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Formation de voies vibroacoustique pour la détection d'une source monopolaire dans une coque cylindrique remplie de fluide lourd : Développements numériques et expérimentaux

Abstract : The safety of nuclear reactors represents a necessary and vital condition for the exploitation of nuclear plants with liquid-cooled cores. This safety passes by the ability to detect and anticipate the earliest stages of a water leak into sodium within the heat generator. The study detailed in this manuscript has been initiated in a framework aiming to develop nonintrusive detection techniques for sodium water chemical reactions. Its main goal is to uncover the signal of a water leak into sodium, based on the measurements of the vibratory field recorded by the means of accelerometers externally mounted on the heat generator shell. However, such a spectrum is masked by the plant general background noise, especially that generated by heavy fluid flow (i.e. sodium flow) during actual operating times of the power plant. In order to increase the signal-to-noise ratio of the leak, beamforming technique for the acceleration measurements of the mechanical system is considered. The aforementioned system is characterized by a strong non-linear coupling between the the heat generator’s cylindrical shell and the heavy fluid in motion. In particular, fluid motion and the acoustic emission of the leak seem to excite some eigen modes of the cylinder, at these same frequencies where the acoustic signature of the leak is at its highest amplitude. For the purpose of our study, a cylindrical mock-up connected by some very rigid links to a hydraulic circuit is considered. A hydrophone emission excites the mock-up from within and is being accounted for the acoustic leak. Water flows inside the cylinder at turbulent Reynolds number. An array of twenty-five accelerometers is mounted on the mock-up shell using ceramic insulators. The main goal is to combine the twenty-five signals in such a way that allows the increase of the SNR for the acoustic source while rejecting water flow noise. Two beamforming techniques are applied and compared: classical Bartlett beamforming as well as optimized beamforming for SNR maximization (Max SN
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https://tel.archives-ouvertes.fr/tel-02066872
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Submitted on : Wednesday, March 13, 2019 - 5:15:08 PM
Last modification on : Wednesday, July 8, 2020 - 12:42:27 PM
Long-term archiving on: : Friday, June 14, 2019 - 4:59:38 PM

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  • HAL Id : tel-02066872, version 1

Citation

Souha Kassab. Formation de voies vibroacoustique pour la détection d'une source monopolaire dans une coque cylindrique remplie de fluide lourd : Développements numériques et expérimentaux. Vibrations [physics.class-ph]. Université de Lyon, 2018. Français. ⟨NNT : 2018LYSEI047⟩. ⟨tel-02066872⟩

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