Mechanism Study on Passive Siphon Break of a Low-Pressure System

Siphon break has great influence on the Loss of Coolant-Accident（LOCA） for the nuclear safety. Experimental researches were carried out to study the siphon breaking process in a passive air-water two-phase flow loop. Flow processes were observed and important parameters were measured including pressure drops, water flowrate, and water level. Flow pattern in downward flow pipe is found to be bubbly flow, slug flow and falling film flow in turn. Experimental results show that the passive siphon breaking system could significantly increase pressure drop and reduce water flowrate. Therefore, under the LOCA condition, the goal to reduce the exposing risk of the reactor core can be realized by the siphon breaking effect.