There are analytical models, which work for very simple detector configurations, but fail for anything more complex. Technology Computer Aided Design (TCAD) programs can simulate this process in microelectronic devices, but these TCAD codes costs hundreds of thousands of dollars and they require huge computing resources. In addition, in certain cases they fail to predict the correct behavior. Here a simulation model based on the Gunn theorem was developed and used with the COMSOL Multiphysics framework, version 3.5. In the model, the induced current can be calculated both directly and in certain cases using the powerful adjoint method. A brief description of the model will be given in the paper with examples for detectors and microelectronic devices using both the direct and the adjoint method.

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TYPE Conference YEAR 2011
OSTIScopus

Ion beam characterization of advanced luminescent materials for application in radiation effects microscopy

Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms

Branson, J.V.; Hattar, K.; Rossi, P.; Vizkelethy, G.; Powell, Cody J.; Hernandez-Sanchez, Bernadette A.; Doyle, Barney L.

The ion photon emission microscope (IPEM) is a technique developed at Sandia National Laboratories (SNL) to study radiation effects in integrated circuits with high energy, heavy ions, such as those produced by the 88" cyclotron at Lawrence Berkeley National Laboratory (LBNL). In this method, an ion-luminescent film is used to produce photons from the point of ion impact. The photons emitted due to an ion impact are imaged on a position-sensitive detector to determine the location of a single event effect (SEE). Due to stringent resolution, intensity, wavelength, decay time, and radiation tolerance demands, an engineered material with very specific properties is required to act as the luminescent film. The requirements for this material are extensive. It must produce a high enough induced luminescent intensity so at least one photon is detected per ion hit. The emission wavelength must match the sensitivity of the detector used, and the luminescent decay time must be short enough to limit accidental coincidences. In addition, the material must be easy to handle and its luminescent properties must be tolerant to radiation damage. Materials studied for this application include plastic scintillators, GaN and GaN/InGaN quantum well structures, and lanthanide-activated ceramic phosphors. Results from characterization studies on these materials will be presented; including photoluminescence, cathodoluminescence, ion beam induced luminescence, luminescent decay times, and radiation damage. Results indicate that the ceramic phosphors are currently proving to be the ideal material for IPEM investigations.

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TYPE Conference YEAR 2011
ScopusOSTI

Electron strippers for compact neutron generators

AIP Conference Proceedings

Terai, K.; Tanaka, N.; Kisaki, M.; Tsugawa, K.; Okamoto, A.; Kitajima, S.; Sasao, M.; Takeno, T.; Antolak, Arlyn J.; Leung, K.N.; Wada, M.

The next generation of compact tandem-type DD or DT neutron generators requires a robust electron stripper with high charge exchange efficiency. In this study, stripping foils of various types were tested, and the H- to H+ conversion efficiency, endurance to the heat load, and durability were investigated in terms of suitability in the tandem-type neutron generator. In the experiments, a H- beam was accelerated to about 180 keV, passes through a stripping foil, and produces a mixed beam of H -, H0, and H+. These ions were separated by an electric field, and detected by a movable Faraday cup to determine the conversion efficiency. The experimental results using thin foils of diamond-like carbon, gold, and carbon nano-tubes revealed issues on the robustness. As a new concept, a H- beam was injected onto a metal surface with an oblique angle, and reflected H+ ions are detected. It was found that the conversion efficiency, H+ fraction in the reflected particles, depends on the surface condition, with the maximum value of about 90%.© 2011 American Institute of Physics.

