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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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At least 1,675 records · Page 93
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Optimization of Si:H films at the onset of nanocrystallinity for applications in silicon solar cells

The Si:H films at the onset of nanocrystallinity has proved to be an extremely useful material for stable a-Si:H based solar cells. In the present work it has been targeted to grow the improved a-Si:H matrix at the onset of nanocrystallization at a high growth rate. By optimizing the electrode separation in the RF glow discharge reactor and the effective gas pressure in the plasma, a significantly conducting (σ{sub D} ∼10{sup −5} S.cm{sup −1}), optically absorbing, low H-content (C{sub H} ∼2.2 at%) Si:H material at the onset of nanocrystallinity (X{sub C} ∼53%) has been obtained at a relatively high growth rate (r{sub d} = 102 Å/min), suitable for the desired technological applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

A Critical Review of the Experimentally Known Properties of U-Pu-Zr Alloys. Part 2: Thermal and Mechanical Properties

Although U-Pu-Zr alloys have been investigated for more than 60 years, relatively little experimental information is available, and many of the original values are in government reports that appeared more than 40 years ago. Information about the technologically important alloy U-20Pu-10Zr (wt%) is even more limited. U-Pu-Zr alloys are difficult materials to study experimentally, and it is therefore important to understand what results have already been obtained, how reliable they are, and where they were reported. This paper provides a summary and critical assessment of the available experimental measurements of thermal and mechanical properties of U-Pu-Zr alloys. Knowledge of these properties is crucial for understanding and modeling fuel constituent redistribution, fuel swelling and creep, fission gas release under normal reactor operations, and melting or formation of liquid phases under reactor transient scenarios. This paper builds on a previous paper that assessed experimental data about phases and phase diagrams in U-Pu-Zr alloys. Both papers are intended as resources for fuel designers and modelers and as guides for prioritizing future experimental work.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2023

TRISO Burnup-Dependent Failure Analysis of a HTGR Design-Basis Accident Using BISON

Here, this work assesses the failure behavior of the silicon carbide (SiC) layer in TRIstructural ISOtropic (TRISO) fuel particles with BISON during both steady-state and transient conditions for the MHTGR-350 design by General Atomics. A one-dimensional BISON model for a uranium oxycarbide–bearing TRISO is developed to simulate a power level of 50 mW/particles up to 12.4% fissions per initial metal atom (FIMA). Stress predictions for the materials of interest are presented as a function of burnup, along with the SiC failure probability computed using Weibull statistics under the assumption of realistic SiC quality.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Design of a Novel Variable Geometry Divertor for Tokamaks

The divertor is a key component of fusion reactors, allowing exhaust of gas, impurities, and helium ash to preserve plasma purity. The divertor geometry strongly affects plasma performance, and it is designed to be compatible with different plasma shapes in present-day fusion experiments. Here, we present a novel concept for a variable geometry divertor, in which the divertor baffle tiles are reorientable by external actuation. Implementation of this concept in a medium-sized research tokamak would uniquely provide the flexibility to tailor divertor geometry to the plasma configuration and also enable study of the effect of divertor closure on plasma performance. To ensure compatibility with typical tokamak operations, the adjustable divertor must withstand the effects of significant mechanical and thermal stresses such as MW/m 2 -scale heat fluxes and large electromagnetic fields, e.g., disruption forces. The technological solutions for actuation mechanisms, cooling system, gas baffling and plasma-facing components are assessed. A functional reduced-scale model with movable outer divertor target baffle tiles is developed and the actuation mechanism is tested.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Influence of a Buffer Layer on the Formation of a Thin-Film Nickel Catalyst for Carbon Nanotube Synthesis

The formation of nanoparticles of a thin-film nickel catalyst applied on a buffer layer in the form of pure titanium, titanium oxide, or titanium nitride has been studied. It has been shown that if nanotubes are synthesized in three stages (oxidation, reduction, and growth of nanotubes), the situation may arise when the metallic catalyst becomes isolated from the surface, and hence, from the hydrocarbon flux, as a result of which the nanotube growth stops. Isolation takes place when the interface between titanium oxide and the gas phase in the reactor moves. In this case, titanium oxide goes round a nickel oxide nanoparticle and insulates it. The displacement rate of this interface and the coefficient of hydrogen diffusion in titanium dioxide have been determined.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Production of Nanoscale Detonation Carbon using a Pulse Gas-Detonation Device

Combustion and thermal decomposition of hydrocarbon fuels are used to produce different forms of carbon. Combustion in the detonation mode is of particular interest, as nanocarbon obtained under these conditions differs in properties from products synthesized by other techniques. A pulsed gas-detonation device designed on the basis of a CCDS2000 detonation spraying facility opens up new possibilities for manufacturing of nanocarbon. The device operates in a flow mode of gas supply into the reactor at the atmospheric pressure, which ensures high productivity and industrial safety of this method. Using detonation of acetylene-oxygen mixtures rich in acetylene, nanoscale carbon was obtained with particle morphology depending on the ratio of the components in the gaseous mixture.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2025

