In past designs of supercritical water-cooled reactors, the core flow rate has had to be kept high enough to satisfy the minimum deterioration heat flux ratio criterion where the deterioration heat flux is a function of the core flow rate. Refinement of transient criteria related to the fuel rod design is undertaken, and new dominant transient criteria are proposed in which the cladding temperature is <610°C for Type 316 stainless steel and <840°C for Inconel 700 to reduce the balance of the plant and improve the thermal efficiency. The safety analysis for the high-temperature core using these new criteria is carried out. All the analyzed events satisfy the new criteria. A new formula for the heat transfer correlation at supercritical pressure is proposed based on numerical simulation.