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Modified approach to use of DOE-STD-3009 example risk matrices

DOE-STD-3009, Preparation Guide for US Department of Energy Non-reactor Nuclear Facilities Documented Safety Analyses, identifies a methodology for selection of high risk accidents and hazard scenarios for Hazard Category 1, 2, and 3 Nuclear Facilities and their controls. It provides examples of risk matrices which can be used as a part of this methodology. It also states, 'There is no one correct approach or presentation'. Sandia has used a modified version of these examples to focus control selection on controls that provide the highest risk to the public and the workers. Sandia's matrix assigns a lower risk level to high probability, low consequence events that are covered by institutional safety programs. The objective of this paper is to serve as a point of discussion on the benefits of using this modification to the DOE-STD-3009 examples. The paper relates to the workshop subtopic of Lessons Learned and Hazards Analysis since it provides lessons learned in hazard analysis process at SNL.

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TYPE Conference YEAR 2008
OSTI

Foam structure and rheology in thin gaps

Kraynik, Andrew M.

The cell structure and rheology of gas-liquid foams confined between parallel plates depend on the ratio H/R, where H is the plate spacing and R is the (equivalent spherical) bubble radius. We consider ordered three-dimensional foams that consist of 1-3 layers of bubbles. In the 'dry' limit, where the gas fraction is unity, one confined layer is composed of hexagonal cylinders; two layers contain Fejes Toth cells; and three or more layers are modeled as Kelvin cells sandwiched between Fejes Toth cells. We also consider wet foams where all of the liquid is assumed to be located in either conventional Plateau borders or wall Plateau borders adjacent to the plates. The Surface Evolver is used to calculate the foam structure and stress as a function of H/R, which enables us to evaluate elastic behavior. A relationship between the two-dimensional structure at the wall and bubble size has application to foam characterization.

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TYPE Conference YEAR 2008
OSTI

Object-oriented design patterns for multiphysics modeling in Fortran 2003

Rouson, Damian R.; Adalsteinsson, Helgi

The objectives of this presentation are to: catalog object-oriented software design patterns for multiphysics modeling; demonstrate them in Fortran 2003 and C++; and compare the capabilities of the two languages. The conclusions are: the presented patterns integrate multiple abstractions, allowing much of the numerics and physics to be determined at compile-time or runtime; negligible lines of Fortran emulate the required C++ features; and C++ requires considerable effort (or considerable reliance on libraries to relive that effort) to emulate the required Fortran 2003 features.

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TYPE Conference YEAR 2008
OSTI

Sandia National Laboratories California Air Quality Program Annual Report

Gardizi, Leslee P.

The annual program report provides detailed information about all aspects of the SNL/CA Air Quality Program. It functions as supporting documentation to the SNL/CA Environmental Management System Program Manual. The program report describes the activities undertaken during the past year, and activities planned in future years to implement the Air Quality Program, one of six programs that supports environmental management at SNL/CA.

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TYPE SAND Report YEAR 2008
DOIOSTI

Thermal contact algorithms in SIERRA mechanics : mathematical background, numerical verification, and evaluation of performance

Carnes, Brian; Copps, Kevin D.

We examine algorithms for the finite element approximation of thermal contact models. We focus on the implementation of thermal contact algorithms in SIERRA Mechanics. Following the mathematical formulation of models for tied contact and resistance contact, we present three numerical algorithms: (1) the multi-point constraint (MPC) algorithm, (2) a resistance algorithm, and (3) a new generalized algorithm. We compare and contrast both the correctness and performance of the algorithms in three test problems. We tabulate the convergence rates of global norms of the temperature solution on sequentially refined meshes. We present the results of a parameter study of the effect of contact search tolerances. We outline best practices in using the software for predictive simulations, and suggest future improvements to the implementation.

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TYPE SAND Report YEAR 2008
DOIOSTI

Issues in benchmarking human reliability analysis methods : a literature review

Hendrickson, Stacey M.; Forester, John A.

There is a diversity of human reliability analysis (HRA) methods available for use in assessing human performance within probabilistic risk assessment (PRA). Due to the significant differences in the methods, including the scope, approach, and underlying models, there is a need for an empirical comparison investigating the validity and reliability of the methods. To accomplish this empirical comparison, a benchmarking study is currently underway that compares HRA methods with each other and against operator performance in simulator studies. In order to account for as many effects as possible in the construction of this benchmarking study, a literature review was conducted, reviewing past benchmarking studies in the areas of psychology and risk assessment. A number of lessons learned through these studies are presented in order to aid in the design of future HRA benchmarking endeavors.

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TYPE SAND Report YEAR 2008
DOIOSTI

ITS Version 6 : the integrated TIGER series of coupled electron/photon Monte Carlo transport codes

Franke, Brian C.; Kensek, Ronald P.; Laub, Thomas W.

