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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 OSTI2015

Current Issues in Nuclear Data Evaluation Methodology: {sup 235}U Prompt Fission Neutron Spectra and Multiplicity for Thermal Neutrons

Issues in evaluation methodology of the prompt fission neutron spectra (PFNS) and neutron multiplicity for the thermal-neutron-induced fission of the {sup 235}U are discussed. The inconsistency between the experimental differential and integral data is addressed. By using differential data as ”shape data” good consistency was achieved between available sets of differential data. Integral dosimetry data have been used to define the PFNS slope at high outgoing neutron energies, where the quality of the differential data is poor. The inclusion into the fit of measured integral (spectrum-averaged) cross sections had a very small impact in the region where differential PFNS data are abundant and accurate, but removed the discrepancy with integral data at higher neutron emission energies. All experimental data are consistently fitted giving a PFNS average energy of 2.008 MeV. The impact on criticality prediction of the newly evaluated PFNS was tested. The highly enriched {sup 235}U solution assemblies with high leakage HEU-SOL-THERM-001 and HEU-SOL-THERM-009 benchmarks are the most sensitive to the PFNS. Criticality calculations for those solutions show a significant increase in reactivity if the average neutron energy of the fission neutrons is reduced from the ENDF/B-VI.5 value of 2.03 MeV. The proposed reduction of the PFNS average energy by 1.1% can be compensated by reducing the average number of neutrons per fission ν{sup ¯} at the thermal energy to the Gwin et al. measured value. The simple least-squares PFNS fit was confirmed by a more sophisticated combined fit of differential PFNS data for {sup 233,235}U, {sup 239}Pu and {sup 252}Cf nuclides with the generalised least-squares method using the GMA and GANDR codes.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Nuclear Data Sheets for A=190

The evaluated experimental data are presented and evaluated for 15 known nuclides of mass 190 (Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, Po). This work supersedes earlier full evaluations of A=190 by 2003Si05, 1990Si09, 1982Le22 and 1973Sc42. For 190Hf, only the isotopic identification has been made, with no information about the half-life of the ground state or its decay properties. For 190 Ta, only one excited state as an isomer has been identified, but with no knowledge about its decay properties. For 190 W, 190 Re, 190 Bi and 190 Po, available spectroscopic data are scarce. Here, the decay schemes of 190 Ta, 190 W, 190 Au, 190 Hg, 190 Au isomer decay, 190 Tl (both the activities), 190 Pb, and 190 Bi (both the activities) are considered incomplete by the evaluators. At present, extensive level structures, both the low-spin and high-spin, are known for 190 Os, 190 Ir, 190 Pt, 190 Au, 190 Hg, 190 Tl and 190 Pb, but data for level lifetimes, and γ-ray transition probabilities are generally lacking.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Zr Nuclear Data Campaign: Measurement of (n,γ) cross section of 90,91 Zr [Abstract]

The isotopes of Zr with mass number A = [90; 91; 92; 94] make up more than 97% of naturally occurring Zr and are important to many nuclear applications due to their desirable mechanical and nuclear properties. For example, the zirconium alloys are used as cladding material in nuclear reactors. In addition to the mechanical properties, Zr-90 has a closed neutron shell, hence the capture cross sections of the zirconium isotopes are relatively small, such that they improve the neutron economy in reactors by preferentially scattering neutrons rather than absorbing them. This same quality also presents a challenge to measuring the capture cross section, σ γ (E), of Zr isotopes. For incident neutron energies < 0.1 MeV, the ENDF library reports a relative uncertainty of approximately 20% and uncertainty greater than 20% above this energy. This motivates the Nuclear Criticality Safety Program (NCSP) to perform new neutron induced cross section measurements to accurately evaluate these four isotopes of Zr.

ENDF↗
DOE OSTI2012

Analysis of differences in the ENDL99 and ENDL2009 nuclear data libraries pertaining to 238 U

A careful analysis is performed on the differences exhibited in the evaluated elastic and inelastic channels between the ENDL99 and ENDL2009 libraries for neutrons incident on 238 U. The two libraries are compared with experimental data as well as results obtained from calculations utilizing a new Hauser-Feshbach reaction code and two modern, high-quality optical potentials. Overall, the ENDL2009 evaluation is found to be more physical, and a better representation of experimental data. The only exception is that the angular distributions for the elastic channel in the ENDL99 library are in better agreement at backward angles for incident neutron energies in the range 0.7-1.3 MeV. Other issues with the inelastic scattering data in ENDL2009 are pointed out.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2026

Nuclear Data Sheets for A=69

Experimental data on ground- and excited-state properties for all known nuclei with mass number A=69 have been compiled and evaluated. States populated in radioactive decay, as well as in nuclear reactions, have been considered. For these nuclei, level and decay schemes, as well as tables of nuclear properties, are given in detail. In conclusion, this work supersedes the 2013 evaluation by C.D. Nesaraja (2014Ne01).

Nesaraja, Caroline D. [Oak Ridge National Laborato↗
DOE OSTI2022

Nuclear Data Sheets for A=267,271,275,279,283,287,291,295,299

Information on the production, identification, half-lives and decay modes for experimentally known nuclides with mass numbers of 267, 271, 275, 279, 283, 287, and 291, along with attempts to observe nuclides with mass numbers of 295 and 299, are presented along with the recommended values. Data here supersede data from the previous evaluation in this region, 2005Gu33. Since the previous evaluation many new and conclusive experiments have explored the region of superheavy nuclei, thus significantly expanding our knowledge of the nuclear chart in this area.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Nuclear Data Sheets for A=269,273,277,281,285,289, and 293

Herein, information on the production, identification, half-lives and decay modes for experimentally known nuclides with mass numbers of 269, 273, 277, 281, 285, 289, and 293 are presented along with the recommended values. Data here supersede data from the previous evaluation in this region, 2005Gu33. Since the previous evaluation many new and conclusive experiments have explored the region of superheavy nuclei, thus significantly expanding our knowledge of the nuclear chart in this area.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