The Quantum-Kinetic (Q-K) chemical reaction model is implemented in a Navier-Stokes solver, US3D, and tested on the Bow Shock UltraViolet flight experiments. The chemical reaction rates predicted by the Q-K model are compared to a commonly used Park model for flows in thermal non-equilibrium. The results show that in thermal equilibrium the reaction rates between these two models are comparable. The Q-K model predicts greater rates for some chemical reactions and lesser rates for other reactions in an five species air chemistry model. In thermal non-equilibrium, the Q-K model maintains comparable rates near thermal equilibrium, while avoiding issues of strong thermal non-equilibrium seen in the Park model. The application of the Q-K model to the Bow Shock UltraViolet flight experiments show that the model remains consistent with previous Navier-Stokes and DSMC computations over altitudes ranging from 53:5 km up to 87:5 km despite the enforcement of translational-rotational equilibrium. The commonly used Park model was unable to match this performance.
Deployed on a commercial airplane, proton exchange membrane (PEM) fuel cells may offer emissions reductions, thermal efficiency gains, and enable locating the power near the point of use. This work seeks to understand whether on-board fuel cell systems are technically feasible, and, if so, if they could offer a performance advantage for the airplane when using today’s off-the-shelf technology. Through hardware analysis and thermodynamic simulation, we found that an additional fuel cell system on a commercial airplane is technically feasible using current technology. Recovery and on-board use of the heat and water that is generated by the fuel cell is an important method to increase the benefit of such a system. Although the PEM fuel cell generates power more efficiently than the gas turbine generators currently used, when considering the effect of the fuel cell system on the airplane’s overall performance we found that an overall performance penalty (i.e., the airplane will burn more jet fuel) would result if using current technology for the fuel cell and hydrogen storage. Although applied to a Boeing 787-type airplane, the method presented is applicable to other airframes as well.
A hands-on critical-experiment training class has been developed by the US DOE Nuclear Criticality Safety Program using the water-moderated pin-fueled critical experiments at Sandia National Laboratories. The class is offered as part of the NCSP training program for Nuclear Criticality Safety Engineers in a facility that allows attendance by both cleared and uncleared personnel. Laboratory exercises have been developed that demonstrate the effects of varying a number of the parameters that are considered important to criticality safety. Accompanying the experiments is a series of classroom presentations that emphasize the concepts that are demonstrated in the experiments.
For critical infrastructure facilities, mitigation techniques for insider threats are primarily non-technical in nature and rely heavily on policies/procedures. Traditional access control measures (access cards, biometrics, PIN numbers, etc.) are built on a philosophy of trust that enables those with appropriate permissions to access facilities without additional monitoring or restrictions. Systems based on these measures have three main limitations: 1) access is typically bound to a single authentication occurrence; 2) the authentication factors have little impact against human (insider) threats to security systems; and 3) many of the authentication systems inconvenience end-users. In order to mitigate the aforementioned deficiencies, we propose utilizing the concept of Ephemeral Biometrics to construct strong, persistent authentication protocols.
Thermochemical cycles that divide the energetically unfavorable thermolysis of water or carbon dioxide into two or more reactions were used for solar driven fuel production. A large number of diverse metal oxides have been proposed for solar thermochemical fuel production (STFP) including stoichiometric compounds such as ferrites and other transition metal spinels. The design parameter is determined by a set of interacting factors, including reaction thermodynamics, target efficiency, and durability of reactor materials. Operating temperature window is determined by a set of interacting factors, including reaction thermodynamics, target efficiency, and durability of reactor materials. In the absence of kinetic data, however, it can be stated that achieving high average annual solar-to-fuel efficiencies (AASFE) requires that energy consumption of the reactions, and hence the reaction rates, be matched to the solar flux entering the system.
The Seven Percent Critical Experiment (7uPCX) at Sandia National Laboratories was designed to provide benchmark criticality and reactor physics data for water-moderated pin-fueled nuclear reactor cores in the 5 to 10 percent enrichment range. Approach-to-critical experiments were performed on fifteen roughly cylindrical pure water-moderated and -reflected 7uPCX configurations with a fuel-to-water volume ratio of 0.52. Those configurations are described and the results of the measurements are reported in this paper.
