The imminent revival of nuclear power has progressed in recent years and many countries, including the U.S., are planning construction of new NPPs (nuclear power plants). This movement is called "Nuclear Renaissance."In the fuel assembly design of a nuclear reactor, the heat-removal limit (critical power, critical heat flux), below which generated heat can be removed without a sudden rise of fuel temperature, is one of the design limits. From the perspective of ensuring reliability and safety of nuclear reactors, it is very important to predict this limit with sufficient precision.The purpose of this paper is to review the following items:(1) State-of-the-art simulation techniques to predict the heat-removal limit (2) Cutting-edge design concepts to enhance the heat-removal limit (3) A challenge beyond the heat-removal limit by introducing the post-BT (boiling transition) criteriaIn this paper, aiming for more efficient processes and a higher level of optimization in the nuclear fuel design, the importance of some key physical models and relevant experimental data is focused in order to improve prediction accuracy of the heat transfer including the post BT region.