Publications

Energy demand and GDP per capita are strongly correlated, while public concern over the role of energy in climate change is growing. Nuclear power plants produce 16% of world electricity demands without greenhouse gases. Generation-IV advanced nuclear energy systems are being designed to be safe and economical. Minimizing the handling and storage of nuclear waste is important. NIF and ITER are bringing sustainable fusion energy closer, but a significant gap in fusion technology development remains. Fusion-fission hybrids could be a synergistic step to a pure fusion economy and act as a technology bridge. We discuss how a pulsed power-driven Z-pinch hybrid system producing only 20 MW of fusion yield can drive a sub-critical transuranic blanket that transmutes 1280 kg of actinide wastes per year and produces 3000 MW. These results are applicable to other inertial and magnetic fusion energy systems. A hybrid system could be introduced somewhat sooner because of the modest fusion yield requirements and can provide both a safe alternative to fast reactors for nuclear waste transmutation and a maturation path for fusion technology. The development and demonstration of advanced materials that withstand high-temperature, high-irradiation environments is a fundamental technology issue that is common to both fusion-fission hybrids and Generation-IV reactors. © 2008 Elsevier B.V. All rights reserved.

Geometric features with characteristic lengths on the order of the size of the contact patch interface may be at least partly responsible for the variability observed in experimental measurements of structural stiffness and energy dissipation per cycle in a bolted joint. Experiments on combinations of two different types of joints (statically determinate single-joint and statically indeterminate three-joint structures) of nominally identical hardware show that the structural stiffness of the tested specimens varies by up to 25% and the energy dissipation varies by up to nearly 300%. A pressure-sensitive film was assembled into the interfaces of jointed structures to gain a qualitative understanding of the distribution of interfacial pressures of nominally conformal surfaces. The resultant pressure distributions suggest that there are misfit mechanisms that may influence contact patch geometry and also structural response of the interface. These mechanisms include local plateaus and machining induced waviness. The mechanisms are not consistent across nominally machined hardware interfaces. The proposed misfit mechanisms may be partly responsible for the variability in energy dissipation per cycle of joint experiments.

Damping in a micro-cantilever beam was measured for a very broad range of air pressures from atmosphere (10 5 Pa) down to 0.2 Pa. The beam was in open space free from squeeze films. The damping ratio, due mainly to air drag, varied by a factor of 10 4 within this pressure range. The damping due to air drag was separated from other sources of energy dissipation so that air damping could be measured at 10 -6 of critical damping factor. The linearity of the damping was confirmed over a wide range of beam vibration levels. Lastly, the measured damping was compared with several existing theories for air-drag damping for both rarified and viscous flow gas theories. The measured data indicate that, in the rarefied regime the air damping is proportional to pressure, independent of viscosity, and in the viscous regime the damping is determined by viscosity.

The development of transmitter and receiver Multichip Module subassemblies implemented in LTCC for an S-band radar application followed an approach that reduces the number of discrete devices and increases reliability. The LTCC MCM incorporates custom GaAs RF integrated circuits in faraday cavities, novel methods of reducing line resistance and enhancing lumped element Q, and a thick film back plane which attaches to a heat sink. The incorporation of PIN diodes on the receiver and a 50W power amplifier on the transmitter required methods for removing heat beyond what thermal vias can accomplish. The die is a high voltage pHEMT GaAs power amplifier RFIC chip that measures 6.5 mm × 8 mm. Although thermal vias are adequate in certain cases, the thermal solution includes heat spreaders and thermally conductive backplates. Processing hierarchy, including gold-tin die attach and various use of polymeric attachment, must allow rework on these prototypical devices. LTCC cavity covers employ metallic coatings on their exterior surfaces. The processing of the LTCC and its effect on the function of the transmitter and receiver circuits is discussed in the poster session.

