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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 1,531 records · Page 85
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Summary of DASSH-CFD Inter-Assembly Heat Transfer Comparison

Fast reactor core design requires integration of detailed power distributions obtained from neutronics models and thermal fluids calculations to determine temperature distributions and flow conditions. During the design phase, calculations may be repeated as specifications change and computational expense must be balanced with solution accuracy, creating an opportunity for the use of intermediate-fidelity codes. To that end, the Ducted Assembly Steady-State Heat Transfer Software (DASSH) has been developed at Argonne National Laboratory to perform full-core, steady state coolant and fuel pin temperature calculations in reactors consisting of hexagonal, ducted assemblies. DASSH is a first-order, finite volume subchannel code based on methodologies initially introduced in the legacy thermal hydraulics codes SUPERENERGY-2 and SE2-ANL. It can work coupled with the Argonne Reactor Computational (ARC) code suite to obtain neutron and gamma power distributions based on neutron transport solutions and features many improvements and new capabilities compared to its predecessors. DASSH calculates temperatures by balancing energy between subchannels and relies on correlations to account for flow distribution and coolant mixing.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2023

An attribution of the low single-scattering albedo of biomass burning aerosol over the southeastern Atlantic

Abstract. Aerosol over the remote southeastern Atlantic is some of the most sunlight-absorbing aerosol on the planet: the in situ free-tropospheric single-scattering albedo at the 530 nm wavelength (SSA530 nm) ranges from 0.83 to 0.89 within ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) aircraft flights from late August–September. Here we seek to explain the low SSA. The SSA depends strongly on the black carbon (BC) number fraction, which ranges from 0.15 to 0.4. Low organic aerosol (OA)-to-BC mass ratios of 8–14 and modified combustion efficiency values >0.975 point indirectly to the dry, flame-efficient combustion of primarily grass fuels, with back trajectories ending in the miombo woodlands of Angola. The youngest aerosol, aged 4–5 d since emission, occupied the top half of a 5 km thick plume sampled directly west of Angola with a vertically consistent BC:ΔCO (carbon monoxide) ratio, indicating a homogenization of the source emissions. The younger aerosol, transported more quickly off of the continent by stronger winds, overlaid older, slower-moving aerosol with a larger mean particle size and fraction of BC-containing particles. This is consistent with ongoing gas condensation and the coagulation of smaller non-BC particles upon the BC-containing particles. The particle volumes and OA:BC mass ratios of the older aerosol were smaller, attributed primarily to evaporation following fragmentation, instead of dilution or thermodynamics. The CLARIFY (CLoud–Aerosol–Radiation Interaction and Forcing: Year 2017) aircraft campaign sampled aerosols that had traveled further to reach the more remote Ascension Island. CLARIFY reported higher BC number fractions, lower OA:BC mass ratios, and lower SSA yet larger mass absorption coefficients compared to this study's. Values from one ORACLES 2017 flight, held midway to Ascension Island, are intermediate, confirming the long-range changes. Overall the data are most consistent with continuing oxidation through fragmentation releasing aerosols that subsequently enter the gas phase, reducing the OA mass, rather than evaporation through dilution or thermodynamics. The data support the following best fit: SSA530nm=0.801+0055⋅(OA:BC) (r=0.84). The fires of southern Africa emit approximately one-third of the world's carbon; the emitted aerosols are distinct from other regional smoke emissions, and their composition needs to be represented appropriately to realistically depict regional aerosol radiative effects.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1979

The Shaw meteorite - History of a chondrite consisting of impact-melted and metamorphic lithologies

Three intermingled lithologies are identified in the Shaw L-group chondrite: a light-colored lithology with a poikilitic texture, consisting of olivine and augite crystals surrounded by larger orthopyroxene grains; a dark-colored lithology containing remnant chondrules and exhibiting a microgranular texture; and a gray lithology which appears to be intermediate between the other two. Contrary to published opinions, the Shaw meteorite contains normal L-group chondrite abundances of metal and troilite, though these phases are irregularly distributed. The lithological analyses suggest that 4.52 Byr ago an impact took place on the L-group chondrite parent object of Shaw.

