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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,459 records · Page 81
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DOE OSTI2021

L 98-59: A Benchmark System of Small Planets for Future Atmospheric Characterization

The M3V dwarf star L 98-59 hosts three small (R < 1.6 R {sub ⊕}) planets. The host star is bright (K = 7.1) and nearby (10.6 pc), making the system a prime target for follow-up characterization with the Hubble Space Telescope (HST) and the upcoming James Webb Space Telescope (JWST). Herein, we use simulated transmission spectroscopy to evaluate the detectability of spectral features with HST and JWST assuming diverse atmospheric scenarios (e.g., atmospheres dominated by H{sub 2}, H{sub 2}O, CO{sub 2}, or O{sub 2}). We find that H{sub 2}O and CH{sub 4} present in a low mean molecular weight atmosphere could be detected with HST in one transit for the two outermost planets, while H{sub 2}O in a clear steam atmosphere could be detected in six transits or fewer with HST for all three planets. We predict that observations using JWST/NIRISS would be capable of detecting a clear steam atmosphere in one transit for each planet and H{sub 2}O absorption in a hazy steam atmosphere in two transits or less. In a clear, desiccated atmosphere, O{sub 2} absorption may be detectable for all three planets with NIRISS. If the L 98-59 planets possess a clear, Venus-like atmosphere, NIRSpec could detect CO{sub 2} within 26 transits for each planet, but the presence of H{sub 2}SO{sub 4} clouds would significantly suppress CO{sub 2} absorption. The L 98-59 system is an excellent laboratory for comparative planetary studies of transiting multiplanet systems, and observations of the system via HST and JWST would present a unique opportunity to test the accuracy of the models presented in this study.

47 OTHER INSTRUMENTATION↗
DOE OSTI2017

Kepler-11 is a Solar Twin: Revising the Masses and Radii of Benchmark Planets via Precise Stellar Characterization

The six planets of the Kepler-11 system are the archetypal example of a population of surprisingly low-density transiting planets revealed by the Kepler mission. We have determined the fundamental parameters and chemical composition of the Kepler-11 host star to unprecedented precision using an extremely high-quality spectrum from Keck-HIRES (R ≃ 67,000, S/N per pixel ≃260 at 600 nm). Contrary to previously published results, our spectroscopic constraints indicate that Kepler-11 is a young main-sequence solar twin. The revised stellar parameters and new analysis raise the densities of the Kepler-11 planets by between 20% and 95% per planet, making them more typical of the emerging class of “puffy” close-in exoplanets. We obtain photospheric abundances of 22 elements and find that Kepler-11 has an abundance pattern similar to that of the Sun with a slightly higher overall metallicity. We additionally analyze the Kepler light curves using a photodynamical model and discuss the tension between spectroscopic and transit/TTV-based estimates of stellar density.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Benchmark transiting brown dwarf lhs 6343 c: spitzer secondary eclipse observations yield brightness temperature and mid-t spectral class

There are no field brown dwarf analogs with measured masses, radii, and luminosities, precluding our ability to connect the population of transiting brown dwarfs with measurable masses and radii and field brown dwarfs with measurable luminosities and atmospheric properties. LHS 6343 C, a weakly irradiated brown dwarf transiting one member of an M+M binary in the Kepler field, provides the first opportunity to probe the atmosphere of a non-inflated brown dwarf with a measured mass and radius. Here, we analyze four Spitzer observations of secondary eclipses of LHS 6343 C behind LHS 6343 A. Jointly fitting the eclipses with a Gaussian process noise model of the instrumental systematics, we measure eclipse depths of 1.06 ± 0.21 ppt at 3.6 μm and 2.09 ± 0.08 ppt at 4.5 μm, corresponding to brightness temperatures of 1026 ± 57 K and 1249 ± 36 K, respectively. We then apply brown dwarf evolutionary models to infer a bolometric luminosity log(L{sub ⋆}/L{sub ⊙})=−5.16±0.04. Given the known physical properties of the brown dwarf and the two M dwarfs in the LHS 6343 system, these depths are consistent with models of a 1100 K T dwarf at an age of 5 Gyr and empirical observations of field T5-6 dwarfs with temperatures of 1070 ± 130 K. We investigate the possibility that the orbit of LHS 6343 C has been altered by the Kozai–Lidov mechanism and propose additional astrometric or Rossiter–McLaughlin measurements of the system to probe the dynamical history of the system.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Benchmark datasets for SARS-CoV-2 surveillance bioinformatics

