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Conference Spotlight
Nuclear Energy Conference & Expo (NECX)
September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
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Ho Nieh nominated to the NRC
Nieh
President Trump recently nominated Ho Nieh for the role of commissioner in the Nuclear Regulatory Commission through the remainder of a term that will expire June 30, 2029.
Nieh has been the vice president of regulatory affairs at Southern Nuclear since 2021, though he is currently working as a loaned executive at the Institute of Nuclear Power Operations, where he has been for more than a year.
Nieh’s experience: Nieh started his career at the Knolls Atomic Power Laboratory, where he worked primarily as a nuclear plant engineer and contributed as a civilian instructor in the U.S. Navy’s Nuclear Power Program.
From there, he joined the NRC in 1997 as a project engineer. In more than 19 years of service at the organization, he served in a variety of key leadership roles, including division director of Reactor Projects, division director of Inspection and Regional Support, and director of the Office of Nuclear Reactor Regulation.
Toshihiro Yamamoto, Hiroki Sakamoto
Nuclear Science and Engineering | Volume 199 | Number 9 | September 2025 | Pages 1365-1375
Research Article | doi.org/10.1080/00295639.2025.2463815
Articles are hosted by Taylor and Francis Online.
The calculation of the inverse reactor period α, which is a fundamental mode eigenvalue of the α-mode nonlinear Boltzmann eigenvalue equation, depends on the kinetics parameters (delayed neutron fractions, precursor decay constants, and delayed neutron spectra) used in the calculation. Recently, we developed a Monte Carlo method to calculate the derivatives of the k-eigenvalue with respect to α. Here, the k-eigenvalue is not a critical eigenvalue; rather, it is a fictitious eigenvalue introduced to determine the α value that satisfies the α-mode nonlinear equation. The sensitivity coefficients of α with respect to the kinetics parameters are expressed as the ratio of the two derivatives: the derivative of the k-eigenvalue with respect to the kinetics parameters and that with respect to α.
This study introduces a new step for calculating the derivatives of the k-eigenvalue with respect to kinetics parameters using the differential operator sampling method. The sensitivity coefficients obtained using the Monte Carlo method have been validated based on their close agreement with the reference solutions obtained using a deterministic method.