Safety Relief Valves (SRVs) are an important component of the safety case for a Light Water Reactor (LWR). The number and types of SRVs in LWRs vary from plant to plant, but they generally operate to perform the same safety function. During accidents in which the coolant pressurizes beyond a predetermined set-point, the SRV will open, releasing coolant from the primary system and into the containment. Once enough coolant has been released to lower the coolant pressure, the SRV will reset. This cycle will continue until the SRV fails, in either a "Failed to Open (FTO)" or "Failed To Close (FTC)" mode. These failures can be caused either through cyclic loading or as a result of thermalinduced stresses from the coolant passing through the valve. SRV failures can be important, because an SRV that has FTC will cause a small "Loss of Cooling Accident", which depressurizes the primary system. Alternatively, SRVs that have FTO will allow system pressure to rise until it reaches the next SRV set-point. If the pressure is not reduced through the successful operation of other safety systems, either creep rupture elsewhere in the system, such as in the steam line, or high-pressure core damage may occur. While some SRV failure data is recorded in NUREG/CR-6928, the spread of the epistemic uncertainty distributions for FTO and FTC are wide. These large uncertainties may cause an analyst to be overconfident in the results of a severe accident simulation that uses only point-estimates calculations of FTO and FTC.
A second set of experiments in the Seven Percent Critical Experiment (7uPCX) has been completed. Additionally, an evaluation of the experiments as criticality safety benchmark experiments has been performed. The Reviews of the benchmark evaluation have been completed. This evaluation will be published in the 2013 edition of the International Handbook of Evaluated Criticality Benchmark Experiments as LEU-COMP-THERM-078 (LCT078). This presentation is a brief tour of these experiments.
Scalable parallel computing is essential for processing large scale-free (power-law) graphs. The distribution of data across processes becomes important on distributed-memory computers with thousands of cores. It has been shown that two dimensional layouts (edge partitioning) can have significant advantages over traditional one-dimensional layouts. However, simple 2D block distribution does not use the structure of the graph, and more advanced 2D partitioning methods are too expensive for large graphs. We propose a new two-dimensional partitioning algorithm that combines graph partitioning with 2D block distribution. The computational cost of the algorithm is essentially the same as 1D graph partitioning. We study the performance of sparse matrix-vector multiplication (SpMV) for scale-free graphs from the web and social networks using several different partitioners and both 1D and 2D data layouts. We show that SpMV run time is reduced by exploiting the graph's structure. Contrary to popular belief, we observe that current graph and hypergraph partitioners often yield relatively good partitions on scale-free graphs. We demonstrate that our new 2D partitioning method consistently outperforms the other methods considered, for both SpMV and an eigensolver, on matrices with up to 1.6 billion nonzeros using up to 16,384 cores. Copyright 2013 ACM.
A systematic approach to defining margin in a manner that incorporates statistical information and accommodates data uncertainty, but does not require assumptions about specific forms of the tails of distributions is developed. This approach extends to calculations underlying validation assessment and quantitatively conservative predictions.
World Renewable Energy Forum, WREF 2012, Including World Renewable Energy Congress XII and Colorado Renewable Energy Society (CRES) Annual Conferen
Johnson, Jay; Bower, Ward I.; Quintana, Michael A.
Arc faults in photovoltaic (PV) modules have caused multiple rooftop fires. The arc generates a high-temperature plasma that ignites surrounding materials and subsequently spreads the fire to the building structure. While there are many possible locations in PV systems and PV modules where arcs could initiate, bypass diodes have been suspected of triggering arc faults in some modules. In order to understand the electrical and thermal phenomena associated with these events, a finite element model of a busbar and diode was created. Thermoelectrical simulations found Joule and internal diode heating from normal operation would not normally cause bypass diode or solder failures. However, if corrosion increased the contact resistance in the solder connection between the busbar and the diode leads, enough voltage potential would be established to arc across micron-scale electrode gaps. Lastly, an analytical arc radiation model based on observed data was employed to predicted polymer ignition times. The model predicted polymer materials in the adjacent area of the diode and junction box ignite in less than 0.1 seconds.
The earth isn't flat, and radar beams don't travel straight. This becomes more noticeable as range increases, particularly at shallow depression/grazing angles. This report explores models for characterizing this behavior.
The Signal-to-Noise Ratio (SNR) of a radar echo signal will vary across a range swath, due to spherical wavefront spreading, atmospheric attenuation, and antenna beam illumination. The antenna beam illumination will depend on antenna pointing. Calculations of geometry are complicated by the curved earth, and atmospheric refraction. This report investigates optimizing antenna pointing to maximize the minimum SNR across the range swath.
This paper presents a case study of a 3 kW photovoltaic system with Enphase microinverters. A brief introduction to microinverters and central inverters is first presented, followed by an overview of the installation, features, operation, monitoring, and costs of the system. The monthly and annual energy production during the first three years is presented and compared against modeled results using the System Advisor Model. Various factors that have impacted the performance (e.g., shading, weather, temperature, wind, tilt, orientation) are discussed, and the performance of the system is compared against a simulated optimized system. The optimal sizing of microinverters is also discussed to explain why the power rating of the microinverter may be less than the power rating of the module to achieve maximum energy production.
