Oscillatory Flows Induced by Direct Contact Condensation of Flowing Steam with Injected Water

Abstract

When subcooled water in accumulator tanks is injected during a loss-of-coolant accident of a pressurized water reactor, violent condensation takes place in cold legs because of direct contact of flowing steam with the injected water. An experiment is performed to determine the condensation and mixing processes of steam and water under oscillatory conditions. The observed flow patterns are classified into three groups and boundaries of these flow patterns are correlated in terms of the condensability of the injected water. The mutual relation of the condensation phenomena to the mixing behavior of steam with water are studied by applying synchronous measurements of pressures to flow observation with high speed movie. The test results confirm that the condensation is a driving force to produce the restoring force to the plugging water motion. Good consistency is observed between the condensation efficiency and the mixing pattern of steam with water. A correlation for the oscillation period is developed which agrees with test data within an error of ±20%. The correlation shows that the oscillation period is proportional to the square root of the plugging water mass.