Large-scale simulation on two-phase flow in the fuel assemblies of LWR by the mechanistically based method

Ono, Ayako ; Yamashita, Susumu   ; Suzuki, Takayuki*; Yoshida, Hiroyuki  

JAEA is developing the methodology to predict the critical heat flux based on a mechanism in order to reduce the cost for full mock-up test. The evaluation method based on a mechanism is expected to be able to predict in the wide range of parameter under the unexpected conditions including the severe accident. In this study, the JUPITER code developed by JAEA is examined to apply for the two-phase flow simulation of LWR fuel assembly. The simulation results and previous study relating to the observation of two-phase flow in fuel bundle are compared to validate the simulation result and extract the issue to be considered.