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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 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Cladding Profilometry Analysis of Experimental Breeder Reactor-II Metallic Fuel Pins with HT9, D9, and SS316 Cladding

BISON finite element method fuel performance simulations were conducted using an existing automated process that couples the Fuels Irradiation & Physics Database (FIPD) and the Integral Fast Reactor Materials Information System database by writing input files and comparing the BISON output to post-irradiation fuel pin profilometry measurements contained within the databases. The importance of this work is to demonstrate the ability to benchmark fuel performance metallic fuel models within BISON using Experimental Breeder Reactor-II fuel pin data for a number of similar pins, while building off previous modeling efforts. Changes to the generic BISON input file include implementing pin specific axial power and flux profiles, pin specific fluences, frictional contact, and irradiation-induced volumetric swelling models for cladding. A statistical analysis of irradiation-induced volumetric swelling models for HT9, D9, and SS316 was performed for experiments X421/X421A, X441/X441A, and X486. Between these three experiments, there were 174 post-irradiation examination (PIE) profilometries used for validating the swelling models presented using a standard error of the estimate (SEE) method. Implementation of the volumetric swelling models for D9 and SS316 claddings was found to have a significant impact on the BISON profilometry simulated, where HT9 clad pins had an insignificant change due to low fluence values. BISON profilometry simulated for HT9, D9, and SS316 fuel pins agreed with PIE profilometry measurements, with assembly SEE values being 4.4 × 10−3 for X421A, 2.0 × 10−3 for X441A, and 2.8 × 10−3 for X486. D9 clad pins in X421/X421A had the highest SEE values, which is due to the BISON simulated profilometry being shifted axially. While this work accomplished its purpose to demonstrate the modeling of multiple fuel pins from the databases to help validate models, the results suggest that the continued development of metallic fuel models is necessary for qualifying new metallic fuel systems to better capture some physical performance phenomena, such as the hot pressing of U-Pu-Zr and the fuel cladding chemical interaction.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

Dynamic Deformation in Nuclear Graphite and Underlying Mechanisms

Time-dependent deformation in nuclear graphite is influenced by the creation and migration of radiation-induced defects in the reactor environment. This study investigates the role of pre-existing defects such as point defect clusters and Mrozowski cracks in nuclear graphite IG-110. Separate specimens were irradiated with a 2.8 MeV Au 2+ beam with a fluence of 4.38 × 10 14 cm −2 and an 8 MeV C 2+ beam with a fluence of 1.24 × 10 16 cm −2 . Microscopic specimens were either mechanically loaded inside a transmission electron microscope (TEM) or subjected to ex situ indentation-based creep loading. In situ TEM tests showed significant plasticity in regions highly localized around the Mrozowski cracks, resembling slip or ripplocation bands. Slip bands were also seen near regions without pre-existing defects but at very high stresses. Ex situ self-ion irradiation embrittled the specimens and decreased the creep displacement and rate, while heavy ion irradiation resulted in the opposite behavior. We hypothesize that the large-sized gold ions (compared to the carbon atoms) induced interplanar swelling as well as cross-plane channels for increased defect mobility. These findings illustrate the role of pre-existing defects in the dynamic relaxation of stresses during irradiation and the need for more studies into the radiation environment’s impact on the mechanical response of nuclear graphite.

creep deformation↗
DOE OSTI2020

A Study of the Radiation Tolerance of CVD Diamond to 70 MeV Protons, Fast Neutrons and 200 MeV Pions

