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Nuclear Energy Conference & Expo (NECX)
September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
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Moving past Sayre’s Law on low-dose radiation
Craig Piercycpiercy@ans.org
So, President Trump has just kicked the low-dose radiation hornets’ nest.
Specifically, his recently signed executive order “Ordering the Reform of the Nuclear Regulatory Commission” calls for the NRC to “reconsider reliance” on the linear no-threshold (LNT) theory and the ALARA (as low as reasonably achievable) standard for radiation protection.
This directive will certainly reignite a vociferous debate within the radiation research community over the continued efficacy of using LNT as the basis for protecting the public and the environment, a community that has been wracked with controversy on this matter for the last few years.
I must admit that whenever the low-dose issue comes up, my first thoughts always go to Sayre’s Law.
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.