抄録
Fast Breeder Reactor (FBR) is designed with safety in mind. However, there is billion to one possibility that a hypothetical Core Disruptive Accident (CDA) occurs. When CDA occurs, the Post Accident Heat Removal (PAHR) must be achieved. In the PAHR, the molten material is required to be fragmented and solidified in sodium coolant. In order to estimate whether the molten material jet is completely solidified in sodium coolant or not, it is important to estimate jet breakup length, which is the distance from the location where the jet penetrates into coolant to the location where the jet column disappears. Although, the jet breakup length is influenced with fragmentation behavior, the correlation between the jet breakup length and fragmentation behavior are not clear yet. Therefore, it is strongly required to clarify the mechanism of the fragmentation behavior on the jet surface. The objective of the present study is to clarify the flow structure surrounding the jet surface injected into liquid on fragmentation experimentally. Tap water and Fluorinert^<TM> (FC-3283) are used as simulated coolant and molten material. FC-3283 is transparent and color less liquid and its density is higher than water. FC-3283 is injected into water pool, and the jet breakup and the fragmentation behavior of the jet are observed by using a high speed video camera. In order to clarify the surrounding flow structure of the jet, velocity measurement with Particle Image Velocimetry (PIV) is conducted. We also identify the position of the interface with the back lighting technique simultaneously. The interfacial wave behavior on the jet surface is observed. The interface of the jet is deformed and interfacial wave is generated on the jet surface. Also, the velocity of surrounding flow has high values near the interface of the jet. The deformation of the jet surface and the flow structure of the interface are discussed.
