Publications

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Spontaneous Raman scattering images of liquid and near liquid methane released through 1 and 1.25 mm diameter orifices were taken using a pulsed planar laser sheet. The methane back pressure was varied between 2 and 6 bar_abs with methane temperatures between 130 and 220 K. Analysis of the Raman images resulted in the planar concentration and temperature fields of the methane jets. The measured methane concentration was compared with empirical relationships for warm gas releases and found to be in agreement in terms of centerline concentration decay rate, self-similarity, and half-width decay rate. Comparisons were then made for anticipated real-world CNG and LNG releases showing similar extents of flammable mass for the two fuel options. Measured images were compared to a cold gas release model, which showed good agreement over the range of methane release temperatures, pressures, and nozzle sizes. The collected measurements provide validation of this cold release model which will be used to model additional scenarios and inform LNG safety codes and standards.

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TRISO nuclear fuel particles that are less than 1 mm in diameter are designed with multiple barrier layers to retain fission products both during reactor operations and for long-term geological disposal. The primary barrier is a 35 μm thick silicon carbide (SiC-a highly impermeable semi-metal) layer for which data are available on the diffusion of short-lived fission products at high temperatures (> 1000 °C). However, for a geological repository, this layer may contact brine and hence corrode even at ambient temperatures. As an initial approach to assess the effectiveness of the SiC barrier for geological repositories, ranges of fission product diffusivities and corrosion rates for SiC are modeled concurrently with the simultaneous effect of radioactive decay. Using measured corrosion rates of SiC, if the diffusivity is more than about 10^-20 m²/s, fission product releases may occur before the SiC barrier has corroded to the point of breach. For diffusivities less than about 10^-21m² /s there may not be significant diffusional releases prior to SiC barrier removal/breach by corrosion. This work shows the importance of estimating diffusivities in SiC at geological repository temperatures, and highlights the relevance of evaluating the porosity/permeability evolution of the SiC layer in a geologic environment.

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Methods have been developed to combine signals of various frequencies in a manner to produce clearer images in the presence of noise. Ground Penetrating Radar (GPR) scans at various frequencies are no exception. Methods using an optimization problem solver, the Expectation-Maximization (EM) Algorithm, define weights used to perform the task of combining GPR scans. In this paper, we explore using the Gaussian Mixture Model (GMM) feature of the EM Algorithm on GPR scans taken at various heights above ground ("Stand Off' GPR). This method demonstrates the same measured improvement toward producing a cleaner image as GPR scans taken at ground level using the same EM Algorithm method.

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Many earth materials and minerals are seismically anisotropic; however, due to the weakness of anisotropy and for simplicity, the earth is often approximated as an isotropic medium. Specific circumstances, such as in shales, tectonic fabrics, or oriented fractures, for example, require the use of anisotropic simulations in order to accurately model the earth. This report details the development of a new massively parallel 3-D full seismic waveform simulation algorithm within the principle coordinate system of an orthorhombic material, which is a specific form of anisotropy common in layered, fractured media. The theory and implementation of Pararhombi is described along with verification of the code against other solutions.

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Neutron bang times for a series of MagLIF (Magnetic Liner Inertial Fusion) experiments with D₂-filled targets have been measured at the Z facility. The emitted neutrons were detected as current-mode pulses in a multichannel, neutron time-of-flight (nTOF) diagnostic with conventional, scintillator-photomultiplier-tube (PMT) detectors. In these experiments, the detectors were fielded at known, fixed distances L (690-2510 cm) from the target, and on three, non-coplanar (but convergent) lines-of-sight (LOS). The primary goal of this diagnostic was to estimate a fiducial time (bang time) relative to an externally generated time-base for synchronizing all the diagnostics in an experiment. Recorded arrival times (A7) of the pulses were characterized experimentally by three numerical methods: a first-moment estimate (centroid) and two nodal measures — Savitzky-Golay (SG) smoothing and a single point peak estimate of the raw data. These times were corrected for internal detector time delays (transit and impulse-response function) — an adjustment that linked the recorded ATs to the corresponding arrival of uncollided neutrons at each detector. The bang time was then estimated by linearly regressing the arrival times against the associated distances to the source; t_bang (on the system timescale) was taken as the temporal intercept of the regression equation at distance L = 0. This article reports the analysis for a representative shot #2584 for which (a) the recorded ATs — even without detector corrections — agreed by method in each channel to within 1-2 ns; (b) internal corrections were each ~3 — 5 ns; and (c) a 95% uncertainty (confidence) interval for t_bang in this shot was estimated at ±3 ns with 4 degrees of freedom. A secondary goal for this diagnostic was to check that the bang time measurements corresponded to neutrons emitted by the D(d,n)³He reaction in a thermalized DD plasma. According to the theoretical studies by Brysk, such neutrons should be emitted with an isotropic Gaussian distribution of mean kinetic energy $ \overline{E}$ of 2.449 MeV; this energy translates to a mean neutron speed $ \overline{u}$ of 2.160 cm/ns [D. H. Munro, Nuclear Fusion, 56(3) 036001 (2016)]. In the MagLIF series of shots there was no evidence of spatial asymmetry in the time-distance regressions, and it was possible to extract the mean neutron speed from the slope of these fits. In shot 2584 $ \overline{u}$ was estimated at 2.152 cm/ns ± 0.010 cm/ns [95 % confidence, 4 dof] and the mean kinetic energy $ \overline{E}$ (with relativistic corrections) was 2.431 MeV ± 0.022 MeV [95 % confidence, 4 dof] — results supporting the assumption that D-D neutrons were, in fact, measured.

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This study developed and tested biologically inspired computational methods to detect anomalous signals in data streams that could indicate a pending outbreak or bio-weapon attack. Current large-scale biosurveillance systems are plagued by two principal deficiencies: (1) timely detection of disease-indicating signals in noisy data and (2) anomaly detection across multiple channels. Anomaly detectors and data fusion components modeled after human immune system processes were tested against a variety of natural and synthetic surveillance datasets. A pilot scale immune-system-based biosurveillance system performed at least as well as traditional statistical anomaly detection data fusion approaches. Machine learning approaches leveraging Deep Learning recurrent neural networks were developed and applied to challenging unstructured and multimodal health surveillance data. Within the limits imposed of data availability, both immune systems and deep learning methods were found to improve anomaly detection and data fusion performance for particularly challenging data subsets.

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The challenges of diagnosing infectious disease, especially in the developing world, and the shortcomings of available instrumentation have exposed the need for portable, easy-to-use diagnostic tools capable of detecting the wide range of causative microbes while operating in low resource settings. We present a centrifugal microfluidic platform that combines ultrasensitive immunoassay and isothermal amplification-based screening for the orthogonal detection of both protein and nucleic acid targets at the point-of-care. A disposable disc with automatic aliquoting inlets is paired with a non-contact heating system and precise rotary control system to yield an easy-to-use, field-deployable platform with versatile screening capabilities. The detection of three enterotoxins (cholera toxin, Staphylococcal enterotoxin B, and Shiga-like toxin 1) and three enteric bacteria (C. jejuni, E. coli, and S. typhimurium) were performed independently and shown to be highly sensitive (limit of detection = 1.35–5.50 ng/mL for immunoassays and 1–30 cells for isothermal amplification), highly exclusive in the presence of non-specific targets, and capable of handling a complex sample matrix like stool. The full panel of toxins and bacteria were reliably detected simultaneously on a single disc at clinically relevant sample concentrations in less than an hour. The ability of our technology to detect multiple analyte types in parallel at the point-of-care can serve a variety of needs, from routine patient care to outbreak triage, in a variety of settings to reduce disease impact and expedite effective treatment.

This monthly report is intended to communicate the status of North Slope ARM facilities managed by Sandia National Labs.

In order for Concentrating Solar Power plants (CSP) to achieve the desired cost breakpoint, significant improvement in performance is required resulting in the need to increase temperatures of fluid systems. A US DOE Small Business Voucher project was established at Sandia to explore the performance characteristics of Ceramic Tubular Products (CTP) silicon carbide TRIPLEX tubes in key categories relating to its performance as a solar receiver in next generation CSP plants. Along these lines, the following research tasks were completed : (1) Solar Spectrum Testing, (2) Corrosion Testing in Molten Chloride Salt, (3) Mechanical Shock Testing, and (4) Thermal Shock Testing. Through the completion of these four tasks, it has been found that the performance of CTP's material across all of these categories is promising, and merits further investigation beyond this initial investigation. Through 50 solar aging cycles, the CTP material exhibited excellent stability to high temperatures in air, exhibited at or above 0.95 absorptance, and had measured emittances within the range of 0.88-0.90. Through molten salt corrosion testing at 750°C it was found that SiC exhibits significantly lower mass change (— 90 times lower) than Haynes 230 during 108 hours of salt exposure. The CTP TRIPLEX material performed significantly better than the SiC monolithic tube material in mechanical shock testing, breaking at an average height of 3 times that for the monolithic tubes. Through simulated rain thermal shock testing of CTP composite tubes at 800°C it was found that CTP's SiC composite tubes were able to survive thermal shock, while the SiC monolithic tubes did not.