Toluene Adsorption and TPD

Raw data for toluene adsorption and TPD experiments on two different adsorbents using a custom flow-through, bench-top reactor capable of controlling gas compositions and temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Ceramic composites: A review of toughening mechanisms and demonstration of micropillar compression for interface property extraction

We present that ceramic fiber–matrix composites (CFMCs) are exciting materials for engineering applications in extreme environments. By integrating ceramic fibers within a ceramic matrix, CFMCs allow an intrinsically brittle material to exhibit sufficient structural toughness for use in gas turbines and nuclear reactors. Chemical stability under high temperature and irradiation coupled with high specific strength make these materials unique and increasingly popular in extreme settings. This paper first offers a review of the importance and growing body of research on fiber–matrix interfaces as they relate to composite toughening mechanisms. Second, micropillar compression is explored experimentally as a high-fidelity method for extracting interface properties compared with traditional fiber push-out testing. Three significant interface properties that govern composite toughening were extracted. For a 50-nm-pyrolytic carbon interface, the following were observed: a fracture energy release rate of ~2.5 J/m 2 , an internal friction coefficient of 0.25 ± 0.04, and a debond shear strength of 266 ± 24 MPa. Lastly, this research supports micromechanical evaluations as a unique bridge between theoretical physics models for microcrack propagation and empirically driven finite element models for bulk CFMCs.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2015

Hydrogen Selective Exfoliated Zeolite Membranes

The objective of this project was to develop and evaluate an innovative membrane technology at process conditions that would be representative of Integrated Gasification Combined Cycle (IGCC) advanced power generation with pre-combustion capture of carbon dioxide (CO 2 ). This research focused on hydrogen (H 2 )-selective zeolite membranes that could be utilized to separate conditioned syngas into H 2 -rich and CO 2 -rich components. Both experiments and process design and optimization calculations were performed to evaluate the concept of ultra-thin membranes made from zeolites nanosheets. In this work, efforts in the laboratory were made to tackle two fundamental challenges in application of zeolite membranes in harsh industrial environments, namely, membrane thickness and membrane stability. Conventional zeolite membranes have thicknesses in the micron range, limiting their performance. In this research, we developed a method for fabrication of ultimately thin zeolite membranes based on zeolite nanosheets. A range of layered zeolites (MWW, RWR, NSI structure types) suitable for hydrogen separation was successfully exfoliated to their constituent nanosheets. Further, membranes were made from one of these zeolites, MWW, to demonstrate the potential of this group of materials. Moreover, long-term steam stability of these zeolites (up to 6 months) was investigated in high concentrations of steam (35 mol% and 95 mole%), high pressure (10 barg), and high temperatures (350 °C and 600 °C) relevant to conditions of water-gas-shift and steam methane reforming reactions. It was found that certain nanosheets are stable, and that stability depends on the concentration of structural defects. Additionally, models that represent a water-gas-shift (WGS) membrane reactor equipped with the zeolite membrane were developed for systems studies. These studies had the aim of analyzing the effect of the membrane reactor integration into IGCC plants in terms of performance and economic aspects of the plants. Specifically, simulation and design optimization studies were performed using the developed stand-alone membrane reactor models to identify the membrane selectivity and permeance characteristics necessary to achieve desired targets of CO 2 capture and H 2 recovery, as well as guide the selection of the optimal reactor design that minimizes the membrane cost as a function of its surface area required. The isothermal membrane reactor model was also integrated into IGCC system models using both the MATLAB and Aspen software platforms and techno-economic analyses of the integrated plants have been carried out to evaluate the feasibility of replacing current technologies for pre-combustion capture by the proposed novel approach in terms of satisfying stream constraints and achieving the DOE target goal of 90% CO 2 capture. The results of the performed analyses based on present value of annuity calculations showed break even costs for the membrane reactor within the feasible range for membrane fabrication. However, the predicted membrane performance used in these simulations exceeded the performance achieved experimentally. Therefore, further work is required to improve membrane performance.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2018

Ex Situ Catalytic Fast Pyrolysis of Lignocellulosic Biomass to Hydrocarbon Fuels: 2018 State of Technology and Future Research

This report will update modeled costs for a fixed bed ex situ catalytic fast pyrolysis process for the conversion of biomass to liquid hydrocarbon fuels based on recent bench-scale experimental results. It will also update previously published information for this conversion pathway in the DOE Bioenergy Technologies Office 2016 Multi-Year Program Plan with current understanding of research goals achievable by 2022 and associated modeled cost reductions. All costs will be updated to a consistent set of assumptions in 2016 dollars.