ITS is a powerful and user-friendly software package permitting state-of-the-art Monte Carlo solution of lineartime-independent coupled electron/photon radiation transport problems, with or without the presence of macroscopic electric and magnetic fields of arbitrary spatial dependence. Our goal has been to simultaneously maximize operational simplicity and physical accuracy. Through a set of preprocessor directives, the user selects one of the many ITS codes. The ease with which the makefile system is applied combines with an input scheme based on order-independent descriptive keywords that makes maximum use of defaults and internal error checking to provide experimentalists and theorists alike with a method for the routine but rigorous solution of sophisticated radiation transport problems. Physical rigor is provided by employing accurate cross sections, sampling distributions, and physical models for describing the production and transport of the electron/photon cascade from 1.0 GeV down to 1.0 keV. The availability of source code permits the more sophisticated user to tailor the codes to specific applications and to extend the capabilities of the codes to more complex applications. Version 6, the latest version of ITS, contains (1) improvements to the ITS 5.0 codes, and (2) conversion to Fortran 90. The general user friendliness of the software has been enhanced through memory allocation to reduce the need for users to modify and recompile the code.

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TYPE SAND Report YEAR 2008
DOIOSTI

Fabrication techniques for creating a thermally isolated TM-FPA (thermal microphotonic focal plane array)

Proceedings of SPIE - The International Society for Optical Engineering

Watts, Michael W.; Watts, Michael W.; Nielson, Gregory N.

A novel fabrication strategy has produced optical microring-resonator-based thermal detectors. The detectors are based on the thermo-optic effect and are thermally isolated from a silicon wafer substrate so as to maximize the temperature excursion for a given amount of incident radiation and minimize the impact of thermal phonon noise. The combination of high-Q, thermal isolation, and lack of Johnson noise offers thermal microphotonic detectors the potential to achieve significantly greater room temperature sensitivity than standard bolometric techniques. Several batch fabrication strategies were investigated for producing thermal microphotonic detectors using waveguide materials such as LPCVD Silicon Nitride (Si3N4) on Oxide and Silicon on Insulator (SOI). Fabrication challenges and loss reduction strategies will be presented along with some initial infrared detection results.

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TYPE Conference YEAR 2008
ScopusOSTI

Challenges of designing and processing extreme low-G Micro Electrical-Mechanical System (MEMS) accelerometers

Proceedings of SPIE - The International Society for Optical Engineering

Swiler, Thomas P.; Krishnamoorthy, Uma; Baker, Michael S.; Clews, Peggy J.; Tanner, Danelle M.

There is an increasing demand to build highly sensitive, low-G, microscale acceleration sensors with the ability to sense accelerations in the nano-G (10-8 m/s2) regime. To achieve such sensitivities, these sensors require compliant mechanical springs attached to large masses. The high sensitivities and the difficulty in integrating robust mechanical stops into these designs make these parts inherently weak, lacking the robustness to survive even the low level accelerations encountered in standard handling, from release processing, where supporting interlayers present during fabrication are etched away, through packaging. Thus, the process of transforming a MEMS-based acceleration sensor from an unreleased state to a protected functional state poses significant challenges. We summarize prior experiences with packaging such devices and report on recent work in packaging and protecting a highly sensitive acceleration sensor that optically senses displacement through the use of sub-wavelength nanogratings. We find that successful implementation of such sensors requires starting with a clean and robust MEMS design, performing careful and controlled release processing, and designing and executing a robust handling and packaging solution that keeps a fragile MEMS device protected at all times.

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TYPE Conference YEAR 2008
OSTIScopus

A methodology for quadrilateral finite element mesh coarsening

Engineering with Computers

Staten, Matthew L.

High fidelity finite element modeling of continuum mechanics problems often requires using all quadrilateral or all hexahedral meshes. The efficiency of such models is often dependent upon the ability to adapt a mesh to the physics of the phenomena. Adapting a mesh requires the ability to both refine and/or coarsen the mesh. The algorithms available to refine and coarsen triangular and tetrahedral meshes are very robust and efficient. However, the ability to locally and conformally refine or coarsen all quadrilateral and all hexahedral meshes presents many difficulties. Some research has been done on localized conformal refinement of quadrilateral and hexahedral meshes. However, little work has been done on localized conformal coarsening of quadrilateral and hexahedral meshes. A general method which provides both localized conformal coarsening and refinement for quadrilateral meshes is presented in this paper. This method is based on restructuring the mesh with simplex manipulations to the dual of the mesh. Finally, this method appears to be extensible to hexahedral meshes in three dimensions.

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TYPE Journal Article YEAR 2008
OSTIDOI

A MEMS light modulator based on diffractive nanohole gratings

Optics Express

Skinner, Jack L.; Talin, Albert A.; Horsley, David A.

We present the design, fabrication, and testing of a microelectromechanical systems (MEMS) light modulator based on pixels patterned with periodic nanohole arrays. Flexure-suspended silicon pixels are patterned with a two dimensional array of 150 nm diameter nanoholes using nanoimprint lithography. A top glass plate assembled above the pixel array is used to provide a counter electrode for electrostatic actuation. The nanohole pattern is designed so that normally-incident light is coupled into an in-plane grating resonance, resulting in an optical stop-band at a desired wavelength. When the pixel is switched into contact with the top plate, the pixel becomes highly reflective. A 3:1 contrast ratio at the resonant wavelength is demonstrated for gratings patterned on bulk Si substrates. The switching time is 0.08 ms and the switching voltage is less than 15V. © 2008 Optical Society of America.

