A1 Journal article (refereed), original research

Frequency analysis of chugging condensation in pressure suppression pool system with pattern recognition


Open Access publication

Publication Details
Authors: Hujala Elina, Tanskanen Vesa, Hyvärinen Juhani
Publisher: Elsevier
Publication year: 2018
Language: English
Related Journal or Series Information: Nuclear Engineering and Design
Volume number: 339
Start page: 244
End page: 252
Number of pages: 9
ISSN: 0029-5493
eISSN: 1872-759X
JUFO-Level of this publication: 3
Open Access: Open Access publication
Location of the parallel saved publication: http://urn.fi/URN:NBN:fi-fe2018100437400

Abstract


Direct
contact condensation (DCC) phenomena in boiling water reactor (BWR) pressure
suppression pool systems need to be understood to properly assess the
performance of the pool as a heat sink and as a safety critical structure.
Condensation oscillations in the form of chugging are challenging to predict by
computational fluid dynamics (CFD) methods but safety relevant because of
associated high dynamic loads on in-pool structures and the pool itself. Recently, new measurement methods for CFD
validation purposes have become available. One of these techniques is visual
observation using the high-speed cameras and suitable data processing method.
Pattern recognition is a well suited technique for the determination of large
oscillating bubble dynamics in a pressure suppression pool.





In this
work, the formation and collapse of the steam bubbles in chugging condensation
mode are evaluated by using the pattern recognition algorithm. The pattern
recognition algorithm is based on video material recorded during the direct
contact condensation experiment DCC-05 of the PPOOLEX test facility. The
formation speed, the shape and size of the steam bubbles and the acceleration
of collapsing bubbles are estimated with the algorithm. Fast Fourier transform
(FFT) is used for frequency analysis of the pattern recognized data. The
frequencies found are compared to the frequency data of the pressure
transducers collected during the experiment and to the previous results of the
NEPTUNE_CFD simulations of the same experiment.





The
frequency analysis shows that the chugging frequencies of the steam bubbles
range from 1 to 3 Hz, as predicted. Also the natural frequencies of the bubbles
are visible around 53 Hz. Another frequency spike was observed close to the 125
Hz. This frequency is close to the mechanical resonance frequencies of the
suppression pool and the blowdown pipe. Because of neither the pressure
suppression pool nor the blowdown pipe are visible to the pattern recognition,
the spike of the higher frequencies is most likely from the interfacial area of
the bubble which resonates with the suppression pool system, affecting rapid
condensation at a certain point.




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Last updated on 2019-13-03 at 12:00

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