Visualization study on interaction of jet internal flow and surrounding flow through interface in pool

For the safety design of the Fast Breeder Reactor (FBR), it is strongly required that the Post Accident Heat Removal (PAHR) is achieved after a hypothetical Core Disruptive Accident (CDA). In the PAHR, it is important that the molten core material is fragmented to be solidified by the sodium coolant and it is necessary to evaluate the jet breakup length. Although there are many previous studies on the jet breakup length, the tendency of jet breakup length is different for the previous studies. To estimate jet breakup length, it is necessary to clarify the influence of fragmentation behavior on jet surface and on jet breakup behavior in coolant. In present study, experiments are conducted to obtain interfacial fragmentation behavior by injecting transparent fluid in water. Internal and external velocity distributions of the jet are measured by PIV technique. Reynolds stress, turbulent energy and shear stress are evaluated from the velocity data. As the results, Reynolds stress and turbulent energy become large in the vicinity of jet surface. Vortex around interfacial wave is observed. Local shear stress acts on the interfacial wave. Mechanism of fragmentation and interaction of jet internal flow and surrounding flow through interface are discussed. (author)