Performance Analysis of the Safety Injection Tank with the Small Scale Experiment

Abstract

SIT (Safety Injection Tank) with passive flow controlling device, has technical issues to be analyzed. The emergency core cooling water discharge flow rate from the SIT, pressure loss coefficient of the fluidic device, and nitrogen entrainment phenomena are them. In this paper, the technical issues of a SIT were discussed with the experimental analysis over the one-tenth scale model of the SIT. The experiment was carried out with the visualization of the fluidic device. The fluidic device was simplified as a vortex chamber connected with the single control pipe line and single stand pipe line. The experiment was done at the room temperature. The discharge water flow rate, pressure inside the SIT, pressure difference over the fluidic device, and temperature inside the SIT were measured. The discharge mass flow rate ratio of high flow mode and low flow mode was between 4 and 5. With initial pressure of 10 bar, 39% of nitrogen gas in the SIT was discharged during the flow mode transition. The percentage of the entrained nitrogen decreased through the decrease of the initial pressure. Nitrogen entrainment started when the water level is 7mm above from the top of the stand pipe which indicates the vortex sink in the SIT at the time. The nitrogen entrainment criteria was brought out with the concept of equilibrium water level which is the stand pipe water level to compensate the pressure loss at the control pipe. Entrainment of nitrogen last until the equilibrium water level reaches 19.5 cm with the initial pressure of 10 bar.