Taylor, G. J.↗
NASA NTRS1982

Creep and rupture of an ODS alloy with high stress rupture ductility

The creep and stress rupture properties of an oxide (Y2O3) dispersion strengthened nickel-base alloy, which also is strengthened by gamma-prime precipitates, was studied at 760 and 1093 C. At both temperatures, the alloy YDNiCrAl exhibits unusually high stress rupture ductility as measured by both elongation and reduction in area. Failure was transgranular, and different modes of failure were observed including crystallographic fracture at intermediate temperatures and tearing or necking almost to a chisel point at higher temperatures. While the rupture ductility was high, the creep strength of the alloy was low relative to conventional gamma prime strengthened superalloys in the intermediate temperature range and to ODS alloys in the higher temperature range. These findings are discussed with respect to the alloy composition; the strengthening oxide phases, which are inhomogeneously dispersed; the grain morphology, which is coarse and elongated and exhibits many included grains; and the second phase inclusion particles occurring at grain boundaries and in the matrix. The creep properties, in particular the high stress dependencies and high creep activation energies measured, are discussed with respect to the resisting stress model of creep in particle strengthened alloys.

Mcalarney, M. E.↗
NASA NTRS1987

Fluoride salts and container materials for thermal energy storage applications in the temperature range 973 to 1400 K

Multicomponent fluoride salt mixtures were characterized for use as latent heat of fusion heat storage materials in advanced solar dynamic space power systems with operating temperatures in the range of 973 to 1400 K. The melting points and eutectic composition for many systems with published phase diagrams were verified, and several new eutectic compositions were identified. Additionally, the heats of fusion of several binary and ternary eutectics and congruently melting intermediate compounds were measured by differential scanning calorimetry. The extent of corrosion of various metals by fluoride melts was estimated from thermodynamic considerations, and equilibrium conditions inside a containment vessel were calculated as functions of the initial moisture content of the salt and free volume above the molten salt. Preliminary experimental data on the corrosion of commercial, high-temperature alloys in LiF-19.5CaF2 and NaF-27CaF2-36MgF2 melts are presented and compared to the thermodynamic predictions.

Misra, Ajay K.↗
NASA NTRS1987

Fluoride salts and container materials for thermal energy storage applications in the temperature range 973 - 1400 K

Multicomponent fluoride salt mixtures were characterized for use as latent heat of fusion heat storage materials in advanced solar dynamic space power systems with operating temperatures in the range of 973 to 1400 K. The melting points and eutectic composition for many systems with published phase diagrams were verified, and several new eutectic compositions were identified. Additionally, the heats of fusion of several binary and ternary eutectics and congruently melting intermediate compounds were measured by differential scanning calorimetry. The extent of corrosion of various metals by fluoride melts was estimated from thermodynamic considerations, and equilibrium conditions inside a containment vessel were calculated as functions of the initial moisture content of the salt and free volume above the molten salt. Preliminary experimental data on the corrosion of commercial, high-temperature alloys in LiF-19.5CaF2 and NaF-27CaF2-36MgF2 melts are presented and compared to the thermodynamic predictions.

Misra, Ajay K.↗
NASA NTRS1987

Resonant interactions between cometary ions and low frequency electromagnetic waves

The conditions for resonant wave amplification in a plasma with a ring-beam distribution which is intended to model pick-up ions in a cometary environment are investigated. The inclination between the interplanetary field and the solar wind is found to play a crucial role in governing both the resonant frequency and the growth rate of any unstable mode. It is suggested that the low-frequency MHD mode should experience the most rapid amplification for intermediate inclination. In the frame of the solar wind, such waves should propagate along the field in the direction upstream toward the sun with a phase speed lower than the beaming velocity of the pick-up ions. This mechanism may account for the presence of the interior MHD waves noted by satellites over a region surrounding comets Giacobini-Zinner and Halley.

