Multistep Criticality Search and Power Shaping in Nuclear Microreactors with Deep Reinforcement Learning
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22 GENERAL STUDIES OF NUCLEAR REACTORS↗
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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Grid Voltage Control Analysis for Heavy-Duty Electric Vehicle Charging Stations
This paper presents an analysis of grid voltage control strategies for heavy-duty electric vehicle charging stations. The performance of three voltage control approaches—including power factor control, standardized volt-volt ampere reactive (VAR) curve control, and customized volt-VAR curve control—are investigated and evaluated for three different sizes of charging stations, including a single-port charging station, a midsized three-port charging station, and six-port travel center. The charging stations are placed on multiple locations of four different types of distribution systems to obtain a comprehensive performance analysis of the voltage control approaches under different scenarios. To quantitively compare the performance of the three voltage control approaches, a series of metrics are designed to quantify the performance and contribute to the comprehensive analysis.
47 OTHER INSTRUMENTATION↗
Impacts of Voltage-Based Grid Support Functions on Energy Production of PV Customers
This paper presents the impact of inverter grid- support functions (GSFs) on photovoltaic (PV) customer energy production on a real distribution feeder in Oahu, HI. These autonomous GSFs based on local voltage measurements are good alternatives to increase PV hosting capacity. However, these functions can result in PV energy curtailment to the customer, and this study addresses the concerns about the impact of inverter GSFs through detailed quasi-static time series (QSTS) simulations. It proposes four metrics: maximum and average GSF curtailment, average increased generation and average net generation change, to assess the impact of a given control on PV systems located on customer sites. It was found that curtailment of PV production is negligible for customers where peak voltage is within ANSI C84.1 range. A reliable relationship between curtailment and peak customer voltage is demonstrated, suggesting that peak voltage could be used as an indicator of customer curtailment.
24 POWER TRANSMISSION AND DISTRIBUTION↗
Dynamic Modeling of Full Converter Adjustable-speed Pumped Storage Hydropower (FC AS-PSH)
Full converter adjustable-speed pumped storage hydropower (FC AS-PSH) technology, as one of advanced-PSH technology, is developed from wind turbine technology. By making the synchronous machine connect to the grid through a full-size converter, FC AS-PSH has a wider adjustment range of speed and a better reactive power control capability compared with a doubly-fed asynchronous generator AS-PSH technology. When it plays as an energy backup in the power system, FC AS-PSH can provide a much faster response than conventional-PSH (C-PSH) which makes this technology provide better ancillary service for a high renewable penetrated system. In this paper, the dynamic modeling of FC AS-PSH is fully studied. We develop a detailed model of this technology in the IEEE 14-bus system based on GE Positive Sequence Load Flow (PSLF) platform. Especially, the first governor model is developed based on the Engineer’s Program Control Language (EPCL) user-defined model in this platform. All operation modes are validated and studied under a system contingency. Besides, comparison cases between FC AS-PSH and C-PSH are studied to show advantages providing from FC AS-PSH when it works with renewable energy.
50 EE - Wind and Water Power Program - Water (EE-4↗
Vapor-phase grafting of functional silanes on atomic layer deposited Al 2 O 3
Fundamental studies are needed to advance our understanding of selective adsorption in aqueous environments and develop more effective sorbents and filters for water treatment. Vapor-phase grafting of functional silanes is an effective method to prepare well-defined surfaces to study selective adsorption. In this investigation, we perform vapor phase grafting of five different silane compounds on aluminum oxide (Al2O3) surfaces prepared by atomic layer deposition. These silane compounds have the general formula L3Si–C3H6–X where the ligand, L, controls the reactivity with the hydroxylated Al2O3 surface and the functional moiety, X, dictates the surface properties of the grafted layer. We study the grafting process using in situ Fourier transform infrared spectroscopy and ex situ x-ray photoelectron spectroscopy measurements, and we characterize the surfaces using scanning electron microscopy, atomic force microscopy, and water contact angle measurements. Here, we found that the structure and density of grafted aminosilanes are influenced by their chemical reactivity and steric constraints around the silicon atom as well as by the nature of the anchoring functional groups. Methyl substituted aminosilanes yielded more hydrophobic surfaces with a higher surface density at higher grafting temperatures. Thiol and nitrile terminated silanes were also studied and compared to the aminosilane terminated surfaces. Uniform monolayer coatings were observed for ethoxy-based silanes, but chlorosilanes exhibited nonuniform coatings as verified by atomic force microscopy measurements.