As utility interconnected photovoltaic systems (PV) become integrated into the electrical power system (EPS) at an increasing rate, utilities and regulators have become concerned about the potential for increased voltage and frequency deviations as well as EPS reliability and resiliency. These concerns have initiated the need to amend the utility interconnection standard to allow advanced inverter control functionalities that provide: (1) reactive power control for voltage support, (2) real (active) power control for frequency support and (3) voltage and frequency ride- through for bulk system support. The new real and reactive power modulation are intended to reduce EPS voltage and frequency deviations by mimicking the droop and excitation controls of conventional generation. The new ride-through capabilities are needed to prevent a large quantity of generation from autonomously de-energizing or disconnecting in response to a voltage or frequency deviation. These changes, however, may have the potential to interfere with autonomous anti-islanding, especially when multiple inverters from different vendors are co-located on one bus. This report presents results from an investigation of multi-inverter autonomous anti- islanding with advanced functions, and the development of a means to mitigate adverse interaction between the two.

Shor's groundbreaking quantum algorithm for integer factoring provides an exponential speedup over the best-known classical algorithms. In the 20 years since Shor's algorithm was conceived, only a handful of fundamental quantum algorithmic kernels, generally providing modest polynomial speedups over classical algorithms, have been invented. To better understand the potential advantage quantum resources provide over their classical counterparts, one may consider other resources than execution time of algorithms. Quantum Approximation Algorithms direct the power of quantum computing towards optimization problems where quantum resources provide higher-quality solutions instead of faster execution times. We provide a new rigorous analysis of the recent Quantum Approximate Optimization Algorithm, demonstrating that it provably outperforms the best known classical approximation algorithm for special hard cases of the fundamental Maximum Cut graph-partitioning problem. We also develop new types of classical approximation algorithms for finding near-optimal low-energy states of physical systems arising in condensed matter by extending seminal discrete optimization techniques. Our interdisciplinary work seeks to unearth new connections between discrete optimization and quantum information science.

In this paper, the question is asked, how should a country plan a new denuclearization verification regime? Should it concentrate on accounting for fissile material, should it try to "verify" a declaration of the program's history, or,as some analysts have suggested, should it simply redirect the weapons scientists toward peaceful purposes after dismantling the weapons infrastructure and monitor their activity?

ParaChoice supports the VTO mission using early-stage research to help in the development of technology that will improve affordability of transportation, while encouraging innovation and reducing dependence on petroleum. Analysis with the ParaChoice model enables exploration of key factors that influence consumer choice, and technology, fuel, and infrastructure development for the vehicle mix. Because of the distinct differences between requirements, needs, and use patterns for light duty vehicles (LDVs) relative to heavy duty vehicles (HDVs), this project models the dynamics of each of these segments to characterize the factors that influence technology adoption.

This report shows the results of constructing predictive atmospheric models for the Source Physics Experiments 1-6. Historic atmospheric data are combined with topography to construct an atmospheric model that corresponds to the predicted (or actual) time of a given SPE event. The models are ultimately used to construct atmospheric Green's functions to be used for subsequent analysis. We present three atmospheric models for each SPE event: an average model based on ten one-hour snap shots of the atmosphere and two extrema models corresponding to the warmest, coolest, windiest, etc. atmospheric snap shots. The atmospheric snap shots consist of wind, temperature, and pressure profiles of the atmosphere for a one-hour time window centered at the time of the predicted SPE event, as well as nine additional snap shots for each of the nine preceding years, centered at the time and day of the SPE event.

We invert far field infrasound data for the equivalent seismo-acoustic time domain moment tensor to assess the relative importance of two assumed seismoacoustic source mechanisms. The infrasound data were produced by a four of the underground chemical explosions that were conducted during the Source Physics Experiment (SPE). For each SPE event that we invert, we produce three set of atmospheric Green's functions: an average model based on ten years of atmospheric data, as well as two extrema models designed to maximize the variability of atmospheric conditions for the given time-of-day and day-of-year for each SPE event. To parameterize the inversion, we assume that the source of infrasonic energy results from the linear combination of explosion-induced surface spall and linear seismic-to-elastic mode conversion at the Earth's free surface. We find that the inversion yields relatively repeatable results for the estimated spall source whereas the estimated isotropic explosion source is highly variable. This suggests that the majority of the observed acoustic energy is produced by the spall source and/or our modeling of the elastic energy propagation, and data are subsequent conversion to acoustic energy via linear elastic-to-acoustic coupling at the surface, is too simplistic.

Sandia National Laboratories and Gryphon Scientific, as supported and directed by the CDC Center for Preparedness and Response (CPR), studied the process of risk assessment and risk-based decision-making in facilities expected to continue possessing poliovirus strains. The first phase of the study was conducted in anticipation of developing a tool to support decision-making processes for poliovirus containment to minimize the risk of facility-associated re-introduction of poliovirus. The study results supported the starting assumption that risk management of poliovirus will be aided by more rigorous and consistent risk assessment and that experience-based risk assessment is, by itself, inadequate to understand risk in a post-eradication world. These results were derived from review of polio virus literature, oversight documents, current and expected practices, and from discussions with affected facilities. Based on these results and on additional discussions with facilities, the study team recommends development of a quantitative risk assessment tool as well as improving access to and the quality of data for informing risk-based decision-making.

As of 2018, renewable energy sources such as wind and solar have the lowest unsubsidized levelized cost of energy, and grid-scale storage solutions are being aggressively developed and deployed. However, for a carbon-free energy generation paradigm to be realistic, any impediments to scalability must be addressed. In the wind industry, dependence on rare-earth (RE) magnets in direct-drive generators represents a significant roadblock to widespread technology proliferation. Sandia’s Twistact technology is a fundamentally new rotary electrical contact with only rolling metal-to- metal contact that eliminates the need for RE magnets by enabling a wire-wound generator architecture with no efficiency or cost penalties. This report summarizes work funded by an LDRD in FY16—18, in which we advanced the technology readiness level (TRL) of Twistact technology to TRL 5 and proved the viability of a Twistact-based generator for utility-scale, direct-drive wind turbines. We conducted coupon-level tests of rolling metallic contacts and developed a tribological model that predicts operation in either a low-wear or high-wear regime. We also built device-level testing apparatuses and observed operation of full-scale Twistact devices, which corroborated the predictions of the tribological model and demonstrated over 50 million rotation cycles (30-year lifetime in a direct-drive generator). Indeed, the present work demonstrated that Twistact technology has potential to be an enabling technology that eliminates RE magnet dependence in the wind industry. The next logical step is commercialization of Twistact technology (currently at TRL 5) in partnership with a generator original equipment manufacturer that already has an established presence in the wind power industry.

For Drainage 13 Demonstration: Two storm water treatment (bioretention) devices have been installed downstream of the scrap yard at Livermore. The bioretention basins are sized to contain the 85th percentile storm. It is expected that this bioretention basins will lower the Fe and Al concentrations below the NALs. In addition, the sampling location ST-13-1 will be moved to the combined overflow of the bioretention basins. Since the basins are sized to retain the 85th percentile storm, it is expected that samples will only be able to be collected during large storms. For Drainage 20 Demonstration: All corrodible metal stored outside of the machine shops at buildings 906 and 907 have been removed.

The nanometer scale characterization technique of Frequency Modulated Kelvin Probe Force Microscopy (FM-KPFM) will be used to assess a preliminary diffusion study on thin metal films that undergo accelerated aging. The KPFM technique provides a relatively easy, non-destructive methodology that does not require high-vacuum facilities to obtain nanometer spatial resolution of surface chemistry changes and will be exercised in an effort to explore its capacity to map surface potential contrast caused by Cu diffusion in a manner that allows for a qualitative assessment of diffusion rate kinetics. Supporting data will be obtained from traditional techniques: AES, XPS and UPS. An aging study was conducted on thin metal test specimens comprised of Ti or Cr/Cu/Au layer thicknesses of 50nm/500nm/500nm up to 4μm respectively. The accelerated aging process, was performed in air at aging temperatures of 60°C, 100°C, and 125°C for aging times of 8 hours, 24 hours, 96 hours (4 days), and 216 hours (9 days). A calibration method was developed using Au, Al and Ni standards to establish precision and repeatability of the KPFM technique. Average CPDs and standard deviations for each metal were found and summarized.