09 BIOMASS FUELS↗
DOE OSTI2013

Fuel Assembly Facility, Operation

This unit process estimates input and output flows for assembling enriched UF6 into UO2 fuel assemblies for loading into nuclear reactors, including electricity, natural gas, and water use; air, water, solid waste, and radionuclide emissions. To access the model referenced in the report, please visit https://www.netl.doe.gov/energy-analysis/details?id=0A3C1D7F-234C-477E-AB7F-979CFCA690FD

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2019

The Degradation of Strength under Varying Oxidizing Conditions for Nuclear Graphite

Strength behavior of fine and medium grain size nuclear graphite grades are presented after being subjected to varying oxidation conditions. This study provides valuable information for design and eventual licensing considerations for the oxidation behavior of graphite components within a gas-cooled High Temperature Reactor design and the eventual structural integrity of graphite core components. These tests address the underlying oxidized strength of nuclear graphite components for oxidized mass losses up to and beyond the current limits recommended for graphite components in the ASME code (maximum mass loss = 10%) over a range of oxidation temperatures (550° C – 750° C). Preliminary results generally demonstrate that low temperature oxidation can result in higher strength reductions than oxidation at higher temperatures for similar mass loss levels. Since the graphite component strength is a critical parameter necessary to determine the core structural integrity, determining the actual residual strength after oxidation is essential for determining actual component oxidation limits within the ASME code.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2023

High-throughput methane pyrolysis for low-cost, emissions-free hydrogen

Palo Alto Research Center (PARC) and its partners will explore a targeted molten metal as a catalyst in a methane pyrolysis mist reactor to convert natural gas into hydrogen and solid carbon at a low cost without carbon dioxide emissions. The technology could augment or replace current H 2 production methods, while simultaneously sequestering carbon in high value materials.

08 HYDROGEN↗
DOE OSTI2026

SuperLab 2.0 Showcase: Connecting Five Labs to Tackle Grid Complexity and Unlock Unique Grid Asset Potential

SuperLab 2.0 (a five-lab demonstration) is a collaborative, national-scale experiment showcasing the coordination of geographically distributed energy assets in real time. The demonstration integrates 25 physical and digital assets, spanning wind, photovoltaics, batteries, electrolyzers, DC fast chargers, microgrid controllers, building automation systems, small modular reactors, control centers, and gas turbines, across five U.S. Department of Energy (DOE) national laboratories: National Laboratory of the Rockies (NLR), Idaho National Laboratory, National Energy Technology Laboratory, Lawrence Berkeley National Laboratory, and Sandia National Laboratories. These assets are unified using Energy Sciences Network (ESnet), a low-latency, high-performance DOE network, and are controlled via a centralized energy controller hosted at NLR's Advanced Research on Integrated Energy Systems facility. The demonstration validates the ability to stress-test hybrid energy systems under dynamic scenarios to de-risk advanced control strategies for greater resilience and flexibility.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2024

Investigation of Point-Contact Strategies for CFD Simulations of Pebble-Bed Reactor Cores

This study numerically investigated the effects of various contact strategies on the thermal hydraulic behavior within a structured bed of 100 explicitly modeled pebbles. Four contact strategies and two thermal hydraulic conditions were considered. The strategies to avoid contact singularities include decreasing the pebble diameter, increasing the pebble diameter, bridging the pebble surfaces near the contact region, and capping the pebble surfaces near the contact region. One strategy, Strategy 3a, which involves bridging with a cylinder equal to 10% of the pebble diameter, was selected as the baseline strategy because it addressed the contact singularity while minimizing the geometric changes that affect the bed porosity. The two thermal hydraulic conditions were full-power operation (Case 1) and pressurized loss of forced cooling or PLOFC (Case 2). Simulations of the conjugate heat transfer within the structured bed were performed using the Reynolds-averaged Navier–Stokes approach with the realizable k-ϵ turbulence model and two-layer all y + wall treatment. The thermal-fluid quantities of interest were compared between the contact strategies for each case. In Case 1, the hydraulic behavior was sensitive to the contact strategy, with large differences in the pressure drop (30%) and volume-average velocity (4%). The thermal behavior was not sensitive, with less than a 0.5% difference across the strategies. To better understand the separate effects of each heat transfer mode, Case 2 was divided into the following subcases: conduction (Case 2a); conduction/radiation (Case 2b); and conduction/radiation/convection (Case 2c). Case 2a represents an early phase of the PLOFC transient. Case 2b represents an intermediate phase of the PLOFC transient, with the pebble temperatures sufficiently high for the radiative heat transfer to be non-negligible. Case 2c represents a late phase of the PLOFC transient after the establishment of the natural circulation of the heat transfer fluid. For Case 2, large differences in the contact strategy were observed only in Case 2a with only conduction. The difference in the maximum pebble temperature was 23% in Case 2a, 2% in Case 2b, and 0.3% in Case 2c.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