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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 901 records · Page 50
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

A MULTIDIMENSIONAL AND MULTIPHYSICS APPROACH TO NUCLEAR FUEL BEHAVIOR SIMULATION

Important aspects of fuel rod behavior, for example pellet-clad mechanical interaction (PCMI), fuel fracture, oxide formation, non-axisymmetric cooling, and response to fuel manufacturing defects, are inherently multidimensional in addition to being complicated multiphysics problems. Many current modeling tools are strictly 2D axisymmetric or even 1.5D. This paper outlines the capabilities of a new fuel modeling tool able to analyze either 2D axisymmetric or fully 3D models. These capabilities include temperature-dependent thermal conductivity of fuel; swelling and densification; fuel creep; pellet fracture; fission gas release; cladding creep; irradiation growth; and gap mechanics (contact and gap heat transfer). The need for multiphysics, multidimensional modeling is then demonstrated through a discussion of results for a set of example problems. The first, a 10-pellet rodlet, demonstrates the viability of the solution method employed. This example highlights the effect of our smeared cracking model and also shows the multidimensional nature of discrete fuel pellet modeling. The second example relies on our the multidimensional, multiphysics approach to analyze a missing pellet surface problem. As a final example, we show a lower-length-scale simulation coupled to a continuum-scale simulation.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2012

Monitoring phase behavior of hydrogen confined in carbon nanopores by in-situ small angle neutron scattering technique

We report on the use of in-situ small angle neutron scattering (SANS) technique to study the phase behavior of hydrogen confined in narrow pores of ultramicroporous carbon (UMC) with a very large surface area (2630 m2/g) and pore volume (1.3 cm3/g). The effect of pore size and pressure on hydrogen adsorbed on UMC at room temperature and pressures up to ~200 bar were investigated. In a previous experiment, we have measured the density of adsorbed H2 gas in the nanopores and mesopores of polyfurfuryl alcohol-derived activated carbon (PFAC) by SANS techniques. Here, a comparative SANS study between the UMC and PFAC was conducted in order to further investigate the densification of H2 as a function of pore size and pressure. Initial results suggest that the density of confined H2 in both UMC and PFAC is considerably higher than that of the bulk hydrogen gas. The density is systematically higher in the narrow pores and decreases with increasing pore size. These results clearly demonstrate the advantage of adsorptive storage over compressed gas storage and emphasize the greater efficiency of micropores over mesopores in the adsorption process, which can be used to guide the development of new carbon adsorbents tailored for maximum H2 storage capacities at near-ambient temperatures.

adsorption↗
DOE OSTI2012

Microscopic analysis of irradiated AGR-1 coated particle fuel compacts

The AGR-1 experiment involved irradiation of 72 TRISO-coated particle fuel compacts to a peak burnup of 19.5% FIMA with no in-pile failures observed out of 3×105 total particles. Irradiated AGR-1 fuel compacts have been cross-sectioned and analyzed with optical microscopy to characterize kernel, buffer, and coating behavior. Five compacts have been examined so far, spanning a range of irradiation conditions (burnup, fast fluence, and irradiation temperature) and including all four TRISO coating variations irradiated in the AGR-1 experiment. The cylindrical specimens were sectioned both transversely and longitudinally, then polished to expose between approximately 40-80 individual particles on each mount. The analysis focused primarily on kernel swelling and porosity, buffer densification and fracturing, buffer-IPyC debonding, and fractures in the IPyC and SiC layers. Characteristic morphologies have been identified, over 800 particles have been classified, and spatial distributions of particle types have been mapped. No significant spatial patterns were discovered in these cross sections. However, some trends were found between morphological types and certain behavioral aspects. Buffer fractures were found in approximately 23% of the particles, and these fractures often resulted in unconstrained kernel swelling into the open cavities. Fractured buffers and buffers that stayed bonded to IPyC layers appear related to larger pore size in kernels. Buffer-IPyC interface integrity evidently factored into initiation of rare IPyC fractures. Fractures through part of the SiC layer were found in only three particles, all in conjunction with IPyC-SiC debonding. Compiled results suggest that the deliberate coating fabrication variations influenced the frequencies of IPyC fractures, IPyC-SiC debonds, and SiC fractures.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2014

Simulating Pelletization Strategies to Reduce the Biomass Supply Risk at America’s Biorefineries