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the cause of coronavirus disease 2019 (COVID-19), has spread globally and is being surveilled with an international genome sequencing effort. Surveillance consists of sample acquisition, library preparation, and whole genome sequencing. This has necessitated a classification scheme detailing Variants of Concern (VOC) and Variants of Interest (VOI), and the rapid expansion of bioinformatics tools for sequence analysis. These bioinformatic tools are means for major actionable results: maintaining quality assurance and checks, defining population structure, performing genomic epidemiology, and inferring lineage to allow reliable and actionable identification and classification. Additionally, the pandemic has required public health laboratories to reach high throughput proficiency in sequencing library preparation and downstream data analysis rapidly. However, both processes can be limited by a lack of a standardized sequence dataset. We identified six SARS-CoV-2 sequence datasets from recent publications, public databases and internal resources. In addition, we created a method to mine public databases to identify representative genomes for these datasets. Using this novel method, we identified several genomes as either VOI/VOC representatives or non-VOI/VOC representatives. To describe each dataset, we utilized a previously published datasets format, which describes accession information and whole dataset information. Additionally, a script from the same publication has been enhanced to download and verify all data from this study.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

Benchmark Specifications and Results for ßeff in a HEU Metal System Using ORSphere

In the early 1970s Dr. John T. Mihalczo (team leader), J.J. Lynn, and J.R. Taylor performed experiments at the Oak Ridge Critical Experiments Facility (ORCEF) with highly enriched uranium (HEU) metal (called Oak Ridge Alloy or ORALLOY) in an attempt to recreate GODIVA I results with greater accuracy than those performed at Los Alamos National Laboratory in the 1950s (HEU-MET-FAST-001). The purpose of the Oak Ridge ORALLOY Sphere (ORSphere) experiments was to estimate the unreflected and unmoderated critical mass of an idealized sphere of uranium metal corrected to a density, purity, and enrichment such that it could be compared with the GODIVA I experiments. Part of the experimental series was the measurement of the delayed neutron fraction, ßeff, using time correlation measurements and using the central void reactivity measurement. The time correlations measurements were rejected by the experimenter. The measurements using the central void reactivity measurement yielded a ßeff value of 0.00657, which agrees well with the value measured with GODIVA I (0.0066). This measurement is evaluated, found to be acceptable, and discussed in extensive detail in “ORSphere: Physics Measurements for Bare, HEU(93.2) Metal Sphere". In order to determine the delayed neutron fraction using the central void reactivity delayed neutron parameters must be used. The experimenter utilized the delayed neutron parameters set forth by Keepin, Wimment, and Zeigler. If the derivation of the ßeff is repeated with different delayed neutron parameters from various modern nuclear data sets the resulting values vary greatly from the expected results.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Benchmarking and Disclosing Resilience Performance

This fact sheet provides an overview of trends and barriers related to disclosure of climate and resilience performance. It reviews major reporting frameworks for resilience, compares the frameworks, and provides next steps for building owners.

Resilience, Resiliency, Benchmarking, Sustainabili↗
DOE OSTI2017

Benchmarking of activation rate in special core in LR-0 reactor

The experiments focused on the determination of activation reaction rates of selected IRDFF materials activated in a well-defined special core assembled in the LR-0 reactor are presented in the paper. The used core is designed and verified for IRDFF library testing by reactivity characterization, fission rates distribution and also neutron spectra measurement at the center of the core. {sup 23}Na(n,2n), {sup 75}As(n,2n), {sup 89}Y(n,2n) and {sup 90}Zr(n,2n) reaction cross sections were measured in this special core. The presented neutron cross sections were derived from experimentally determined reaction rates of irradiated samples of NaF, As{sub 2}O{sub 3}, Y{sub 2}O{sub 3}, and ZrO{sub 2}. These reaction rates are derived from gamma activities of the activation products of studied activation reactions. Net Peak Areas (NPA) of photons accompanying decay were measured using a semiconductor High Purity Germanium (HPGe) detector. Despite the fact that mentioned reactions have a threshold above 10 MeV, where the neutron spectrum in the special LR-0 core is nearly undistinguishable from {sup 235}U prompt fission neutron spectrum, the measured integral cross sections averaged in LR-0 spectrum were corrected for spectral shift. The obtained values of {sup 235}U spectral average cross section are: (3.84 ± 0.19) μb for {sup 23}Na(n,2n); (0.320 ± 0.015) mb for {sup 75}As(n,2n); (0.171 ± 0.006) mb for {sup 89}Y(n,2n); (0.107 ± 0.005) mb for {sup 90}Zr(n,2n). (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2016