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TYPE Conference YEAR 2011
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EPRI/NRC-RES fire human reliability analysis guidelines

Proceedings of Risk Management - For Tomorrow's Challenges

Cooper, Susan E.; Hill, Kendra; Julius, Jeff; Grobbelaar, Jan; Kohlhepp, Kaydee; Forester, John; Hendrickson, Stacey M.; Hannaman, Bill; Collins, Erin; Najafi, Bijan

Over the past 2 decades, the U.S. nuclear power plant (NPP) fire protection community and overseas has been transitioning toward risk-informed and performance-based (RI/PB) practice in design, operation and regulation. To make more realistic decisions for risk-informed regulation, fire probabilistic risk analysis (PRA) methods needed further development. To address this need, in 2001, the U.S. Nuclear Regulatory Commission's (NRCs) Office of Nuclear Regulatory Research (RES) and the Electric Power Research Institute (EPRI) collaborated under a joint Memorandum of Understanding (MOU) to develop NUREG/CR-6850 (EPRI 101989), "EPRI/NRC-RES Fire PRA Methodology for Nuclear Power Facilities," a state-of-art fire PRA methodology. The fire human reliability analysis (HRA) guidance provided in NUREG/CR-6850 included: (1) a process for identification and inclusion of the human failure events (HFEs), (2) a methodology for assigning quantitative screening values to these HFEs, and (3) initial considerations of performance shaping factors (PSFs) and related fire effects that might need to be addressed in developing best-estimate human error probabilities (HEPs). However, NUREG/CR-6850 did not identify or produce a methodology to develop these best-estimate HEPs given the PSFs and the fire-related effects. In 2007, EPRI and RES embarked upon another cooperative project - building on existing HRA methods - to develop explicit guidance for estimating HEPs for human error events under fire-generated conditions. This collaborative project produced draft NUREG-1921, "EPRI/NRC-RES Fire Human Reliability Analysis Guidelines." The guidance presented in this report is intended to be both an improvement upon and an expansion of the initial guidance provided in NUREG/CR-6850. This paper will summarize the fire HRA guidance developed through this collaborative project, which addresses the range of fire procedures used in existing plants, the range of strategies for main control room (MCR) abandonment, and the potential impact of fire-induced electrical spurious actuation effects on crew performance. This guidance presents a three tiered, progressive approach for fire HRA quantification. The quantification approaches include: a screening approach per NUREG/CR-6850 guidance, a scoping approach, and detailed quantification using either EPRI's Cause-Based Decision Tree (CBDT) and Human cognitive Reliability/Operator Reliability Experiment (HCR/ORE) or NRC's A Technique for Human Event ANAlysis (ATHEANA) approach with modifications to account for fire effects. The newly developed scoping approach is intended to be less resource intensive than a detailed HRA, while providing less conservative HEPs than rough screening. The expectation is that the majority of the actions can be quantified using the scoping approach, thus detailed HRA will only be used for the more complex actions that do not meet the criteria for the scoping approach. It is anticipated that this guidance will be used by the industry as part of transition to the risk-informed, performance-based fire protection rule, 10 CFR 50.48c, that endorsed National Fire Protection Association (NFPA) 805, "Performance-Based Standard for Fire Protection for Light Water Reactor Electric Generating Plants" and possibly in response to other regulatory issues such as multiple spurious operation (MSO) and operator manual actions (OMAs). As the methodology is applied at a wide variety of NPPs, the guidance may benefit from future improvements to better support industry wide issues being addressed by fire PRAs.

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TYPE Conference YEAR 2011
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A communication-avoiding, hybrid-parallel, rank-revealing orthogonalization method

Proceedings - 25th IEEE International Parallel and Distributed Processing Symposium, IPDPS 2011

Hoemmen, Mark F.

Orthogonalization consumes much of the run time of many iterative methods for solving sparse linear systems and eigenvalue problems. Commonly used algorithms, such as variants of Gram-Schmidt or Householder QR, have performance dominated by communication. Here, "communication" includes both data movement between the CPU and memory, and messages between processors in parallel. Our Tall Skinny QR (TSQR) family of algorithms requires asymptotically fewer messages between processors and data movement between CPU and memory than typical orthogonalization methods, yet achieves the same accuracy as Householder QR factorization. Furthermore, in block orthogonalizations, TSQR is faster and more accurate than existing approaches for orthogonalizing the vectors within each block ("normalization"). TSQR's rank-revealing capability also makes it useful for detecting deflation in block iterative methods, for which existing approaches sacrifice performance, accuracy, or both. We have implemented a version of TSQR that exploits both distributed-memory and shared-memory parallelism, and supports real and complex arithmetic. Our implementation is optimized for the case of orthogonalizing a small number (5 - 20) of very long vectors. The shared-memory parallel component uses Intel's Threading Building Blocks, though its modular design supports other shared-memory programming models as well, including computation on the GPU. Our implementation achieves speedups of 2 times or more over competing orthogonalizations. It is available now in the development branch of the Trilinos software package, and will be included in the 10.8 release. © 2011 IEEE.