Placing sensors in municipal water networks to protect against a set of contamination events is a classic p-median problem for most objectives when we assume that sensors are perfect. Many researchers have proposed exact and approximate solution methods for this p-median formulation. For full-scale networks with large contamination event suites, one must generally rely on heuristic methods to generate solutions. These heuristics provide feasible solutions, but give no quality guarantee relative to the optimal placement. In this paper we apply a Lagrangian relaxation method in order to compute lower bounds on the expected impact of suites of contamination events. In all of our experiments with single objectives, these lower bounds establish that the GRASP local search method generates solutions that are provably optimal to to within a fraction of a percentage point. Our Lagrangian heuristic also provides good solutions itself and requires only a fraction of the memory of GRASP. We conclude by describing two variations of the Lagrangian heuristic: an aggregated version that trades off solution quality for further memory savings, and a multi-objective version which balances objectives with additional goals. © 2008 ASCE.

We study proton and heavy ion irradiation effects on Phase Change Memories (PCM) with MOSFET and BJT selectors and the effect of the irradiation on the retention characteristics of these devices. Proton irradiation produces noticeable variations in the cell distributions in PCM with MOSFET selectors mostly due to leakage currents affecting the transistors. PCM with BJT selectors show only small variations after proton irradiation. PCM cells do not appear to be impacted by heavy-ion irradiation. Using high temperature accelerated retention tests, we demonstrate that the retention capability of these memories is not compromised by the irradiation. © 2006 IEEE.

Abstract not provided.

This paper summarizes operational histories of three Russian-designed photovoltaic (PV) lighthouses in Norway and Russia. All lighthouses were monitored to evaluate overall system and Nickel Cadmium (NiCad) battery bank performance to determine battery capacity, charging trends, temperature, and reliability. The practical use of PV in this unusual mode, months of battery charging followed by months of battery discharging, is documented and assessed. This paper presents operational data obtained from 2004 through 2007.

In order for the IAEA to draw valid safeguards conclusions, they must be assured that the data used to draw those conclusions are authentic. In order to provide that assurance, authentication measures are applied to the safeguards equipment and the data from the equipment. These authentication measures require that IAEA personnel have direct electronic and physical access to the equipment and severely limit access to the equipment by the operator. Providing the necessary access for the IAEA personnel can be intrusive and potentially disruptive to plant operations. If the equipment is to be used jointly by the operator and the IAEA, the authentication measures can cause difficulties for the operator by limiting his ability to repair and maintain the hardware. In many cases, tamper indicating conduit and enclosures are also required. The installation, sealing, and inspection of this tamper indicating hardware also add to the intrusiveness of the safeguards activities and increase the cost of safeguards. This paper discusses these impacts and proposes methods for mitigating them.

The Cognitive Foundry is a unified collection of tools for Cognitive Science and Technology applications, supporting the development of intelligent agent models. The Foundry has two primary components designed to facilitate agent construction: the Cognitive Framework and Machine Learning packages. The Cognitive Framework provides design patterns and default implementations of an architecture for evaluating theories of cognition, as well as a suite of tools to assist in the building and analysis of theories of cognition. The Machine Learning package provides tools for populating components of the Cognitive Framework from domain-relevant data using automated knowledge-capture techniques. This paper describes the Cognitive Foundry with a focus on its application within the context of agent behavior modeling.

A non-selective electrode array is presented for the quantification of fructose, galactose, and glucose in mixed solutions. A unique feature of this electrode array relative to other published work is the wide diversity of electrode materials incorporated within the array, being constructed of 41 different metals and metal alloys. Cyclic voltammograms were acquired for solutions containing a single sugar at varying concentrations, and the correlation between current and sugar concentration was calculated as a function of potential and electrode array element. The correlation plots identified potential regions and electrodes that scaled most linearly with sugar concentration, and the number of electrodes used in building predictive models was reduced to 15. Partial least squares regression models relating electrochemical response to sugar concentration were constructed using data from single electrodes and multiple electrodes within the array, and the predictive abilities of these models were rigorously compared using a non-parametric Wilcoxon test. Models using single electrodes (Pt:Rh (90:10) for fructose, Au:Ni (82:18) for galactose, and Au for glucose) were judged to be statistically superior or indistinguishable from those built with multiple electrodes. Additionally, for each sugar, interval partial least squares regression successfully identified a subset of potentials within a given electrode that generated a model of statistically equivalent predictive ability relative to the full potential model. While including data from multiple electrodes offered no benefit in predicting sugar concentration, use of the array afforded the versatility and flexibility of selecting the best single electrode for each sugar. © 2008 Elsevier B.V. All rights reserved.