Time resolved neutron detection will provide important information of MagLIF implosions. To aid the design of such detectors Lasnex has been used to simulate the neutron production rates for two MagLIF configurations. The results are shown in Fig 1 a) B=15 T, preheat=1.1 kJ, D₂ density=1.05 mg/cc and b) B=10 T, preheat=0.8 kJ, D₂ density=0.7 mg/cc.

For weapon safety assessments, Sandia has an interest in accurately predicting failure of pressure vessels at high temperature. In order to assess Sandia's predictive capability for these problems, a simplified validation problem for thermo-mechanical failure due to pressurization was developed and is referred to as the pipe bomb problem. In this study, several pipes were heated in a non-isothermal manner and pressurized until failure. The previous attempt to accurately predict the pipe bombs' failure pressures demonstrated a notable unconservative prediction. Due to this large bias in the simulation failure pressures toward higher pressures, we assumed that a mechanism driving failure or another aspect of the tests was missed in the original models. The goal of this work was to investigate potential sources of this bias focusing on geometric uncertainty and material model assumptions. As with the previous work, our simulations of the pipe bomb experiments using the BCJ material model over predicted the failure pressures. While success cannot be claimed for the simulated failure pressures, we believe we accurately identified the remaining sources of error in the simulations. Specifically, the temperature mapping algorithm and the geometry are believed to be the primary contributors to the errors. As a result, future work should focus on improving the temperature mapping algorithm and consider using temperature fields determined by a calibrated thermal model that includes convection. Additionally, CT scans of remaining portions of the pipe bomb material inner diameter should be taken to further understand the variability this unmachined surface introduced to the pipe bomb specimens.

Clean energy and sustainability, long at the core of the United States (U.S.) Department of Energy (DOE) mission and championed at Sandia National Laboratories (SNL), are reinforced in Executive Order (EO) 13834, Efficient Federal Operations. Though no longer in effect as of May 2018, EO 13693, Planning for Federal Sustainability in the Next Decade, is referenced throughout this document. DOE's Strategic Sustainability Performance Plan (SSPP) embodies the Department's sustainability commitment and establishes the foundation for DOE to meet the objectives of the EO. The SNL Site Sustainability Plan (SSP) is prepared annually to support DOE's Strategic Sustainability Performance Plan (SSPP) and the National Nuclear Security Administration's (NNSA) sustainability goals and broader sustainability program. Accordingly, the content of this SSP covers the SNL contributions toward meeting the DOE sustainability goals, including the DOE requirement to comply with EO 13834. This SSP fulfills the contractual requirement for National Technology & Engineering Solutions of Sandia, LLC (NTESS), the management and operating (M&O) contractor for SNL, to deliver an annual sustainability plan to the NNSA and Sandia Field Office (SFO). The SNL Environmental Management System (EMS) implements sustainable practices for enhancing environmental, energy, and transportation management performance. SNL's EMS is a quality-based system modeled on the Plan-Do-Check-Act structure for continuous improvement. The EMS is a part of SNL's Integrated Safety Management System and functions within the overall Laboratory Operating System. The SNL EMS is International Organization for Standardization (ISO) 14001 certified and incorporates all relevant federal, state, local, and DOE requirements. The EMS is coordinated and implemented through 20 environmental programs, five of which are included within the scope of this SSP: Air Quality Compliance (AQC); Materials; Sustainability & Pollution Prevention; Energy and Water; Fleet Services; and, Waste Management.

Energy policy can often be narrow and take a short-term view as well as beholden to public opinion as demonstrated by the early decommissioning of nuclear power plants (NPPs) in Germany and Belgium after the Fukushima Daiichi event. The subsequent pursuit of renewable electric power generating capacity should not lose sight of the value of technological diversity in an energy portfolio. Domestic market incentives have failed to maintain the U.S.'s technological diversity as demonstrated by the dwindling state of the nuclear power industry. The nuclear power industry faces many challenges, such as aging infrastructure, policy driven production disincentives, and licensing delays, which leave the nuclear power industry at a cross roads. However, there is an opportunity to identify both a socially beneficial technology mix which includes NPPs and corresponding strategies for retaining NPPs in the U.S. energy portfolio. This paper proposes three technical approach options to identify strategies to assist NPPs that will hopefully prove publicly unobtrusive, economically affordable, and potentially profitable.

The goal of this project, started in FY17, is to develop and execute methods of characterizing uncertainty in data products that are developed and distributed by the DOE Consequence Management (CM) Program. This report presents the results of uncertainty analyses performed in FY18 for additional scenarios of increased complexity, including different time phases and radionuclide source terms.

From July 24th -27th, 2018, Sandia National Laboratories (SNL) was conducting a series of explosive tests (referred to as Block VIII Tests) at Thunder Range. Thunder Range is an explosive testing range located on Kirtland Air Force Base and operated by SNL. The testing occurred on Range 7, a fragmentation range that is authorized for activities up to a maximum of 2,000 pounds net explosive weight (NEW). The maximum NEW for the Block VIII tests was 114 lbs. The specific management concern is that although the Thunder Range team identified controls to provide protection for essential personnel, those controls were not adequately evaluated before testing occurred. There were several controls in place at Thunder Range when the block VW test was executed. Engineered controls including Fire Control Point (FCP) placement, FCP structure design, and administrative controls involving communications. These controls were in place but not thoroughly evaluated for adequacy in meeting requirements related to sound pressure and fragments before the test was executed. Compliance with the remaining requirements was achieved. The lack of evaluation did not result in harm to personnel, equipment, or structures but was deemed as an opportunity to further understand how compliance with DOE-STD-1212-2012 could be better achieved with defensible evidence. The information provided in the remainder of this report discusses these controls and the deficiencies that contributed to this management concern.

The brochure highlighted Sandia program portfolios: nuclear deterrence, global security, national security programs, energy & homeland security, and, advanced science and technology. Funding and subcontract statistics are reviewed.

The Model Authorized Product Realization (MAP-R) project was a collaboration between Sandia National Laboratories (SNL) and Kansas City National Security Campus (KCNSC) to advance the Nuclear Security Enterprise's (NSE) ability to quantify the differences between the current drawing centric/drawing-based process and a part centric/model-based process. In short, MAP-R identified the key business benefits of the part centric model-based process using quantifiable data. MAP-R builds upon the past, but leverages current advances in technology, processes/standards, and the motivation of our current workforce to use a part-centric/model- based design and manufacturing method.

Coupling interests in small modular reactors (SMR) as efficient and effective method to meet increasing energy demands with a growing aversion to cost and schedule overruns traditionally associated with the current fleet of commercial nuclear power plants (NPP), SMRs are attractive because they offer a significant relative cost reduction to current-generation nuclear reactors-- increasing their appeal around the globe. Sandia's Global Nuclear Assurance and Security (GNAS) research perspective reframes the discussion around the "complex risk" of SMRs to address interdependencies between safety, safeguards, and security. This systems study provides technically rigorous analysis of the safety, safeguards, and security risks of SMR technologies. The aims of this research is three-fold. The first aim is to provide analytical evidence to support safety, safeguards, and security claims related to SMRs (Study Report Volume I). Second, this study aims to introduce a systems-theoretic approach for exploring interdependencies between the technical evaluations (Study Report Volume II). The third aim is to demonstrate Sandia's capability for timely, rigorous, and technical analysis to support emerging complex GNAS mission objectives.

An overview of experimental and computational studies of prompt secondary gamma production and transport, executed under the auspices of the Readiness in Technical Base and Facilities (RTBF) program, is presented. Relevant experiments at the Annular Core Research Reactor (ACRR) were conducted in the FY2012 -- FY2014 timeframe and pertain to the performance of various elemental calorimeters and the analytic fractionation of dose contributions to the calorimeter discs. In particular, the influence of the choice of prompt capture gamma production databases on the computed disc heating factors is discussed. Finally, the results of a polyurethane foam moderation experiment are detailed.

