A Numerical Study of Air Entrainment by the Pipe Rupture Size for Downward Flow Research Reactor

Many research reactors are open-pool type, and the pressure distribution of the cooling system could be computed by the pool water head and pressure difference in reactor core. Besides, pool outlet pipes are placed at higher position to guarantee the pool water inventory at LOCA. For these reasons, the negative pressure could be observed at the highest pipe position. Thus, the air could be flowed into the highest position of cooling system at the pipe rupture accident. In the present study, prior to the experimental study of air entrainment, numerical simulations are conducted by the pipe rupture size. This study was performed to analyze the flow phenomena on the air entrainment and calculate the air flow rate according to the pipe rupture size. All simulations were conducted for the cases with negative pressure at the highest pipe position. As the rupture size is increased, the pressure difference between inside pipe and atmosphere is decreased and air entrainment amount is increased.