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2025 ANS Winter Conference & Expo
November 9–12, 2025
Washington, DC|Washington Hilton
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Latest News
Senate EPW Committee to hold Nieh nomination hearing
Nieh
The Senate Environment and Public Works Committee will hold a nomination hearing Wednesday for Ho Nieh, President Donald Trump’s nominee to serve as commission at the Nuclear Regulatory Commission.
Trump nominated Nieh on July 30 to serve as NRC commissioner the remainder of a term that will expire June 30, 2029, as Nuclear NewsWire previously reported.
Nieh has been vice president of regulatory affairs at Southern Nuclear since 2021, though since June 2024 he has been at the Institute of Nuclear Power Operations as a loaned executive.
A return to the NRC: If confirmed by the Senate, Nieh would be returning to the NRC after three previous stints totaling nearly 20 years.
Jesse C. Holmes, Ayman I. Hawari, Michael L. Zerkle
Nuclear Science and Engineering | Volume 184 | Number 1 | September 2016 | Pages 84-113
Technical Paper | doi.org/10.13182/NSE15-89
Articles are hosted by Taylor and Francis Online.
The S(α, β) double-differential thermal neutron scattering law tabulated in Evaluated Nuclear Data File (ENDF) File 7 is, by convention, produced theoretically through fundamental scattering physics models. Currently, no published ENDF evaluations contain covariance data for S(α, β) or associated scattering cross sections. Furthermore, no accepted methodology exists for quantifying or representing these covariances. Thermal scattering cross sections depend on the interatomic structure and dynamics of the material. For many solids, the influence of these properties on inelastic scattering cross sections can be adequately described through the phonon energy spectrum. The phonon spectrum can be viewed as a probability density function and is commonly the fundamental input for calculating S(α, β). Probable variation in the shape of the phonon spectrum may be established that characterizes uncertainties in the physics models and methodology employed in its production. Through Monte Carlo sampling of perturbations from the reference phonon spectrum, an S(α, β) covariance matrix may be generated. With appropriate sensitivity information, the S(α, β) covariance matrix can be propagated to generate covariance data for differential and integral cross sections. In this work, hexagonal graphite is used as an example material for demonstrating the proposed procedures for analyzing, calculating, and processing uncertainty information for theoretically generated thermal neutron inelastic scattering data.