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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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2024 ANS Winter Conference and Expo
November 17–21, 2024
Orlando, FL|Renaissance Orlando at SeaWorld
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!
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Latest News
NRC okays construction permits for Hermes 2 test facility
The Nuclear Regulatory Commission announced yesterday that it has directed staff to issue construction permits to Kairos Power for the company's proposed Hermes 2 nonpower test reactor facility to be built at the Heritage Center Industrial Park in Oak Ridge, Tenn. The permits authorize Kairos to build a facility with two 35-MWt test reactors that would use molten salt to cool the reactor cores.
Hunter Belanger, Davide Mancusi, Amélie Rouchon, Andrea Zoia
Nuclear Science and Engineering | Volume 197 | Number 4 | April 2023 | Pages 534-557
Technical Paper | doi.org/10.1080/00295639.2022.2126719
Articles are hosted by Taylor and Francis Online.
Neutron noise in nuclear power reactors refers to the small fluctuations around the average neutron flux at steady state resulting from time-dependent perturbations inside the core. The neutron noise equations in the frequency domain can be solved using Monte Carlo simulation codes, which are capable of obtaining reference solutions involving almost no approximations but are hindered by severe issues affecting the statistical convergence: The simultaneous presence of positive and negative particles, which is required by the nature of the complex noise equations, leads to catastrophically large variance in the tallies. In this work, we consider the important case of neutron noise problems induced by mechanical vibrations. First, we derive a new exact sampling strategy for the noise source. Then, building upon our previous findings in other contexts, we show that weight cancellation methods can be highly beneficial in dealing with the presence of negative weights, enabling extremely large gains in the figure of merit. We successfully demonstrate our results on a benchmark configuration consisting of a fuel assembly with a vibrating pin, and we discuss possible pathways for further improvements.