The most important priority of nuclear power plant design is "safety." The accident at Fukushima Dai-ichi Nuclear Power Plant following the Great East Japan Earthquake has re-emphasized the importance of nuclear safety, requiring us to make a strong effort to improve safety. Mitsubishi Heavy Industries, Ltd. (MHI) has been working on improving the accuracy and reliability of safety design evaluations to ensure safer and more flexible operations of pressurized-water reactors (PWRs). In this context, MHI has developed and utilized a new concept for critical heat flux correlations.