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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.
Tuomas Viitanen, Jaakko Leppänen
Nuclear Science and Engineering | Volume 177 | Number 1 | May 2014 | Pages 77-89
Technical Paper | doi.org/10.13182/NSE13-37
Articles are hosted by Taylor and Francis Online.
The target motion sampling (TMS) temperature treatment technique, previously known as “explicit treatment of target motion,” is a stochastic method for taking the effect of thermal motion on reaction rates into account on-the-fly during Monte Carlo neutron tracking. The method is based on sampling target velocities at each collision site and dealing with the collisions in the target-at-rest frame using cross sections below the actual temperature of the nuclide or, originally, 0 K. Previous results have shown that transport with the original implementation of the TMS method requires about two to four times more CPU time than conventional transport methods, depending on the case. In the present paper, it is observed that the overhead factor may increase even above 10 in cases involving burned fuel. To make the method more practical for everyday use, some optimization is required. This paper discusses a TMS optimization technique in which the temperatures of the basis cross sections are elevated above 0 K. Comparisons show that the TMS method is able to reproduce the NJOY-based reference results within statistical accuracy, both with and without the newly implemented optimization technique. In the specific test cases, the optimization saved 35% to 83% of the calculation time, depending on the case.