Proposal for an alternative type of helium-cooled blanket for DEMO

In this paper, an attempt to modify the blanket design proposed and analysed by the CEA in the framework of DEMO, featuring Li-Pb as breeder-multiplier and water as coolant, is presented. The aim of the proposed modifications is to improve the safety and tritium breeding performances of the blanket by the use of helium instead of water, and by the substitution of the martensitic steel structural material by a vanadium alloy. The existing geometry and the general hydraulic configuration are maintained in the breeding zones and in the first wall: the former is cooled by poloidal single-wall U-bent tubes, and the latter by toroidal-radial oriented tubes buried in the first wall panels and fed by headers located behind the back plate. Neutronic calculations have been brought forward in order to evaluate the volumetric power deposition and the tritium production (TBR). Due to the harder neutron spectrum a 30% Li-6 enrichment seems to be adequate. Thermal hydraulic calculations show that the selected helium parameters are standard ones for modern plants. (orig.)