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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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

A Physics-Informed Deep Learning Description of Knudsen Layer Reactivity Reduction

A physics-informed neural network (PINN) is used to evaluate the fast ion distribution in the hot spot of an inertial confinement fusion target. The use of tailored input and output layers to the neural network is shown to enable a PINN to learn the parametric solution to the Vlasov–Fokker–Planck equation in the absence of any synthetic or experimental data. As an explicit demonstration of the approach, the specific problem of Knudsen layer fusion yield reduction is treated. Here, the predictions from the Vlasov–Fokker–Planck PINN are used to provide a non-perturbative solution of the fast ion tail in the vicinity of the hot spot, thus allowing the spatial profile of the fusion reactivity to be evaluated for a range of collisionalities and hot spot conditions. Excellent agreement is found between the predictions of the Vlasov–Fokker–Planck PINN and the results from traditional numerical solvers with respect to both the energy and spatial distribution of fast ions and the fusion reactivity profile, demonstrating that the Vlasov–Fokker–Planck PINN provides an accurate and efficient means of determining the impact of Knudsen layer yield reduction across a broad range of plasma conditions.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Investigation of Degradation Mechanisms of Cr-coated Zirconium Alloy Cladding in Reactivity-Initiated Accident

Reactivity-initiated accident testing has been performed on two baseline fuel rodlets which were fabricated from Zr-4 cladding and utilized fresh UO 2 fuel pellets. These experiments are part of a larger series of transient irradiations to explore Cr-coated zirconium alloy cladding under Reactivity-initiated accident conditions to evaluate ballooning and burst and sever oxidation characteristic of late-stage failure. The first two irradiations have been completed and post-transient examinations have been performed. In one rod, ballooning and burst occurred, along with oxidation. The second rod leaked and as a result did not balloon as much during the transient. This second rod also experienced increased oxidation compared to the first due to higher temperatures.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2026

Towards Robust Calibration of the AWSD Reactive Burn Model

Calibration of a reactive burn model for detonation of high explosive is an important step towards predictive hy drodynamic simulations of detonation. A typical calibration consists of varying model parameters (e.g., rate constants, activation energies) until results of hydrodynamic simulations match the experimental data for a certain set of ex periments. Hydrodynamic simulations of the dependence of steady detonation velocity on the radius of a cylindrical high-explosive charge - often used in such calibrations - can be computationally expensive. In this work, we propose a method where such expensive simulations are performed infrequently, and only to parameterize and refine a surrogate model for the dependence of the detonation velocity on calibrated parameters. The method is developed, implemented and applied to an example problem - calibration of the AWSD reactive burn model for important high explosive PBX 9502. Two different flavors of the surrogate model are investigated, and the calibration is performed successfully.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Key nuclear data for non-LWR reactivity analysis

An assessment of nuclear data performance for non-light-water reactor (non-LWR) reactivity calculations was performed at Oak Ridge National Laboratory that involved a thorough literature review to collect related observations made across different research institutions, an interrogation of the latest ENDF/B evaluated nuclear data libraries, and propagation of nuclear data uncertainties to key figures of merit associated with reactor safety for six non-LWR benchmarks. The outcome of this comprehensive study was published in a technical report issued by the US Nuclear Regulatory Commission. This paper provides a summary of the study’s key observations and conclusions and demonstrates with two examples how the various methods available in the SCALE code system were used to identify key cross section uncertainties for non-LWR reactivity analyses.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2021

On the Representation of Hyporheic Exchange in Models for Reactive Transport in Stream and River Corridors

Efforts to include more detailed representations of biogeochemical processes in basin-scale water quality simulation tools face the challenge of how to tractably represent mass exchange between the flowing channels of streams and rivers and biogeochemical hotspots in the hyporheic zones. Multiscale models that use relatively coarse representations of the channel network with subgrid models for mass exchange and reactions in the hyporheic zone have started to emerge to address that challenge. Two such multiscale models are considered here, one based on a stochastic Lagrangian travel time representation of advective pumping and one on multirate diffusive exchange. The two models are formally equivalent to well-established integrodifferential representations for transport of non-reacting tracers in steady stream flow, which have been very successful in reproducing stream tracer tests. Despite that equivalence, the two models are based on very different model structures and produce significantly different results in reactive transport. In a simple denitrification example, denitrification is two to three times greater for the advection-based model because the multirate diffusive model has direct connections between the stream channel and transient storage zones and an assumption of mixing in the transient storage zones that prevent oxygen levels from dropping to the point where denitrification can progress uninhibited. By contrast, the advection-based model produces distinct redox zonation, allowing for denitrification to proceed uninhibited on part of the hyporheic flowpaths. These results demonstrate that conservative tracer tests alone are inadequate for constraining representation of mass transfer in models for reactive transport in streams and rivers.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