We measured the radiation tolerance of commercially available diamonds grown by the Chemical Vapor Deposition process by measuring the charge created by a 120 GeV hadron beam in a 50 μm pitch strip detector fabricated on each diamond sample before and after irradiation. We irradiated one group of samples with 70 MeV protons, a second group of samples with fast reactor neutrons (defined as energy greater than 0.1 MeV), and a third group of samples with 200 MeV pions, in steps, to (8.8±0.9) × 1015 protons/cm2, (1.43±0.14) × 1016 neutrons/cm2, and (6.5±1.4) × 1014 pions/cm2, respectively. By observing the charge induced due to the separation of electron–hole pairs created by the passage of the hadron beam through each sample, on an event-by-event basis, as a function of irradiation fluence, we conclude all datasets can be described by a first-order damage equation and independently calculate the damage constant for 70 MeV protons, fast reactor neutrons, and 200 MeV pions. We find the damage constant for diamond irradiated with 70 MeV protons to be 1.62±0.07(stat)±0.16(syst)× 10−18 cm2/(p μm), the damage constant for diamond irradiated with fast reactor neutrons to be 2.65±0.13(stat)±0.18(syst)× 10−18 cm2/(n μm), and the damage constant for diamond irradiated with 200 MeV pions to be 2.0±0.2(stat)±0.5(syst)× 10−18 cm2/(π μm). The damage constants from this measurement were analyzed together with our previously published 24 GeV proton irradiation and 800 MeV proton irradiation damage constant data to derive the first comprehensive set of relative damage constants for Chemical Vapor Deposition diamond. We find 70 MeV protons are 2.60 ± 0.29 times more damaging than 24 GeV protons, fast reactor neutrons are 4.3 ± 0.4 times more damaging than 24 GeV protons, and 200 MeV pions are 3.2 ± 0.8 more damaging than 24 GeV protons. We also observe the measured data can be described by a universal damage curve for all proton, neutron, and pion irradiations we performed of Chemical Vapor Deposition diamond. Finally, we confirm the spatial uniformity of the collected charge increases with fluence for polycrystalline Chemical Vapor Deposition diamond, and this effect can also be described by a universal curve.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Impact of Glass Irradiation on Laser-Induced Breakdown Spectroscopy Data Analysis

Increased absorption of optical materials arising from exposure to ionizing radiation must be accounted for to accurately analyze laser-induced breakdown spectroscopy (LIBS) data retrieved from high-radiation environments. We evaluate this effect on two examples that mimic the diagnostics placed within novel nuclear reactor designs. The analysis is performed on LIBS data measured with 1% Xe gas in an ambient He environment and 1% Eu in a molten LiCl-KCl matrix, along with the measured optical absorption from the gamma- and neutron-irradiated low-OH fused silica and sapphire glasses. Significant changes in the number of laser shots required to reach a 3σ detection level are observed for the Eu data, increasing by two orders of magnitude after exposure to a 1.7 × 1017 n/cm2 neutron fluence. For all cases examined, the spectral dependence of absorption results in the introduction of systematic errors. Moreover, if lines from different spectral regions are used to create Boltzmann plots, this attenuation leads to statistically significant changes in the temperatures calculated from the Xe II lines and Eu II lines, lowering them from 8000 ± 610 K to 6900 ± 810 K and from 15,800 ± 400 K to 7200 ± 800 K, respectively, for exposure to the 1.7 × 1017 n/cm2 fluence. The temperature range required for a 95% confidence interval for the calculated temperature is also broadened. In the case of measuring the Xe spectrum, these effects may be mitigated using only the longer-wavelength spectral region, where radiation attenuation is relatively small, or through analysis using the iterative Saha–Boltzmann method.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2022

