Experimental investigation on entrainment of fourth stage automatic depressurization system in AP1000

In order to investigate the entrainment process of the fourth stage automatic depressurization system (ADS-4), ADS-4 Depressurization and Entrainment Test Loop (ADETEL) scaled after AP1000 was constructed. The phenomenon of the entrainment was recorded by a high speed camera and analyzed particularly. The data was compared with the existing data and correlations. It discovers that the entrainment rate declined rapidly with the decrease of liquid level in hot leg when the liquid level is low. The onset of entrainment is more likely to happen in the condition of small ratio of branch-head line. The ADS-4 entrainment rate in AP1000 is lower than that in AP600 at the same relative hot leg liquid level.