36 MATERIALS SCIENCE↗
Tandem In 2 O 3 -Pt/Al 2 O 3 catalyst for coupling of propane dehydrogenation to selective H 2 combustion
Tandem catalysis couples multiple reactions and promises to improve chemical processing, but precise spatiotemporal control over reactive intermediates remains elusive. We used atomic layer deposition to grow In 2 O 3 over Pt/Al 2 O 3 , and this nanostructure kinetically couples the domains through surface hydrogen atom transfer, resulting in propane dehydrogenation (PDH) to propylene by platinum, then selective hydrogen combustion by In 2 O 3 , without excessive hydrocarbon combustion. Other nanostructures, including platinum on In 2 O 3 or platinum mixed with In 2 O 3 , favor propane combustion because they cannot organize the reactions sequentially. The net effect is rapid and stable oxidative dehydrogenation of propane at high per-pass yields exceeding the PDH equilibrium. Tandem catalysis using this nanoscale overcoating geometry is validated as an opportunity for highly selective catalytic performance in a grand challenge reaction.
Yan, Huan↗
Modeling of the TRIGA IPR-R1 research reactor with the Serpent2/RINNOVO Nodal core analysis package
The Serpent2/RINNOVO nodal core analysis code system, a dedicated tool for modeling research reactors, has the capability to accurately predict important core physics parameters involved in the safety of reactor operation, such as various reactivity coefficients, control rod and bank worths including the shutdown margin, power distributions as well as local neutron flux predictions at various core locations of high importance, e.g., at irradiation rigs. In this work, a hexagonal model of the unrodded initial core of the Brazilian IPR-R1 Mark I type TRIGA nuclear reactor has been created using the Serpent2/RINNOVO code system. The choice of employing a hexagonal core geometry representation has mainly been made to facilitate subsequent fuel shuffling operations and core follow calculations of this reactor. Numerical results in terms of the core eigenvalue and the assembly power distribution have then been compared against corresponding full core Serpent2 results to prove feasibility of using the Serpent2/RINNOVO code system for modeling small and highly heterogeneous TRIGA reactors. Overall, RINNOVO predicts the power distribution very accurately but the eigenvalue error still remains quite large. In light of being the very first evaluation of a TRIGA reactor with the RINNOVO nodal core simulator, these results are also considered to be very preliminary. Improved accuracy is expected by incorporating a proper methodology in the current code system for computing discontinuity factors for multi-assembly configurations. Furthermore, improved results are expected by increasing the number of energy groups used by RINNOVO in these core calculations.
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
Scoping Studies on the Impacts of Increased Enrichment on Nuclear Criticality Safety
Fuel vendors and industry are increasingly interested in new fuel designs with increased enrichment. These fuel types are categorized as high-assay low-enriched uranium: their fuel enrichment is low in the regulatory sense, but it is much higher than industry’s typical operating enrichment bounds. It should be demonstrated that the appropriate mechanisms have been established to control this increased reactivity, and the conditions that arise from common operational occurrences must be considered. This report presents case studies that were conducted to determine whether increased burnable absorber loading can be used to offset increased enrichment. Increases in integral fuel burnable absorber and gadolinium bearing rods in pressurized water reactor (PWR) and boiling water reactor (BWR) assemblies must be examined. Increases in reactivity were shown to be feasibly controlled by increased burnable absorber loading, even when operational specificities were considered, as in BWR partial length rods and PWR annular fuel blankets.
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
HFIR LEU High Density Silicide Dispersion Optimized Design Neutronics Analyses with PHAME
A high-fidelity neutronics model of the Oak Ridge National Laboratory High Flux Isotope Reactor (HFIR) with the low-enriched uranium (LEU) high-density silicide dispersion Optimized fuel design was updated and analyzed to generate reactor physics-based metrics to support follow-on thermal hydraulic and transient analyses of this design. The Python HFIR Analysis and Measurement Engine (PHAME) was also updated to enhance the automation capabilities of the framework developed and maintained to perform these reactor physics modeling and simulation efforts. The automated framework significantly increases the efficiency and reproducibility to design and thoroughly analyzes HFIR LEU core designs, changes, and uncertainties. Reactor physics metrics evaluated include but are not limited to fuel depletion, cycle length, fission rate density distributions, axial power peaking factors, kinetics data, reactivity coefficients, control element worths, heat deposition rates, and decay heat. These neutronics results provide essential input to follow-on steady state thermal, thermal hydraulic and reactor transient analyses, which are subject of other reports. The Optimized design operates at 95 MW to maintain HFIR’s current highly enriched uranium core performance level at 85 MW.
