Quantification of large steam bubble oscillations and chugging using image analysis
Hujala, Elina (2019-11-01)
Väitöskirja
01.11.2019
Lappeenranta-Lahti University of Technology LUT
Acta Universitatis Lappeenrantaensis
School of Energy Systems
School of Energy Systems, Energiatekniikka
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Julkaisun pysyvä osoite on
https://urn.fi/URN:ISBN:978-952-335-425-8
https://urn.fi/URN:ISBN:978-952-335-425-8
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Tiivistelmä
The pressure suppression pool of a boiling water reactor as a safety system has vital importance from the nuclear reactor safety point of view. If a loss-of-coolant accident occurs, a large amount of steam is pushed through the blowdown pipes to the suppression pool. Rapid condensation of steam causes high dynamic loads on the suppression pool structures and demands a great deal of its strength. These loads should be recognized and avoided.
A pattern recognition based image analysis algorithm for vertical vent pipes was designed and developed in this study. The direct contact condensation experiment (DCC-05) of the PPOOLEX test facility was used as a reference test. The algorithm consists of three parts: pre-processing, where all image processing takes place, pattern recognition, where the edges of the bubbles are detected, and postprocessing part, where all images are analysed and data collected. The algorithm evaluates basic properties of large steam bubbles, such as volume, surface area, surface velocity and acceleration, and different frequencies.
Frequency analysis was also conducted on the DCC-05 case. The analysis showed two main frequencies 53 Hz and 126 Hz. The algorithm was also applied to computational fluid dynamics (CFD) simulations, where the algorithm was used to determine critical wavelengths of condensation driven Rayleigh-Taylor instability in succession to establish the most suitable grid density for the simulations. A frequency analysis was also performed for the CFD simulation cases and compared to the results of the algorithm.
The algorithm was extended to cover cases where multiple bubbles travel at the same time in the frame being analysed. The extended algorithm tracks multiple bubble properties in the same image. The evaluation of surface velocities and acceleration were also improved.
The algorithms work well in evaluating volume, surface area, velocities and accelerations of large steam bubbles. The research verified that even from moderate quality video material, it is possible to acquire high quality quantitative data, if the frame rate of video had been high enough and the most obtrusive objects could be filtered out from it as well. The algorithms can help to understand phenomena that underlay the design of boiling water reactor (BWR) safety systems.
A pattern recognition based image analysis algorithm for vertical vent pipes was designed and developed in this study. The direct contact condensation experiment (DCC-05) of the PPOOLEX test facility was used as a reference test. The algorithm consists of three parts: pre-processing, where all image processing takes place, pattern recognition, where the edges of the bubbles are detected, and postprocessing part, where all images are analysed and data collected. The algorithm evaluates basic properties of large steam bubbles, such as volume, surface area, surface velocity and acceleration, and different frequencies.
Frequency analysis was also conducted on the DCC-05 case. The analysis showed two main frequencies 53 Hz and 126 Hz. The algorithm was also applied to computational fluid dynamics (CFD) simulations, where the algorithm was used to determine critical wavelengths of condensation driven Rayleigh-Taylor instability in succession to establish the most suitable grid density for the simulations. A frequency analysis was also performed for the CFD simulation cases and compared to the results of the algorithm.
The algorithm was extended to cover cases where multiple bubbles travel at the same time in the frame being analysed. The extended algorithm tracks multiple bubble properties in the same image. The evaluation of surface velocities and acceleration were also improved.
The algorithms work well in evaluating volume, surface area, velocities and accelerations of large steam bubbles. The research verified that even from moderate quality video material, it is possible to acquire high quality quantitative data, if the frame rate of video had been high enough and the most obtrusive objects could be filtered out from it as well. The algorithms can help to understand phenomena that underlay the design of boiling water reactor (BWR) safety systems.
Kokoelmat
- Väitöskirjat [1152]