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TYPE Conference YEAR 2011
OSTIScopus

Simulation of polyethylene-moderated plutonium neutron multiplicity measurements

Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Miller, E.C.; Dennis, B.; Clarke, S.D.; Pozzi, S.A.; Mattingly, John K.

Neutron multiplicity measurements are a useful technique for the characterization of special nuclear material. This technique relies on the detection of correlated neutrons from fission events. As correlated events are detected it is possible to determine the neutron multiplicity distribution for the sample. This distribution is useful for identifying the material and estimating the mass. This work focuses on the ability of the Monte Carlo code MCNP-PoliMi to simulate measured distributions. The experiment used as the basis of comparison consisted of a 4.5 kg plutonium metal sphere surrounded by up to 6 in. of polyethylene. A bank of 15 3He detectors was used to detect the correlated neutron events. MCNP-PoliMi was used to simulate the particle transport and a post-processing algorithm was developed to apply detector deadtime effects and to determine the neutron multiplicity distributions. These simulated distributions were then compared to the measured results. The simulation provided an adequate estimation of the measured data. However, we observed a systematic over-prediction in both the mean and the variance of the measured distribution. © 2011 Elsevier B.V.

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Solid state bonding of CuCrZr to 316L stainless steel for ITER applications

Fusion Engineering and Design

Goods, Steven H.; Puskar, J.D.

Dissimilar metal bonds between CuCrZr and 316L stainless steel were prepared using two different solid state joining techniques. In the first instance, hot isostatic pressing, a high temperature diffusion bonding process was used to join the copper alloy to the stainless steel substrate at temperatures near 1000 °C. In the second instance, explosion bonding at ambient temperature was employed. These two techniques both yielded mechanically robust joints, where the strength of the interface exceeded that of the copper alloy, the weaker of the two substrates. However, the two bonding techniques produced near-joint microstructures that were very different. The microstructure and mechanical performance of CuCrZr/316L stainless steel joints prepared via both techniques are compared. Microstructural analysis of the joints included scanning electron microscopy, electron microprobe analysis and Auger spectroscopy techniques. The bulk mechanical properties of the substrate alloys were very different as well and are described. Particular emphasis is placed on the residual mechanical properties of the CuCrZr after thermal processing that simulate beryllium tile bonding since once the Be tiles are in place, the copper alloy cannot be solutionized and age-hardened to return it to full strength. © 2010 Elsevier B.V. All rights reserved.

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Neutron detection and identification using ZnS:Ag/6LiF in segmented antineutrino detectors

Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Kiff, Scott D.; Bowden, Nathaniel; Lund, Jim; Reyna, David R.

Antineutrino detection using inverse beta-decay conversion has demonstrated capability to measure nuclear reactor power and fissile material content for nuclear safeguards. Current efforts focus on aboveground deployment scenarios, for which a successful background rejection strategy will be needed to measure the anticipated antineutrino event rates. In this paper, we report on initial studies to quantify the intrinsic capture efficiency and particle identification capabilities of a new scintillation-based segmented design that uses layers of ZnS:Ag/6LiF to capture and identify neutrons created in the inverse beta-decay reaction. Laboratory efficiency measurements are consistent with MCNP5 calculations, estimating 6Li neutron conversion efficiency above 50% for practical full-scale detector configurations. © 2010 Elsevier B.V.

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TYPE Conference YEAR 2011
ScopusOSTI
Results 68001–68200 of 101,000
Results 68001–68200 of 101,000
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