DEVELOPMENT OF THE LEAD LITHIUM (DCLL) BLANKET CONCEPT

Liquid metal breeders such as Lithium or the eutectic Lead-Lithium alloy PbLi have the potential for attractive breeding blankets, especially if the liquid metal serves as breeder and coolant. However, cooling of first wall and blanket structure is a challenging task because the magnetic field degrades the heat transfer and can cause a really high pressure drop. To overcome these problems, dual coolant blankets with helium cooled FW/blanket structure and a self-cooled breeding zone had been proposed, with electrical insulation by ceramic-coatings or sandwich flow channel inserts. Such concepts are in principle simpler than helium cooled blankets, but the thermal efficiency is limited to similar to 35 % as in any helium cooled blankets with steel structure. A much higher efficiency up to about 45 % became feasible when the sandwich insulator was replaced by flow channel inserts (FCI) made of a SiC composite. This FCI serves as thermal insulator too, allowing an exit temperature of similar to 700 degrees C, suitable for a BRAYTON cycle power conversion system. The subject of this paper is a description of the Lead-Lithium blanket development and the major improvements on the dual coolant Lead-Lithium (DCLL) blanket concept achieved in the US during the last 10 years.