Demand for cellulosic ethanol and other advanced biofuels has been on the rise, due in part to federal targets enacted in 2005 and extended in 2007. The industry faces major challenges in meeting these worthwhile and ambitious targets. The challenges are especially severe in the logistics of timely feedstock delivery to biorefineries. Logistical difficulties arise from seasonal production that forces the biomass to be stored in uncontrolled field-side environments. In this storage format physical difficulties arise; transportation is hindered by the low bulk density of baled biomass and the unprotected material can decay leading to unpredictable losses. Additionally, uncertain yields and contractual difficulties can exacerbate these challenges making biorefineries a high-risk venture. Investors’ risk could limit business entry and prevent America from reaching the targets. This paper explores pelletizer strategies to convert the lignocellulosic biomass into a denser form more suitable for storage. The densification of biomass would reduce supply risks, and the new system would outperform conventional biorefinery supply systems. Pelletizer strategies exhibit somewhat higher costs, but the reduction in risk is well worth the extra cost if America is to grow the advanced biofuels industry in a sustainable manner.

09 BIOMASS FUELS↗
DOE OSTI2015

Proton conducting ceramics in membrane separations

Perovskite materials of the general formula SrCeO.sub.3 and BaCeO.sub.3 are provided having improved conductivity while maintaining an original ratio of chemical constituents, by altering the microstructure of the material. A process of making Pervoskite materials is also provided in which wet chemical techniques are used to fabricate nanocrystalline ceramic materials which have improved grain size and allow lower temperature densification than is obtainable with conventional solid-state reaction processing.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Hardface coating systems and methods for metal alloys and other materials for wear and corrosion resistant applications

The present disclosure relates generally to hardface coating systems and methods for metal alloys and other materials for wear and corrosion resistant applications. More specifically, the present disclosure relates to hardface coatings that include a network of titanium monoboride (TiB) needles or whiskers in a matrix, which are formed from titanium (Ti) and titanium diboride (TiB.sub.2) precursors by reactions enabled by the inherent energy provided by the process heat associated with coating deposition and, optionally, coating post-heat treatment. These hardface coatings are pyrophoric, thereby generating further reaction energy internally, and may be applied in a functionally graded manner. The hardface coatings may be deposited in the presence of a number of fluxing agents, beta stabilizers, densification aids, diffusional aids, and multimode particle size distributions to further enhance their performance characteristics.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Fuel cell system with interconnect

The present invention includes a fuel cell system having an interconnect that reduces or eliminates diffusion (leakage) of fuel and oxidant by providing an increased densification, by forming the interconnect as a ceramic/metal composite.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2016

PRELIMINARY TESTING OF NANOPARTICLE EFFECTIVENESS IN BINDER JETTING APPLICATIONS

Binder jetting works by selectively depositing a binder with an inkjet print head into layers of powdered material. Compared with other metal Additive Manufacturing (AM) processes, binder jetting has significant potential for near-term adoption in manufacturing environments due to its reliability and throughput. The Achilles heel of binder jetting, however, is the inability to produce fully dense, single-alloy materials. The lack of density in printed binder jet parts is strictly dictated by the packing factor of the powder feedstock. Adding nanoparticles during printing will not only increase the part s packing factor but may also serve as a sintering aid. This study focuses on the effect of both the binder and nanoparticles on the final part density. As an unintended consequence of high nanoparticle loading, printed parts underwent a significant increase in porosity during the curing process. This unintended consequence is the apparent result of the nanoparticles blocking the exit of the solvent vapor during the curing step. Additionally, nanoparticle use for densification is validated with SEM imagery.

