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research article

Neutron-Gamma Noise Measurements in a Zero-Power Reactor Using Organic Scintillators

Darby, Flynn B.
•
Pakari, Oskari Ville  
•
Hua, Michael Y.
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May 1, 2024
Ieee Transactions On Nuclear Science

Noise measurements in light water reactor systems aid in generating validation data for integral point kinetic parameter predictions and generating monitoring parameters for reactor safety and safeguards. The CROCUS zero-power reactor has been used to support both efforts via measurements with thermal neutron detectors to observe neutron noise and inorganic scintillators to observe gamma noise. The cross-correlation of gamma and neutron noise has been investigated at CROCUS with separate gamma-only and neutron-only detectors. Organic scintillators, sensitive to both neutrons and gamma rays, can be used to cross-correlate gamma-ray and neutron noise with a single detector type. Herein, we present noise measurements using organic scintillators in a light-water, zero-power research reactor for the first time. We discuss data obtained with two 5.08 cm-length by 5.08 cm-diameter cylindrical trans-stilbene detectors and two 6-mm cubic scintillators - one trans-stilbene and one organic glass - set in the water reflector of CROCUS and outside the reactor vessel. The prompt neutron decay constant was estimated to be alpha(CPSD) = (154 +/- 1) s(-1) at 3 mW critical from the (gamma, gamma) signal, which agrees within one standard deviation overlap with previous measurements with CeBr3 and simulation in Serpent 2. The (n, n) estimate of alpha(CPSD) = (145 +/- 23) s(-1) at 3 mW critical lacked precision but agreed within one standard deviation overlap with previous U-235 fission chamber estimates and simulation in Serpent 2. The 6-mm cubic scintillators were too inefficient to estimate alpha, but informed possible small-cell, high-volume detection systems to improve the (n, n) estimate capabilities. Based on the high precision estimate of alpha from the (gamma ,gamma) CPSD signal we suggest the further development of theory to calculate beta(eff) and Lambda from gamma-ray noise measurements and recommend gamma noise measurements for future simulation validation and as a method of reactor monitoring.

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Type
research article
DOI
10.1109/TNS.2023.3337657
Web of Science ID

WOS:001226402700008

Author(s)
Darby, Flynn B.
Pakari, Oskari Ville  
Hua, Michael Y.
Lamirand, Vincent  
Clarke, Shaun D.
Pautz, Andreas
Pozzi, Sara A.
Date Issued

2024-05-01

Publisher

Ieee-Inst Electrical Electronics Engineers Inc

Published in
Ieee Transactions On Nuclear Science
Volume

71

Issue

5

Start page

1033

End page

1040

Subjects

Technology

•

Neutron Noise

•

Organic Scintillators

•

Power Spectral Density (Psd)

•

Pulse-Shape Discrimination

•

Reactor Noise

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
LRS  
FunderGrant Number

Consortium for Monitoring, Technology, and Verification under the Department of Energy National Nuclear Security Administration

Available on Infoscience
June 19, 2024
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/208617
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