Thorne, Richard M.↗
DOE OSTI2015

Potential sterile neutrino search utilizing spectral distortion in a two-reactor/one-detector configuration

There is an observed deficit of about 6% in the expected rate of anti-neutrino interactions when averaging over many different reactor experiments. While the significance of the deficit is low (98.6 % CL), there is speculation that a non-interacting “sterile” neutrino could be the cause. Here, we explore the possibility of a two-reactor/one-detector experiment at intermediate distances (100-500 meters) to look for a sterile neutrino in the mass range implied by this deficit. A method for probing Δm 2 phase space is developed using interference patterns between two oscillated spectra at different baselines. This method is used to investigate the potential sensitivity of the Double Chooz experiment, which has a single Near Detector at distances of 351 m and 465 m from two reactors of identical design. We conclude that Double Chooz could investigate sterile neutrino in the Δm 2 range of 0.002 to 0.5 eV 2 over 5 years of near detector running.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Synthesis and characterization of La{sub 0.6}Sr{sub 0.4}Fe{sub 0.8}Cu{sub 0.2}O{sub 3−δ} oxide as cathode for Intermediate Temperature Solid Oxide Fuel Cells

Nanocrystalline La{sub 0.6}Sr{sub 0.4}Fe{sub 0.8}Cu{sub 0.2}O{sub 3−δ} (LSFCu) material was synthetized by combustion method using EDTA as fuel/chelating agent and NH{sub 4}NO{sub 3} as combustion promoter. Structural characterization using thermodiffraction data allowed to determine a reversible phase transition at 425 °C from a low temperature R-3c phase to a high temperature Pm-3m phase and to calculate the thermal expansion coefficient (TEC) of both phases. Important characteristics for cathode application as electronic conductivity and chemical compatibility with Ce{sub 0.9}Gd{sub 0.1}O{sub 2−δ} (CGO) electrolyte were evaluated. LSFCu presented a p-type conductor behavior with maximum conductivity of 135 S cm{sup −1} at 275 °C and showed a good stability with CGO electrolyte at high temperatures. This work confirmed that as prepared LSFCu has excellent microstructural characteristics and an electrical conductivity between 100 and 60 S cm{sup −1} in the 500–700 °C range which is sufficiently high to work as intermediate temperature Solid Oxide Fuel Cells (IT-SOFCs) cathode. However a change in the thermal expansion coefficient consistent with a small oxygen loss process may affect the electrode-electrolyte interface during fabrication and operation of a SOFC. - Graphical abstract: Nanocrystalline La{sub 0.6}Sr{sub 0.4}Fe{sub 0.8}Cu{sub 0.2}O{sub 3−δ} was prepared by gel combustion and characterized by X-ray thermodiffraction and its conductivity was determined. The phase shows a reversible rhombohedral to cubic structural phase transition at 425 °C and a semiconductor to metallic phase transition at 275 °C. - Highlights: • LSFCu was prepared by gel combustion route using EDTA and NH{sub 4}NO{sub 3}. • LSFCu shows a reversible phase transition at 425 °C from R-3c to Pm-3m phase. • The sample has a maximum conductivity value of 135 S cm{sup −1} at 275 °C. • LSFCu shows a good chemical compatibility with CGO at 900 °C.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Characterization of Low Level and Intermediate Nuclear Waste: improvements in calorimetric measurement combined radiological modelling - 16144

Since 40 years, calorimetry allows to determine precisely amounts of nuclear material within a container. Combined with gamma spectrometry, calorimetric measurements give plutonium contents with a low level of uncertainty for each isotope. Calorimetry is used in a lot of nuclear facilities all around the world for plutonium or tritium inventories. It is one of the best solutions to estimate the overall quantity of nuclear material on a wide range of mass, from a few milligrams up to kilograms of radionuclides. In the case of drums containing nuclear waste, characterization was very challenging due to complex matrix, volume and low level activities. The measurement time was a real problem with large volume container and organic matrix with high air content. New designs of SETARAM calorimeters allow to measure nuclear material contents in very large container (up to 385 liters) and/or with a very low detection limit (10 μWatt). These new concepts are based on single measurement cell and vacuum chamber for low level uncertainties. The acquisition system and electronic temperature regulation are highly improved to increase the detection limit, accuracy and precision of the measurement. These modern technological developments within the calorimetry field give the promise of faster measurement times and precise measurements. These devices can be used in waste management of nuclear facilities with a better accuracy and lower uncertainties than others techniques. It is a non-destructive and non-intrusive method. There is no matrix effect which can bias the results. Waste can also be in solid, liquid or gas phase. The new calorimeters are able to give amounts of plutonium, tritium or others alpha or beta emitter radionuclides and allow determining the classification of waste (low level or intermediate). A measurement approach combining very large volume calorimeter, gamma spectrometry and radiological modelling will be presented as an integrated automatic waste characterization system. This system with a calculation step is taking into account the gamma emitters contribution on the total thermal power measured within the calorimeter. The aim of the system is to give a precise quantification of the radionuclides in the waste container with a precise value of the total uncertainties. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2014