Bailey, Alta C↗
DOE OSTI2016

Engineering Platinum Alloy Electrocatalysts in Nanoscale for PEMFC Application

Fuel cells are expected to be a key next-generation energy source used for vehicles and homes, offering high energy conversion efficiency and minimal pollutant emissions. However, due to large overpotentials on anode and cathode, the efficiency is still much lower than theoretically predicted. During the past decades, considerable efforts have been made to investigate synergy effect of platinum alloyed with base metals. But, engineering the alloy particles in nanoscale has been a challenge. Most important challenges in developing nanostructured materials are the abilities to control size, monodispersity, microcomposition, and even morphology or self-assembly capability, so called Nanomaterials-by-Design, which requires interdisciplinary collaborations among computational modeling, chemical synthesis, nanoscale characterization as well as manufacturing processing. Electrocatalysts, particularly fuel cell catalysts, are dramatically different from heterogeneous catalysts because the surface area in micropores cannot be electrochemically controlled on the same time scale as more transport accessible surfaces. Therefore, electrocatalytic architectures need minimal microporous surface area while maximizing surfaces accessible through mesopores or macropores, and to "pin" the most active, highest performance physicochemical state of the materials even when exposed to thermodynamic forces, which would otherwise drive restructuring, crystallization, or densification of the nanoscale materials. In this presentation, results of engineering nanoscale platinum alloy particles down to 2 ~ 4 nm will be discussed. Based on nature of alloyed base metals, various synthesis technologies have been studied and developed to achieve capabilities of controlling particle size and particle microcomposition, namely, core-shell synthesis, microemulsion technique, thermal decomposition process, surface organometallic chemical method, etc. The results show that by careful engineering the particle size and microcomposition in nanoscale, it is able to achieve superior electrocatalytic activities comparing with traditional preparative methods. Examples to be discussed are high surface area carbon supported Pt, PtM binary, and PtMN ternary alloys, their synthesis processes, characterizations and electrocatalytic activities towards molecular oxygen reduction.

Alloy↗
DOE OSTI2016

Determination of Experimental Fuel Rod Parameters using 3D Modelling of PCMI with MPS Defect

An in-reactor experiment is being designed in order to validate the pellet-cladding mechanical interaction (PCMI) behavior of the BISON fuel performance code. The experimental parameters for the test rod being placed in the Halden Research Reactor are being determined using BISON simulations. The 3D model includes a missing pellet surface (MPS) defect to generate large local cladding deformations, which should be measureable after typical burnup times. The BISON fuel performance code is being developed at Idaho National Laboratory (INL) and is built on the Multiphysics Object-Oriented Simulation Environment (MOOSE) framework. BISON supports both 2D and 3D finite elements and solves the fully coupled equations for solid mechanics, heat conduction and species diffusion. A number of fuel performance effects are included using models for swelling, densification, creep, relocation and fission gas production & release. In addition, the mechanical and thermal contact between the fuel and cladding is explicitly modelled using a master-slave based contact algorithm. In order to accurately predict PCMI effects, the BISON code includes the relevant physics involved and provides a scalable and robust solution procedure. The depth of the proposed MPS defect is being varied in the BISON model to establish an optimum value for the experiment. The experiment will be interrupted approximately every 6 months to measure cladding radial deformation and provide data to validate BISON. The complete rodlet (~20 discrete pellets) is being simulated using a 180° half symmetry 3D model with MPS defects at two axial locations. In addition, annular pellets will be used at the top and bottom of the pellet stack to allow thermocouples within the rod to measure the fuel centerline temperature. Simulation results will be presented to illustrate the expected PCMI behavior and support the chosen experimental design parameters.

BISON↗
DOE OSTI2016

Analysis of Experimental Fuel Rod Parameters using 3D Modelling of PCMI with MPS Defect

An in-reactor experiment is being designed in order to validate the pellet-cladding mechanical interaction (PCMI) behavior of the BISON fuel performance code. The experimental parameters for the test rod being placed in the Halden Research Reactor are being determined using BISON simulations. The 3D model includes a missing pellet surface (MPS) defect to generate large local cladding deformations, which should be measureable after typical burnup times. The BISON fuel performance code is being developed at Idaho National Laboratory (INL) and is built on the Multiphysics Object-Oriented Simulation Environment (MOOSE) framework. BISON supports both 2D and 3D finite elements and solves the fully coupled equations for solid mechanics, heat conduction and species diffusion. A number of fuel performance effects are included using models for swelling, densification, creep, relocation and fission gas production & release. In addition, the mechanical and thermal contact between the fuel and cladding is explicitly modelled using a master-slave based contact algorithm. In order to accurately predict PCMI effects, the BISON code includes the relevant physics involved and provides a scalable and robust solution procedure. The depth of the proposed MPS defect is being varied in the BISON model to establish an optimum value for the experiment. The experiment will be interrupted approximately every 6 months to measure cladding radial deformation and provide data to validate BISON. The complete rodlet (~20 discrete pellets) is being simulated using a 180° half symmetry 3D model with MPS defects at two axial locations. In addition, annular pellets will be used at the top and bottom of the pellet stack to allow thermocouples within the rod to measure the fuel centerline temperature. Simulation results will be presented to illustrate the expected PCMI behavior and support the chosen experimental design parameters.

