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Conference Spotlight
Nuclear Energy Conference & Expo (NECX)
September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
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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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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.
Tim H. J. J. van der Hagen
Nuclear Technology | Volume 83 | Number 2 | November 1988 | Pages 171-181
Technical Paper | Fission Reactor | doi.org/10.13182/NT88-A34158
Articles are hosted by Taylor and Francis Online.
The effective time constant related to heat transfer from fuel to coolant is a very important parameter for the dynamic behavior and thus the stability of a nuclear reactor. Usually a single time constant of a lumped parameter model is used. Both experimentally, via two independent methods of analysis, and theoretically, it is determined that a more elaborate model, using two or three time constants, is necessary. Heat transfer for high frequencies is governed by the small fuel time constants that stem from the outer region of the fuel. The bulk follows slow variations with time constants of >5 s.
