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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Charge radii of exotic potassium isotopes challenge nuclear theory and the magic character of N = 32

Nuclear charge radii are sensitive probes of different aspects of the nucleon–nucleon interaction and the bulk properties of nuclear matter, providing a stringent test and challenge for nuclear theory. Experimental evidence suggested a new magic neutron number at N = 32 in the calcium region, whereas the unexpectedly large increases in the charge radii open new questions about the evolution of nuclear size in neutron-rich systems. By combining the collinear resonance ionization spectroscopy method with β-decay detection, we were able to extend charge radii measurements of potassium isotopes beyond N = 32. Here we provide a charge radius measurement of 52 K. It does not show a signature of magic behaviour at N = 32 in potassium. The results are interpreted with two state-of-the-art nuclear theories. The coupled cluster theory reproduces the odd–even variations in charge radii but not the notable increase beyond N = 28. This rise is well captured by Fayans nuclear density functional theory, which, however, overestimates the odd–even staggering effect in charge radii. These findings highlight our limited understanding of the nuclear size of neutron-rich systems, and expose problems that are present in some of the best current models of nuclear theory.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Initial Scoping Efforts for a Plant-Wide Digital Infrastructure Modernization Business Case Study

This research report describes the preparatory efforts to perform a BCA on an expanded set of digital upgrades envisioned for implementation at the Luminant?s Comanche Peak nuclear plant. It captures efforts to scope the digital upgrade effort to enable performance of the BCA. The final BCA will be the subject of a subsequent report. LWRS pilot research in this area is intended to enable this effort and to provide a roadmap to others to follow. INL appreciates the Luminant?s participation in this research.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2025

Probing the limits of statistical neutron capture for the r process: Experimental constraints on 141 Cs nuclear level densities

The r-process abundance peaks, particularly near mass number A ∼ 130, reflect underlying nuclear structure effects such as closed neutron shells, yet modeling the nucleosynthesis in this region remains hindered by uncertain neutron-capture rates. These rates are especially sensitive to nuclear level densities (NLDs) and γ-ray strength functions of neutron-rich nuclei, where experimental data are scarce. We present the first experimental constraint on the NLD of 141 Cs using the β-Oslo method, extending sensitivity to the neutron-rich regime near the N = 82 closed shell. Our data allow for critical calibration of microscopic NLD models and reveal that 141 Cs lies near the limit of statistical model applicability. Using this experimental input, we evaluate radiative neutron-capture rates across neighboring isotones using both Hauser–Feshbach (HF) and High Fidelity Resonance (HFR) models. Our results show order-of-magnitude rate increases for nuclei along the N = 86 line, signaling a transition to resonance-dominated capture in this region. These findings underscore the importance of constraining NLDs to improve r-process reaction network predictions, particularly in environments where the validity of statistical models breaks down.

Nuclear level density↗
DOE OSTI2025

Decarbonization and technology cost drivers: considerations for potential future thermoelectric water use in the power sector

The power sector is currently undergoing significant changes, driven by a combination of factors, including decarbonization and technology innovation. This study aims to assess implications of these drivers on U.S. power sector technology futures and the associated water and environmental implications for cooling thermoelectric power plants. Specifically, we evaluate four decarbonization scenarios for the contiguous United States that vary in assumptions concerning demand growth and technology costs, with technology costs driving alternative outcomes that prioritize either technologies that require low amounts of water (such as wind, solar, and battery) or high amounts of water (such as nuclear and carbon capture and storage). These scenarios are executed in a power sector capacity expansion model and compared to two reference scenarios that assume status quo with policy and cost drivers. Our analysis indicates that future U.S. thermoelectric water withdrawals could decrease by 25%–60%, but water consumption could more than triple in some scenarios. These changes are driven by a combination of retirement of some power facilities, shifts in cooling technologies, and new technology deployment. The water use patterns vary across the United States, with the eastern regions demonstrating a lot more variability in water consumption across scenarios than western regions. However, local concerns can influence these possible investments, since increased water consumption can exacerbate water scarcity, leading to conflicts among competing users and affecting regional social, environmental, and economic dynamics. Future work should consider possible costs associated with alternate water sources, as well as improve the representation of water constraints within simulations. Inclusion of extreme events and alternate modeling platforms (e.g. production cost modeling and resource adequacy) may also be warranted to further stress test the robustness of these possible technology futures. Such assessments will be critical for ensuring decarbonization and other infrastructure-oriented investments lead to a reliable and resilient power grid.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2023

The Influence of Disk Composition on the Evolution of Stars in the Disks of Active Galactic Nuclei

