Conceptual design of a water and steam cooled blanket for the compact reversed shear tokamak reactor

The possibility of developing a cost competitive fusion power plant with a water-cooled blanket concept, which has much experience in nuclear power pl ants, was examined. The new blanket design is based on using reduced activa tion ferritic steel components and an advanced super-heated steam cycle whi ch is used to realize high thermal efficiency. The high value of thermal ef ficiency is very effective in reducing the cost of electricity. The allowable temperature range of the structure material, reduced activati on ferritic steel, is assumed to be 350K to 900K based on expectations from the material research and development program. A mixture of lithium oxide pebbles and beryllium pebbles is installed in the breeding zone fbr high tr itium breeding ratio and high thermal conductivity. Mixture ratio of beryll ium and lithium-6 enrichment were optimized from the viewpoint of temperatu re distribution in the breeding zone, achievable tritium breeding ratio and its reduction due to burn up. The reference blanket system has a local tri tium breeding ratio of 1.37. The arrangement of cooling channels in the bre eding zones and flow rate and inlet temperature of the coolant were also op timized to keep the temperatures of structure materials, breeding materials and coolant in the allowable range. The first wall is cooled by pressurize d water at about 570 K. The coolant out of the first wall is led to the bre eding zone and starts to boil. The steam is super-heated up to 750 K in the blanket. This high temperature raises the thermal efficiency of the turbin e to 41 %.