Measurement of the Gas Velocity in a Water-Air Mixture in CROCUS Using Neutron Noise Techniques
Artikel i vetenskaplig tidskrift, 2020

The possibility of measuring the gas-phase velocity in a two-phase mixture through the use of neutron noise techniques is demonstrated in the zero-power reactor CROCUS of the Ecole Polytechnique Federale de Lausanne. It is the first step toward the experimental validation of an existing theoretical model whose objective is the reconstruction of the void profile in a channel. The use of zero-power research reactors is advantageous due to their clean environment in terms of signal fluctuations. To this end, a channel was installed in the reflector of CROCUS. A two-component mixture is generated inside the channel through the injection of compressed air. The signal fluctuations of neutron detectors located at various axial locations next to the channel are processed to determine the transit time of the gas phase between detectors. Four methods are presented based on the detector signal time series either in the time domain (time correlations between signals) or in the frequency domain (phase of the cross-power spectral density. All four methods returned consistent transit times and similar experimental uncertainty. The largest possible gas injection rates as well as the highest possible neutron flux level improve the visibility of the traveling perturbation and reduce the experimental uncertainty on the transit time for a given acquisition time. © 2020, © 2020 American Nuclear Society.

Neutron noise measurement

gas velocity measurement

two-phase flow


Mathieu Hursin

Ecole Polytechnique Federale de Lausanne (EPFL)

Paul Scherrer Institut

Oskari Pakari

Ecole Polytechnique Federale de Lausanne (EPFL)

Gregory Perret

Paul Scherrer Institut

Pavel Frajtag

Ecole Polytechnique Federale de Lausanne (EPFL)

Vincent Lamirand

Paul Scherrer Institut

Ecole Polytechnique Federale de Lausanne (EPFL)

Imre Pazsit

Chalmers, Fysik, Subatomär, högenergi- och plasmafysik

Victor Dykin

Chalmers, Fysik, Subatomär fysik och plasmafysik

Gábor Pór

Budapesti Muszaki es Gazdasagtudomanyi Egyetem

Henrik Nylén

Ringhals AB

Andreas Pautz

Ecole Polytechnique Federale de Lausanne (EPFL)

Paul Scherrer Institut

Nuclear Technology

0029-5450 (ISSN) 19437471 (eISSN)

Vol. 206 10 1566-1583


Acceleratorfysik och instrumentering

Atom- och molekylfysik och optik




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