THERMAL CONTROL OF CERAMIC BREEDER BLANKETS

Thermal control is an important issue for ceramic breeder blankets since the breeder needs to operate within its temperature window for the tritium release and inventory to be acceptable. A thermal control region is applicable not only to situations where the coolant can be run at low temperature, such as for the International Thermonuclear Experimental Reactor (ITER) base blanket, but also to ITER test module and power reactor situations, where it would allow for ceramic breeder operation over a wide range of power densities in space and time. Four thermal control mechanisms applicable to ceramic breeder blanket designs are described: a helium gap, a beryllium sintered block region, a beryllium sintered block region with a metallic felt at the beryllium-cladding interface, and a beryllium packed-bed region. Key advantages and issues associated with each of these mechanisms are discussed. Experimental and modeling studies focusing on beryllium packed-bed thermal conductivity and wall conductance, and beryllium sintered block-stainless steel cladding contact resistance are then described. Finally, an assessment of the potential of the different mechanisms for both passive and active control is carried out based on example calculations for a given set of ITER-like conditions.