Design concepts for NET first wall and blankets

For the design of NET-blankets including the first wall emphasis is given to availability, safety and reactor relevance. An optimum general blanket scheme is proposed with individually supplied long poloidal breeding modules, which are assembled into segments and handled from above. For a water cooled LiPb-eutectic breeder a design concept has been developed with prospects to meet the design objectives. In particular a low failure frequency is expected mainly due to a drastic reduction of the number of vulnerable coolant tubes and welds compared to other recent blanket designs. This concept would, however, require martensitic steel. For a helium cooled Li-ceramic breeder, the designs studied so far are less promising mainly due to the complications imposed by the neutron multiplier and in-situ tritium extraction. A helium-cooled first wall in austenitic steel would most likely require a grooved erosion layer with not more than 2 mm thickness under the grooves. (author)