BISON↗
DOE OSTI2017

Review of CTF’s Fuel Rod Modeling Using FRAPCON-4.0’s Centerline Temperature Predictions

Coolant Boiling in Rod Arrays–Two Fluid (COBRA-TF), or CTF1 [1], is a nuclear thermal hydraulic subchannel code used throughout academia and industry. CTF’s fuel rod modeling is originally developed for VIPRE code [2]. Its methodology is based on GAPCON [3] and FRAP [4] fuel performance codes, and material properties are included from MATPRO handbook [5]. This work focuses on review of CTF’s fuel rod modeling to address shortcomings in CTF’s temperaturepredictions. CTF is compared to FRAPCON which is U.S. NRC’s steady-state fuel performance code for light-water reactor fuel rods. FRAPCON calculates the changes in fuel rod variables and temperatures including the eects of cladding hoop strain, cladding oxidation, hydriding, fuel irradiation swelling, densification, fission gas release and rod internal gas pressure. It uses fuel, clad and gap material properties from MATPRO. Additionally, it has its own models for fission gas release, cladding corrosion and cladding hydrogen pickup. It allows finite dierence or finite element approaches for its mechanical model.In this study, FRAPCON-4.0 [6] is used as a reference fuel performance code. In comparison, Halden Reactor Data for IFA432 Rod 1 and Rod 3. CTF simulations are performed in two ways; informing CTF with gap conductance value from FRAPCON, and using CTF’s dynamic gap conductance model.First case is chosen to show temperature is predicted correctly with CTF’s models for thermal and cladding conductivities once gap conductance is provided. Latter is to review CTF’s dynamic gap conductance model. These Halden test cases are selected to be representative of cases with and without any physical contact between fuel-pellet and clad while reviewing functionality of CTF’s dynamic gap conductance model. Improving the CTF’s dynamic gap conductance model will allowprediction of fuel and cladding thermo-mechanical behavior under irradiation, and better temperature feedbacks from CTF in transient calculations.

Toptan, Aysenur↗
DOE OSTI2017

Boride Based Electrode Materials with Enhanced Stability Under Extreme Conditions for MHD Direct Power Extraction. Final Scientific Report

Coal power currently makes up almost 40% of global electricity production. This method of extracting energy from coal can be added to any coal plant, improving its energy output. Not only would this prepare us to keep up with the ever-increasing energy demands but it could also allow us to significantly cut the greenhouse gas emissions for the coal power industry. Hafnium diboride (HfB 2 ), Zirconium diboride (ZrB 2 ), and their solid solution mixtures were studied, primarily for electrode coating applications in coal-fired magnetohydrodynamic (MHD) direct power extraction plants. MHD works by directly extracting current from superheated plasma flame (2725 °C) seeded with potassium salts. Obviously, the electrodes near this flame are subject to extreme temperatures and corrosive environments. The coating material needs to protect the electrodes from salt corrosion, oxidation, and melting, while still providing electrical conductivity. Transition metal diborides have many of the desired properties but need improvement for oxidation resistance above 1200 °C. Two main methods of oxidation resistance improvements were investigated during this research. The first was through electrochemical anodization, a process where a thin protective oxide layer is grown on the surface to prevent further detrimental oxidation at high temperatures. Several solutions, voltages, and methods were used to find an oxide layer that would protect at high temperatures. The second method was to use various additives and mixture ratios to improve densification and oxidation resistance. Ratios of HfB 2 and ZrB 2 tested were 1:4, 1:1, 4:1 and 1:1 with additives of Ta, Hf, and Zr metals, bringing the boron to metal ratio down to 1.86. Additionally, 1.8 mol% Gd 2 O 3 and LaB 6 were added to the 1:1 ratio HfB 2 -ZrB 2 . Hydrogen evolution reaction kinetics were also investigated to shed some light on the ability of these materials to resist corrosion. Aqueous corrosion tests were also performed in several solutions of different pH. The 1:1 ratio solution added with LaB 6 gave the best overall results both in high temperature and room temperature aqueous experiments. Further work will be needed to evaluate the efficacy of these materials for such applications.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2018

Hardface coating systems and methods for metal alloys and other materials for wear and corrosion resistant applications

The present disclosure relates generally to hardface coating systems and methods for metal alloys and other materials for wear and corrosion resistant applications. More specifically, the present disclosure relates to hardface coatings that include a network of titanium monoboride (TiB) needles or whiskers in a matrix, which are formed from titanium (Ti) and titanium diboride (TiB 2 ) precursors by reactions enabled by the inherent energy provided by the process heat associated with coating deposition and, optionally, coating post-heat treatment. These hardface coatings are pyrophoric, thereby generating further reaction energy internally, and may be applied in a functionally graded manner. The hardface coatings may be deposited in the presence of a number of fluxing agents, beta stabilizers, densification aids, diffusional aids, and multimode particle size distributions to further enhance their performance characteristics.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Quantized grain boundary states controls nanoparticle coalescence during crystallization

