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Nuclear Criticality Safety
NCSD provides communication among nuclear criticality safety professionals through the development of standards, the evolution of training methods and materials, the presentation of technical data and procedures, and the creation of specialty publications. In these ways, the division furthers the exchange of technical information on nuclear criticality safety with the ultimate goal of promoting the safe handling of fissionable materials outside reactors.
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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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Latest News
NRC’s David Wright visits the Hill and more NRC news
Wright
The Nuclear Regulatory Commission is in the spotlight today for three very different reasons. First, NRC Chair David Wright was on Capitol Hill yesterday for his renomination hearing in front of the Senate’s Environment and Public Works Committee. Second, the NRC released its updated milestone schedules according to the Nuclear Energy Innovation and Modernization Act (NEIMA) and the executive orders signed by President Trump last month; and third, as reported by Reuters on Tuesday, 28 former NRC officials have condemned the dismissal of Commissioner Hanson earlier this month.
Renomination: EPW Committee chair Sen. Shelley Moore Capito (R., W.Va.) opened the hearing with a statement praising Wright’s experience and emphasized the urgency of stable leadership at the NRC.
“China is executing a rapid build-out of its nuclear industry,” Capito said. “The demand for clean, baseload power is skyrocketing as we position America to win the AI race.”
H. van Dam
Nuclear Science and Engineering | Volume 129 | Number 3 | July 1998 | Pages 273-282
Technical Paper | doi.org/10.13182/NSE98-A1981
Articles are hosted by Taylor and Francis Online.
An analysis is presented of reactor dynamics during inherent shutdown and recriticality after loss of cooling without scram. The influence of the strength of external neutron sources is studied, and the dynamics of fission product decay heat is explicitly taken into account. It is shown that decay heat and (in thermal reactors) xenon dynamics play a dominant role in inherent reactor shutdown. Fission power level at first spontaneous recriticality is determined by both the strength of the external/inherent neutron sources and the reactivity ramp rate induced by xenon decay and cooling down of the subcritical reactor core. The first power surge after recriticality is only very weakly dependent on the external/inherent neutron source strength, and the amplitude of fission power oscillations is mainly determined by the reactivity ramp rate at first recriticality. Frequency and stability of the power oscillations after recriticality depend on the thermal inertia of the core and the power-reactivity defect. Stability is slightly deteriorated by the fission product decay dynamics, but the influence of xenon dynamics is negligible.
