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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Design of the cryogenic moderator system for the second target station

The Second Target Station (STS) at Oak Ridge National Laboratory will be a 700 kW pulsed spallation neutron source designed to provide the world's highest brightness cold neutron beams. In order to produce the required neutron performance, two compact liquid hydrogen moderators are located adjacent to the tungsten spallation target and must be supplied with less than 20 K hydrogen and a para hydrogen fraction of 99.8% or greater. The Cryogenic Moderator System (CMS) will consist of a single hydrogen loop feeding the two moderators in series cooled by a helium refrigerator with a cooling capacity of 2.5 kW at 17 K. The hydrogen loop consists of a hydrogen circulator, hydrogen helium heat exchanger, ortho-para converter, accumulator, transfer lines and heater. The design of the hydrogen loop is based on the CMS design of the First Target Station at the Spallation Neutron Source and some of the component designs may be reused. General hydrogen temperature control is provided by controlling the flowrate of helium to the heat exchanger. The hydrogen loop will have a constant flowrate of 0.5 L/s and remove a nuclear heat load of about 850 W from the two moderators, which is deposited both directly in the hydrogen and the adjacent hydrogen containing structures. Because the nuclear heat load is accelerator driven, the hydrogen system must remain stable when the heat load is removed instantaneously during beam trips. System stability is maintained passively with the accumulator and actively with the heater. Ionizing radiation which interacts with the liquid hydrogen drives backconversion of the hydrogen from parahydrogen to orthohydrogen. The STS moderator performance is very sensitive to small fractions of orthohydrogen requiring an ortho-para converter to maintain the hydrogen supplied to the moderators at near equilibrium parahydrogen concentration. STS CMS is in the early stage of preliminary design and current focus is evaluating component sizing and system stability during beam transients.

Janney, Jim↗
DOE OSTI2024

Proton beam power limits for stationary water-cooled tungsten target with different cladding materials

The proton beam power limit for a solid-tungsten spallation target is largely determined by beam induced thermomechanical structural loads and decay heat power deposition, while its lifetime is limited by radiation damage and fatigue life of the target materials. In this paper, we studied the power limits of a stationary water-cooled solid tungsten target concept. Tantalum clad tungsten was considered as a reference case. Being a low activation material, zircaloy 2 cladding option was studied and its decay heat driven power limit was compared with the reference case. Zirconium alloys have proven operations records in spallation target and nuclear fission environments, supported by materials data obtained from post irradiation examinations. Recent study also demonstrated feasibility of diffusion bonding zirconium to tungsten using vanadium foil inter layer. Particle transport simulations code FLUKA was used to calculate energy deposition and decay heat power deposition in the target, based on the beam parameters technically feasible at the Second Target Station of the Spallation Neutron Source at Oak Ridge National Laboratory. The energy deposition data were used for flow, thermal, and structural analyses to determine the beam intensity limit on the target concept studied. The decay heat deposition data were used to calculate the transient temperature evolution in the tungsten volumes in a loss of coolant accident (LOCA) scenario to determine its beam power limit. For a 1.3 GeV proton beam, the power limit on a stationary target was 400 kW for a tantalum clad target model and 800 kW for a zircaloy 2 clad target model.

Lee, Yong Joong↗
NASA NTRS1976

Microcraters formed in hot glass by hypervelocity projectiles

Microcraters were formed in heated soda-lime glass by the normal incidence of spheres of plastic or fused silica with diameters between 0.8 and 4.5 microns and velocities between 2.5 and 10 km/s. The morphology of the craters in targets at temperatures up to 800 C is little different from those formed in unheated glass. Spallation still occurs to the same extent and above the same velocity threshold, but the spalls sag and sharp edges become dull in a few seconds at temperatures above the softening point. There is a small increase in the flow of glass from the central pit into a narrow lip at the higher temperatures, but this lip is often removed by spallation, especially at the higher velocities of impact. There is no evidence of a splashed lip with strings of melt overlying the spalled area. The results in conjunction with other evidence suggest that most lunar craters of micrometer size with a smooth central pit, splashed lip, and a spallation zone are the result of primary impacts.