SNEWPY: A Data Pipeline from Supernova Simulations to Neutrino Signals

Current neutrino detectors will observe hundreds to thousands of neutrinos from Galactic supernovae, and future detectors will increase this yield by an order of magnitude or more. With such a data set comes the potential for a huge increase in our understanding of the explosions of massive stars, nuclear physics under extreme conditions, and the properties of the neutrino. However, there is currently a large gap between supernova simulations and the corresponding signals in neutrino detectors, which will make any comparison between theory and observation very difficult. SNEWPY is an open-source software package that bridges this gap. The SNEWPY code can interface with supernova simulation data to generate from the model either a time series of neutrino spectral fluences at Earth, or the total time-integrated spectral fluence. Data from several hundred simulations of core-collapse, thermonuclear, and pair-instability supernovae is included in the package. This output may then be used by an event generator such as sntools or an event rate calculator such as the SuperNova Observatories with General Long Baseline Experiment Simulator (SNOwGLoBES). Additional routines in the SNEWPY package automate the processing of the generated data through the SNOwGLoBES software and collate its output into the observable channels of each detector. In this paper we describe the contents of the package, the physics behind SNEWPY, the organization of the code, and provide examples of how to make use of its capabilities.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Search for Solar Flare Neutrinos with the KamLAND Detector

Abstract We report the result of a search for neutrinos in coincidence with solar flares from the GOES flare database. The search was performed on a 10.8 kton-year exposure of KamLAND collected from 2002 to 2019. This large exposure allows us to explore previously unconstrained parameter space for solar flare neutrinos. We found no statistical excess of neutrinos and established 90% confidence level upper limits of 8.4 × 10 7 cm −2 (3.0 × 10 9 cm −2 ) on the electron antineutrino (electron neutrino) fluence at 20 MeV normalized to the X12 flare, assuming that the neutrino fluence is proportional to the X-ray intensity.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

GRB 221009A: The BOAT

GRB 221009A has been referred to as the brightest of all time (BOAT). We investigate the veracity of this statement by comparing it with a half century of prompt gamma-ray burst observations. This burst is the brightest ever detected by the measures of peak flux and fluence. Unexpectedly, GRB 221009A has the highest isotropic-equivalent total energy ever identified, while the peak luminosity is at the ~99th percentile of the known distribution. We explore how such a burst can be powered and discuss potential implications for ultralong and high-redshift gamma-ray bursts. By geometric extrapolation of the total fluence and peak flux distributions, GRB 221009A appears to be a once-in-10,000-year event. Thus, it is almost certainly not the BOAT over all of cosmic history; it may be the brightest gamma-ray burst since human civilization began.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Corrosion Behavior of Laser-Interference Structured AA2024 Coated with a Chromate-Containing Epoxy Primer

In this study, the corrosion behavior of laser-interference treated AA2024-T3 specimens, which are coated with a primer, is presented. The surface of as-received AA2024-T3 specimens were laser-interference structured by splitting the primary beam of a Q-switched Nd:YAG pulsed nanosecond laser into two beams and focusing them to the same spot on the specimen surface. After being stored in plastic cases for up to 70 d, without any additional cleaning, the specimens were spray painted with a chromate-containing epoxy primer, CA7233, compliant to MIL-PRF-23377 Type I Class C2 specification. The corrosion behavior of laser-interference specimens was assessed against that of specimens prepared by chromated conversion coating and sulfuric acid anodizing treatments. After the ASTM B117 corrosion exposure, it was found that the laser processed specimens exhibited only few blisters. On one hand, most specimens prepared at a laser fluence of 1.78 J/cm 2 , without any additional chemical cleaning, were found to develop one very small blister after only 96 h of exposure. However, the growth of these blisters was not significant even after 1,000 h of salt spray exposure. On the other hand, only a fraction of the specimens prepared at a laser fluence of 1.24 J/cm 2 and acetone wiped right after the laser structuring were found to develop several tiny blisters after 790 h and longer exposure. Overall, it was found that the corrosion damage was minimized at a laser rastering speed of 4 mm/s, a condition for which only 33% of specimens developed very minor corrosion damage. Furthermore, the ASTM D1654 creepage ratings, which was used to evaluate the corrosion damage along the scribe lines, were found to be at least nine for all coated panels. These results indicate that the laser-interference technique with the additional acetone wiping has the potential to be further developed as a nonchemical surface preparation technique for chromate-containing epoxy primers coating systems.