Benchmark for Free-Gas Elastic Scattering with the Heavy-Gas Model and Piecewise-Constant Cross Sections

Accurate Monte Carlo calculations involving thermal neutrons require that codes implement the thermal scattering physics correctly. The heavy-gas model, which is valid for large atomic mass, with constant cross sections in energy has an analytic solution for the thermal neutron spectrum that can be readily used to verify the implementation of the free-gas thermal scattering routines. Previous work has shown that MCNP6.1 correctly computes the free-gas thermal flux with constant cross sections. This summary extends the verification to piecewise-constant cross sections in energy that can better approximate physically realistic cross sections. The obtained solutions for the piecewise-constant cases agree with the respective thermal spectra obtained by MCNP6.1, further verifying that it is accurately simulating the free-gas model. (authors)

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Criticality Benchmarking of the Oregon State TRIGA Reactor Using the MCNP Burn Option

Neutronic analyses of the Oregon State TRIGA Reactor (OSTR) have historically been performed using a thoroughly validated MCNP model. This model was originally created in 1997 in support of boron neutron capture therapy (BNCT) research, when the core still utilized highly-enriched uranium (HEU) fuel. The OSTR core was converted to low-enriched uranium (LEU) in the fall of 2008. To more accurately represent the converted state of the core, the MCNP model was modified to incorporate fuel material information from the fuel manufacturer (AREVA). In previous versions of the model, the fuel elements were assumed to have a uniform isotopic composition. Chemical analysis from AREVA provided far more resolved material information, allowing for increased fidelity in the representation of the fuel. The model was also updated to ENDF/B-VII.1 cross section libraries as the previous model utilized ENDF/B-VI. The primary impetus for the update of the MCNP model was the desire to have a more accurate assessment of criticality conditions of the OSTR. The OSTR utilizes three core configurations which are defined by the contents of the B1 grid position. If fuel resides in B1, this is designated as the 'normal' core. Otherwise, there are two aluminum in-core irradiation tubes (ICITs) that can be placed in B1. There is an unlined tube, designated simply as the ICIT, and there is a cadmium-lined tube, designated as the CLICIT. Table 1 contains a summary of the results of a series of MCNP criticality calculations which used the original 'fresh fuel' isotopics from the fall of 2008 in conjunction with critical rod height data from December 2013. Calculations were performed at 15 W, which is where the daily core excess measurements are taken, and at 1 MW, which is the current full-power level at the OSTR. The k-effective values indicate that the fresh fuel material cards are highly inaccurate and over-predict the criticality by at least $1.20 in every core configuration (based on a β{sub eff} value of 0.0075), thus it was desired to perform a depletion calculation to obtain more accurate fuel information. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2017

Investigation of Treat M2 and M3 calibration experiments for benchmark analysis

The Transient Reactor Test Facility (TREAT) located at Idaho National Laboratory is a graphite moderated and reflected, air cooled core. This reactor was originally designed and operated to experimentally test fuel under extreme transient conditions. To this end, TREAT successfully performed many series of steady-state and transient tests until operations were discontinued in 1994. With the restart of the reactor planned for 2018, accurate models of previous reactor experiments are necessary to verify the ability to predict conditions for planned upcoming tests. In this work, the methodology for modeling the M2 and M3 calibration experiments (M2/M3CAL) will be described along with results from the variation of key parameters including the boron concentration. Additionally, this model will be used to demonstrate the correlation between reactor behavior and the implementation of 'nuclear graphite' thermal scattering law (TSL) data to capture the behavior of thermal neutrons in the TREAT core.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