Droplet measurement and generation techniques in a rod bundle geometry for a reflood heat transfer test

During the reflood phase of a postulated loss of coolant accident in a nuclear reactor, the entrainment of liquid droplets can occur at a quench front of a reflooding water. It is widely recognized that the behavior of the entrained droplet crucially affects the reflood heat transfer by decreasing the superheated steam temperature and interacting with a rod bundle and spacer grids. This paper describes a measurement and a generation techniques that were proposed to investigate droplet behavior in a rod bundle geometry. An image processing technique and a vibrating nozzle method were selected for the droplet measurement and generation, respectively, considering the applicability to the test sections. A preliminary test for the measurement method was performed in a 2 x 2 rod array. The proposed droplet generation method was also tested independently in a rectangular channel. These test results were presented in this paper