Abstract Disks of gas accreting onto supermassive black holes, powering active galactic nuclei (AGN), can capture stars from nuclear star clusters or form stars in situ via gravitational instability. The density and thermal conditions of these disks can result in rapid accretion onto embedded stars, dramatically altering their evolution in comparison to stars in the interstellar medium. Theoretical models predict that, when subjected to sufficiently rapid accretion, fresh gas replenishes hydrogen in the cores of these stars as quickly as it is burned into helium, reaching a quasi-steady state. Such massive, long-lived (“immortal”) stars may be capable of dramatically enriching AGN disks with helium, and would increase the helium abundance in AGN broad-line regions relative to that in the corresponding narrow-line regions and hosts. We investigate how the helium abundance of AGN disks alters the evolution of stars embedded therein. We find, in agreement with analytical arguments, that stars at a given mass are more luminous at higher helium mass fractions, and so undergo more radiation-driven mass loss. We further find that embedded stars tend to be less massive in disks with higher helium mass fractions, and that immortal stars are less common in such disks. Thus, disk composition can alter the rates of electromagnetic and gravitational wave transients as well as further chemical enrichment by embedded stars.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

A Semi-analytical Model for Stellar Evolution in AGN Disks

Disks of gas accreting onto supermassive black holes may host numerous stellar-mass objects, formed within the disk or captured from a nuclear star cluster. We present a simplified model of stellar evolution in these dense environments, which exhibits exceptional agreement with full stellar evolution calculations at a minuscule fraction of the cost. Although the model presented here is limited to stars burning hydrogen in their cores, it is sufficient to determine the evolutionary fate of disk-embedded stars: whether they proceed to later stages of nuclear burning and leave behind a compact remnant, reach a quasi-steady state where mass loss and accretion balance one another, or whether accretion proceeds faster than stellar structure can adjust, causing a runaway. We highlight how various disk parameters and phenomena such as gap opening affect stellar evolution outcomes. We also highlight how our model can accommodate time-varying conditions, such as those experienced by a star on an eccentric orbit, and can couple to N -body integrations. This model will enable more detailed studies of stellar populations and their interaction with accretion disks than have previously been possible.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1975

On the nature of the globular cluster X-ray sources

It is suggested that the globular cluster X-ray sources can be interpreted in terms of mass shed by evolving postmain-sequence stars in the central regions of the globular cluster and accreting onto a massive (approximately 100-1000 solar masses) central black hole. Tentative indications that support this hypothesis include the high central escape velocities and the distribution of metallicities among the four globular clusters containing luminous X-ray sources. We argue that these X-ray sources cannot be explained as a consequence of the close capture of a nuclear burning star by a compact stellar remnant.

Silk, J.↗
NASA NTRS1978

Gamma-ray lines - A new window to the Universe

Gamma-ray emission is considered in terms of its usefulness in determining the physics of nucleosynthesis, the interstellar medium, solar flares, supernovae, and neutron stars. The mechanism of gamma-ray line emission is reviewed, i.e., nuclear deexcitation, radiative capture, positron annihilation, and possibly cyclotron radiation in the strong magnetic fields of neutron stars. Various gamma-ray spectra, obtained from balloon and satellite data, are analyzed with attention to solar particle energies and densities, including particle emission from black-hole supernova remnants.

Lingenfelter, R. E.↗
NASA NTRS1980

Cosmic gamma-ray lines - Theory

The various processes that lead to gamma-ray line emission and the possible astrophysical sources of such emission are reviewed. The processes of nuclear excitation, radiative capture, positron annihilation, and cyclotron radiation, which may produce gamma-ray line emission from such diverse sources as the interstellar medium, novas, supernovas, pulsars, accreting compact objects, the galactic nucleus and the nuclei of active galaxies are considered. The significance of the relative intensities, widths, and frequency shifts of the lines are also discussed. Particular emphasis is placed on understanding those gamma-ray lines that have already been observed from astrophysical sources.

Lingenfelter, R. E.↗
DOE OSTI2023

Achieving Economy-wide Net-Zero Emissions: Is it an impossible goal?

Meeting growing energy demands while eliminating emissions, maintaining affordability, and ensuring energy justice is one of the most significant grand challenges of our time. Governments and private industry around the world have established aggressive goals to achieve net-zero emissions by mid-century. In the U.S., this equates to a net-zero electricity sector by 2035 and across all energy use sectors—including electricity, industry, and transportation—by 2050. The key question then becomes: Can we get there from here? Meeting these aggressive goals demands immediate action, and they require us to think more holistically about our clean energy options. Currently, almost 85% of global energy demands are met by unabated fossil fuels. That means we have a lot of work to do, and we need to consider all of the non-emitting generation options available in each region—including fossil with carbon capture, renewables, and nuclear. And we need to reach our goal while establishing energy justice, which refers to the goal of achieving equity in social and economic participation in the energy system, while remediating past social, economic, and health burdens on communities that have been brought about by our energy system. This presentation will describe U.S. and global efforts focused on novel energy system solutions that strive to maximize use of all clean energy generation options to meet our energy demands, while ensuring sustainability, customer affordability, and a just energy system.