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
Feasibility Analyses for the Microgrid of the Mountain in the Cordillera Central Region of Puerto Rico
Distributed energy resource (DER) development can benefit communities through improvement of access to reliable electricity and a resilient energy system. Many place-specific considerations must be accounted for when designing electrical systems with co-located generation and loads. This paper presents an overview of four studies focusing on different aspects for regional DER development in the Cordillera Central region of Puerto Rico, including a grid and load stability study with the introduction of solar energy generation, microgrid design based on the solar resource in the area, resilience considerations during power outage scenarios, and qualitative risk aspects for components in the microgrid. Additionally, a conceptual substation microgrid analysis is conducted using the Microgrid Design Toolkit (MDT) to evaluate trade-offs between cost and energy availability, providing insights into optimal design strategies. A microgrid resilience assessment is performed using the Resilient Nodal Cluster Analysis Tool (ReNCAT) to identify critical loads and evaluates their accessibility during outages, emphasizing the importance of community needs. Finally, a qualitative risk assessment utilizing Hazard and Operability Analysis (HAZOP) methods highlights potential hazards and mitigations for microgrid components, ensuring robust system design and operation.
24 POWER TRANSMISSION AND DISTRIBUTION↗
Redox-controlled reorganization and flavin strain within the ribonucleotide reductase R2b–NrdI complex monitored by serial femtosecond crystallography
Redox reactions are central to biochemistry and are both controlled by and induce protein structural changes. Here, we describe structural rearrangements and crosstalk within the Bacillus cereus ribonucleotide reductase R2b–NrdI complex, a di-metal carboxylate-flavoprotein system, as part of the mechanism generating the essential catalytic free radical of the enzyme. Femtosecond crystallography at an X-ray free electron laser was utilized to obtain structures at room temperature in defined redox states without suffering photoreduction. Together with density functional theory calculations, we show that the flavin is under steric strain in the R2b–NrdI protein complex, likely tuning its redox properties to promote superoxide generation. Moreover, a binding site in close vicinity to the expected flavin O 2 interaction site is observed to be controlled by the redox state of the flavin and linked to the channel proposed to funnel the produced superoxide species from NrdI to the di-manganese site in protein R2b. These specific features are coupled to further structural changes around the R2b–NrdI interaction surface. The mechanistic implications for the control of reactive oxygen species and radical generation in protein R2b are discussed
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Skylab reactivation mission report
On July 11, 1979, Skylab impacted the Earth's surface. The debris dispersion area stretched from the South Eastern Indian Ocean across a sparsely populated section of Western Australia. The events leading to the reentry of Skylab are discussed and a final assessment of the Skylab debris impact footprint is presented. Also included are detailed evaluations of the various Skylab systems that were reactivated when control of Skylab was regained in mid-1978 after having been powered down since February 4, 1974.
Chubb, W. B.↗
Wind turbine generator interaction with conventional diesel generators on Block Island, Rhode Island. Volume 1: Executive summary
Primary results are summarized for a three-part study involving the effects of connecting a MOD-OA wind turbine generator to an isolated diesel power system. The MOD-OA installation considered was the third of four experimental nominal 200 kW wind turbines connected to various utilities under the Federal Wind Energy Program and was characterized by the highest wind energy penetration levels of four sites. The study analyses address: fuel displacement, dynamic interaction, and three modes of reactive power control. These analyses all have as their basis the results of the data acquisition program conducted on Block Island, Rhode Island.
Wilreker, V. F.↗
Wind turbine generator interaction with conventional diesel generators on Block Island, Rhode Island. Volume 2: Data analysis
Assessing the performance of a MOD-OA horizontal axis wind turbine connected to an isolated diesel utility, a comprehensive data measurement program was conducted on the Block Island Power Company installation on Block Island, Rhode Island. The detailed results of that program focusing on three principal areas of (1) fuel displacement (savings), (2) dynamic interaction between the diesel utility and the wind turbine, (3) effects of three models of wind turbine reactive power control are presented. The approximate two month duration of the data acquisition program conducted in the winter months (February into April 1982) revealed performance during periods of highest wind energy penetration and hence severity of operation. Even under such conditions fuel savings were significant resulting in a fuel reduction of 6.7% while the MOD-OA was generating 10.7% of the total electrical energy. Also, electrical disturbance and interactive effects were of an acceptable level.
