Economically attractive magnetic fusion power plants require high power density and high thermal conversion efficiency to offset the high capital cost. Self-cooling offers a powerful means to provide both high bulk power handling as well as high-temperature operation, leading to high efficiency. Advanced design concepts, such as self-cooled lithium blankets with vanadium alloys as structural materials have these characteristics, however, they also suffer from a number of safety and developmental concerns.

An alternative self-cooled design is proposed using Pb-17Li eutectic as the primary coolant and breeder, and ferritic steel as the pressure vessel material. The coolant is raised to a temperature beyond the limit for steel by employing silicon carbide inserts for thermal isolation between the coolant and steel. In addition to its thermal insulating properties, SiC also is expected to provide sufficient electrical insulation to maintain a low MHD pressure drop. In this way, a liquid metal exit temperature of about 700 C is achievable, allowing either an advanced Rankine steam cycle or a closed-cycle helium gas turbine (Brayton cycle) as power conversion system. A gross thermal efficiency of about 45% can be achieved with either system.

The first wall adopts a separate He-cooled box structure which has been developed and tested in the European blanket development program. The temperature of the entire steel structure is maintained below the 550 C limit. This design is capable of removing at least 0.4 MW/m² of surface heat flux, and is mechanically able to withstand the full pressure from a He coolant breach into the breeding zone.

In this paper, the design will be described, together with performance analyses based on its application in a high power density tokamak. Key issues, such as the temperature limit of compatibility between PbLi and SiC, and the design of the heat exchanger willl be further discussed.