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Title: Patchy nuclear chain reactions

Journal Article · · Communications Physics
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  1. Pôle Sûreté Nucléaire, Fontenay-aux-Roses (France). Institut de Radioprotection et de Sûreté Nucléaire, Laboratoire de Neutronique
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  3. Univ. Paris-Saclay, Gif-sur-Yvette (France)
+ Show Author Affiliations

Stochastic fluctuations of the neutron population within a nuclear reactor are typically prevented by operating the core at a sufficient power, since a deterministic (i.e., exactly predictable) behavior of the neutron population is required by automatic safety systems to detect unwanted power excursions. In order to characterize the reactor operating conditions at which the fluctuations vanish, an experiment was designed and took place in 2017 at the Rensselaer Polytechnic Institute Reactor Critical Facility. This experiment however revealed persisting fluctuations and striking patchy spatial patterns in neutron spatial distributions. Here we report these experimental findings, interpret them by a stochastic modeling based on branching random walks, and extend them using a “numerical twin” of the reactor core. Consequences on nuclear safety will be discussed.

Research Organization:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Sponsoring Organization:
USDOE National Nuclear Security Administration (NNSA), Nuclear Criticality Safety Program (NCSP)
Grant/Contract Number:
89233218CNA000001
OSTI ID:
1835779
Report Number(s):
LA-UR-20-29402; TRN: US2300248
Journal Information:
Communications Physics, Vol. 4, Issue 1; ISSN 2399-3650
Publisher:
Springer NatureCopyright Statement
Country of Publication:
United States
Language:
English

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Figures / Tables (6)

Fig. 1(p. 4)figure Fig. 1
σ agreement for the inner 3He detectors, while a systematic underestimation of the simulated flux appears on the top NoMAD detector. This might be attributed to the positioning of the detector during the experiment, which might have been slightly displaced during the reactor immersion." data-ostiid="1835779">
Fig. 2(p. 5)figure Fig. 2
Fig. 3(p. 6)figure Fig. 3
Fig. 4(p. 7)figure Fig. 4
Fig. 5(p. 8)figure Fig. 5
Fig. 6(p. 9)figure Fig. 6

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