Discovery of a thermally persistent h.c.p. solid-solution phase in the Ni-W system

Although the accepted Ni-W phase diagram does not reveal the existence of h.c.p.-based phases, h.c.p.-like stacking sequences were observed in magnetron-co-sputtered Ni-W thin films at W contents of 20 to 25 at. %, by using transmission electron microscopy and X-ray diffraction. The occurrence of this h.c.p.-like solid-solution phase could be rationalized by first-principles calculations, showing that the vicinity of the system's ground-state line is populated with metastable h.c.p.-based superstructures in the intermediate concentration range from 20 to 50 at. % W. The h.c.p.-like stacking in Ni-W films was observed to be thermally persistent, up to temperatures as high as at least 850 K, as evidenced by extensive X-ray diffraction analyses on specimens before and after annealing treatments. The tendency of Ni-W for excessive planar faulting is discussed in the light of these new findings.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

IMPROVING INTERMEDIATE TEMPERATURE PERFORMANCE OF NI-YSZ CERMET ANODES FOR SOLID OXIDE FUEL CELLS BY INFILTRATION OF NICKEL NANOPARTICLES AND MIXED IONIC ELECTRONIC CONDUCTOR

Solid oxide fuel cells (SOFCs) are one of the most efficient and environment-friendly devices for electricity generation. One critical challenge of SOFC commercialization is high cell operating temperatures (800°C-1000°C), which lead to high material costs, high performance degradation rates, long start-up and shutdown times, and limited portable applications. Intermediate temperature (600°C-800°C) operation of SOFCs is limited by sluggish electrode reaction kinetics. The objective of this research is to improve intermediate temperature performance of commercially available Ni-YSZ cermet anode supported SOFCs by liquid infiltration of the anode. One effective method to improve kinetics of electrochemical reactions at the anode is to increase the density of reaction sites, which are known as the triple phase boundaries (TPBs). The porous Ni-YSZ cermet anodes were liquid infiltrated with Ni nanoparticles, leading to a four-fold increase in TPB density in the anode. The improved electrochemical performance of the infiltrated cells compared to the uninfiltrated cells highlights the effectiveness of anode infiltration in facilitating improved anode electrochemical reaction kinetics. However, the post-electrochemical testing characterization revealed that Ni nanoparticles were not stable due to Ni coarsening and were mostly isolated indicating that not all of the additional TPBs were fully utilized in electrochemical reactions due to the lack of an electronic pathway between the Ni nanoparticles. In order to improve microstructural stability of the infiltrated Ni nanoparticles, and to fully utilize the added TPBs, co-infiltration of Ni with a mixed ionic and electronic conductor (MIEC) was carried out. Two MIEC materials are chosen based on their chemical stability and conductivity in the anode operating environments; Gd 0.1 Ce 0.9 O 2-δ (GDC), a predominantly an ionic conductor, and La 0.6 Sr 0.3 Ni 0.15 Cr 0.85 O 3-δ (LSNC), a predominantly electronic conductor, and cells were successfully co-infiltrated to form Ni-GDC and Ni-LSNC nanostructures with the MIEC phases connecting the Ni nanoparticles. Stability tests demonstrated that both MIECs inhibited Ni nanoparticle coarsening. Electrochemical studies showed that Ni-GDC is the most effective for improved anode kinetics. A long-term (120 hours) electrochemical test indicated that infiltration of Ni-GDC into Ni-YSZ cermet anode effectively improves overall cell performance at intermediate temperatures and maintains the performance gain for a long period of time.

