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Conference Spotlight
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.
Praneel P. Gulabrao, Kevin T. Clarno
Nuclear Science and Engineering | Volume 195 | Number 2 | February 2021 | Pages 161-172
Technical Paper | doi.org/10.1080/00295639.2020.1794455
Articles are hosted by Taylor and Francis Online.
Photon buildup is a function of energy, medium, and geometry and therefore must be specifically calculated for the case of interest. The Martian atmosphere, mostly comprising carbon dioxide, is becoming more relevant to radiation researchers and therefore warrants the study of this gas mixture’s buildup properties for ionizing photon flux resulting from the secondary effects of galactic cosmic rays and solar flares. Specifically, this work uses the MCNP6 code to develop energy absorption buildup factors in finite slab models for energies ranging from 40 keV to 15 MeV with Martian regolith as the backscattering medium. The Martian carbon dioxide cycle is accounted for by determining maximum and minimum mean densities as a function of orbital position. An isotropic point source model for the atmosphere is also developed using the geometric progression fitting function. Buildup is bounded to a factor of approximately 23 at 100 keV for normally incident photons at the top of the atmosphere. For conservatism, the design problem neglects coherent scattering but assumes bremsstrahlung effects and uses Klein-Nishina free-electron cross sections for Compton scattering.