Two-phase flow parameters of a downcomer boiling during a postulated reflood phase of APR1400

摘要

Downcomer boiling phenomena is one of the key issues for a postulated large-break LOCA (LBLOCA) in a conventional pressurized water reactor, because it can degrade the hydraulic head of the coolant in the downcomer and consequently affect the reflood flow rate for a core cooling. To investigate the thermal hydraulic behavior in the downcomer region of the APR 1400, a test program for a downcomer boiling is being progressed for the reflood phase of a postulated LBLOCA. Test was performed in a one side heated rectangular test channel which was designed by adopting a full-pressure, full-height, and full-size downcomer-gap approach, but with the circumferential length was reduced 47.08-fold. The test consists of two steps : (Ⅰ) for the global two-phase flow parameters and (Ⅱ) fur the local two-phase flow parameters. The step-I test has already been completed. In the present paper, the experimental results of the step-Ⅱ test are introduced.