Determination of fracture toughness for metals under quasi-static loading conditions can follow well-established procedures and ASTM standards. The use of metallic materials in impact-related applications requires the determination of dynamic fracture toughness for these materials. There are two main challenges in experiment design that must be overcome before valid dynamic data can be obtained. Dynamic equilibrium over the entire specimen needs to be approximately achieved to relate the crack tip loading state to the far-field loading conditions. The loading rate at the crack tip should be maintained nearly constant during an experiment to delineate rate effects on the values of dynamic fracture toughness. A recently developed experimental technique for determining dynamic fracture toughness of brittle materials has been adapted to measure the dynamic initiation fracture toughness of high strength steel alloys. A split-Hopkinson pressure bar is used to apply the dynamic loading. A pulse shaper is used to achieve constant loading rate at the crack tip and dynamic equilibrium across the specimen. A four-point bending configuration is used at the impact section of the setup. ©2008 Society for Experimental Mechanics Inc.

Simulation of potential radionuclide transport in the saturated zone from beneath the proposed repository at Yucca Mountain to the accessible environment is an important aspect of the total system performance assessment (TSPA) for disposal of high-level radioactive waste at the site. Analyses of uncertainty and sensitivity are integral components of the TSPA and have been conducted at both the sub-system and system levels to identify parameters and processes that contribute to the overall uncertainty in predictions of repository performance. Results of the sensitivity analyses indicate that uncertainty in groundwater specific discharge along the flow path in the saturated zone from beneath the repository is an important contributor to uncertainty in TSPA results and is the dominant source of uncertainty in transport times in the saturated zone for most radionuclides. Uncertainties in parameters related to matrix diffusion in the volcanic units, colloid-facilitated transport, and sorption are also important contributors to uncertainty in transport times to differing degrees for various radionuclides.

The drift-shadow effect describes capillary diversion of water flow around a drift or cavity in porous or fractured rock, resulting in lower water flux directly beneath the cavity. This paper presents computational simulations of drift-shadow experiments using dual-permeability models, similar to the models used for performance assessment analyses of flow and seepage in unsaturated fractured tuff at Yucca Mountain. Results show that the dual-penneability models capture the salient trends and behavior observed in the experiments, but constitutive relations (e.g., fracture capillary-pressure curves) can significantly affect the simulated results. An evaluation of different meshes showed that at the grid refinement used, a comparison between orthogonal and unstructured meshes did not result in large differences.

Uncertainty and sensitivity analyses of the expected dose to the reasonably maximally exposed individual in the Yucca Mountain 2008 total system performance assessment (TSPA) are presented. Uncertainty results are obtained with Latin hypercube sampling of epistemic uncertain inputs, and partial rank correlation coefficients are used to illustrate sensitivity analysis results.