Vedder, J. F.↗
NASA NTRS1978

Helium /3/ rich solar flares

Several aspects of a solar flare model that emphasizes evidence for the formation of current filaments as mechanisms of field dissipation are discussed. The origin of flare magnetic fields is considered, along with the thermal distribution, electron density, and high-energy X ray emission of flares. It is suggested that the extreme He-3 enrichment in some solar flares is due to spallation and the subsequent confinement of spallation products in a high-temperature high-density plasma associated with the magnetic instability that produces the flare. A current filament is assumed to produce the spallation and maintain the temperature that yields the high-energy X-ray spectrum and depletes the isotopes D, Li, Be, and B, as observed.

Colgate, S. A.↗
NASA NTRS1986

Studies on cosmogenic nuclides in meteorites with regard to an application as potential depth indicators

Measurements of stable and radioactive spallation products in meteorites allow to investigate their histories, especially with respect to the exposure to galactic cosmic ray particles and the pre-atmospheric size of the object. While the concentrations of spallation products lead to the determination of exposure and terrestrial ages, production rate ratios are characteristic for the location of the sample in the meteorite. So, one of the aims of this investigation on meteorites is to obtain depth indicators from suitable pairs of cosmogenic nuclides. Because of the different depth profiles for nuclide productions it is necessary to determine the concentrations of a larger number of spallation products in aliquots of a single small sample. Such same sample measurements of Be-10 and light noble gases were performed on 15 ordinary chondrites (7 H- and 8 L-chondrites. Be-10 was determined by accelerator mass spectrometry and the noble gases were measured by static mass spectrometry. The results are summarized and discussed.

Sarafin, R.↗
NASA NTRS1988

Oxidation behavior of FeAl+Hf,Zr,B

The oxidation behavior of Fe-40Al-1Hf, Fe-40Al-1Hf-0.4B, and Fe-40Al-0.1Zr-0.4B (at. percent) alloys was characterized after 900, 1000, and 100 C exposures. Isothermal tests revealed parabolic kinetics after a period of transitional theta-alumina scale growth. The parabolic growth rates for the subsequent alpha-alumina scales were about five times higher than those for NiAl+0.1Zr alloys. The isothermally grown scales showed a propensity toward massive scale spallation due to both extensive rumpling from growth stresses and to an inner layer of HfO2. Cyclic oxidation for 200 1-hr cycles produced little degradation at 900 or 1000 C, but caused significant spallation at 1100 C in the form of small segments of the outer scale. The major difference in the cyclic oxidation of the three FeAl alloys was increased initial spallation for FeAl+Zr,B. Although these FeAl alloys showed many similarities to NiAl alloys, they were generally less oxidation resistant. It is believed that this resulted from nonoptimal levels of dopants and larger thermal expansion mismatch stresses.

Smialek, James L.↗
NASA NTRS1989

Oxidation behavior of FeAl+Hf,Zr,B

The oxidation behavior of Fe-40Al-1Hf, Fe-40Al-1Hf-0.4B, and Fe-40Al-0.1Zr-0.4B (at. percent) alloys was characterized after 900, 1000, and 100 C exposures. Isothermal tests revealed parabolic kinetics after a period of transitional theta-alumina scale growth. The parabolic growth rates for the subsequent alpha-alumina scales were about five times higher than those for NiAl+0.1Zr alloys. The isothermally grown scales showed a propensity toward massive scale spallation due to both extensive rumpling from growth stresses and to an inner layer of Hf02. Cyclic oxidation for 200 1-hr cycles produced little degradation at 900 or 1000 C, but caused significant spallation at 1100 C in the form of small segments of the outer scale. The major difference in the cyclic oxidation of the three FeAl alloys was increased initial spallation for FeAl+Zr,B. Although these FeAl alloys showed many similarities to NiAl alloys, they were generally less oxidation resistant. It is believed that this resulted from nonoptimal levels of dopants and larger thermal expansion mismatch stresses.

Smialek, James L.↗
NASA NTRS1991

Comparative xenology of two angrites

Results are presented on Xe analysis during stepwise heating of the angrite meteorite Lewis Cliff 86010 and the Angra dos Reis angrite. It is shown that both the Lewis Cliff and the Angra dos Reis angrites are poor in trapped Xe and are rich in fission Xe from Pu-244 and in spallation Xe produced by cosmic ray irradiation of Ba and the light REE, and that neither meteorite has an excess of Xe-129 derived from I-129. Both meteorites show significant variations in the composition of the spallation Xe attributable to the separation of the Ba and REE components. The Ba-related spallation in Lewis Cliff differs from that in Angra dos Reis primarily in a lower relative yield of the neutron-sensitive Xe-131 isotope, suggesting a lower neutron flux during cosmic ray exposure for the Lewis Cliff meteorite.

