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At least 1,225 records · Page 68

Alternative Crucibles for U-Mo Microwave Melting

The crucibles used currently for microwave melting of U-Mo alloy at the Y-12 Complex contain silicon carbide (SiC) in a mullite (3Al 2 O 3 -2SiO 2 ) matrix with an erbia coating in contact with the melt. Due to observed silicon contamination, Pacific Northwest National Laboratory has investigated alternative crucible materials that are susceptible to microwave radiation and are chemically compatible with molten U-Mo at 1400 1500C. Recommended crucibles for further testing are: 1) high-purity alumina (Al 2 O 3 ); 2) yttria-stabilized zirconia (ZrO 2 ); 3) a composite of alumina and yttria-stabilized zirconia; 4) aluminum nitride (AlN). Only AlN does not require an erbia coating. The recommended secondary susceptor, for heating at low temperature, is SiC in a “picket fence” arrangement.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

RePED 250: Manufacturing and Market Analysis of High-Temperature Alternators

The novel repetitive pulsed electric drill 250 (RePED 250) has the potential to greatly lower the costs and drilling times of geothermal projects. This tool discharges electric pulses through hard rock formations, shattering the rock in tension and allowing it to be quickly removed. One hurdle in bringing this technology to market is the RePED 250 downhole alternator. This component is essential for supplying power to the electronic drilling tool. There are currently no downhole tools on the market that meet the RePED 250 alternator's high temperature and power requirements. This report focuses on the path to commercialization for this novel alternator technology being developed as part of the RePED 250 project. One aim of this work is to identify the geothermal market size for the RePED 250 alternator, as well as other potential markets for this technology outside of geothermal. The geothermal market is very small, with only approximately 13 wells drilled in the United States each year. The worldwide market is several times this size and growing each year. The ability of the RePED 250 technology to drastically reduce the cost of geothermal projects may also lead to an increase in this market size. Technology developed for the high-temperature, high-power RePED 250 alternator can also be used to create high-temperature and high-power motors. These motors and alternators will have potential applications in oil and gas drilling, a $300 billion dollar industry in the United States alone, as well as in more distant industries such as aircraft, weapon systems, space exploration, and electric vehicles. Other aspects of the RePED 250 alternator's path to commercialization are also analyzed, including the supply chain for production materials and potential manufacturing methods. The supply chain and manufacturing practices for low-temperature motors and alternators are well established and require relatively minor changes for the high-temperature and high-power RePED 250 alternator. Sourcing for high-temperature materials has been identified, as well as potential supply chain risks. These most notably include electrical steel and high-temperature samarium cobalt (SmCo) magnets. Overall, these risks are not expected to be significant at the likely manufacturing scale required for the RePED 250.

15 GEOTHERMAL ENERGY↗

Cost/benefit trade-offs for reducing the energy consumption of commercial air transportation (RECAT)

A study has been performed to evaluate the opportunities for reducing the energy requirements of the U.S. domestic air passenger transport system through improved operational techniques, modified in-service aircraft, derivatives of current production models, or new aircraft using either current or advanced technology. Each of the fuel-conserving alternatives has been investigated individually to test its potential for fuel conservation relative to a hypothetical baseline case in which current, in-production aircraft types are assumed to operate, without modification and with current operational techniques, into the future out to the year 2000.

Gobetz, F. W.↗

A Method for Monitoring Deposition at a Solid Cathode in an Electrorefiner for a Two-Species System Using Electrode Potentials

Currently, process monitoring of spent nuclear fuel electrorefining relies upon sampling and destructive analysis methods coupled with extrapolative thermodynamic process models for non-interrupted operations. Corrections to those models are performed infrequently, jeopardizing both the control of the process and safeguarding of nuclear material. Furthermore, the timeliness of obtaining the results is inadequate for application of international safeguards protocol. Alternatively, a system that dynamically utilizes electrical data such as electrode potentials and cell current can hypothetically be used to achieve real-time process monitoring and more robust control as well as improved safeguards. Efforts to develop an advanced model of the electrorefiner to date have focused on a forward modeling approach by using feed and salt compositions to determine the product composition, cell current and electrode potential response. Alternatively, an inverse model was developed, and reported here, to predict the product deposition rates on a cathode using the cell current, cathode potential, and fundamental relations of electrochemistry. The model was applied to the following cases: pure uranium deposition, co-deposition of uranium and plutonium, and co-deposition of uranium and zirconium. The deposition rates predicted by the inverse model were compared to those of a forward model, ERAD.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

Engineering Upgrades to the Radionuclide Aerosol Sampler/Analyzer for the CTBT International Monitoring System