The Total System Performance Assessment (TSPA) for the proposed high level radioactive waste repository at Yucca Mountain, Nevada, uses a sampling-based approach to uncertainty and sensitivity analysis. Specifically, Latin hypercube sampling is used to generate a mapping between epistemically uncertain analysis inputs and analysis outcomes of interest. This results in distributions that characterize the uncertainty in analysis outcomes. Further, the resultant mapping can be explored with sensitivity analysis procedures based on (i) examination of scatterplots, (ii) partial rank correlation coefficients, (iii) R2 values and standardized rank regression coefficients obtained in stepwise rank regression analyses, and (iv) other analysis techniques. The TSPA considers over 300 epistemically uncertain inputs (e.g., corrosion properties, solubilities, retardations, defining parameters for Poisson processes, ⋯) and over 70 time-dependent analysis outcomes (e.g., physical properties in waste packages and the engineered barrier system, releases from the engineered barrier system, the unsaturated zone and the saturated zone for individual radionuclides, and annual dose to the reasonably maximally exposed individual (RMEI) from both individual radionuclides and all radionuclides. The obtained uncertainty and sensitivity analysis results play an important role in facilitating understanding of analysis results, supporting analysis verification, establishing risk importance, and enhancing overall analysis credibility. The uncertainty and sensitivity analysis procedures are illustrated and explained with selected results for releases from the engineered barrier system, the unsaturated zone and the saturated zone and also for annual dose to the RMEI.

Placing sensors in municipal water networks to protect against a set of contamination events is a classic p-median problem for most objectives when we assume that sensors are perfect. Many researchers have proposed exact and approximate solution methods for this p-median formulation. For full-scale networks with large contamination event suites, one must generally rely on heuristic methods to generate solutions. These heuristics provide feasible solutions, but give no quality guarantee relative to the optimal placement. In this paper we apply a Lagrangian relaxation method in order to compute lower bounds on the expected impact of suites of contamination events. In all of our experiments with single objectives, these lower bounds establish that the GRASP local search method generates solutions that are provably optimal to to within a fraction of a percentage point. Our Lagrangian heuristic also provides good solutions itself and requires only a fraction of the memory of GRASP. We conclude by describing two variations of the Lagrangian heuristic: an aggregated version that trades off solution quality for further memory savings, and a multi-objective version which balances objectives with additional goals. © 2008 ASCE.

It is generally acknowledged that once a highly conductive channel is established between two charged and conducting materials, electrical breakdown is well established and difficult to interrupt. An understanding of the initiation mechanism for electrical breakdown is crucial for devising mitigating methods to avoid catastrophic failures. Both volumetric and surface discharges are of interest. An effort is underway where experiments and theory are being simultaneously developed. The experiment consists of an impedance matched discharge chamber capable of investigating various gases and pressures to ten atmospheres. In addition to current and voltage measurements, a high dynamic range streak camera records streamer velocities. The streamer velocities are particularly valuable for comparison with theory. A streamer model is being developed which includes photo-ionization and particle interactions with an insulating surface. The combined theoretical and experimental effort is aimed at detailed comparisons of streamer development as well as a quantitative understanding of how streamers interact with dielectric surfaces and the resulting effects on breakdown voltage. © 2008 IEEE.

For the Yucca Mountain Project nuclear waste repository design, the emplaced waste packages are covered by a self-supported inverted U-shaped drip shield fabricated from Ti Grade 7 with Ti Grade 29 structural support members. This paper reports experimental results obtained to characterize the corrosion behavior of several titanium alloys. General corrosion rates were obtained using weight loss and electrochemical techniques such as cyclic potentiodynamic polarization and electrochemical impedance spectroscopy. Localized corrosion resistance was assessed from the results of cyclic potentiodynamic polarization and long-term corrosion potential measurements. The results indicate the drip shield titanium alloys are highly resistant to general and localized corrosion under repository-relevant conditions. © 2009 by NACE International.

Historically, (PCM/FM) receivers have used simple detection schemes yielding low performance. Using multi-symbol detection methods, PCM/FM can be received with better error performance than either SOQPSK or multi-h CPM. We present an approximation by which PCM/FM can be reinterpreted as a phase modulation scheme, allowing the use of coherent detection techniques. This is backward compatible with existing receivers. We also present an extension by which the error performance of the approximated PCM/FM can be improved even further with no change to the spectral properties. This improved waveform can be used in systems where compatibility with existing frequency allocation schemes is required. © International Foundation for Telemetering, 2008.

