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Conference Spotlight
2025 ANS Winter Conference & Expo
November 9–12, 2025
Washington, DC|Washington Hilton
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The Standards Committee is responsible for the development and maintenance of voluntary consensus standards that address the design, analysis, and operation of components, systems, and facilities related to the application of nuclear science and technology. Find out What’s New, check out the Standards Store, or Get Involved today!
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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.
Matthew A. Gonzales, Brian C. Kiedrowski, Anil K. Prinja, Forrest B. Brown
Nuclear Science and Engineering | Volume 191 | Number 1 | July 2018 | Pages 1-45
Technical Paper | doi.org/10.1080/00295639.2018.1442546
Articles are hosted by Taylor and Francis Online.
The heavy-gas model with specific energy-dependent absorption cross sections is used to construct analytical, semi-analytical, and numerical free-gas scattering benchmarks for the neutron spectrum, effective multiplication factor k, and temperature coefficient in an infinite, homogeneous medium. The energy dependences considered are piecewise constant, constant plus inverse in energy, and piecewise linear. Analytic forms for k and in terms of hypergeometric functions are obtained for piecewise-constant absorption with two energy ranges and for constant-plus-inverse-in-energy absorption. Analogous semi-analytical integral expressions are obtained for piecewise-linear absorption with two energy ranges. Numerical solutions of a linear system are obtained for piecewise-constant and piecewise-linear absorption for greater than two energy ranges. The heavy-gas model solutions of k are compared with continuous-energy Monte Carlo calculations; the results converge to the heavy-gas model with increasing target mass ratio A, demonstrating the heavy-gas model’s utility as a verification benchmark.