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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.
Liujun Pan, Ruihong Wang, Song Jiang
Nuclear Science and Engineering | Volume 180 | Number 2 | June 2015 | Pages 199-208
Technical Paper | doi.org/10.13182/NSE14-73
Articles are hosted by Taylor and Francis Online.
We propose a modified method to improve the stability of the Monte Carlo fission matrix acceleration (FM) method. In the existing FM method, the weights of fission neutrons are adjusted by the fundamental-mode eigenvector of the fission matrix, which can be calculated by power iteration (PI). In this paper, the PI procedure to calculate the fundamental-mode eigenvector of the fission matrix in each cycle is called the inner iteration to distinguish it from the Monte Carlo iteration cycles. In our proposed method, the fission source distribution tallied during the Monte Carlo simulation is taken as the initial vector for the inner iteration. The weights of the fission neutrons are not adjusted by the fundamental-mode eigenvector of the fission matrix but by the vector obtained with only a few inner iteration steps. We call the proposed method the Monte Carlo fission matrix acceleration method with limited inner iteration (FM_lii). The FM_lii method possesses the following properties: It is more stable than the existing fission matrix acceleration method, and it preserves considerable acceleration efficiency. Moreover, we analyze the stability property of the proposed method for the case of two weakly coupled fissile arrays. A number of numerical tests for practical large-scale, loosely coupled systems are presented that demonstrate the theoretical analysis and efficiency of our scheme.