First order transitions like crystallization are ubiquitous in nature. Yet, mechanistic details of crystallization, i.e. polymorph selection during nucleation, details of particle aggregation, role of pre-alignment during aggregation, remain unclear. At variance with the commonly invoked oriented attachment hypothesis, we show many nanoparticles with different misorientations coalesce to form single crystals. The alignment of nanoparticles after contact irrespective of their initial misorientation is driven by extensive dislocation activity at the interface leading to disintegration of grain boundaries that is followed by surface diffusion aided neck growth and densification. Grain boundaries disintegrate because the classical Read-Shockley description breaks down at the nanoscale and only few discrete energy levels are allowed. This points to a revision of the scope of oriented attachment in crystal growth, and the role of grain boundaries during deformation and grain growth in nanocrystalline materials.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2012

Chemical Pre-Treatment of used Fuel for Long–Term Storage

Repository programs throughout the world have been slowed by the need for increased local public involvement in the siting and licensing process. The result has been an increase in the dry storage of used fuel at reactor sites and the potential that such storage may be extended for many decades, even centuries. While there are sound technical reasons to believe that dry storage can be conducted safely, there are increasing concerns that the ultimate transfer to either a future repository or a centralized separations plant may result in fractured cladding and serious handling issues, including criticality concerns. These concerns would be increased for higher burn-up fuels. Currently, various chemical pre-treatment processes under R&D for application to commercial used oxide fuel have been investigated at the laboratory scale as methods to simplify and increase the safety of the remaining stages of conventional solvent extraction processing. This includes advanced decladding methods and various oxidation/reduction processes designed to release volatile and semi-volatile fission products, produce finely divided uranium oxide powder, and ameliorate the subsequent nitric acid dissolution step. The paper examines the potential for combining several chemical and physical pre-treatment steps to minimize long-term concerns about safe transport of used fuel, possibly providing another option for future nuclear waste management. Laboratory data from both cold and hot testing will provide the basis for the evaluation. An example of a potential pre-treatment process includes shearing, advanced voloxidation and off-gas treatment, the possible mixing of the resulting uranium oxide with a secondary oxide, and densification and recanning in nitric acid-soluble storage containers for extended time periods. Chemical decladding may be feasible to replace shearing. Zirconium recycle may also be feasible, significantly reducing high level waste quantities. Both analytic and experimental data will be applied to the examination of this potential fuel cycle option.

Bresee, James↗
DOE OSTI2021

Binder Jet-Metals

Additive manufacturing is a type of material shaping technology that has many advantages over traditional manufacturing. Binder jet additive manufacturing uses a powder feedstock and an inkjet printhead to shape metal powders into preforms that are then processed in a furnace to reach full density. Because of the high throughput and low cost of the process, binder jetting is growing in popularity among manufacturers, but challenges with the process in terms of densification of the bound preforms still exist. This article will provide an overview of the binder jetting process, contrast binder jetting with the better-known powder bed fusion additive manufacturing technologies, review the metal alloys that have been printed with binder jet and then processed to full density, and provide a path forward for processing lightweight metal powders shaped by binder jetting to full density.

Elliott, Amy↗
DOE OSTI2021

Lanthanum Strontium Cobaltite-Alumina Fiber Composite Contact Material for Solid Oxide Fuel Cells

Short alumina fibers were added to LSCo contact material to enhance the contact strength and improve thermal cycle stability. Alumina fiber from 2.5 v% to 20 v% were mixed with LSCo and sintered at elevated temperatures. Sintering study showed retardation in densification of LSCo matrix with increasing alumina content. Sintered bulk strength exhibited similar behavior where strength greatly reduced at high alumina v%. Coefficient of thermal expansion showed consistent results with prediction from rule of mixture. Contact strength using anode supported YSZ bilayer coupons improved greatly with the presence of small amount (2.5-5 v%) alumina fibers and no substantial reduction after 10 deep thermal cycles. Candidate LSCo-Al2O3 contact materials was validated in a generic stack test fixture for 1000h at 800oC followed by 10 thermal cycles. Results of impedance analysis showed substantial improvement in thermal cycle stability as compared to LSCo parent materials.

SOFC cathode, strength, LSCo, alumina↗