Silicon calorimeters have been used for active radiation dosimetry in the central cavity of the Annular Core Research Reactor (ACRR) for over a decade. Recently, there has been interest in using other materials for calorimetry to accurately measure the prompt gamma-ray energy deposition in the mixed neutron and gamma-ray environment. The calorimeters used in the ACRR use a thermocouple (TC) to measure the change in temperature of specific materials in the radiation environment. The temperature change is related to the instantaneous dose received by the material in a pulse-transient operation. SOLIDWORKS Simulation and ANSYS Mechanical were used to model the calorimeter and analyze the thermal behavior under pulse-transient conditions. This report compares the results from modeling to experimental results for selected calorimeter materials and radiation environments. These materials include bismuth, tin, zirconium, and silicon. Calorimeters assembled with each material were irradiated in the ACRR central cavity in the free- field, LB44, CdPoly, and PLG radiation environments. The neutronics code Monte-Carlo N- Particle (MCNP) was used to calculate the neutron and gamma-ray response of the calorimeter materials at the experimental locations in the central cavity. Different response tallies were used and found to give different results for the gamma-ray energy deposition. It was determined that performing the neutron/gamma-ray/electron transport in MCNP using the *F8 electron tally gave the overall best agreement with the experimental results. The *F8 tally, however, is much more computationally intensive than the neutron/gamma-ray transport calculations. Also, this report contains parametric analyses that examine the ways to improve the current design of the calorimeters. One finding from the parametric analysis was that the TC should be placed closer to the outer radius of the disks to obtain a measurement closer to the maximum temperature of the disk. Also, the parametric analysis showed that the most dominant mechanism of heat loss in the calorimeters is conduction through the alumina posts. In future designs, the conduction should be minimized to reduce the effect of heat loss on the measurements.

The goal of the DOE OE Energy Storage System Safety Roadmap is to foster confidence in the safety and reliability of energy storage systems. There are three interrelated objectives to support the realization of that goal: research, codes and standards (C/S) and communication/coordination. The objective focused on C/S is "To apply research and development to support efforts that refocused on ensuring that codes and standards are available to enable the safe implementation of energy storage systems in a comprehensive, non-discriminatory and science-based manner

This report is one of numerous initiatives launched to support and facilitate energy sector preparedness and resilience to extreme weather at national, regional and local levels. The U.S. Department of Energy's vision is a U.S. energy system that is reliable and resilient in the face of all hazards. The U.S. Department of Energy is committed to ensuring the resiliency of the U.S. energy infrastructure and systems through innovating technology development and deployment, enabling policy frameworks, robust analytical modeling, and assessment capabilities to address energy issues of national and regional importance.

In ultralow Pu analyses, the gold standard is thermal ionization mass spectrometry (TIMS), which requires pure sources to achieve its performance. This purity is achieved through step-wise purifications. In this work single, anion-exchange beads were trapped in the tubing to allow for dynamic solution cycling over the surface of the beads to improve the rates of metal complex uptake. Here, rates of Pu sorption on single ~900 μm SIR-1200 and ~620 μm Reillex-HPQ beads were determined for single beads trapped in a tube with syringe pump driven dynamic solution cycling over the bead, improving sorption and desorption rates. A static control was used as a comparison. Using ²³⁸Pu to enable facile activity-based measurements, rates were determined by measuring the residual Pu after contact with beads using liquid scintillation analysis (LSA) for fixed periods of time. Syringe pump driven dynamic solution cycling results in ~5 and ~15-fold improvements in the sorption rates for SIR-1200 and Reillex-HPQ. Impacts on desorption were also examined.

National security missions require understanding third-party software binaries, a key element of which is reasoning about how data flows through a program. However, vulnerability analysts protecting software lack adequate tools for understanding data flow in binaries. To reduce the human time burden for these analysts, we used human factors methods in a rolling discovery process to derive user-centric visual representation requirements. We encountered three main challenges: analysis projects span weeks, analysis goals significantly affect approaches and required knowledge, and analyst tools, techniques, conventions, and prioritization are based on personal preference. To address these challenges, we initially focused our human factors methods on an attack surface characterization task. We generalized our results using a two-stage modified sorting task, creating requirements for a data flow visualization. We implemented these requirements partially in manual static visualizations, which we informally evaluated, and partially in automatically generated interactive visualizations, which have yet to be integrated into workflows for evaluation. Our observations and results indicate that 1) this data flow visualization has the potential to enable novel code navigation, information presentation, and information sharing, and 2) it is an excellent time to pursue research applying human factors methods to binary analysis workflows.

Recent interest in topological quantum computing has driven research into topological nanowires, one-dimensional quantum wires that support topological modes, including Majorana fermions. Most topological nanowire designs rely on materials with strong spin-orbit coupling, such as InAs or InSb, used in combination with superconductors. It would be advantageous to fabricate topological nanowires with Si owing to its mature technology. However, the intrinsic spin-orbit coupling in Si is weak. One approach that could circumvent this material deficiency is to rotate the electron spins with nanomagnets. Here we perform detailed simulations of realistic Si/SiGe systems with an artificial spin-orbit gap induced by a nanomagnet array. Most of our results are generalizable to other nanomagnet-based topological nanowire designs. By studying several concrete examples, we gain insight into the effects of nanomagnet arrays, leading to design rules and guidelines. In particular, we develop a recipe for eliminating unwanted gaps that result from realistic nanomagnet designs. Lastly, we present an experimentally realizable design using magnets with a single polarization.

The adsorption of chemical warfare agents and their simulants by Zr (UiO-66) and rare-earth (Y, UiO-66-DOBDC analog)-based metal-organic frameworks (MOFs) is explored here using density functional theory. In particular, we investigate the role of linker functional group (OH, H) and metal atom identity on the binding energies of organophosphorous compounds. Commonly used cluster approximations for MOF secondary building units and various optimization constraints are compared with three-dimensional periodic results. An in-depth scan of potential binding sites and orientations reveals little effect due to metal identity, whereas the effect of linker functionalization depends on the substrate. This finding strongly suggests that full linkers and functional groups should be included in cluster models. Importantly, defect sites show considerably improved binding of organophosphorous compounds as compared to ideal clusters. Favorable binding is also demonstrated at two additional adsorption sites, ZrOH and μ3-OH, that likely play a role in the initial adsorption process. The results presented here portray the importance of including full three-dimensional pore structures in the adsorption process of organophosphorous compounds in MOFs; a critical first step in the degradation of these harmful chemicals.

Use of electrolytes, in the form of LiBH4/KBH4 and LiI/KI/CsI eutectics, is shown to significantly improve (by more than a factor of 10) both the dehydrogenation and full rehydrogenation of the MgH2/Sn destabilized hydride system and the hydrogenation of MgB2 to Mg(BH4)2. The improvement revealed that interparticle transport of atoms heavier than hydrogen can be an important rate-limiting step during hydrogen cycling in hydrogen storage materials consisting of multiple phases in powder form. Electrolytes enable solubilizing heavy ions into a liquid environment and thereby facilitate the reaction over full surface areas of interacting particles. The examples presented suggest that use of electrolytes in the form of eutectics, ionic liquids, or solvents containing dissolved salts may be generally applicable for increasing reaction rates in complex and destabilized hydride materials.

The fate of biological aerosols in the atmosphere depends on the unique and dynamic environmental conditions it is exposed to during transport. There exist many processes that can impact the effectiveness of an aerosol release, and its fate in the environment. Aerosol properties may be modified if biological particles that are released into the atmosphere interact with free radicals, volatile organic compounds(VOC), semi-volatile organic compounds, and inorganic gasphase compounds, such as NOx and SOx. Meteorological conditions such as ultraviolet(UV)- light, relative humidity(RH), and temperature have also been shown to affect biological aerosols, with interactions dependent on both the organism and aerosol's chemical make-up. Oxidation or secondary-organic aerosol (SOA) formations on the particle can also lead to changes in surface proteins and extra-cellular nucleic acids that may agent detection technologies, at a different rate than the infectivity of the agents. Once modified, agents may then be transported via many atmospheric processes such as deposition or incorporation into cloud condensation nuclei(CCN). Although these processes are known, it is unclear what the resulting form and potency ofthe bioaerosol may be after alteration by these processes.

Knowledge and foundational understanding of phenomena associated with the behavior of materials at the nanoscale is one of the key scientific challenges toward a sustainable energy future. Size reduction from bulk to the nanoscale leads to a variety of exciting and anomalous phenomena due to enhanced surface-to-volume ratio, reduced transport length, and tunable nanointerfaces. Nanostructured metal hydrides are an important class of materials with significant potential for energy storage applications. Hydrogen storage in nanoscale metal hydrides has been recognized as a potentially transformative technology, and the field is now growing steadily due to the ability to tune the material properties more independently and drastically compared to those of their bulk counterparts. The numerous advantages of nanostructured metal hydrides compared to bulk include improved reversibility, altered heats of hydrogen absorption/desorption, nanointerfacial reaction pathways with faster rates, and new surface states capable of activating chemical bonds. This review aims to summarize the progress to date in the area of nanostructured metal hydrides and intends to understand and explain the underpinnings of the innovative concepts and strategies developed over the past decade to tune the thermodynamics and kinetics of hydrogen storage reactions. These recent achievements have the potential to propel further the prospects of tuning the hydride properties at nanoscale, with several promising directions and strategies that could lead to the next generation of solid-state materials for hydrogen storage applications.