Dual-modular-redundancy (DMR) architectures use duplication and self-voting asynchronous circuits to mitigate single event transients (SETs). The area and performance of DMR circuitry is evaluated against conventional triple-modular-redundancy (TMR) logic. Benchmark ASIC circuits designed with DMR logic show a 1024% area improvement for flip-flop designs, and a 33% improvement for latch designs. © 2006 IEEE.

A seven cavity LTD system has been assembled and tested in a voltage adder configuration capable of producing approximately 1-MV into a 7-Ω, critically damped load. Individual cavities have been tested with a resistive load. The seven cavity adder has been tested with a large area electron beam diode. The output pulse when tested into a resistive load is that of an RLC circuit. When tested with a dynamic load impedance, the output voltages of the cavities have an added oscillation. The oscillation affects the output pulse shape but is not harmful to the cavity components. © 2008 IEEE.

Functional modeling and SysML/UML are defined communication languages that engineers and related disciplines use to communicate the nature of engineering products. We often see functional modeling and SysML/UML used to describe large, physical entities, such as airplanes or space craft. Systems engineers use functional modeling to decompose these large systems into subsystems. Each subsystem has defined requirements, defined roles and responsibilities (functions), and definable interfaces. Each subsystem consists of electrical hardware, mechanical hardware, and computer software. Functional modeling and SysML/UML can also be used for modeling program/project management processes, systems engineering processes, and manufacturing processes. Many organizations use an array of flow charts, organization charts, network diagrams, and spreadsheets to define engineering processes. This paper presents how Sandia National Laboratories (SNL) used functional modeling and SysML/UML to define the design and development processes and procedures for a product realization process (PRP) called the Integrated Phase Gate (IPG) Process. The use of functional modeling helped the organization more readily accept the use of systematic modeling for developing PRP. Additionally, this paper will explore the value of using SysML/UML over functional modeling in order to completely specify process and process artifacts. © 2008 by Georgia Artery, Mark De Spain and Regina Griego.

We present a rapid method for the identification of viruses using microfluidic chip gel electrophoresis (CGE) of high-copy number proteins to generate unique protein profiles. Viral proteins are solubilized by heating at 95°C in borate buffer containing detergent (5 min), then labeled with fluorescamine dye (10 s), and analyzed using the μChemLab CGE system (5 min). Analyses of closely related T2 and T4 bacteriophage demonstrate sufficient assay sensitivity and peak resolution to distinguish the two phage. CGE analyses of four additional viruses - MS2 bacteriophage, Epstein - Barr, respiratory syncytial, and vaccinia viruses - demonstrate reproducible and visually distinct protein profiles. To evaluate the suitability of the method for unique identification of viruses, we employed a Bayesian classification approach. Using a subset of 126 replicate electropherograms of the six viruses and phage for training purposes, successful classification with non-training data was 66/69 or 95% with no false positives. The classification method is based on a single attribute (elution time), although other attributes such as peak width, peak amplitude, or peak shape could be incorporated and may improve performance further. The encouraging results suggest a rapid and simple way to identify viruses without requiring specialty reagents such as PCR probes and antibodies. © 2008 American Chemical Society.

This report evaluates transportation risk for nuclear material in the proposed Global Nuclear Energy Partnership (GNEP) fuel cycle. Since many details of the GNEP program are yet to be determined, this document is intended only to identify general issues. The existing regulatory environment is determined to be largely prepared to incorporate the changes that the GNEP program will introduce. Nuclear material vulnerability and attractiveness are considered with respect to the various transport stages within the GNEP fuel cycle. It is determined that increased transportation security will be required for the GNEP fuel cycle, particularly for international transport. Finally, transportation considerations for several fuel cycle scenarios are discussed. These scenarios compare the current "once-through" fuel cycle with various aspects of the proposed GNEP fuel cycle.