Lu, Yanchen↗
DOE OSTI2012

Test of the Glauber formula for nucleon-deuteron scattering at intermediate energies

A high-precision test of the Glauber formula for the amplitude of nucleon-deuteron scattering is performed. Nucleon-nucleon amplitudes used in the calculations depend on the spins of interacting particles, phase shifts, and mixing parameters. These amplitudes were derived by using the Njim I, Njim II, Njim 93, and Reid 93 realistic potentials. The differential cross sections for nucleon-deuteron scattering were calculated for the projectile-nucleon energies of 65, 95, 135, 150, 190, and 250 MeV, and the results of these calculations were compared with experimental data.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Invariants in the Yukawa system's thermodynamic phase diagram

This paper shows that several known properties of the Yukawa system can be derived from the isomorph theory, which applies to any system that has strong correlations between its virial and potential-energy equilibrium fluctuations. Such “Roskilde-simple” systems have a simplified thermodynamic phase diagram deriving from the fact that they have curves (isomorphs) along which structure and dynamics in reduced units are invariant to a good approximation. We show that the Yukawa system has strong virial potential-energy correlations and identify its isomorphs by two different methods. One method, the so-called direct isomorph check, identifies isomorphs numerically from jumps of relatively small density changes (here 10%). The second method identifies isomorphs analytically from the pair potential. The curves obtained by the two methods are close to each other; these curves are confirmed to be isomorphs by demonstrating the invariance of the radial distribution function, the static structure factor, the mean-square displacement as a function of time, and the incoherent intermediate scattering function. Since the melting line is predicted to be an isomorph, the theory provides a derivation of a known approximate analytical expression for this line in the temperature-density phase diagram. The paper's results give the first demonstration that the isomorph theory can be applied to systems like dense colloidal suspensions and strongly coupled dusty plasmas.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2011

The ferroelectric phase of CdTiO{sub 3}: A powder neutron diffraction study

The synthesis of bulk samples of polycrystalline CdTiO{sub 3} in both the rhombohedral ilmenite and orthorhombic perovskite forms is described and the structures of these have been refined using powder neutron diffraction data. This involved the preparation of samples enriched in {sup 114}Cd. Cooling perovskite-type CdTiO{sub 3} to 4 K induces a ferroelectric phase transition, with the neutron data suggesting the low temperature structure is in Pna2{sub 1}. Mode analysis shows the polar mode to be dominant at low temperatures. The ilmenite-structure of CdTiO{sub 3} is compared with that of ZnTiO{sub 3}. The refined scattering length of the {sup 114}Cd is estimated to be 5.56 fm. Attempts to dope CdTiO{sub 3} with Ca and Sr are described. - Graphical abstract: The structure of three phases of CdTiO{sub 3} have been refined using high resolution powder neutron diffraction data. This involved the preparation of samples enriched in {sup 114}Cd. Cooling perovskite-type CdTiO{sub 3} to 4 K results in a ferroelectric phase in Pna2{sub 1}. Highlights: > Both the ilmenite and perovskite forms of CdTiO{sub 3} have been prepared using {sup 114}Cd. > Cooling the perovskite form results in a ferroelectric phase. > The structures of these are refined from powder neutron diffraction data. > Attempts to dope CdTiO{sub 3} are described.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2011

Programmable Oscillator

A programmable oscillator is a frequency synthesizer with an output phase that tracks an arbitrary function. An offset, phase-locked loop circuit is used in combination with an error control feedback loop to precisely control the output phase of the oscillator. To down-convert the received signal, several stages of mixing may be employed with the compensation for the time-base distortion of the carrier occurring at any one of those stages. In the Goldstone Solar System Radar (GSSR), the compensation occurs in the mixing from an intermediate frequency (IF), whose value is dependent on the station and band, to a common IF used in the final stage of down-conversion to baseband. The programmable oscillator (PO) is used in the final stage of down-conversion to generate the IF, along with a time-varying phase component that matches the time-base distortion of the carrier, thus removing it from the final down-converted signal.

Quirk, Kevin J.↗
NASA NTRS2005

Gas-Phase Formation Rates of Nitric Acid and Its Isomers Under Urban Conditions

Ozone formation in urban smog is controlled by a complex set of reactions which includes radical production from photochemical processes, catalytic cycles which convert NO to NO2, and termination steps that tie up reactive intermediates in long-lived reservoirs. The reaction OH + NO2 + M -4 HONO2 + M (la) is a key termination step because it transforms two short-lived reactive intermediates, OH and NO2, into relatively long-lived nitric acid. Under certain conditions (low VOC/NOx), ozone production in polluted urban airsheds can be highly sensitive to this reaction, but the rate parameters are not well constrained. This report summarizes the results of new laboratory studies of the OH + NO2 + M reaction including direct determination of the overall rate constant and branching ratio for the two reaction channels under atmospherically relevant conditions.

Air pollution↗