Gate-controllable spin-orbit coupling is often one requisite for spintronic devices. For practical spin field-effect transistors, another essential requirement is ballistic spin transport, where the spin precession length is shorter than the mean free path such that the gate-controlled spin precession is not randomized by disorder. In this letter, we report the observation of a gate-induced crossover from weak localization to weak anti-localization in the magneto-resistance of a high-mobility two-dimensional hole gas in a strained germanium quantum well. From the magneto-resistance, we extract the phase-coherence time, spin-orbit precession time, spin-orbit energy splitting, and cubic Rashba coefficient over a wide density range. The mobility and the mean free path increase with increasing hole density, while the spin precession length decreases due to increasingly stronger spin-orbit coupling. As the density becomes larger than ∼6 × 1011 cm-2, the spin precession length becomes shorter than the mean free path, and the system enters the ballistic spin transport regime. We also report here the numerical methods and code developed for calculating the magneto-resistance in the ballistic regime, where the commonly used HLN and ILP models for analyzing weak localization and anti-localization are not valid. These results pave the way toward silicon-compatible spintronic devices.

We present an analytic band-to-trap tunneling model developed using the open boundary scattering approach. The new model explicitly includes the effect of heterojunction band offset, in addition to the well known electric field effect. Its analytic form enables straightforward implementation into TCAD device and circuit simulators. The model is capable of simulating both electric field and band offset enhanced carrier recombination due to the band-to-trap tunneling in the depletion region near a heterojunction. Simulation results of an InGaP/GaAs heterojunction bipolar transistor reveal that the proposed model predicts significantly increased base currents, because the hole-to-trap tunneling from the base to the emitter is greatly enhanced by the emitter base heterojunction band offset. The results compare favorably with experimental observations. The developed method can be applied to all one dimensional potentials which can be approximated to a good degree such that the approximated potentials lead to piecewise analytic wave functions with open boundary conditions.

We present an analytic band-to-trap tunneling model developed using the open boundary scattering approach. The new model explicitly includes the effect of heterojunction band offset, in addition to the well known electric field effect. Its analytic form enables straightforward implementation into TCAD device and circuit simulators. The model is capable of simulating both electric field and band offset enhanced carrier recombination due to the band-to-trap tunneling in the depletion region near a heterojunction. Simulation results of an InGaP/GaAs heterojunction bipolar transistor reveal that the proposed model predicts significantly increased base currents, because the hole-to-trap tunneling from the base to the emitter is greatly enhanced by the emitter base heterojunction band offset. The results compare favorably with experimental observations. The developed method can be applied to all one dimensional potentials which can be approximated to a good degree such that the approximated potentials lead to piecewise analytic wave functions with open boundary conditions.

Acoustic-structure coupling can substantially alter the frequency response of air-filled structures. Coupling effects typically manifest as two resonance peaks at frequencies above and below the resonant frequency of the uncoupled structural system. In this study, a dynamic substrucuring approach is applied to a simple acoustic-structure system to expose how the system response depends on the damping in the acoustic subsystem. Parametric studies show that as acoustic damping is increased, the frequencies and amplitudes of the coupled resonances in the structural response undergo a sequence of changes. For low levels of acoustic damping, the two coupled resonances have amplitudes approximating the corresponding in vacuo resonance. As acoustic damping is increased, resonant amplitudes decrease dramatically while the frequency separation between the resonances tends to increase slightly. When acoustic damping is increased even further, the separation of the resonant frequencies decreases below their initial separation. Finally, at some critical value of acoustic damping, one of the resonances abruptly disappears, leaving just a single resonance. Counterintuitively, increasing acoustic damping beyond this point tends to increase the amplitude of the remaining resonance peak. Finally, these results have implications for analysts and experimentalists attempting to understand, mitigate, or otherwise compensate for the confounding effects of acoustic-structure coupling in fluid-filled test structures.

While the concept of aggregating and controlling renewable distributed energy resources (DERs) to provide grid services is not new, increasing policy support of DER market participation has driven research and development in algorithms to pool DERs for economically viable market participation. Sandia National Laboratories recently undertook a three-year research program to create the components of a real-world virtual power plant (VPP) that can simultaneously participate in multiple markets. Our research extends current state-of-the-art rolling horizon control through the application of stochastic programming with risk aversion at various time resolutions. Our rolling horizon control consists of (1) day-ahead optimization to produce an hourly aggregate schedule for the VPP operator and (2) sub-hourly optimization for real-time dispatch of each VPP subresource. Both optimization routines leverage a two-stage stochastic program (SP) with risk aversion, and integrate the most up-to-date forecasts to generate probabilistic scenarios in real operating time. Our results demonstrate the benefits to the VPP operator of constructing a stochastic solution regardless of the weather. In more extreme weather, applying risk optimization strategies can dramatically increase the financial viability of the VPP. As a result, the methodologies presented here can be further tailored for optimal control of any VPP asset fleet and its operational requirements.

Total hemispherical emissivities are a commonly used property in radiative heat transfer analysis. Measurements made in the course of testing become far more useful to thermal analysts if they are compiled with a sufficient level of detail, and summarized in a manner that allows the most appropriate value or trend to be located quickly. This report collects emissivity measurements from recent years, made in the course of testing metallic surfaces at Sandia's Radiant Heat Test Facility, and compares them to a selection of previous summary documents. These measurements are organized by material type, surface finish, and degree of oxidation. The comparisons also consider the temperature dependence of total hemispherical emissivity. Materials considered include Inconel 600, SS304, 17-4PH SS, silicon carbide, and aluminum alloys. A limited selection of high-temperature paints and other surface coatings are also considered. Recommendations are made for frequency of measurements and level of detail in reporting emissivities in future test series. A more limited scope is recommended for the use of high-temperature paints at Sandia's Radiant Heat Test Facility; pre-oxidation of Inconel and stainless steel surfaces is preferred in many circumstances.

Abuse tests are designed to determine the safe operating limits of HEV\PHEV energy storage devices. Testing is intended to achieve certain worst-case scenarios to yield quantitative data on cell\module\pack response, allowing for failure mode determination and guiding developers toward improved materials and designs. Standard abuse tests with defined start and end conditions are performed on all devices to provide comparison between technologies. New tests and protocols are developed and evaluated to more closely simulate real world failure conditions. While robust mechanical models for vehicles and vehicle components exist, there is a gap for mechanical modeling of EV batteries. The challenge with developing a mechanical model for a battery is the heterogeneous nature of the materials and components (polymers, metals, metal oxides, liquids). Our work will provide empirical data on the mechanical behavior of batteries under compressive load to understand how a battery may behave in a vehicle crash scenario. This work is performed in collaboration with the U.S. Council for Automotive Research (USCAR) and Computer Aided Engineering of Batteries (CAEBAT). These programs have supported the design and development of a drop tower testing apparatus to close the gap between cell/string level testing and full scale crash testing with true dynamic rate effects.

Addressing the Greatest Challenges in Our Communities: Sandia National Laboratories (Sandia) is committed to being an informed, compassionate and contributing neighbor in our local communities. This commitment has been demonstrated throughout Sandia's history and is an enduring part of our future. New Mexico faces many challenges, including the highest childhood poverty rate in the United States. According to a recent community perception survey, the biggest issue facing Albuquerque is crime, followed by unemployment, and concerns that the educational system is poor. Lack of affordable housing and insufficient educational achievement are issues in the Bay Area near our Livermore site. In 2018, National Technology and Engineering Solutions of Sandia contributed $1.4M to non-profits and organizations that provide critical resources and services to address the greatest challenges in Sandia's communities.

Summary of community commitment funding allocations for 2018.

The Texas Tech University (TTU) research group is actively studying wind turbine wake development, as part of developing innovative wake control strategies to improve the performance of wind farms. The team has a set of eight ground lidars to perform field measurements at the Sandia National Laboratories SWiFT site. This document describes tests details including configurations, timeframe, hardware, and the required collaboration from the Sandia team. This test plan will facilitate the coordination between both TTU and the Sandia team in terms of site accessibility, staff training, and data sharing to meet the specific objectives of the tests.

Quasi-static time-series (QSTS) simulation provides an accurate method to determine the impact that new PV interconnections including control strategies would have on a distribution feeder. However, the QSTS computational time currently makes it impractical for use by the industry. A vector quantization approach [1- 2] leverages similarities in power flow solutions to avoid re-computing identical power flows resulting in significant time reduction. While previous work arbitrarily quantized similar power flow scenarios, this paper proposes a novel circuit-specific quantization algorithm to balance speed and accuracy. This sensitivity-based method effectively quantizes the power flow scenarios prior to running the quantized QSTS simulation. The results show vast computational time reduction while maintaining specified bounds for the error.