Module temperature is modeled using a transient heat-flow model. Module temperature predicted in this fashion is important in the calculation of cell temperature, a vital input in performance modeling. Parameters important to the model are tested for sensitivity, and optimized to a single day of measured module temperature using simultaneous non-linear least squares regression. These optimized parameters are then tested for accuracy using a year's worth of data for one location. The results obtained from this analysis are compared with modeled data from a different site, as well as to results obtained using a steadystate model. We find that the transient model best captures the variability in module temperature, and that the transient model works best when calibrated for a specific location.
Module temperature is modeled using a transient heat-flow model. Module temperature predicted in this fashion is important in the calculation of cell temperature, a vital input in performance modeling. Parameters important to the model are tested for sensitivity, and optimized to a single day of measured module temperature using simultaneous non-linear least squares regression. These optimized parameters are then tested for accuracy using a year's worth of data for one location. The results obtained from this analysis are compared with modeled data from a different site, as well as to results obtained using a steadystate model. We find that the transient model best captures the variability in module temperature, and that the transient model works best when calibrated for a specific location.
The modeling work described herein represents Sandia National Laboratories (SNL) portion of a collaborative three-year project with Northrop Grumman Electronic Systems (NGES) and the University of Missouri to develop an advanced, thermal ground-plane (TGP), which is a device, of planar configuration, that delivers heat from a source to an ambient environment with high efficiency. Work at all three institutions was funded by DARPA/MTO; Sandia was funded under DARPA/MTO project number 015070924. This is the final report on this project for SNL. This report presents a numerical model of a pulsating heat pipe, a device employing a two phase (liquid and its vapor) working fluid confined in a closed loop channel etched/milled into a serpentine configuration in a solid metal plate. The device delivers heat from an evaporator (hot zone) to a condenser (cold zone). This new model includes key physical processes important to the operation of flat plate pulsating heat pipes (e.g. dynamic bubble nucleation, evaporation and condensation), together with conjugate heat transfer with the solid portion of the device. The model qualitatively and quantitatively predicts performance characteristics and metrics, which was demonstrated by favorable comparisons with experimental results on similar configurations. Application of the model also corroborated many previous performance observations with respect to key parameters such as heat load, fill ratio and orientation.
This document is a draft Security-by-Design (SeBD) handbook produced to support the Work Plan of the Nuclear Security Summit to share best practices for nuclear security in new facility design. The Work Plan calls on States to “encourage nuclear operators and architect/engineering firms to take into account and incorporate, where appropriate, effective measures of physical protection and security culture into the planning, construction, and operation of civilian nuclear facilities and provide technical assistance, upon request, to other States in doing so.” The materials for this document were generated primarily as part of a bilateral project to produce a SeBD handbook as a collaboration between the Japan Atomic Energy Agency (JAEA) Nuclear Nonproliferation Science and Technology Center and Sandia National Laboratories (SNL), which represented the US Department Energy (DOE) National Nuclear Security Administration (NNSA) under a Project Action Sheet PAS-PP04. Input was also derived based on tours of the Savannah River Site (SRS) and Japan Nuclear Fuel Limited (JNFL) Rokkasho Mixed Oxide Fuel fabrication facilities and associated project lessons-learned. For the purposes of the handbook, SeBD will be described as the system-level incorporation of the physical protection system (PPS) into a new nuclear power plant or nuclear facility resulting in a PPS design that minimizes the risk of malicious acts leading to nuclear material theft; nuclear material sabotage; and facility sabotage as much as possible through features inherent in (or intrinsic to) the design of the facility. A four-element strategy is presented to achieve a robust, durable, and responsive security system.
This report documents the results of Task 3 of Project Action Sheet PP05 between the United States Department of Energy (DOE) and the Republic of Korea (ROK) Ministry of Education, Science, and Technology (MEST) for Support with Review of an ROK Risk Evaluation Process. This task was to have Sandia National Laboratories collaborate with the Korea Institute of Nuclear Nonproliferation and Control (KINAC) on several activities concerning how to determine the Probability of Neutralization, PN, and the Probability of System Effectiveness, PE, to include: providing descriptions on how combat simulations are used to determine PN and PE; comparisons of the strengths and weaknesses of two neutralization models (the Neutralization.xls spreadsheet model versus the Brief Adversary Threat-Loss Estimator (BATLE) software); and demonstrating how computer simulations can be used to determine PN. Note that the computer simulation used for the demonstration was the Scenario Toolkit And Generation Environment (STAGE) simulation, which is a stand-alone synthetic tactical simulation sold by Presagis Canada Incorporated. The demonstration is provided in a separate Audio Video Interleave (.AVI) file.