A Computational Study of the Shear Behavior of Reinforced Concrete Beams Affected from Alkali–Silica Reactivity Damage

In this study, an investigation of the shear behavior of full-scale reinforced concrete (RC) beams affected from alkali–silica reactivity damage is presented. A detailed finite element model (FEM) was developed and validated with data obtained from the experiments using several metrics, including a force–deformation curve, rebar strains, and crack maps and width. The validated FEM was used in a parametric study to investigate the potential impact of alkali–silica reactivity (ASR) degradation on the shear capacity of the beam. Degradations of concrete mechanical properties were correlated with ASR expansion using material test data and implemented in the FEM for different expansions. The finite element (FE) analysis provided a better understanding of the failure mechanism of ASR-affected RC beam and degradation in the capacity as a function of the ASR expansion. The parametric study using the FEM showed 6%, 19%, and 25% reduction in the shear capacity of the beam, respectively, affected from 0.2%, 0.4%, and 0.6% of ASR-induced expansion.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Reactive Oxygen Ion Beam-Induced Deposition for Concurrent Purification of Platinum Nanostructures

Oxygen-focused ion beam induced deposition (O-FIBID) enables the direct-write fabrication of Pt nanostructures while simultaneously enhancing purity concurrently through reactive oxygen–deposit interactions. By systematically varying the dwell time, accelerating voltage, and precursor pressure, the Pt content and conductivity can be controlled. Under optimum conditions, the Pt content reached 63 at.%. Across the dwell-time range used for resistivity measurements, the Pt content increased from 20 to 33 at.%, while the resistivity decreased from 2.9 × 10 4 μΩ·cm to 1.2 × 10 3 μΩ·cm, which is consistent with enhanced percolation through Pt grains and the lower intrinsic resistivity of the purer Pt deposit. The simulation results support a purification mechanism driven by the beam-induced activation of implanted oxygen balanced against the preferential sputtering of Pt. These results demonstrate O-FIBID as a viable method for the nanoscale direct write of conductive Pt without post-processing, and some deviations from conventional FIBID wisdom are observed. These results serve as a foundation for exploring nascent, reactive focused ion beam-induced deposition processes.

deposit purification↗
DOE OSTI2021

A Deep Learning Modeling Framework to Capture Mixing Patterns in Reactive-Transport Systems

Prediction and control of chemical mixing are vital for many scientific areas such as subsurface reactive transport, climate modeling, combustion, epidemiology, and pharmacology. Due to the complex nature of mixing in heterogeneous and anisotropic media, the mathematical models related to this phenomenon are not analytically tractable. Numerical simulations often provide a viable route to predict chemical mixing accurately. However, contemporary modeling approaches for mixing cannot utilize available spatial-temporal data to improve the accuracy of the future prediction and can be compute-intensive, especially when the spatial domain is large and for long-term temporal predictions. To address this knowledge gap, in this work we will present in this paper a deep learning (DL) modeling framework applied to predict the progress of chemical mixing under fast bimolecular reactions. This framework uses convolutional neural networks (CNN) for capturing spatial patterns and long short-term memory (LSTM) networks for forecasting temporal variations in mixing. By careful design of the framework—placement of non-negative constraint on the weights of the CNN and the selection of activation function, the framework ensures non-negativity of the chemical species at all spatial points and for all times. Our DL-based framework is fast, accurate, and requires minimal data for training. The time needed to obtain a forecast using the model is a fraction (≈ O(-6)) of the time needed to obtain the result using a high-fidelity simulation. To achieve an error of 10% (measured using the infinity norm) for capturing local-scale mixing features such as interfacial mixing, only 24% to 32% of the sequence data for model training is required. To achieve the same level of accuracy for capturing global-scale mixing features, the sequence data required for model training is 64% to 70% of the total spatial-temporal data. Hence, the proposed approach—a fast and accurate way to forecast long-time spatial-temporal mixing patterns in heterogeneous and anisotropic media—will be a valuable tool for modeling reactive-transport in a wide range of applications.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS2000

