Research and development activities for light water rector power plant have been reviewed focusing on those of multiphase technology in last ten years. In various fields such as reactor safety research, development of thermal-hydraulic analysis codes, improvement of reactor components, design of advanced, nextgeneration, or innovative light water reactors, researches related to multiphase technology have been performed. In future, demands for cost reduction and prevention for severe accident will be increased in development of future light water reactors. There will be increasing interest in replacing the current constitutive relation models with more mechanically or micro-mechanically-based models to make developmental work more efficient.
