Abstract
In order to decommission nuclear reactors and to improve its safety, it is important to estimate the falling behavior of molten core jet in the reactor vessel when an accident occurred as is seen from Fukushima Daiichi nuclear power plant accident. Since the BWR (Boiling Water Reactor) lower plenum is consisted with various complicated structures, it is suggested that the jet falling behavior is affected by these structures. Thus, we are developing the numerical simulation method to estimate the molten core falling behavior in the BWR, and the purpose of this study is to clarify the effect of these structures on behavior of jet breakup and fragmentation, and to construct the benchmarks of the numerical simulation via experiment. In this study, we measured jet falling behavior and fragment diameter using image processing techniques, and evaluated the equation of fragment diameter.