Cell signaling by reactive nitrogen and oxygen species in atherosclerosis

The production of reactive oxygen and nitrogen species has been implicated in atherosclerosis principally as means of damaging low-density lipoprotein that in turn initiates the accumulation of cholesterol in macrophages. The diversity of novel oxidative modifications to lipids and proteins recently identified in atherosclerotic lesions has revealed surprising complexity in the mechanisms of oxidative damage and their potential role in atherosclerosis. Oxidative or nitrosative stress does not completely consume intracellular antioxidants leading to cell death as previously thought. Rather, oxidative and nitrosative stress have a more subtle impact on the atherogenic process by modulating intracellular signaling pathways in vascular tissues to affect inflammatory cell adhesion, migration, proliferation, and differentiation. Furthermore, cellular responses can affect the production of nitric oxide, which in turn can strongly influence the nature of oxidative modifications occurring in atherosclerosis. The dynamic interactions between endogenous low concentrations of oxidants or reactive nitrogen species with intracellular signaling pathways may have a general role in processes affecting wound healing to apoptosis, which can provide novel insights into the pathogenesis of atherosclerosis.

Review, Tutorial↗
NASA NTRS2020

Chemical Reactivity of In-Situ Lunar Dust

Is in-situ lunar dust less, the same, or more chemically reactivity reactive than the Apollo samples currently stored in curation facilities here on Earth? This question has been debated extensively across the community of scientists that have focused on lunar dust biotoxicity. A definitive answer will further mitigate exploration risks to future human explorers on the Moon and will provide useful information for astrobiologists and space biologists as well.

Lunar Dust↗
NASA NTRS2021

Effective radiative forcing from emissions of reactive gases and aerosols - a multi-model comparison

This paper quantifies the pre-industrial (1850) to present-day (2014) effective radiative forcing (ERF) of anthropogenic emissions of NOX, volatile organic compounds (VOCs; including CO), SO2, NH3, black carbon, organic carbon, and concentrations of methane, N2O and ozone-depleting halocarbons, using CMIP6 models. Concentration and emission changes of reactive species can cause multiple changes in the composition of radiatively active species: tropospheric ozone, stratospheric ozone, stratospheric water vapour, secondary inorganic and organic aerosol, and methane. Where possible we break down the ERFs from each emitted species into the contributions from the composition changes. The ERFs are calculated for each of the models that participated in the AerChemMIP experiments as part of the CMIP6 project, where the relevant model output was available. The 1850 to 2014 multi-model mean ERFs (± standard deviations) are −1.03 ± 0.37 W/sq.m for SO2 emissions, −0.25 ± 0.09 W/sq.m for organic carbon (OC), 0.15 ± 0.17 W/sq.m for black carbon (BC) and −0.07 ± 0.01 W/sq.m for NH3. For the combined aerosols (in the piClim-aer experiment) it is −1.01 ± 0.25 W/sq.m. The multi-model means for the reactive well-mixed greenhouse gases (including any effects on ozone and aerosol chemistry) are 0.67 ± 0.17 W/sq.m for methane (CH4), 0.26 ± 0.07 W/sq.m for nitrous oxide (N2O) and 0.12 ± 0.2 W/sq.m for ozone-depleting halocarbons (HC). Emissions of the ozone precursors nitrogen oxides (NOx), volatile organic compounds and both together (O3) lead to ERFs of 0.14 ± 0.13, 0.09 ± 0.14 and 0.20 ± 0.07 W/sq.m respectively. The differences in ERFs calculated for the different models reflect differences in the complexity of their aerosol and chemistry schemes, especially in the case of methane where tropospheric chemistry captures increased forcing from ozone production.

