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Conference Spotlight
Nuclear Energy Conference & Expo (NECX)
September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
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Latest News
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.
Kazuo Azekura
Nuclear Technology | Volume 77 | Number 3 | June 1987 | Pages 255-262
Technical Paper | Fission Reactor | doi.org/10.13182/NT87-A33965
Articles are hosted by Taylor and Francis Online.
An analysis model has been proposed to evaluate reactivity due to horizontal fast breeder reactor (FBR) core deformation in seismic events by direct three-dimensional eigenvalue calculations, which are impossible for current neutronic analysis programs. The model is based on a current-centered finite difference neutron diffusion calculation method. Macroscopic neutron reaction cross sections are defined, which take into account changes in both mesh volume and material composition. Further, the expression of vertical neutron current is modified in such a way as to take into account changes in vertical mesh interface areas. By using these macroscopic neutron cross sections and the modified expression for vertical neutron current, it is possible to calculate the effective multiplication factor of a deformed FBR core within the bounds of a finite difference diffusion calculation method using the same mesh division used for the normal nondeformed core. Computation time and computer core memory required by the presented model are almost the same as in current finite difference methods. The calculated reactivities for simple one-dimensional slab, two-dimensional slab, and three-dimensional hexagonal systems agreed within 5% of those obtained by either a finite element method or a finite difference method. The agreement was particularly good (within 2%) for cases in which fuel assembly pitches decrease around the horizontal core midplane; therefore, large reactivity is inserted.
