RELAP5/MOD3 SIMULATION OF THE WATER CANNON PHENOMENON

The results of the transient behavior of the water cannon phenomenon determined by RELAP5/MOD3 Version 5m5 are presented. The physical system consists of a 0.7112-m-long, 0.0381-m-i.d. vertical tube partially immersed in a reservoir of subcooled water. The tube is closed at the top and initially filled with saturated steam. The water cannon is created when a liquid slug is drawn into the tube because of the rapid condensation of the steam. In a fraction of a second, the liquid slug strikes the top end of the tube and causes a large pressure spike. The primary objective is to apply the RELAP5/MOD3 computer code to analyze the water cannon event and assess the ability of RELAP5/MOD3 to simulate fast two-phase transients. The sensitivity of time-step size and mesh size has been studied. It is found that RELAP5/MOD3 adequately simulated the transient process with a mesh size of 0.07112 m (i.e., ten nodes) and a time-step size of 10(-5) s. The calculated peak pressure of the first pressure spike is of the same order of magnitude as experimental data from literature. The effect of reservoir temperature on the magnitude of the first pressure spike is also studied, and it is found that the pressure peak value decreased with increasing reservoir temperature.