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TYPE Journal Article YEAR 2008
ScopusOSTIDOI

Thought leadership: A new indicator for national and institutional comparison

Scientometrics

Boyack, Kevin W.

This article introduces a new method for evaluating national publication activities. This new indicator, thought leadership, captures whether the nation is a thought leader (building on the more recently cited literature for that field) or follower (building on the older cited literature for that field). Publication data for 2003 are used to illustrate which nations tend to build on the more recent discoveries in chemistry and clinical medicine. Finally, implications for national and laboratory policy are discussed.

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TYPE Journal Article YEAR 2008
OSTIDOI

Components for integral evaluation in quantum chemistry

Journal of Computational Chemistry

Kenny, Joseph; Janssen, Curtis L.; Valeev, Edward F.; Windus, Theresa L.

Sharing low-level functionality between software packages enables more rapid development of new capabilities and reduces the duplication of work among development groups. Using the component approach advocated by the Common Component Architecture Forum, we have designed a flexible interface for sharing integrals between quantum chemistry codes. Implementation of these interfaces has been undertaken within the Massively Parallel Quantum Chemistry package, exposing both the IntV3 and Cints/Libint integrals packages to component applications. Benchmark timings for Hartree-Fock calculations demonstrate that the overhead due to the added interface code varies significantly, from less than 1% for small molecules with large basis sets to nearly 10% for larger molecules with smaller basis sets. Correlated calculations and density functional approaches encounter less severe performance overheads of less than 5%. While these overheads are acceptable, additional performance losses occur when arbitrary implementation details, such as integral ordering within buffers, must be handled. Integral reordering is observed to add an additional overhead as large as 12%; hence, a common standard for such implementation details is desired for optimal performance. © 2007 Wiley Periodicals, Inc.

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TYPE Journal Article YEAR 2008
ScopusOSTIDOI

Verification and validation benchmarks

Nuclear Engineering and Design

Oberkampf, William L.; Trucano, Timothy G.

Verification and validation (V&V) are the primary means to assess the accuracy and reliability of computational simulations. V&V methods and procedures have fundamentally improved the credibility of simulations in several high-consequence fields, such as nuclear reactor safety, underground nuclear waste storage, and nuclear weapon safety. Although the terminology is not uniform across engineering disciplines, code verification deals with assessing the reliability of the software coding, and solution verification deals with assessing the numerical accuracy of the solution to a computational model. Validation addresses the physics modeling accuracy of a computational simulation by comparing the computational results with experimental data. Code verification benchmarks and validation benchmarks have been constructed for a number of years in every field of computational simulation. However, no comprehensive guidelines have been proposed for the construction and use of V&V benchmarks. For example, the field of nuclear reactor safety has not focused on code verification benchmarks, but it has placed great emphasis on developing validation benchmarks. Many of these validation benchmarks are closely related to the operations of actual reactors at near-safety-critical conditions, as opposed to being more fundamental-physics benchmarks. This paper presents recommendations for the effective design and use of code verification benchmarks based on manufactured solutions, classical analytical solutions, and highly accurate numerical solutions. In addition, this paper presents recommendations for the design and use of validation benchmarks, highlighting the careful design of building-block experiments, the estimation of experimental measurement uncertainty for both inputs and outputs to the code, validation metrics, and the role of model calibration in validation. It is argued that the understanding of predictive capability of a computational model is built on the level of achievement in V&V activities, how closely related the V&V benchmarks are to the actual application of interest, and the quantification of uncertainties related to the application of interest. © 2007 Elsevier B.V. All rights reserved.

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TYPE Conference YEAR 2008
OSTIScopus

Towards Coulomb drag in vertically coupled quantum wires with independent contacts

Physica E: Low-Dimensional Systems and Nanostructures

Laroche, D.; Bielejec, E.S.; Reno, John L.; Gervais, G.; Lilly, M.P.

We report the details of design and fabrication of independently contacted, vertically coupled quantum wires using the epoxy-bond-and-stop-etch (EBASE) technique. These nanostructures are fabricated in high quality GaAs/AlGaAs parallel double quantum well heterostructures and are intended for Coulomb drag measurements of quantum wires. They will allow us to explore Coulomb drag in one-dimensional structures in a regime of small interlayer separation where the drag signal is expected to be stronger and less affected by phonon drag. © 2007 Elsevier B.V. All rights reserved.

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TYPE Conference YEAR 2008
ScopusOSTI

Graph analysis with high-performance computing

Computing in Science and Engineering

Hendrickson, Bruce A.; Berry, Jonathan W.

Large, complex graphs arise in many settings including the Internet, social networks, and communication networks. To study such data sets, the authors explored the use of highperformance computing (HPC) for graph algorithms. They found that the challenges in these applications are quite different from those arising in traditional HPC applications and that massively multithreaded machines are well suited for graph problems. © 2008 IEEE.

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TYPE Journal Article YEAR 2008
ScopusOSTI
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