The Radionuclide Aerosol Sampler/Analyzer (RASA) is an automated aerosol collection and analysis system designed by Pacific Northwest National Laboratory in the 1990’s and is deployed in several locations around the world as part of the International Monitoring System (IMS) required under the Comprehensive Nuclear-Test-Ban Treaty (CTBT). The utility of such an automated system is the reduction of human intervention and the production of perfectly uniform results. However, maintainability and down time issues threaten this utility, even for systems with over 90% data availability. Engineering upgrades to the RASA are currently being pursued to address these issues, as well as Fukushima lessons learned. Current work includes a new automation control unit, and other potential improvements such as alternative detector cooling and sampling options are under review. This paper presents the current state of upgrades and improvements under investigation

Forrester, Joel B.↗

Laser-Based Means for Accelerating Nuclear Decay Rate

This project aims to replicate and build upon a reported series of results whereby nuclear decay of unstable species has been accelerated under laser irradiation in the presence of resonantly excited plasmonic nanoparticles. We are currently utilizing a laser system similar to that used within these reports as well as optimizing nanoparticle solution environments in an attempt to replicate reported results or provide alternative pathways that may explain some perceived discrepancies. The current work is being performed with equipment and techniques currently available at SRNL, including nanoparticle synthesis and pulsed lasers for plasmon excitation. The results of these experiments could provide quantitative data that can be used to resolve the discrepancies in the calculations and better estimate the ultimate utility of the process. If verified, this would represent a pathway for using readily available and scalable technology to reduce the long-term radiological storage requirements of certain forms of nuclear waste.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

Miniature Biosensor with Health Risk Assessment Feedback

Heart rate (HR) monitoring is a medical requirement during exercise on the International Space Station (ISS), fitness tests, and extravehicular activity (EVA); however, NASA does not currently have the technology to consistently and accurately monitor HR and other physiological data during these activities. Performance of currently available HR monitor technologies is dependent on uninterrupted contact with the torso and are prone to data drop-out and motion artifact. Here, we seek an alternative to the chest strap and electrode based sensors currently in use on ISS today. This project aims to develop a high performance, robust earbud based biosensor with focused efforts on improved HR data quality during exercise or EVA. A health risk assessment algorithm will further advance the goals of autonomous crew health care for exploration missions.

Hanson, Andrea↗

A statistical model for telecommunication link design

An evaluation is conducted of the current telecommunication link design technique and a description is presented of an alternative method, called the probability distribution method (PDM), which is free of the disadvantages of the current technique while retaining its advantages. The PDM preserves the simplicity of the design control table (DCT) format. The use of the DCT as a management design control tool is continued. The telecommunication link margin probability density function used presents the probability of achieving any particular value of link performance. It is, therefore, possible to assess the performance risk and other tradeoffs.

Yuen, J. H.↗

Simulation of Line Profiles of the Krypton Spectra Emitted by the Plasma of Current Sheets

Line profiles of the krypton spectra emitted by the plasma of current sheets are simulated. Current sheets are formed under the impact of magnetic fields with singular X-lines. The spectral line profiles are calculated by the method of the energy matrix diagonalization of an atom in an electric field. The dependence of the behavior of the line profiles on the parameters of an alternating electric field arising inside the plasma of current sheets and the dependence of these profiles on the plasma temperature are investigated. The criteria which allow one to reveal spectral lines serving as the indicators of the appearance of anomalous electric fields inside current sheets are suggested.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Assessment of the Performance of Hydrofluoroolefins, Hydrochlorofluoroolefins, and Halogen-Free Foam Blowing Agents in Cellular Plastic Foams

Oak Ridge National Laboratory has conducted a literature search to identify relevant information available on alternative materials and technologies that are proposed for foam blowing agents applications. For comparison, similar information was collected for available hydrofluorocarbons (HFC), hydrofluoroolefin (HFO), and hydrochlorofluoroolefins (HCFO) materials. The publicly available literature was analyzed and assessed for technical accuracy for each alternative, and a gap analysis was conducted to understand if additional studies are required to fully assess the viability of an alternative. In assessing these alternatives, this project focused on relevant performance and safety attributes. The performance attributes collected include insulation value per unit thickness, which impacts energy usage of buildings and insulated equipment such as refrigerators. We also assessed the impact of blowing agents on foam mechanical properties and flammability characteristics, and the ability of current processing equipment and techniques to utilize these alternatives. Diffusion of blowing agents through foam cells and its impact on foam aging was also examined. The applications covered in this study are spray foam, boardstock, panels, and appliances. Some of the most relevant findings are summarized below.