Hohenberg, Charles M.↗
NASA NTRS2003

Universal Responses of Cyclic-Oxidation Models Studied

Oxidation is an important degradation process for materials operating in the high-temperature air or oxygen environments typical of jet turbine or rocket engines. Reaction of the combustion gases with the component material forms surface layer scales during these oxidative exposures. Typically, the instantaneous rate of reaction is inversely proportional to the existing scale thickness, giving rise to parabolic kinetics. However, more realistic applications entail periodic startup and shutdown. Some scale spallation may occur upon cooling, resulting in loss of the protective diffusion barrier provided by a fully intact scale. Upon reheating, the component will experience accelerated oxidation due to this spallation. Cyclic-oxidation testing has, therefore, been a mainstay of characterization and performance ranking for high-temperature materials. Models simulate this process by calculating how a scale spalls upon cooling and regrows upon heating (refs. 1 to 3). Recently released NASA software (COSP for Windows) allows researchers to specify a uniform layer or discrete segments of spallation (ref. 4). Families of model curves exhibit consistent regularity and trends with input parameters, and characteristic features have been empirically described in terms of these parameters. Although much insight has been gained from experimental and model curves, no equation has been derived that can describe this behavior explicitly as functions of the key oxidation parameters.

Smialek, James L.↗
NASA NTRS2011

Fracture Mechanics Analyses of Subsurface Defects in Reinforced Carbon-Carbon Joggles Subjected to Thermo-Mechanical Loads

Coating spallation events have been observed along the slip-side joggle region of the Space Shuttle Orbiter wing-leading-edge panels. One potential contributor to the spallation event is a pressure build up within subsurface voids or defects due to volatiles or water vapor entrapped during fabrication, refurbishment, or normal operational use. The influence of entrapped pressure on the thermo-mechanical fracture-mechanics response of reinforced carbon-carbon with subsurface defects is studied. Plane-strain simulations with embedded subsurface defects are performed to characterize the fracture mechanics response for a given defect length when subjected to combined elevated-temperature and subsurface-defect pressure loadings to simulate the unvented defect condition. Various subsurface defect locations of a fixed-length substrate defect are examined for elevated temperature conditions. Fracture mechanics results suggest that entrapped pressure combined with local elevated temperatures have the potential to cause subsurface defect growth and possibly contribute to further material separation or even spallation. For this anomaly to occur, several unusual circumstances would be required making such an outcome unlikely but plausible.

Knight, Norman F., Jr.↗
NASA NTRS2017

Plume-Surface Interaction Modeling for a Human-Scale Mars Lander

Landing vehicles impart thermal and strain energy onto the landing site from the retrorocket exhaust. Depending on the design of the vehicle, the energy may be great enough to cause spallation at the landing site. This damage may be minor and repairable in the case of landing on a terrestrial landing pad. For missions to other planetary bodies, the spallation may cause the landing site to become uneven and unstable, as well as damage. Simulating this phenomenon in a laboratory or computationally would require a significant amount of time and other resources. These resources typically are not available during the design phase of a mission. This paper presents a computationally-efficient model for the temperature and stress distributions that arise during landing. These quantities can be used along with existing failure criteria, such as the Hoek-Brown criterion for geological materials, to quickly determine whether spallation will occur. The stress and temperature distributions at the landing site are inherently 3D; however, there is a plane of symmetry and in that plane the distributions are 2D. Both quantities are modeled using series solutions to their governing partial differential equations (PDEs). The stress is modeled using the Airy stress potential function and its governing PDE is the biharmonic equation. The temperature is governed by Fourier's law. The models assume that stress due to gravity can be neglected, the points in the plane do not accelerate, and that the material properties are constant.