To determine risk of an electric shock to firefighter personnel due to contact with live parts of a damaged PV system, simulated PV arrays were constructed with multiple 'modules' connected to a central inverter. The results of this analysis demonstrate that ungrounded arrays are significantly safer than grounded arrays for reasonable module isolation resistances. Ungrounded arrays provide current hazards to personnel up to three orders of magnitude smaller than for a grounded array counterpart. While the size of the array does not affect the current hazard in grounded arrays for body resistances above 100,Ω, in ungrounded arrays, increased array size yields increased current hazards- considering that the overall fault current level is still significantly smaller than for grounded arrays. In both grounded and ungrounded arrays, the current hazard has a direct correlation to array voltage. Since the level of fault current in a grounded array can be significant, this work shows that the non- linearity of the array IV curve must be taken into account for body resistances below 600 Ω and array voltages above 1000V for accurate fault current determination. Although module and array isolation resistance is not a factor that modulates fault current in a grounded array, this resistance, Riso, has a significant effect on current hazard to the firefighter for ungrounded arrays.

Fast deployment of renewable energy resources in distribution networks, especially solar photovoltaic (PV) systems, have motivated the need for inverter-based voltage regulation. Integration studies are often necessary to fully understand the potential impacts of PV inverter settings on the various elements of the distribution system, including voltage regulators and capacitor banks. A year long quasi-static time series (QSTS) at second-level granularity provides a comprehensive assessment of these impacts, however the computational burden associated with running QSTS limits its applicability. This paper proposes a fast QSTS simulation technique capable of modeling the smart inverter dynamic VAR control functionality and accurately estimating the states of controllable elements including voltage regulators and capacitor banks at each time step. Consequently, the complex interactions between various legacy voltage regulation devices is also captured. The efficacy of the proposed algorithm is demonstrated on the IEEE 13-bus test case with a 98% reduction in computation time.

A computational study was performed to assess influences of geometric design parameters and material properties on thermally induced interfacial stresses within a packaged solar cell assembly. A Latin Hypercube Sampling approach was used, varying 36 total geometric, initial condition, and material property parameters representative of available solar cell designs, to assess the sensitivity of computed interfacial stresses to each input. Simulations consisted of a laminated 3D assembly of two cells connected by an interconnect ribbon, with resolution of the glass, encapsulant, ribbon, solder, cell, and backsheet, cycled through a temperature change of - 40°C to 85 °C. Geometry and mesh creation were automated to enable sampling over varying cell designs. The purpose of this study was to develop a methodology to investigate the interplay between cell designs and thermally induced stresses, particularly those occurring over component interfaces subject to delamination. Information on the expected drivers of interfacial stresses as well as the primary directions in which stresses arise will better define interface adhesion tests and inform accelerated stress testing to more completely characterize delamination phenomena.

This letter presents the concept of the Total Internal Reflection metasurface (TIR-MS) which supports the realization of structure-embedded subwavelength acoustic shields for elastic waves propagating in thin waveguides. The proposed metasurface design exploits extreme phase gradients, implemented via locally resonant elements, in order to achieve operating conditions that are largely beyond the critical angle. Such artificial discontinuity is capable of producing complete reflection of the incoming waves regardless of the specific angle of incidence. From a practical perspective, the TIR-MS behaves as a sound hard barrier that is impenetrable to long-wavelength modes at a selected frequency. The TIR metasurface concept is first conceived for a flat interface embedded in a rectangular waveguide and designed to block longitudinal S0-type guided modes. Then, it is extended to circular plates in order to show how enclosed areas can be effectively shielded by incoming waves. Given the same underlying physics, an equivalent dynamic behavior was also numerically and experimentally illustrated for flexural A0-type guided modes. This study shows numerical and experimental evidence that, when the metasurface is excited at the target frequency, significant vibration isolation can be achieved in the presence of waves having any arbitrary angle of incidence. These results open interesting paths to achieve vibration isolation and energy filtering in certain prototypical structures of interest for practical engineering applications.

As PV penetration on the distribution system increases, there is growing concern about how much PV each feeder can handle. A total of 14 medium-voltage distributions feeders from two utilities have been analyzed in detail for their individual PV hosting capacity and the locational PV hosting capacity at all the buses on the feeder. This paper discusses methods for analyzing PV interconnections with advanced simulation methods to study feeder and location-specific impacts of PV to determine the locational PV hosting capacity and optimal siting of PV. Investigating the locational PV hosting capacity expands the conventional analytical methods that study only the worst-case PV scenario. Previous methods are also extended to include single-phase PV systems, especially focusing on long single-phase laterals. Finally, the benefits of smart inverters with volt-var is analyzed to demonstrate the improvements in hosting capacity.

In relativistic electron beam diodes, the self-generated magnetic field causes electron-beam focusing at the center of the anode. Generally, plasma is formed all over the anode surface during and after the process of the beam focusing. In this work, we use visible-light Zeeman-effect spectroscopy for the determination of the magnetic field in the anode plasma in the Sandia 10 MV, 200 kA (RITS-6) electron beam diode. The magnetic field is determined from the Zeeman-dominated shapes of the Al III 4s–4p and C IV 3s–3p doublet emissions from various radial positions. Near the anode surface, due to the high plasma density, the spectral line-shapes are Stark-dominated, and only an upper limit of the magnetic field can be determined. The line-shape analysis also yields the plasma density. The data yield quantitatively the magnetic-field shielding in the plasma. In conclusion, the magnetic-field distribution in the plasma is compared to the field-diffusion prediction and found to be consistent with the Spitzer resistivity, estimated using the electron temperature and charge-state distribution determined from line intensity ratios.

As space programs increase in number and scope, there is an increasing need for radiation-hardened electronic devices and circuits. In particular, missions to high-radiation environments, such as Europa, would greatly benefit from improved radiation hardness in electronic devices. In pursuit of this goal, resistive memory (RRAM) devices were fabricated at SUNY Polytechnic Institute and evaluated for radiation hardness. Our objectives were to produce RRAM devices resistant to high levels of radiation damage and to demonstrate that these devices would improve mission lifetime in high-radiation environments. Furthermore, the underlying mechanisms of radiation were investigated to provide recommendations for radiation-hardening RRAM devices, which could be applied to any candidate RRAM devices being considered for space applications. Devices were fabricated using several fabrication approaches, including patterning by shadow mask, photolithography-based etching, and photolithography-based liftoff. In each of these cases, total ionizing dose (TID) effects and displacement damage dose (DDD) effects were measured. TID effects from exposure to a 60Co gamma source were not observed to cause changes in device resistance or switching parameters in any experiments, with each device tested to at least 20 Mrad(Si). DDD was measured as radiation-generated oxygen vacancies per cm³ since oxygen vacancies are generally considered to be the active species involved in switching these devices. The lowest DDD level that caused a device to change resistance state was 10²¹ vacancies per cm³, and most devices failed at 1022 vacancies per cm³. This is an extremely high DDD level, even for RRAM devices, which have been reported to fail in the range of 10¹⁷-10²⁰ vacancies per cm³. For comparison, an example flash memory device failed at 10¹⁵ vacancies per cm³. Vendor-fabricated devices with a similar composition to our own were also tested against TID and DDD. The vendor-fabricated devices did not exhibit changes due to TID, up to the tested level of 30 Mrad(Si). Meanwhile, vendor devices exhibited resistance state changes at 10²¹ vacancies per cm³, similar to our own devices. These results indicate that Ta0x-based RRAM devices may be particularly resilient to both TID and DDD effects. The very high tolerance to radiation effects is most likely due to the high intrinsic concentration of oxygen vacancies within our devices. Based on X-ray photoelectron spectroscopy (XPS) measurements, there are approximately 10²² oxygen vacancies per cm³ in our devices as deposited. Most devices failed when the radiation-induced vacancies reached this level, indicating suggesting that a high intrinsic vacancy concentration protects against lower levels of displacement damage. High vacancy concentration likely also protects against TID by facilitating leakage of trapped charge out of the oxide. The use of a thin switching oxide (25 nm Ta0_x, for our devices) is also expected to improve radiation hardness, as there is less room for charge trapping. Therefore, those wishing to produce very radiation-tolerant RRAM devices can probably achieve this by using a thin oxide that contains a high intrinsic concentration of oxygen vacancies. Our devices appear to be very tolerant of radiation effects, and would greatly increase the expected lifetime of a mission to Europa or another high-radiation target compared to flash memory devices. The similar radiation performance of vendor-fabricated devices is promising for adoption of RRAM devices as radiation-hardened memory devices for use in space. With continued commercial development of these devices, RRAM devices are strong candidates for next-generation memories that are inherently rad-hard.