36 MATERIALS SCIENCE↗

Assessment of Alternative Fueling Infrastructure in the United States

NHTSA uses the Corporate Average Fuel Economy (CAFE) Model to analyze potential CAFE standards and their impact on emissions and vehicle fleet composition. The CAFE model analyzes the application of potential technologies to the current automotive industry vehicle fleet to determine the feasibility of future CAFE standards and the associated costs and benefits of the standards. A significant portion of the engineering input development is related to the effectiveness (energy consumption reduction) of each fuel-saving technology and the combination of several fuel-saving technologies, including AFVs. The purpose of this report is to deepen NHTSA's understanding of alternative fueling infrastructure and its potential impact on the adoption of alternative fuel vehicles (AFVs) so that AFVs can be more accurately and comprehensively incorporated into the CAFE Model. This report analyzes the current state of alternative fueling infrastructure in the United States and its relationship to the light-, medium-, and heavy-duty AFV markets; explores the costs associated with alternative fueling infrastructure; investigates trends driving the deployment of alternative fueling infrastructure; explores how the adoption of various vehicle and fuel technologies may look in the future; and analyzes the evolution of alternative fueling corridors.

33 ADVANCED PROPULSION SYSTEMS↗

Analysis of strategic environmental assessment in Taiwan energy policy and potential for integration with life cycle assessment

Highlights: • An innovative strategic environmental assessment process integrated with life cycle assessment. • A number of shortcomings of the current SEA process were identified. • Proposals were made by which use of LCA could greatly improve SEA. Strategic environmental assessment (SEA) has been implemented in many policies in the European Union since 2001. In Taiwan, SEA has been implemented for 28 cases since 2001, which includes various types of policies. National energy policy is the most challenging type. There are three most important steps in SEA process: alternative planning, scoping, and impact assessment. However, the current limitation of method application affects the effectiveness of SEA. In this case, life cycle assessment (LCA) is integrated with SEA for clarifying the role of LCA in whole SEA process. The method of combining LCA and SEA has been developed and is applied in a case of Taiwan's energy policy. Benefits from LCA in alternative planning, scoping, and impact assessment steps are explored. Finally, suggestions for enhancing LCA's application, for scoping operation, and for the improvement of SEA are proposed.

54 ENVIRONMENTAL SCIENCES↗

A New Computational Method for Membrane Compressibility: Bilayer Mechanical Thickness Revisited

Because lipid bilayers can bend and stretch in ways similar to thin elastic sheets, physical models of bilayer deformation have utilized mechanical constants such as the moduli for bending rigidity (κ C ) and area compressibility (K A ). However, the use of these models to quantify the energetics of membrane deformation associated with protein-membrane interactions, and the membrane response to stress is often hampered by the shortage of experimental data suitable for the estimation of the mechanical constants of various lipid mixtures. Although computational tools such as molecular dynamics simulations can provide alternative means to estimate K A values, current approaches suffer significant technical limitations. Here, in this study, we present a novel, to our knowledge, computational framework that allows for a direct estimation of K A values for individual bilayer leaflets. The theory is based on the concept of elasticity and derives K A from real-space analysis of local thickness fluctuations sampled in molecular dynamics simulations. We explore and validate the model on a large set of single and multicomponent bilayers of different lipid compositions and sizes, simulated at different temperatures. The calculated bilayer compressibility moduli agree with values estimated previously from experiments and those obtained from a standard computational method based on a series of constrained tension simulations. We further validate our framework in a comparison with an existing polymer brush model and confirm the polymer brush model’s predicted linear relationship with proportionality coefficient of 24, using elastic parameters calculated from the simulation trajectories. The robustness of the results that emerge from the method allows us to revisit the origins of the bilayer mechanical (compressible) thickness and in particular its dependence on acyl-chain unsaturation and the presence of cholesterol.

59 BASIC BIOLOGICAL SCIENCES↗

Catalysis as an Enabling Science for Sustainable Polymers

The replacement of current petroleum-based plastics with sustainable alternatives is a crucial but formidable challenge for the modern society. Catalysis presents an enabling tool to facilitate the development of sustainable polymers. This review provides a system-level analysis of sustainable polymers and outlines key criteria with respect to the feedstocks the polymers are derived from, the manner in which the polymers are generated, and the end-of-use options. Specifically, we define sustainable polymers as a class of materials that are derived from renewable feedstocks and exhibit closed-loop life cycles. Among potential candidates, aliphatic polyesters and polycarbonates are promising materials due to their renewable resources and excellent biodegradability. The development of renewable monomers, the versatile synthetic routes to convert these monomers to polyesters and polycarbonate, and the different end-of-use options for these polymers are critically reviewed, with a focus on recent advances in catalytic transformations that lower the technological barriers for developing more sustainable replacements for petroleum-based plastics.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Cooling the motion of diamond nanocrystals in a magneto-gravitational trap in high vacuum

Levitated diamond nanocrystals with nitrogen-vacancy (NV) centres in high vacuum have been proposed as a unique system for experiments in fundamental quantum mechanics, including the generation of large quantum superposition states and tests of quantum gravity. This system promises extreme isolation from its environment while providing quantum control and sensing through the NV centre spin. While optical trapping has been the most explored method of levitation, recent results indicate that excessive optical heating of the nanodiamonds under vacuum may make the method impractical with currently available materials. Here, we study an alternative magneto-gravitational trap for diamagnetic particles, such as diamond nanocrystals, with stable levitation from atmospheric pressure to high vacuum. Magnetic field gradients from permanent magnets confine the particle in two dimensions, while confinement in the third dimension is gravitational. Furthermore, we demonstrate that feedback cooling of the centre-of-mass motion of a trapped nanodiamond cluster results in cooling of one degree of freedom to less than 1 K.