Hart, Kenneth↗
NASA NTRS2016

In Situ Measurement of Atmospheric Krypton and Xenon on Mars with Mars Science Laboratory

Mars Science Laboratorys Sample Analysis at Mars (SAM) investigation has measured all of the stable isotopes of the heavy noble gases krypton and xenon in the martian atmosphere, in situ, from the Curiosity Rover at Gale Crater, Mars. Previous knowledge of martian atmospheric krypton and xenon isotope ratios has been based upon a combination of the Viking missions krypton and xenon detections and measurements of noble gas isotope ratios in martian meteorites. However, the meteorite measurements reveal an impure mixture of atmospheric, mantle, and spallation contributions. The xenon and krypton isotopic measurements reported here include the complete set of stable isotopes, unmeasured by Viking. The new results generally agree with Mars meteorite measurements but also provide a unique opportunity to identify various non-atmospheric heavy noble gas components in the meteorites. Kr isotopic measurements define a solar-like atmospheric composition, but deviating from the solar wind pattern at 80Kr and 82Kr in a manner consistent with contributions originating from neutron capture in Br. The Xe measurements suggest an intriguing possibility that isotopes lighter than 132Xe have been enriched to varying degrees by spallation and neutron capture products degassed to the atmosphere from the regolith, and a model is constructed to explore this possibility. Such a spallation component, however, is not apparent in atmospheric Xe trapped in the glassy phases of martian meteorites.

Conrad, P. G.↗
NASA NTRSDate not supplied

Investigating Material Behavior in Atmospheric Entry Conditions: Arc-Jet Testing Insights from Meteorite Ablation to High-Temperature Coatings.

Arc-jet testing is an indispensable tool in elucidating the complex interactions materials undergo when subjected to the extreme thermal and mechanical stresses of atmospheric entry. By replicating these harsh conditions, arc-jets enable researchers to explore critical phenomena such as ablation, melting, and spallation, generating invaluable data that informs the development of sophisticated, physics-based models. These models are pivotal not only in predicting material performance for spacecraft re-entry systems but also in assessing the threat posed by celestial bodies as they encounter Earth’s atmosphere. One of the leading facilities for such investigations is the Hypersonic Materials Environmental Test System (HyMETS) at NASA’s Langley Research Center. A pioneering test campaign conducted at HyMETS focused on unraveling the ablation mechanisms of an ordinary chondrite meteorite (Tamdakht H5) and a terrestrial analog (basalt). These studies unveiled distinct material behaviors: Tamdakht demonstrated a remarkably stable melt flow, with mass loss primarily driven by the volatilization of elements such as iron and sodium, whereas basalt exhibited more aggressive surface degradation due to the rapid decomposition of hydrated minerals, culminating in significant spallation and surface material ejection. Beyond meteorite analysis, HyMETS has also been integral in the exploration of advanced Thermal Protection Systems (TPS) such as Phenolic Impregnated Carbon Ablator (PICA), a material with extensive flight heritage in missions like Stardust, Mars Science Laboratory, Mars 2020, and Osiris-REx. PICA, when coated with NuSil CV-1144-0—a polysiloxane resin designed to prevent particle shedding—undergoes a remarkable transformation upon heating. The resin pyrolyzes to form a thin, oxidation-resistant silicon oxycarbide layer that profoundly influences the material’s thermal response through a sophisticated four-stage process. Initially, the silicon oxycarbide acts as a formidable barrier, impeding reactive interactions with the PICA char and effectively suppressing surface temperature rise and material recession. However, as the heating persists, the protective layer decomposes via carbothermal reduction, exposing the underlying char, which in turn leads to a dramatic spike in surface temperature and accelerated material erosion. In the final stage, equilibrium is reached, with recession rates aligning with those of the virgin material. This intricate understanding of PICA-NuSil behavior under extreme conditions offers valuable insights, enhancing material response models and advancing the development of next-generation TPS for space exploration.

Chemistry↗
DOE OSTI2026

Early-stage uranium-hydrogen corrosion kinetics and mechanism

Research into the early-stage uranium-hydrogen degradation mechanism lacks unified interpretation and understanding due to inadequate temporal and spatial characterization resolution required to unify reaction observations. In this study, white-light interferometry was adapted to characterize the uranium-hydrogen reaction at a temperature of 50 °C and hydrogen pressure of 13.8 kPa. The uranium surface remained unchanged for 62 min during the hydride induction period before the first hydride blister appeared. This blister was monitored from induction through critical spallation and UH₃ powder release during rapid surface hydriding. The critical spallation dimensions measured for height, diameter, area, and perimeter of the first blister were 1.79 µm, 17.58 µm, 187.7 µm 2 and 59.79 µm. Hydriding growth kinetics were assessed by tracking the first hydride site over the reaction time. Analysis shows that the spall-front velocity of the hydride was changing at a rate of 0.91 µm/min which compares favorably with legacy Sievert’s experiments in literature. Total percentage of the surface area hydrided after 242 min was 42.7%, and post-characterization of the UH 3 powders shows both α-UH 3 and β-UH 3 . This work highlights the strength of characterizing the early-stage uranium-hydrogen reaction using white-light interferometry, but more importantly, unifying the understanding and mechanism of the uranium-hydrogen reaction kinetics.

