Conceptual design of a hybrid HCPB blanket

Following previous studies on helium cooled pebble bed (HCPB) blanket concepts based on different structural materials, a hybrid HCPB blanket has been proposed to combine the high load capability of the steel concepts with the high thermal efficiency of the SiCf/SiC ones. A radial division of the blanket in two components allows us to design the first wall and the first breeder zone with steel as the structural material, while a second breeder zone uses SiCf/SiC with the possibility to increase the helium outlet temperature. At the same time an advantageous maintenance strategy based on the radial division of the blanket zone into components of different lifetimes can be adopted; this strategy promises a considerable waste reduction and lower fabrication cost. Neutronic and thermohydraulic calculations show that the proposed requirements can be met; on their basis a design of an outboard segment is presented.