Wilreker, V. F.↗
Measured effects of wind turbine generation at the Block Island Power Company
Data measurements made on the NASA MOD-OA 200-kw wind-turbine generator (WTG) installed on a utility grid form the basis for an overall performance analysis. Fuel displacement/-savings, dynamic interactions, and WTG excitation (reactive-power) control effects are studied. Continuous recording of a large number of electrical and mechanical variables on FM magnetic tape permit evaluation and correlation of phenomena over a bandwidth of at least 20 Hz. Because the wind-power penetration reached peaks of 60 percent, the impact of wind fluctuation and wind-turbine/diesel-utility interaction is evaluated in a worst-case scenario. The speed-governor dynamics of the diesel units exhibited an underdamped response, and the utility operation procedures were not altered to optimize overall WTG/utility performance. Primary findings over the data collection period are: a calculated 6.7-percent reduction in fuel consumption while generating 11 percent of the total electrical energy; acceptable system voltage and frequency fluctuations with WTG connected; and applicability of WTG excitation schemes using voltage, power, or VARS as the controlled variable.
Wilreker, V. F.↗
Microgravity Processing of Oxide Superconductors
Considerable effort has been concentrated on the synthesis and characterization of high T(sub c) oxide superconducting materials. The YBaCuO system has received the most intense study, as this material has shown promise for the application of both thin film and bulk materials. There are many problems with the application of bulk materials- weak links, poor connectivity, small coherence length, oxygen content and control, environmental reactivity, phase stability, incongruent melting behavior, grain boundary contamination, brittle mechanical behavior, and flux creep. The extent to which these problems are intrinsic or associated with processing is the subject of controversy. This study seeks to understand solidification processing of these materials, and to use this knowledge for alternative processing strategies, which, at the very least, will improve the understanding of bulk material properties and deficiencies. In general, the phase diagram studies of the YBaCuO system have concentrated on solid state reactions and on the Y2BaCuO(x) + liquid yields YBa2Cu3O(7-delta) peritectic reaction. Little information is available on the complete melting relations, undercooling, and solidification behavior of these materials. In addition, rare earth substitutions such as Nd and Gd affect the liquidus and phase relations. These materials have promising applications, but lack of information on the high temperature phase relations has hampered research. In general, the understanding of undercooling and solidification of high temperature oxide systems lags behind the science of these phenomena in metallic systems. Therefore, this research investigates the fundamental melting relations, undercooling, and solidification behavior of oxide superconductors with an emphasis on improving ground based synthesis of these materials.
Olive, James R.↗
Hybrid Modeling for Testing Intelligent Software for Lunar-Mars Closed Life Support
Intelligent software is being developed for closed life support systems with biological components, for human exploration of the Moon and Mars. The intelligent software functions include planning/scheduling, reactive discrete control and sequencing, management of continuous control, and fault detection, diagnosis, and management of failures and errors. Four types of modeling information have been essential to system modeling and simulation to develop and test the software and to provide operational model-based what-if analyses: discrete component operational and failure modes; continuous dynamic performance within component modes, modeled qualitatively or quantitatively; configuration of flows and power among components in the system; and operations activities and scenarios. CONFIG, a multi-purpose discrete event simulation tool that integrates all four types of models for use throughout the engineering and operations life cycle, has been used to model components and systems involved in the production and transfer of oxygen and carbon dioxide in a plant-growth chamber and between that chamber and a habitation chamber with physicochemical systems for gas processing.
Malin, Jane T.↗
Rationalizing Burned Carbon with Carbon Monoxide Exported from South America
We present several estimates cross-checking the fluxes of carbon to the atmosphere from burning, comparing models that are based on simple land-surface parameterizations and atmospheric transport dynamics. Both estimates made by NASA Ames and USP modeling techniques are quite high compared to some detailed satellite/land-use studies of emissions. The flux of carbon liberated to the atmosphere via biomass burning is important for several reasons. This flux is a fundamental statistic for the parameterization of the large-scale flux of gases controlling the reactive greenhouse gases methane and ozone. Similarly, it is central to the estimation of the translocation of nitrogen and pyrodenitrification in the tropics. Thirdly, CO2 emitted from rainforest clearing contributes directly to carbon lost from the rainforest system as it contributes to greenhouse gas forcing. While CO2 from pasturage, agriculture, etc, is considered to be reabsorbed seasonally, and so "off budget" for the carbon cycle, it must also be accounted. CO2 anomalies related to daily weather and interannual climatic variation are strong enough to perturb our scientific perception of long-term carbon storage trends. We compare fluxes deduced from land-use statistics (originally, W.M. Hao) and from satellite hot pixels (A. Setzer) with atmospheric fluxes determined by the mesoscale/continental scale models RAMS and MM5, and point to some new work with highly resolved global models (the NASA Data Assimilation Office's GEOS4). Our simulations are tied to events, so that measured tracers like CO tie the models directly to the burning and meteorology of a specific period. We point out a particular sensitivity in estimates based on CO, and indicate how analysis of CO2 along with other biomass-burning tracers may lead to an improved multi-species estimator of carbon burned.
Chatfield, R.↗