AN EXPERIMENTAL STUDY ON VOID GENERATION AROUND HOT METAL PARTCLE QUENCHED INTO WATER POOL

摘要

Motivated to understand the void formation in fuel coolant interactions during a postulated severe accident of light water reactors, an experimental study was carried out to characterize void generation and evolution from stainless steel spheres quenched into a subcooled water pool. The major experimental parameters ranged from variations in water subcooling as well as the initial temperature and the diameter of the spheres which were kept still or falling in the water pool. The experimental results show that under the stagnant condition, axisymmetric vapor waves develop at the stagnation point which travels through the droplet's rear periphery and subsequently detaches into almost equal size bubbles at regular intervals in the stable film boiling regime, but a sharp decrease in the bubble detachment frequency was observed due to a transition in boiling regime. The effect of the water subcooling on the detached vapor volume is significant. The number of bubbles detached from the sphere periphery drastically reduces at high subcooling conditions. Under the falling condition, the temperature and diameter of the sphere as well as water subcooling significantly affect the dynamics of the bubbles entrained to the sphere's periphery.