ANS is committed to advancing, fostering, and promoting the development and application of nuclear sciences and technologies to benefit society.
Explore the many uses for nuclear science and its impact on energy, the environment, healthcare, food, and more.
Explore membership for yourself or for your organization.
Conference Spotlight
Nuclear Energy Conference & Expo (NECX)
September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
Standards Program
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!
Latest Magazine Issues
Aug 2025
Jan 2025
Latest Journal Issues
Nuclear Science and Engineering
September 2025
Nuclear Technology
August 2025
Fusion Science and Technology
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.
Edward L. H. Tang
Nuclear Science and Engineering | Volume 69 | Number 1 | January 1979 | Pages 65-75
Technical Paper | doi.org/10.13182/NSE79-A21286
Articles are hosted by Taylor and Francis Online.
The rod-drop experiment has been studied for the purpose of predicting reactor resonance power level. A simplified model, referred to here as the “collective model,” is introduced for experimental analysis of the rod-drop transient response. The mathematical description of this model is formulated by describing the experimentally observed oscillatory response by an overall damping factor and an overall oscillatory frequency. Based on this model, it is found that the overall damping factor is approximately a linear function of the reactor power. Accordingly, we propose an experimental procedure, the method of least-squares approach, which provides an exponential approach to the resonance power level as a function of the number of rod drops. It is shown that the accuracy of measurement in the rod-drop experiment greatly affects this technique for core dynamic analysis. The present results show that for an experiment of negligible experimental error, only two or three rod drops are needed to predict the resonance power level up to an accuracy of 0.2%, while for an experiment of ±5% in error, it requires four to five rod drops to reach an accuracy of 0.8%.