Materials science↗
DOE OSTI2025

Sample changers for direct geometry neutron chopper spectrometers

The advent of higher flux neutron sources has made the use of sample changers appropriate across the instrument suites at neutron scattering facilities. We examine the efficiency, design, and operation of two sample changers used at the thermal chopper spectrometers at the Spallation Neutron Source. We also present case studies of sample holders designed to accommodate multiple single crystal or powder samples for the Cold Neutron Chopper Spectrometer at the Spallation Neutron Source. [This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).]

Stone, Matthew B. [Oak Ridge National Laboratory (↗
DOE OSTI2024

Gallium oxide (Ga 2 O 3 ) energy dependent scintillation response to fast neutrons and flash gamma-rays

Gallium oxide is a newly emerged ultrawide bandgap (4.9 eV) semiconductor that is suitable as a combined electronics and radiation detection platform. We have experimentally demonstrated fast neutron and gamma-ray scintillation from Czochralski-grown β-Ga 2 O 3 in a recent series (October 2023) of experiments at the unmoderated pulsed neutron spallation source located at the Los Alamos Neutron Science Center. Using the neutron time-of-flight (TOF) technique and a fast-gated intensified CCD camera, we observed energy-dependent neutron scintillation for neutron energies ranging from 1 to 400 MeV, including the 14.1 MeV neutron energy relevant to D–T fusion. Neutron flux is quantified and calibrated by cascading the scintillator after the fission chamber, enabling a detailed analysis of temporal and energy-dependent characteristics of the scintillation events. Further, a pronounced scintillation signal from the spallation gamma flash with a temporal full width of half maximum of ~4 ns is indicative of the material’s rapid response. Neutron energy dependent scintillation is observed using the TOF method at a 22.6-m distance from the neutron source. These results highlight the possibility of developing a Ga 2 O 3 based fusion neutron diagnostic platform integrated with both scintillation and electronics functions on the integrated chip scale.

47 OTHER INSTRUMENTATION↗
DOE OSTI2026

Analysis of Second Target Station Target Removal Dose Rates

The Second Target Station (STS) project at Oak Ridge National Laboratory’s spallation neutron source is a crucial initiative for maintaining U.S. leadership in neutron sciences. The STS aims to create the world’s brightest pulsed cold neutron source, enabling cutting-edge research across various scientific disciplines. To ensure safe and efficient maintenance operations, understanding the effects of shutdown dose rates from activated components within the STS target systems is essential. This study establishes a computational framework for calculating decay gamma sources and subsequent shutdown dose rates utilizing advanced methods to account for all activation channels, including high-energy interactions down to thermal neutron capture. This study describes a novel integration of multiple tools and provides an effective means of analyzing activation and shutdown dose rates at spallation neutron facilities. A custom-developed script automates the decay gamma source generation process, ensuring proper sampling during the variance reduction phase, which is critical for accurate predictions of shutdown dose rates.

Transmutation↗
DOE OSTI2024

Privacy Preserving Federated Learning for Advanced Scientific Ecosystems

We present a framework to provide privacy preserving (PP) federating learning (FL) across multiple computational and experimental facilities. This work joins the compute capabilities of National Energy Research Scientific Computing Center (NERSC) and Oak Ridge National Laboratory Research Cloud (ORC) with simulated experimental data, such as those produced at the SLAC National Accelerator Laboratory and Spallation Neutron Source (SNS). We describe the software infrastructure developed to provide privacy for computational and experimental networks. We developed algorithmic privacy across the federated system by embedding database security, computation, and communication into the federation architecture, utilizing scientific tools developed by the experimental community.

Archibald, Rick [ORNL] (ORCID:0000000245389780)↗