The purpose of this memo is to analytically investigate the possible effects of thermal expansion on the electromechanical properties of the Sumida Components GmbH piezoelectric composite disk followed by experimental verification. Linear electromechanical, electrothermal, and thermomechanical constitutive law is assumed.

The Contraves Tower (Building 22-00) was built in 1960 as part of the initial expansion after the initial building at Tonopah Test Range (TTR). Located just west of the main road well to the south of the main Control Point (Area 3) at TTR, the tower was designed to hold a Contraves phototheodolite used in tracking and recording test units dropped from aircraft at the range. The tower was in steady use for the first decade of its existence, after which it was largely replaced by mobile Contraves units that could be placed at the stations as needed for particular tests. The Contraves Tower (Building 22-00) is a contributing element to the Sandia National Laboratories Tonopah Test Range Historic District. Building 22-00 supported TTR's role as an outdoor laboratory and was built in 1960 as part of the range's initial expansion to support increasing test demands. The building provided and represents a key tracking and data capture facility at TTR during its period of significance. The period of significance for the historic district is 1956-1989; 22-00 is a contributing element for 1960-1970.

We introduce the problem of scheduling observations on a constellation of remote sensors, to maximize the aggregate quality of the collections obtained. While automated tools exist to schedule remote sensors, they are often based on heuristic scheduling techniques, which typically fail to provide bounds on the quality of the resultant schedules. To address this issue, we first introduce a novel deterministic mixed-integer programming (MIP) model for scheduling a constellation of one to n satellites, which relies on extensive pre-computations associated with orbital propagators and sensor collection simulators to mitigate model size and complexity. Our MIP model captures realistic and complex constellation-target geometries, with solutions providing optimality guarantees. We then extend our base deterministic MIP model to obtain two-stage and three-stage stochastic MIP models that proactively schedule to maximize expected collection quality across a set of scenarios representing cloud cover uncertainty. Our experimental conclusions on instances of one and two satellites demonstrate that our stochastic MIP models yield significantly improved collection quality relative to our base deterministic MIP model. We further demonstrate that commercial off-the-shelf MIP solvers can produce provably optimal or near-optimal schedules from these models in time frames suitable for sensor operations.

We disclose unprecedented synergistic bimetallic Ni/Ag and Ni/Cu catalysts for regioselective γ,δ-diarylation of unactivated alkenes in simple ketimines with aryl halides and arylzinc reagents. The bimetallic synergy, which generates cationic Ni(II) species during reaction, promotes migratory insertion and transmetalation steps and suppresses β-H elimination and cross-coupling, the major side reactions that cause serious problems during alkene difunctionalization. This diarylation reaction proceeds at remote locations to imines to afford, after simple H+ workup, diversely substituted γ,δ-diaryl ketones that are otherwise difficult to access readily with existing methods.

Here, silicon detectors are an essential measurement tool for Inertial Confinement Fusion and High-Energy-Density Physics Applications, where temporal response of the order of nanoseconds is essential. Soft X-rays (<1 keV), Ultraviolet light, and low-energy electrons (<10 keV) can provide essential information in diagnosing rapidly changing plasma conditions, but reducing the detector dead layer is essential to improving detector response for these shallowly absorbed particles. This paper details a study of silicon detector surface preparation methods such as ion implant parameters, and the addition of a quantum 2D superlattice, to produce fast detectors that are highly sensitive to shallowly absorbed radiation. Measurements of visible light quantum efficiency, electron responsivity, and pulsed x-ray response indicate that detectors with a 2-layer superlattice enjoy a significant benefit over equivalent detectors using an ion implant at the illuminated surface.

Here, the feasibility of Neumann series expansion of Maxwell’s equations in the electrostatic limit is investigated for potentially rapid and approximate subsurface imaging of geologic features proximal to metallic infrastructure in an oilfield environment. While generally useful for efficient modeling of mild conductivity perturbations in uncluttered settings, we raise the question of its suitability for situations, such as oilfield, where metallic artifacts are pervasive, and in some cases, in direct electrical contact with the conductivity perturbation on which the Neumann series is computed. Convergence of the Neumann series and its residual error are computed using the hierarchical finite element framework for a canonical oilfield model consisting of an “L” shaped, steel-cased well, energized by a steady state electrode, and penetrating a small set of mildly conducting fractures near the heel of the well. For a given node spacing h in the finite element mesh, we find that the Neumann series is ultimately convergent if the conductivity is small enough - a result consistent with previous presumptions on the necessity of small conductivity perturbations. However, we also demonstrate that the spectral radius of the Neumann series operator grows as ~ 1/h, thus suggesting that in the limit of the continuous problem h → 0, the Neumann series is intrinsically divergent for all conductivity perturbation, regardless of their smallness. The hierarchical finite element methodology itself is critically analyzed and shown to possess the h² error convergence of traditional linear finite elements, thereby supporting the conclusion of an inescapably divergent Neumann series for this benchmark example. Application of the Neumann series to oilfield problems with metallic clutter should therefore be done with careful consideration to the coupling between infrastructure and geology. Here, the methods used here are demonstrably useful in such circumstances.

The negative thermal expansion (NTE) material Zr2(WO4)(PO4)2 has been investigated for the first time within the framework of the density functional perturbation theory (DFPT). The structural, mechanical, and thermodynamic properties of this material have been predicted using the Perdew, Burke and Ernzerhof for solid (PBEsol) exchange-correlation functional, which showed superior accuracy over standard functionals in previous computational studies of the NTE material α-ZrW2O8. The bulk modulus calculated for Zr2(WO4)(PO4)2 using the Vinet equation of state at room temperature is K0 = 63.6 GPa, which is in close agreement with the experimental estimate of 61.3(8) at T = 296 K. The computed mean linear coefficient of thermal expansion is -3.1 × 10-6 K-1 in the temperature range ∼0-70 K, in line with the X-ray diffraction measurements. The mean Grüneisen parameter controlling the thermal expansion of Zr2(WO4)(PO4)2 is negative below 205 K, with a minimum of -2.1 at 10 K. The calculated standard molar heat capacity and entropy are CP0 = 287.6 and S0 = 321.9 J·mol-1·K-1, respectively. The results reported in this study demonstrate the accuracy of DFPT/PBEsol for assessing or predicting the relationship between structural and thermomechanical properties of NTE materials.

We performed a systematic study of the threshold displacement energy (E_d) in metallic uranium as a function of both the recoil direction and temperature using Molecular Dynamics simulations. We developed a novel orientation sampling scheme that utilizes crystallographic symmetrical geodesic grids to select directions from the orientation fundamental zone to study the directional dependency. Additionally, we studied the temperature dependency by considering both the α-uranium phase, corresponding to the ground state for temperatures ranging from 0 K to 600 K, and the γ-uranium phase, corresponding to high-temperature state for temperatures above 900 K. In this study, we compared several definitions of the threshold energy: a direction-specific threshold displacement energy (E_d (θ,Φ)), an angle-averaged threshold energy ($E_d^{ave}$), a production probability threshold displacement energy ($E_d^{pp}$), and a defect count threshold displacement energy ($E_d^{dc}$). The direction-specific threshold displacement energies showed large angular anisotropy and variations in E_d results in accordance with crystallographic considerations. Specifically, preferred defect channeling directions were observed in the [120], [1$\bar{2}$0], [1$\bar{1}$1] directions for the α-uranium, and [001], [111] directions for the γ-uranium. The production probability threshold displacement energy ($E_d^{pp}$) is calculated as approximately 99.2659 eV at 10 K (α-U), 103.4980 eV at 300 K (α-U), 76.0915 eV at 600 K (α-U), and 42.9929 eV at 900 K (γ-U). With exception of those calculated at 10 K, threshold displacement energies decrease with increasing temperature. Analyses of the stable defect structures showed that the most commonly observed interstitial configuration in α-uranium consists of a ( 0 1 0 ) dumbbell-like interstitial; while in γ-uranium no preferential defect configuration could be identified due to thermally-induced lattice instabilities at the elevated temperatures.

All future high-efficiency engines will have fuel directly sprayed into the engine cylinder. Engine developers agree that a major barrier to the rapid development and design of these high-efficiency, clean engines is the lack of accurate fuel spray computational fluid dynamic (CFD) models. The spray injection process largely determines the fuel-air mixture processes in the engine, which subsequently drives combustion and emissions in both direct-injection gasoline and diesel systems. More predictive spray combustion models will enable rapid design and optimization of future high-efficiency engines, providing more affordable vehicles and also saving fuel.