36 MATERIALS SCIENCE↗
NASA NTRS1972

Solar cosmic ray hazard to interplanetary and earth-orbital space travel

A statistical treatment of the radiation hazards to astronauts due to solar cosmic ray protons is reported to determine shielding requirements for solar proton events. More recent data are incorporated into the present analysis in order to improve the accuracy of the predicted mission fluence and dose. The effects of the finite data sample are discussed. Mission fluence and dose versus shield thickness data are presented for mission lengths up to 3 years during periods of maximum and minimum solar activity; these correspond to various levels of confidence that the predicted hazard will not be exceeded.

Yucker, W. R.↗
NASA NTRS1972

Damage of thermal control coating properties by energetic mercury ion bombardment.

The thermophysical properties (absorptance and emittance) of five commonly used spacecraft thermal control coatings have been measured in situ after exposure to 1.5 and 3 KeV mercury ions. Sample temperature was varied from 20 to 150 C. The results showed negligible change in emittance but significant degradation of the solar absorptance at fluences of 10 to the 17th power ions/sq cm. Plots of absorptance as a function of ion fluence are presented, along with pre- and post-exposure ex situ spectral absorptance measurements. The widely used Z93 white paint exhibited quantitative degradation from mercury ions similar to that reported by other experimenters for hydrogen and helium ions.

Kelley, L. R.↗
NASA NTRS1973

Effects of electron irradiation and temperature on 1 ohm-cm and 10 ohm-cm silicon solar cells

One OHM-cm and 10 OHM-cm silicon solar cells were exposed to 1.0 MeV electrons at a fixed flux of 10 to the 11th power e/sq cm/sec and fluences of 10 to the 13th power, 10 to the 14th power and 10 to the 15th power e/sq.cm. 1-V curves of the cells were made at room temperature, - 63 C and + or - 143 C after each irradiation. A value of 139.5 mw/sq cm was used as AMO incident energy rate per unit area. The 10 OHM-cm cells appear more efficient than 1 OHM-cm cells after exposure to a fluence greater than 10 to the 14th power e/sq cm. The 1.0 MeV electron damage coefficients for both 1 OHM-cm and 10 OHM-cm cells are somewhat less than those for previously irradiated cells at room temperature. The values of the damage coefficients increase as the cell temperatures decrease. Efficiencies pertaining to maximum power output are about the same as those of n on p silicon cells evaluated previously.

Nicoletta, C. A.↗
NASA NTRS1972

Voltage and power relationships in lithium-containing solar cells.

Photovoltaic characteristics have been measured on a large number of crucible-grown lithium-containing solar cells irradiated by 1-MeV electrons to fluences ranging from 3 x 10 to the 13th power to 3 x 10 to the 15th power electrons per sq cm. These measurements have established empirical relationships between cell photovoltaic parameters and lithium donor density gradient. Short-circuit current and maximum power measured immediately after irradiation decrease logarithmically with lithium gradient. Open-circuit voltage increases logarithmically with lithium gradient both immediately after irradiation and after recovery, the degree of recovery being strongly gradient-dependent at high fluence. As a result, the maximum power and the power at 0.43 V after recovery from 3 x 10 to the 15th power electrons per sq cm increase with increasing lithium gradient.

Faith, T. J.↗
NASA NTRS1973

Proton-radiation damage in Gunn oscillators

The irradiation effects of 22 MeV protons on the electrical characteristics of GaAs continuous-wave Gunn oscillators was studied. The radio frequency power output was reduced by 3 decibels at proton fluences in the neighborhood of 1.5 x 10 to the 12th power protons/sq cm. Conductance measurements indicate that the carrier removal rate at high electric fields remained roughly 40 percent less than at low fields. Diode efficiencies of two device groups were found to be monotonically descreasing functions of fluence. Frequency modulation noise was generally unaffected by radiation, but the magnitude of the noise in the noise power spectrum increased significantly. These effects are partially accounted for, in a qualitative fashion, by a model of electron traps having field-dependent net-carrier capture rates and various response times.