In this report we explore claims that phase conjugation of high energy lasers by stimulated Brillouin scattering (SBS) can compensate optical aberrations associated with severely distorted laser amplifier media and aberrations induced by the atmosphere. The SBS media tested was a gas cell pressurized up to 300 psi with SF6 or Xe or both. The laser was a 10 Hz, 3J, Q-switched Nd:YAG with 25 ns wide pulses. Atmospheric aberrations were created with space heaters, helium jets and phase plates designed with a Kolmogorov turbulence spectrum characterized by a Fried parameter, ro, ranging from 0.6 – 6.0 mm. Phase conjugate tests in the laboratory were conducted without amplification. For the strongest aberrations, D/ro ~ 20, created by combining the space heaters with the phase plate, the Strehl ratio was degraded by a factor of ~50. Phase conjugation in SF6 restored the peak focusable intensity to about 30% of the original laser. Phase conjugate tests at the outdoor laser range were conducted with laser amplifiers providing gain in combination with the SBS cell. A large 600,000 BTU kerosene space heater was used to create turbulence along the beam path. An atmospheric structure factor of Cn2 = 5x10-13 m2/3 caused the illumination beam to expand to a diameter 250mm and overfill the receiver. The phase conjugate amplified return could successfully be targeted back onto glints 5mm in diameter. Use of a lenslet arrays to lower the peak focusable intensity in the SBS cell failed to produce a useful phase conjugate beam; The Strehl ratio was degraded with multiple random lobes instead of a single focus. I will review literature results which show how multiple beams can be coherently combined by SBS when a confocal reflecting geometry is used to focus the laser in the SBS cell.
Over the decades, India and the United States have had very little formal collaboration on nuclear issues. Partly this was because neither country needed collaboration to make progress in the nuclear field. But it was also due, in part, to the concerns both countries had about the other's intentions. Now that the U.S.-India Deal on nuclear collaboration has been signed and the Hyde Act passed in the United States, it is possible to recognize that both countries can benefit from such nuclear collaboration, especially if it starts with issues important to both countries that do not touch on strategic systems. Fortunately, there are many noncontroversial areas for collaboration. This study, funded by the U.S. State Department, has identified a number of areas in the prevention of and response to radiological incidents where such collaboration could take place.
Regulations in the United States that govern the permanent disposal of spent nuclear fuel and high-level radioactive waste in deep geologic repositories require the explicit consideration of hypothetical future human intrusions that disrupt the waste. Specific regulatory requirements regarding the consideration of human intrusion differ in the two sets of regulations currently in effect in the United States; one defined by the Environmental Protection Agency's 40 Code of Federal Regulations part 197, applied only to the formerly proposed geologic repository at Yucca Mountain, Nevada, and the other defined by the Environmental Protection Agencys 40 Code of Federal Regulations part 191, applied to the Waste Isolation Pilot Plant in New Mexico and potentially applicable to any repository for spent nuclear fuel and high-level radioactive waste in the United States other than the proposed repository at Yucca Mountain. This report reviews the regulatory requirements relevant to human intrusion and the approaches taken by the Department of Energy to demonstrating compliance with those requirements.
In the current study, processes to produce either ethanol or a representative fatty acid ethyl ester (FAEE) via the fermentation of sugars liberated from lignocellulosic materials pretreated in acid or alkaline environments are analyzed in terms of economic and environmental metrics. Simplified process models are introduced and employed to estimate process performance, and Monte Carlo analyses were carried out to identify key sources of uncertainty and variability. We find that the near-term performance of processes to produce FAEE is significantly worse than that of ethanol production processes for all metrics considered, primarily due to poor fermentation yields and higher electricity demands for aerobic fermentation. In the longer term, the reduced cost and energy requirements of FAEE separation processes will be at least partially offset by inherent limitations in the relevant metabolic pathways that constrain the maximum yield potential of FAEE from biomass-derived sugars.
This SAND report summarizes research conducted as a part of a two year Laboratory Directed Research and Development (LDRD) project to improve our abilities to model algal cultivation. Algae-based biofuels have generated much excitement due to their potentially large oil yield from relatively small land use and without interfering with the food or water supply. Algae mitigate atmospheric CO2 through metabolism. Efficient production of algal biofuels could reduce dependence on foreign oil by providing a domestic renewable energy source. Important factors controlling algal productivity include temperature, nutrient concentrations, salinity, pH, and the light-to-biomass conversion rate. Computational models allow for inexpensive predictions of algae growth kinetics in these non-ideal conditions for various bioreactor sizes and geometries without the need for multiple expensive measurement setups. However, these models need to be calibrated for each algal strain. In this work, we conduct a parametric study of key marine algae strains and apply the findings to a computational model.