On a measurement approach to support evaluation of thermal scattering law data
Abstract
Inelastic thermal neutron scattering in materials that act as neutron moderators, reflectors, and filters results in shaping the neutron spectrum at low energies. This phenomenon is described using differential scattering cross sections calculated from three components including the bound atom (i.e., nuclear) scattering cross section of the neutron, the ratio of the outgoing and incoming neutron energy, and the thermal scattering law (TSL), i.e., S(α,β), where α and β represent dimensionless momentum and energy exchange variables, respectively. To date, no TSL libraries are generated using measured data. However, valuable information may be derived from measurements and “targeted” experiments that can validate TSL data and the related inelastic scattering cross sections. As a demonstration, a suite of coordinated measurements and experiments is described that was designed and used to support the evaluation of the TSL for “nuclear” graphite. This experimental suite includes neutron powder diffraction (for structure analysis), positron annihilation (for nano porosity assessment), inelastic neutron scattering measurements using a chopper spectrometer, transmission experiments using neutrons with energy below the Bragg cutoff thereby accessing the total (inelastic) cross section, and a slowing-downtime experiment to observe the developing neutron spectrum in the material. We find that this experimental suite was key tomore »
- Authors:
-
- North Carolina State Univ., Raleigh, NC (United States)
- Publication Date:
- Research Org.:
- North Carolina State University, Raleigh, NC (United States)
- Sponsoring Org.:
- USDOE Office of Nuclear Energy (NE); USDOE National Nuclear Security Administration (NNSA), Nuclear Criticality Safety Program (NCSP); The US Naval Nuclear Propulsion Program (NNPP)
- OSTI Identifier:
- 1848122
- Alternate Identifier(s):
- OSTI ID: 1563038
- Grant/Contract Number:
- NE0008444
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Annals of Nuclear Energy
- Additional Journal Information:
- Journal Volume: 135; Journal Issue: C; Journal ID: ISSN 0306-4549
- Publisher:
- Elsevier
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; Nuclear Criticality Safety Program (NCSP); Nuclear Science & Technology; Neutron; Thermal Scattering Law; Cross Section; Measurement; ENDF
Citation Formats
Hawari, Ayman I. On a measurement approach to support evaluation of thermal scattering law data. United States: N. p., 2019.
Web. doi:10.1016/j.anucene.2019.106940.
Hawari, Ayman I. On a measurement approach to support evaluation of thermal scattering law data. United States. https://doi.org/10.1016/j.anucene.2019.106940
Hawari, Ayman I. Tue .
"On a measurement approach to support evaluation of thermal scattering law data". United States. https://doi.org/10.1016/j.anucene.2019.106940. https://www.osti.gov/servlets/purl/1848122.
@article{osti_1848122,
title = {On a measurement approach to support evaluation of thermal scattering law data},
author = {Hawari, Ayman I.},
abstractNote = {Inelastic thermal neutron scattering in materials that act as neutron moderators, reflectors, and filters results in shaping the neutron spectrum at low energies. This phenomenon is described using differential scattering cross sections calculated from three components including the bound atom (i.e., nuclear) scattering cross section of the neutron, the ratio of the outgoing and incoming neutron energy, and the thermal scattering law (TSL), i.e., S(α,β), where α and β represent dimensionless momentum and energy exchange variables, respectively. To date, no TSL libraries are generated using measured data. However, valuable information may be derived from measurements and “targeted” experiments that can validate TSL data and the related inelastic scattering cross sections. As a demonstration, a suite of coordinated measurements and experiments is described that was designed and used to support the evaluation of the TSL for “nuclear” graphite. This experimental suite includes neutron powder diffraction (for structure analysis), positron annihilation (for nano porosity assessment), inelastic neutron scattering measurements using a chopper spectrometer, transmission experiments using neutrons with energy below the Bragg cutoff thereby accessing the total (inelastic) cross section, and a slowing-downtime experiment to observe the developing neutron spectrum in the material. We find that this experimental suite was key to understanding the difference in TSL between “nuclear” and “ideal” graphite and for the inclusion of “nuclear” graphite in the ENDF/B-VIII.0 nuclear data library release.},
doi = {10.1016/j.anucene.2019.106940},
journal = {Annals of Nuclear Energy},
number = C,
volume = 135,
place = {United States},
year = {Tue Jul 30 00:00:00 EDT 2019},
month = {Tue Jul 30 00:00:00 EDT 2019}
}
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Inelastic Thermal Neutron Scattering Cross Sections for Reactor-grade Graphite
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