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  4. High accuracy measurement of the prompt neutron decay constant in CROCUS using Gamma Noise and bootstrapped uncertainties
 
research article

High accuracy measurement of the prompt neutron decay constant in CROCUS using Gamma Noise and bootstrapped uncertainties

Pakari, Oskari Ville  
•
Lamirand, Vincent  
•
Mager, Tom
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June 1, 2022
Annals Of Nuclear Energy

We experimentally demonstrate the advantages of gamma detection for noise measurements to deter-mine the prompt neutron decay constant a of a nuclear reactor using the power spectral density (PSD) method, coupled to a new uncertainty estimation scheme based on bootstrapping. We compare the rel-ative precision of gamma noise measurements and neutron noise measurements performed in the CROCUS research reactor. The reference neutron noise experiment employs two large U-235 fission chambers, whereas the new gamma noise experiment is based on two CeBr3 scintillators. The results demonstrate that gamma noise is superior to neutron noise with respect to precision, giving an advantage with regards to measurement time to reach desired uncertainty levels: the uncertainty budget shows a relative uncertainty of 3.6% and 1.3% on the prompt neutron decay constant with neutron and gamma noise, respectively. Moreover, thanks to bootstrapping, the reporting of full distributions - rather than assuming Gaussian spreads - of kinetic parameters is shown to be relevant in order to provide an accurate rep-resentation of the experimental results in some cases. In addition, we notably discuss the lower level discrimination threshold and its effect on the gamma PSDs. Gamma ray cross PSDs exhibit a behaviour contrary to that of a standard neutron acquisition system, and we discuss the implications. Gamma noise could prove to be a cheaper, more precise, and more flexible method to determine reactor kinetics. (C) 2022 The Author(s). Published by Elsevier Ltd.

  • Details
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Type
research article
DOI
10.1016/j.anucene.2022.109011
Web of Science ID

WOS:000793203800009

Author(s)
Pakari, Oskari Ville  
Lamirand, Vincent  
Mager, Tom
Frajtag, Pavel  
Pautz, Andreas  
Date Issued

2022-06-01

Publisher

PERGAMON-ELSEVIER SCIENCE LTD

Published in
Annals Of Nuclear Energy
Volume

170

Article Number

109011

Subjects

Nuclear Science & Technology

•

neutron noise

•

gamma noise

•

prompt neutron decay constant

•

experimental reactor physics

•

core

•

parameters

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
LRS  
Available on Infoscience
June 6, 2022
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/188290
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