AbstractThe compact reversed shear tokamak, CREST, is a cost competitive power reactor concept based on the reversed shear high beta plasma. As the cooling system of CREST blanket, the direct superheated steam cycle is adopted to simplify the heat transport/power generation system and to achieve high thermal efficiency with a water cooled concept. Thermal-hydraulic design of the blanket was performed for the nominal operation, the start-up operation and the partial load operation. As a result of the study, it was confirmed that the direct steam cycle blanket is promising for a power reactor and is feasible not only at the nominal operation condition but also at the reactor start-up and the partial load conditions.