The DOE project for Co-Optimization of Fuels and Engines seeks to define both fuel properties and engine hardware to create cleaner and more fuel-efficient engines. Fuel spray technologies are central to this goal as the spray injection determines the combustible mixtures formed within the engine. Sprays are known to affect bum rate and efficiency, particulate formation and emissions, as well as temperature and engine knock sites. Computational fluid dynamic models must predict complicated interaction between plumes and vaporization to be useful as a design tool for industry. Changes in fuel properties are expected to affect fuel delivery. While Co-Optima fuels may be selected for chemical criteria, such as high octane number rating, an understanding of how the physical properties affect spray performance is necessary to optimize fuel delivery. Many of the selected Co-Optima fuels have properties that are different than standard gasoline, requiring investigations for their performance. A new continuous-flow spray chamber facility has been completed, offering capability to control the pressure and temperature of the gases at engine-relevant conditions at the time of injection as well as a massive increase in data throughput. Direct-injection multi-hole gasoline sprays for different Co-Optima fuels are investigated in this chamber.

This report outlines a process for the deterministic calibration of MAMBA using the computational toolkit Dakota. The tools and processes for deterministic calibration have been built and are laid out in this report. While completing this milestone, issues emerged with MAMBA that resulted in delays. The consequences for these difficulties to the calibration process are briefly discussed. The report concludes with an outline of a path forward for Bayesian calibration. The Bayesian calibration will be performed next year. This process was laid out by Benjamin Collins, Robert Salko, and Adam Hetzler.

This report describes the results from a series of tests of surrogate pressurized water reactor (PWR) nuclear fuel assemblies in a rail cask during various modes of transportation and cask handling conducted between June and October 2017. The primary purpose of the tests was to measure strain and acceleration on surrogate fuel rods when the assemblies are subjected to normal conditions of transport (NCT) within the Equipos Nucleares, S.A. (ENSA) UNiversal (ENUN) 32P cask. Acceleration on the cask basket, the cask, the cask cradle, and the transport platforms were also measured. A summary of the test details, logistics and operations for performing the tests is included.

We provide a comprehensive overview of mixed integer programming formulations for the unit commitment problem (UC). UC formulations have been an especially active area of research over the past twelve years, due to their practical importance in power grid operations, and this paper serves as a capstone for this line of work. We additionally provide publicly available reference implementations of all formulations examined. We computationally test existing and novel UC formulations on a suite of instances drawn from both academic and real-world data sources. Driven by our computational experience from this and previous work, we contribute some additional formulations for both production upper bound and piecewise linear produc- tion costs. By composing new UC formulations using existing components found in the literature and new components introduced in this paper, we demonstrate that performance can be significantly improved – and in the process, we identify a new state-of-the-art UC formulation.

Redox cycles of doped calcium manganite perovskites (CaMnO3−δ) are studied for cost-effective thermochemical energy storage at temperatures up to 1000 °C for concentrating solar power and other applications. If the thermodynamics and kinetics for heat-driven reduction can be tailored for high temperatures and industrially accessible low O2 partial pressures (PO2⩾10-4 bar), perovskite redox cycles can offer high specific energy storage at temperatures much higher than state-of-the-art molten-salt subsystems. To this end, a range of A-site and B-site doped CaMnO3−δ were screened for their reducibility at 900 °C and PO2≈10-4 bar via thermogravimetric analysis. For compositions with high reducibility, notably A-site doped Ca1−xSrxMnO3−δ (x=0.05 and 0.10) and B-site doped CaCryMn1−yO3−δ (y=0.05 and 0.10), oxygen non-stoichiometry δ with respect to temperature and PO2 were measured and used to fit thermodynamic parameters of a two-reaction, point-defect model of the redox process for the two prominent crystalline phases (orthorhombic and cubic) that the perovskites occupy during the cycle. The fits compare favorably to differential scanning calorimetry measurements with the magnitude of the overall reduction enthalpies decreasing as the degree of reduction increases and the perovskites shift from orthorhombic to cubic crystalline phases. Based on thermodynamic limits, redox cycles of both Ca1−xSrxMnO3−δ compositions between air at 500 °C and PO2≈10-4 bar at 900 °C can store and release up to ≈700 kJ kg−1 with over 50% of the total energy stored as chemical energy. This is approximately 140 kJ kg−1 more chemical energy than the thermodynamic limits for CaCryMn1−yO3−δ compositions under the same cycle conditions. Approaching these thermodynamic limits for the specific energy storage of these redox cycles in a concentrating solar plant requires fast kinetics for perovskite reduction in the solar receiver and for reoxidation in the heat recovery reactor. Isothermal packed-bed redox cycling experiments of Ca1−xSrxMnO3−δ and CaCryMn1−yO3−δ compositions at temperatures up to 1000 °C show that reoxidation is fast compared to reduction. Thus, specific thermochemical energy storage is limited by residence times available for high-temperature reduction. The Sr-doped compositions approach higher fractions (≈90% or more) of the specific energy storage equilibrium limit after 300 s of reduction in the packed bed configuration above 800 °C and completely reoxidize in ⩽20 s in air. Non-isothermal cycling with heating from 500 °C to 900 °C in low PO2≈10-4 bar and subsequent reoxidation during cooling in air back to 500 °C demonstrate excellent chemical stability over 1000 cycles for all doped CaMnO3−δ compositions tested. The results suggest that these redox cycles may offer a viable energy storage subsystem with long-term stability for future concentrating solar plants and other high-temperature energy storage applications.

Hydrologic exchange is a critical mechanism that shapes hydrological and biogeochemical processes along a river corridor. Because of limitations in field accessibility, computational demand, and complexities of geomorphology and subsurface geology, full three-dimensional modelling studies to quantify hydrologic exchange fluxes (HEFs) have been limited mostly to local-scale applications. At reach scales, although surface flow conditions and subsurface physical properties are well-known factors that modulate hydrologic exchanges, quantitative measures that can describe the effects of these factors on the strength and direction of such exchanges do not exist. To address this issue, we developed a one-way coupled surface and subsurface water flow model using the commercial computational fluid dynamics (CFD) software STAR-CCM+ and applied it to simulate HEFs in a 7-km long reach along the main stem of the Columbia River in the United States. The model was validated against flow velocity measurements from an acoustic Doppler current profiler in the river, vertical HEFs estimated from a set of temperature profilers installed across the riverbed, and simulations from a reactive transport model. The validated model then was employed to systematically investigate how HEFs could be influenced by surface water fluid dynamics, subsurface structures, and hydrogeological properties. Our results suggest that reach-scale HEFs are dominated primarily by the thickness of the riverbed alluvium layer, and then by the alluvium permeability, the depth of the underlying impermeable layer, and the pressure boundary condition. Our results also elucidate the scale dependence of HEFs on fluid dynamics that can be captured only by three-dimensional CFD models. That is, while the net HEFs over the entire 7-km domain are not significantly influenced by surface water dynamics pressure, the dynamic pressure induced by fluid dynamics can lead to more than 15% in net HEFs for a river section of a few hundred metres.

Anthrax toxin consists of a cation channel and two protein factors. Translocation of the anthrax protein factors from endosomal to the cytosolic compartment is a complex process which utilizes the cation channel. An atomically detailed understanding of the function of the anthrax translocation machinery is incomplete. We report atomically detailed simulations of the lethal factor and channel mutants. Kinetic and thermodynamic properties of early events in the translocation process are computed within the Milestoning theory and algorithm. Several mutants of the channel illustrate that long-range electrostatic interactions provide the dominant driving force for translocation. No external energy input is required because the lower pH in the endosome relative to the cytosol drives the initial translocation process forward. Channel mutants with variable sizes cause smaller effects on translocation events relative to charge manipulations. Comparison with available experimental data is provided.

The laser damage thresholds of optical coatings can degrade over time due to a variety of factors, including contamination and aging. Optical coatings deposited using electron beam evaporation are particularly susceptible to degradation due to their porous structure. In a previous study, the laser damage thresholds of optical coatings were reduced by roughly a factor of two from 2013 to 2017. The coatings in question were high reflectors for 1054 nm that contained SiO₂ and HfO₂ and/or TiO₂ layers, and they were stored in sealed PETG containers in a class 100 cleanroom with temperature control. At the time, it was not certain whether contamination or thin film aging effects were responsible for the reduced laser damage thresholds. Therefore, to better understand the role of contamination, the coatings were recleaned and the laser damage thresholds were measured again in 2018. Here, the results indicate that contamination played the most dominant role in reducing the laser damage thresholds of these optical coatings, even though they were stored in an environment that was presumed to be clean.