08 HYDROGEN↗
DOE OSTI2021

Urca Cooling in Neutron Star Crusts and Oceans: Effects of Nuclear Excitations

We report the excited-state structure of atomic nuclei can modify nuclear processes in stellar environments. In this Letter, we study the influence of nuclear excitations on Urca cooling (repeated back-and-forth β decay and electron capture in a pair of nuclear isotopes) in the crust and ocean of neutron stars. We provide for the first time an expression for Urca process neutrino luminosity which accounts for a thermal Boltzmann distribution of excited states in both members of an Urca pair. We use our new formula with state-of-the-art nuclear structure inputs to compute neutrino luminosities of candidate Urca cooling pairs. Our nuclear inputs consist of the latest experimental data supplemented with calculations using the projected shell model. We show that, in contrast to previous results that only consider the ground states of both nuclei in the pair, our calculated neutrino luminosities for different Urca pairs vary sensitively with the environment temperature and can be radically different from those obtained in the one-transition approximation. We find that nuclear excitations can lead to an enhancement in total Urca neutrino luminosities in the accreted neutron star crust by about 5 times as compared with the previous Urca results, which is expected to cause significant observational effects.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Angular distribution of 𝛾 rays from a neutron-induced 𝑝-wave resonance of 132 Xe

A neutron-energy dependent angular distribution was measured for individual 𝛾 rays from the 3.2 eV 𝑝-wave resonance of 131 Xe+⁢𝑛, that shows enhanced parity violation owing to a mixing between 𝑠- and 𝑝-wave amplitudes. The 𝛾-ray transitions from the 𝑝-wave resonance were identified, and the angular distribution with respect to the neutron momentum was evaluated as a function of the neutron energy for 7132 keV 𝛾 rays, which correspond to a transition to the 1807 keV excited state of 132 Xe. The angular distribution is considered to originate from the interference between 𝑠- and 𝑝-wave amplitudes, and will provide a basis for a quantitative understanding of the enhancement mechanism of the fundamental parity violation in compound nuclei.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1973

Neutron emission following muon capture in Ce-142, Ce-140, Ba-138, and Sn-120.

Branching ratios to excited nuclear states formed after muon capture have been measured with Ge(Li) detectors. The delayed gamma rays were observed in studies of muonic Ce-142, Ce-140, Ba-138, and Sn-120, using separated isotopes. The resulting isotopes formed indicate at least a 60% probability of neutron emission upon muon capture, with the most likely product resulting from single-neutron emission. No evidence for delayed proton emission with a probability higher than 2% was found. Using our more precise energies for the observed nuclear transitions, we present revised energy levels schemes for La-141, La-139, Cs-137, and In-119.

Lucas, G. R., Jr.↗
NASA NTRS1981

Interpretations and implications of gamma-ray lines from solar flares, the galactic centre and gamma-ray transients

Gamma-ray line emission from the Sun results from the nuclear interactions of energetic protons and nuclei with the solar atmosphere. These interactions produce gamma-ray lines from neutron capture, positron annihilation, and nuclear deexcitation. Observation of such gamma-rays can provide unique information on high energy processes at the Sun. Details of solar gamma-ray spectroscopy are discussed along with the galactic center 0.511 MeV line. The richness of astronomy at 0.511 MeV is indicated by the great variety of astrophysical positron production mechanisms and by the many astrophysical sites where such mechanisms could operate. Attention is also given to lines from gamma-ray transients, and the prospects for gamma-ray line detections, taking into account gamma-ray lines from processes of nucleosynthesis and lines from low-energy cosmic ray interactions.

Ramaty, R.↗
DOE OSTI2025

Potential of deep learning methods to enhance satellite-based monitoring of nuclear power plants focusing on remote operation evaluations

The anticipated expansion of the nuclear industry and the deployment of new nuclear reactors (200 + GW of new nuclear capacity by 2050) require the development of monitoring systems that align with safety and security concerns, providing enhanced evaluation capabilities. A remote monitoring system using satellites and deep learning techniques was evaluated for its ability to detect anomalies and capture various features of nuclear reactors independently of the conditions on the ground. Satellite images of current operational and under-construction nuclear power plants were collected from Google Earth Pro as a surrogate database. Subsequently, five datasets were created from the collected images. Transfer learning technique was used for several classification tasks utilizing VGG16, ResNet50V2, Xception, DenseNet121, and MobileNetV2 pre-trained models. In the first task, the capability of the monitoring system to detect abnormal conditions or processes in a nuclear power plant was investigated. In the second task, the ability to capture operational features remotely was examined. As an example, for the purposes of this study, these features included classifying reactors based on type, power range, or onsite condition. Several evaluation metrics were used to compare the performance of the pre-trained models and the overall monitoring system. Here, the evaluation results demonstrated that deep learning techniques and pre-trained models applied to satellite images have the potential to facilitate further and expand capabilities in monitoring systems to assess plant operation details.

22 - GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2025

Enhanced Nuclear Binding near the Proton Drip Line Opens Possible Bypass of the 64 Ge Rapid Proton Capture Process Waiting Point

Abstract We performed astrophysics model calculations with updated nuclear data to identify a possible bypass of the 64 Ge waiting point, a defining feature of the rapid proton capture (rp) process that powers type I X-ray bursts on accreting neutron stars. We find that the rp-process flow through the 64 Ge bypass could be up to 36% for astrophysically relevant conditions. Our results call for new studies of 65 Se, including the nuclear mass, β -delayed proton emission branching, and nuclear structure as it pertains to the 64 As( p , γ ) reaction rate at X-ray burst temperatures.

Nuclear astrophysics↗