Development of advanced neutronics/thermal-hydraulics coupling simulation system, 6; Measurement of gas-liquid two-phase flow inside a fuel bundle to obtain code validation data

Okamoto, Kaoru*; Makino, Yasushi*; Ono, Ayako ; Yoshida, Hiroyuki  

JAEA has developed an advanced neutronics/thermal-hydraulics coupling simulation system, in which detailed two-phase flow simulation code (TPFIT or JUPITER) is applied to part of thermal-hydraulics. Those detailed codes can predict small-scale thermal-hydraulics behavior inside sub-channels of a fuel bundle, so that measurement data with high-resolutions in time and space are required to achieve the appropriate validation of the codes. In this study, Laser Doppler Velocimetry (LDV) is applied for measurements of velocity and void fraction in air-water dispersed bubbly flows. The LDV can obtain local measurement data without any disturbance to flow field. In particular, fluorescent particles are introduced for liquid velocity measurements in order to clearly distinguish recorded signals between gas and liquid phases. The measurement method and the results will be shown in this presentation.