Johnson, J. W.↗
NASA NTRS1973

Performance of epitaxial back surface field cells

Epitaxial back surface field structures were formed by depositing a 10 micron thick 10 Omega-cm epitaxial silicon layer onto substrates with resistivities of 0.01, 0.1, 1.0 and 10 Omega-cm. A correlation between cell open-circuit voltage and substrate resistivity was observed and was compared to theory. The cells were also irradiated with 1 MeV electrons to a fluence of 5 X 10 to the 15th power e/cm2. The decrease of cell open-circuit voltage was in excellent agreement with theoretical predictions and the measured short circuit currents were within 2% of the prediction. Calculations are presented of optimum cell performance as functions of epitaxial layer thickness, radiation fluence and substrate diffusion length.

Brandhorst, H. W., Jr.↗
NASA NTRS1974

In-situ measurement of the rate of U-235 fission induced by lunar neutrons

The depth profile of the neutron-induced fission rate of U-235 was directly measured to a depth of 350 g/sq cm by the Apollo 17 Lunar Neutron Probe Experiment. The fission rate rises sharply from the surface to a broad maximum from 110 to 160 g/sq cm and drops off at greater depths. The shape of the theoretical depth profile of Lingenfelter et al (1972) fits the measured capture rates well at all depths. The absolute magnitude of the experimental fission rates are (11 plus or minus 17)% lower than those calculated theoretically. The excellent agreement between theory and experiment implies that conclusions drawn previously by interpreting lunar sample data with the theoretical capture rates will not require revision. In particular, lunar surface processes, rather than uncertainties in the capture rates, are required to explain the relatively low neutron fluences observed for surface soil samples compared to the fluences expected for a uniformly mixed regolith.

Woolum, D. S.↗
NASA NTRS1974

Performance of epitaxial back surface field cells

Epitaxial back surface field structures were formed by depositing a 10 micron thick 10 ohm-cm epitaxial silicon layer onto substrates with resistivities of 0.01, 0.1, 1.0 and 10 ohm-cm. A correlation between cell open-circuit voltage and substrate resistivity was observed and was compared to theory. The cells were also irradiated with 1-MeV electrons to a fluence of 5 times 10 to the 15th electrons per sq cm. The decrease of cell open-circuit voltage was in excellent agreement with theoretical predictions and the measured short-circuit currents were within 2% of the prediction. Calculations are presented for optimum cell performance as functions of epitaxial layer thickness, radiation fluence, and substrate diffusion length.

Brandhorst, H. W., Jr.↗
NASA NTRS1975

Project SOLWIND: Space radiation exposure

A special orbital radiation study was conducted for the SOLWIND project to evaluate mission-encountered energetic particle fluxes. Magnetic field calculations were performed with a current field model, extrapolated to the tentative spacecraft launch epoch with linear time terms. Orbital flux integrations for circular flight paths were performed with the latest proton and electron environment models, using new improved computational methods. Temporal variations in the ambient electron environment are considered and partially accounted for. Estimates of average energetic solar proton fluences are given for a one year mission duration at selected integral energies ranging from E greater than 10 to E greater than 100 MeV; the predicted annual fluence is found to relate to the period of maximum solar activity during the next solar cycle. The results are presented in graphical and tabular form; they are analyzed, explained, and discussed.

Stassinopoulos, E. G.↗
NASA NTRS1975

Apollo 17 neutron stratigraphy - Sedimentation and mixing in the lunar regolith

A report is presented concerning the Gd isotopic ratios in ten samples, representing nearly the entire depth of the drill stem which was recovered during the Apollo 17 mission. The lunar neutron energy spectrum is discussed along with questions regarding neutron fluence and neutron flux. The significance of the Apollo 17 deep drill stem is considered and attention is given to the statistical nature of the fluence in the lunar regolith. Vertical mixing models are also described.

Curtis, D. B.↗