radiative forcing↗
NASA NTRSDate not supplied

Dermatitis During Spaceflight Associated With HSV-1 Reactivation- A Case Study

Human alpha herpesviruses herpes simplex virus (HSV-1 or -2) and varicella zoster virus (VZV) establish latency in various cranial nerve ganglia, and often reactivate in response to stress-associated immune system dysregulation. Reactivation of Epstein Barr Virus (EBV), VZV, HSV-1 and Cytomegalovirus (CMV) is typically asymptomatic during spaceflight, though live/infectious virus has been recovered and the shedding rate increases with mission duration. The risk of clinical disease, therefore, may increase for astronauts assigned to extended missions (>180 days). Here, we report for the first time, a case of HSV-1 skin rash (dermatitis) occurring during a long duration spaceflight. The astronaut reported persistent dermatitis during flight, which was treated onboard with oral antihistamines and topical/oral steroids. No HSV-1 DNA was detected in 6-month pre-mission saliva samples, but on flight day 82, a saliva and rash swab both yielded 4.8 copies/ng DNA and 5.3×104 copies/ng DNA, respectively. Post-mission saliva samples continued to have high infectious HSV-1 load (1.67×107 copies/ng DNA). HSV-1 from both rash and saliva samples had 99.4% genotype homology. Additional physiological monitoring, including stress biomarkers (cortisol, dehydroepiandrosterone (DHEA), and salivary amylase), immune markers (adaptive regulatory and inflammatory plasma cytokines) and biochemical profile markers including vitamin/mineral status and bone metabolism are also presented for this case. These data highlight an atypical presentation of HSV-1 during spaceflight and underscore the importance of viral screening during clinical evaluations of in-flight dermatitis, to determine viral etiology and guide treatment.

Herpes, Viral Reactivation, Spaceflight, Dermatiti↗
DOE OSTI2020

Establishing Maximal Core Excess Reactivity Envelope for TREAT Test Vehicle Insertion

The Transient Reactor Test (TREAT) Facility is an air-cooled reactor composed of graphite-urania fuel encapsulated in zirconium alloy canisters and surrounded by ~2 ft (~61 cm) of nuclear grade graphite. The primary role of TREAT is to provide in-pile nuclear-heated safety research via transient testing [1]. The following work represents further analyses building upon previously reported work to support larger volume test vehicles within TREAT [2]. The Broad Use Specimen Transient Experiment Rig (BUSTER) provides ample versatility for numerous transient test concepts. However, future testing and experiment needs will require testing environments of different in-core footprints. The versatility of TREAT allows for the development of variegated core layouts with key limitations emplaced as operational safety temperature restrictions and available core reactivity. The focus of this current effort is to gauge core arrangements for TREAT core loadings to support centralized experimental testing of varying dimensional capacity. The total core excess reactivity (ER) was computed for different arrangements to establish comparison tables that enable ready assessment of core ER available for future experiment concepts. Test vehicle worths would then be necessary to establish available ER to support transient testing requirements and to perform reactor performance and safety calculations [3,4].

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2020

A Future Standard for Reactive Power Measurement

Reactive power is defined for sinusoidal voltage and current. Several different ways to measure the quantity have been developed, and while they all give the same result for sinusoidal voltages and currents, the results are not the same when the inputs are distorted. Work was done with distorted test signals to explore these—sometimes large— differences, and a report summarizing the findings was published by the US National Institute of Standards and Technology (NIST) in 2011. We show in this paper that the differences are smaller, but not negligible, when the waveforms are less distorted. The differences between the results of the various existing methods are discussed from the viewpoint of measurement theory. The paper argues that it is time to select one method. The relevance to the ongoing revision to IEEE standard 1459 (which defines reactive power for the purposes of measurement) is explored.

reactive power, measurement standard, definitions,↗
DOE OSTI2023

Reactivity Coefficient Measurements to Aid in Reducing Compensating Errors in Plutonium Nuclear Data

Compensating errors between several nuclear data observables in a nuclear data library can adversely impact application simulations. The primary goal of the EUCLID project (Experiments Underpinned by Computational Learning for Improvements in Nuclear Data) is to reduce compensating errors between fast (0.1–5 MeV) 239Pu nuclear data for prompt fission neutron spectra (PFNS), average prompt fission neutron multiplicities, and neutron induced fission, capture, elastic, and inelastic cross sections. This work will focus on the design and execution of void reactivity coefficient measurements in the EUCLID experiment, performed on the Planet vertical lift critical assembly machine at the National Criticality Experiments Research Center (NCERC). Two different base configurations were designed and measured, one with high neutron leakage, and one with low neutron leakage. Both were primarily made up of plutonium metal (Zero Power Physics Reactor plates) without interstitial moderators and reflected by half-inch aluminum. Design optimization showed that void reactivity coefficient measurements in three locations per configuration was most impactful to reduce nuclear data uncertainties due to the varying impacts from elastic and inelastic scattering, as well as fission and capture. The locations for measurements were chosen based on preliminary studies which balanced measurement uncertainty and measurement practicality. The measurements were also selected to have sensitivities maximally complementary to previous arrangements. Comparisons across nuclear data libraries highlight the potential impact.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Sulfur Loading and Speciation Control the Hydrophobicity, Electron Transfer, Reactivity, and Selectivity of Sulfidized Nanoscale Zerovalent Iron

