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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.
Kodai Fukuda, Jun Nishiyama, Toru Obara
Nuclear Science and Engineering | Volume 195 | Number 5 | May 2021 | Pages 453-463
Technical Paper | doi.org/10.1080/00295639.2020.1847979
Articles are hosted by Taylor and Francis Online.
To proceed with the decommissioning of the Fukushima Daiichi Nuclear Power Station, analyses of unexpected fuel debris criticality accidents are needed. Supercritical transient analyses have been conducted for fuel debris using the Multiregion Integral Kinetic (MIK) code, which can take the space dependence of fuel debris into account. In those analyses, reactivity is assumed as stepwise insertion because the MIK code does not include delayed neutron effects, which might be negligible. However, reactivity insertion may not always be stepwise. Therefore, it is important to clarify an applicable range of the MIK code for nonstepwise insertion, such as ramp reactivity insertion. To show that kinetics codes without delayed neutron effects could be applied for a supercritical transient induced by ramp reactivity insertion, we established a method to clarify its applicable range. An analysis using the point reactor kinetics model was introduced as a pre-analysis to clarify this range in the case of ramp reactivity insertion in terms of the contribution of delayed neutrons. We applied the methodology to a simple cylindrical fuel debris system and successfully demonstrated a supercritical transient analysis for ramp reactivity insertion using the MIK code.