Abstract: Background: In engineering application of steam generator (SG) for nuclear power plant (NPP), two limitations are imposed on the design of water tanks. One is that the water collected in the water tank cannot spill over to avoid the entrainment of water from the water tank. The other is that the size of the devices used in the SG is limited by the safety consideration and costs. Purpose: This study aims at the drainage performance of drain device in steam generator of CAP1400 to provide reliable data for the design of a drain device. Methods: The drainage performance of drain device in steam generator of CAP1400 was simulated through an experimental method with water and air under ambient temperature and pressure. A video camera is used to record liquid level at certain water flow rates range of 13.8?138.1 m3?h?1, and the recorded video images are processed by MATLAB program. Results: The experimental results show that the maximum water depth level in drain tank linearly increases with the water flow rate while the number of water entrance holes has no obvious effect on the drainage performance of drain device and the value of bottom surface slope angle has a little influence on it. Conclusion: Using a slope bottom plate can help draining water to some extent and the number of orifices has little effect on the liquid level of drain water tank.

Key words: Steam generator, Drain tank, Liquid depth, MATLAB digital image processing