THERMAL HYDRAULIC PHENOMENA IN A WATER POOL DUE TO AIR BUBBLE OSCILLATION

In both a boiling water reactor and an advanced pressurized water reactor such as the one currently under construction in Korea named APR1400, when a pressure relieving system is in operation, water, air and steam discharge successively into a sub-cooled water pool through spargers. Among the phenomena occurring during the discharging processes, the air bubble clouds with a low-frequency and high-amplitude oscillation may result in significant damage to the submerged structures if a resonance between the bubble clouds and structures occur. This study deals with a numerical prediction of the pressure field generated by the oscillation of air bubbles. The analysis was performed by using a commercial thermal hydraulic analysis code, FLUENT, version 4.5. The multiphase flows of water, air and steam were simulated by the VOF (Volume Of Fluid) model contained in the code. Unlike Kim et al.([1]), the LRR (Load Reduction Ring) of the sparger is artificially blocked for the investigation of LRR effects on the pressure field. It also includes the effects of air mass and inlet pressure in the piping on the pressure field. (C) 2004 Elsevier Science Ltd.