36 MATERIALS SCIENCE↗

United polarizable multipole water model for molecular mechanics simulation

We report the development of a united AMOEBA (uAMOEBA) polarizable water model, which is computationally 3–5 times more efficient than the three-site AMOEBA03 model in molecular dynamics simulations while providing comparable accuracy for gas-phase and liquid properties. In this coarse-grained polarizable water model, both electrostatic (permanent and induced) and van der Waals representations have been reduced to a single site located at the oxygen atom. The permanent charge distribution is described via the molecular dipole and quadrupole moments and the many-body polarization via an isotropic molecular polarizability, all located at the oxygen center. Similarly, a single van der Waals interaction site is used for each water molecule. Hydrogen atoms are retained only for the purpose of defining local frames for the molecular multipole moments and intramolecular vibrational modes. The parameters have been derived based on a combination of ab initio quantum mechanical and experimental data set containing gas-phase cluster structures and energies, and liquid thermodynamic properties. For validation, additional properties including dimer interaction energy, liquid structures, self-diffusion coefficient, and shear viscosity have been evaluated. The results demonstrate good transferability from the gas to the liquid phase over a wide range of temperatures, and from nonpolar to polar environments, due to the presence of molecular polarizability. The water coordination, hydrogen-bonding structure, and dynamic properties given by uAMOEBA are similar to those derived from the all-atom AMOEBA03 model and experiments. Thus, the current model is an accurate and efficient alternative for modeling water.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DETECTION OF POTENTIAL TRANSIT SIGNALS IN THE FIRST 12 QUARTERS OF KEPLER MISSION DATA

We present the results of a search for potential transit signals in the first three years of photometry data acquired by the Kepler mission. The targets of the search include 112,321 targets that were observed over the full interval and an additional 79,992 targets that were observed for a subset of the full interval. From this set of targets we find a total of 11,087 targets that contain at least one signal that meets the Kepler detection criteria: periodicity of the signal, an acceptable signal-to-noise ratio, and three tests that reject false positives. Each target containing at least one detected signal is then searched repeatedly for additional signals, which represent multi-planet systems of transiting planets. When targets with multiple detections are considered, a total of 18,406 potential transiting planet signals are found in the Kepler mission data set. The detected signals are dominated by events with relatively low signal-to-noise ratios and by events with relatively short periods. The distribution of estimated transit depths appears to peak in the range between 20 and 30 parts per million, with a few detections down to fewer than 10 parts per million. The detections exhibit signal-to-noise ratios from 7.1{sigma}, which is the lower cutoff for detections, to over 10,000{sigma}, and periods ranging from 0.5 days, which is the shortest period searched, to 525 days, which is the upper limit of achievable periods given the length of the data set and the requirement that all detections include at least three transits. The detected signals are compared to a set of known transit events in the Kepler field of view, many of which were identified by alternative methods; the comparison shows that the current search recovery rate for targets with known transit events is 98.3%.

79 ASTRONOMY AND ASTROPHYSICS↗

First on-line commissioning experiments at the St. Benedict facility

Nuclear beta decays provide an excellent probe of fundamental symmetries due to their mediation by the weak interaction. In particular, precise measurements of these decays provide constraints on the unitarity of the Cabbibo-Kobayashi-Maskawa (CKM) quark-mixing matrix. While superallowed pure Fermi decays currently set the most precise limits, the alternative suite of superallowed mixed mirror decays has been ill-studied. These nuclei can provide an important consistency check of calculation and measurement methods employed for the pure Fermi decays, more critically needed now in the wake of a 2.4σ deviation from unitarity of the CKM matrix. In order to remedy the gap in data for mirror decays, the Superallowed Transition Beta-Neutrino Decay Ion Coincidence Trap (St. Benedict) facility is being commissioned at the University of Notre Dame’s Nuclear Science Laboratory (NSL). In this paper, we present first results of the commissioning of the St. Benedict facility on-line at the TwinSol radioactive beam facility. The results of initial commissioning experiments involving the St. Benedict gas catcher, RF carpet, RFQ ion guide and RFQ cooler-buncher will be presented.

beta decay↗