Microscopic bubble behaviour in suppression pool during wetwell venting

During a severe accident PCV failure should be avoided and fission products inside PCV should be confined as much as possible. In order to minimize FPs release, Wetwell venting is conducted by releasing steam-non-condensable gas mixture carrying FPs from the Drywell to Suppression Pool. Steam is con...

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Bibliographic Details
Published in:IOP conference series. Materials Science and Engineering 2017-10, Vol.249 (1), p.12017
Main Authors: Zablackaite, G, Nagasaka, H, Kikura, H
Format: Article
Language:English
Subjects:
Air Content
Bubbles
Fission products
Gas mixtures
High speed cameras
Low temperature
Parameters
Particle size distribution
Particle tracking
Particle tracking velocimetry
Pressure reduction
Stress concentration
Temperature distribution
Thermal stratification
Velocity measurement
Washing
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Summary:During a severe accident PCV failure should be avoided and fission products inside PCV should be confined as much as possible. In order to minimize FPs release, Wetwell venting is conducted by releasing steam-non-condensable gas mixture carrying FPs from the Drywell to Suppression Pool. Steam is condensed by subcooled water in the pool, and most of FPs are retained into water. The removal of FP in the water pool is referred to as "Pool Scrubbing effect". Hydrodynamic parameters of bubbles have impact on pool scrubbing effect. However, there is only few data available to evaluate quantitatively the bubble behaviour under depressurization and/or thermal stratification conditions. Series of experiments were conducted to evaluate the influence of temperature distribution, non-condensable gas content and pressure in the Wetwell on bubble behaviour. Bubbles were visualized using High Speed Camera and adopting shadowgraphy technique. Applying Particle Tracking Velocimetry, bubble velocity and size distribution were obtained from recorded images. Experimental results show that with increasing suppression pool temperature, bubbles reaching the pool surface decreased in size and traveling velocity became slower. In pressurized wetwell, bubble behaviour was similar to that in the heated up suppression pool case, although bubble parameters were similar to the low temperature case. Higher air content induced water surface movement and bubbles were smaller due to break up.
ISSN:1757-8981
1757-899X
DOI:10.1088/1757-899X/249/1/012017