Sulfidized nanoscale zerovalent iron (SNZVI) is a promising material for groundwater remediation. However, the relationships between sulfur content and speciation and the properties of SNZVI materials are unknown, preventing rational design. Here, the effects of sulfur on the crystalline structure, hydrophobicity, sulfur speciation, corrosion potential, and electron transfer resistance are determined. Sulfur incorporation extended the nano-Fe 0 BCC lattice parameter, reduced the Fe local vacancies, and lowered the resistance to electron transfer. Impacts of the main sulfur species (FeS and FeS 2 ) on hydrophobicity (water contact angles) are consistent with density functional theory calculations for these FeS x phases. These properties well explain the reactivity and selectivity of SNZVI during the reductive dechlorination of trichloroethylene (TCE), a hydrophobic groundwater contaminant. Controlling the amount and speciation of sulfur in the SNZVI made it highly reactive (up to 0.41 L m -2 d -1 ) and selective for TCE degradation over water (up to 240 moles TCE per mole H 2 O), with an electron efficiency of up to 70%, and these values are 54-fold, 98-fold, and 160-fold higher than for NZVI, respectively. These findings can guide the rational design of robust SNZVI with properties tailored for specific application scenarios.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Polarization Switching on the Open Surfaces of the Wurtzite Ferroelectric Nitrides: Ferroelectric Subsystems and Electrochemical Reactivity

Binary ferroelectric nitrides are promising materials for information technologies and power electronics. However, polarization switching in these materials is highly unusual. From the structural perspective, polarization reversal is associated with the change of the effective polarity at the surfaces and interfaces from N‐to‐M terminated, suggesting strong coupling between ferroelectric and chemical phenomena. Phenomenologically, macroscopic studies demonstrate the presence of complex time dependent phenomena including wake‐up. Here, in this study, the polarization switching using the multidimensional high‐resolution piezoresponse force microscopy (PFM) and spectroscopy is explored, detecting both the evolution of induced ferroelectric domain, electromechanical response, and surface deformation during first‐order reversal curve measurements. The presence of two weakly coupled ferroelectric subsystems are demonstrated and the bias‐induced electrochemical reactivity. The observed behaviors are very similar to the recent studies of other wurtzite system but additionally include electrochemical reactivity, suggesting the universality of these behaviors for the wurtzite binary ferroelectrics. These studies suggest potential of high‐resolution multimodal PFM spectroscopies to resolve complex coupled polarization dynamics in materials. Furthermore, these PFM based studies are fully consistent with the recent electron microscopy observations of the shark‐teeth like ferroelectric domains in nitrides. Hence, it is believed that these studies establish the universal phenomenological picture of polarization switching in binary wurtzite.

36 MATERIALS SCIENCE↗
DOE OSTI2023

The Interplay Between Ferroelectricity and Electrochemical Reactivity on the Surface of Binary Ferroelectric Al x B 1–x N

Polarization dynamics and domain structure evolution in ferroelectric Al 0.93 B 0.07 N are studied using piezoresponse force microscopy and spectroscopies in ambient and controlled atmosphere environments. The application of negative unipolar and bipolar first-order reverse curve (FORC) waveforms leads to a protrusion-like feature on the Al 0.93 B 0.07 N surface and a reduction of electromechanical response due to electrochemical reactivity. A surface change is also observed on the application of fast alternating current bias. At the same time, the application of positive biases does not lead to surface changes. Comparatively in a controlled glove box atmosphere, stable polarization patterns can be observed, with minuscule changes in surface morphology. This surface morphology change is not isolated to applying biases to free surface, a similar topographical change is also observed at the electrode edges when cycling a capacitor in an ambient environment. The study suggests that surface electrochemical reactivity may have a significant impact on the functionality of this material in the ambient environment. However, even in the controlled atmosphere, the participation of the surface ions in polarization switching phenomena and ionic compensation is possible.

36 MATERIALS SCIENCE↗