ITER JCT Garching, Boltzmannstrasse 2, D-85748 Garching bei Muenchen, Germany (1)EU Home Team, NET; (2)US Home Team, ANL; (3)RF Home Team, RDIPE; (4)JA Home Team, JAERI
The ITER Blanket is the first component facing the plasma and provides the main thermal, electromagnetic and nuclear shield of the machine. The better understanding of all these functions together has pushed the design towards one where a double wall backplate armoured by thick passive modules provides the cooling of the system and the electrical continuity around the plasma.
The backplate is cooled effectively by its large internal surface and is strong enough to support non symmetric halo currents of 8 MA, that peak up to twice the uniform value. The connection of the modules to the backplate is done by elastic flexible supports, allowing thermal expansion of the armour modules under plasma surface and volumetric heating conditions. The transient thermal analysis of the modules and the backplate, which also contains the cooling manifolds, determines the relative displacements and bowing. Both backplate and the flexible support have been optimised to reduce the reciprocally induced thermal stress.
Keys are foreseen between the blanket modules to fix their rotation. The electromagnetic loads on the modules have been determined with a full 3D transient analysis of the blanket system, including the vacuum vessel. The keys are thick enough to prevent any module distortion load on the flexible supports, which are then fully available to resist pushing and pulling forces. The keys incorporate vertical filler shield inserts between the modules in the outboard blanket.
Backplate manufacturing can be simplified by partially faceting the outboard and introducing tubular connections between the inner and outer plates, which reduce the number of long ribs welded inside the interspace. Nevertheless some ribs need to be vacuum-tight welded to subdivide the modules into smaller groups inside each cooling loop. Leak testing is done first by identifying the faulty loop, then the leaking group and finally by checking individually each module. Special reinforcements are necessary for the outboard midplane and for the top port openings, where standard mounts have been developed for the diagnostics.
This paper summarises the recent design improvements of the ITER shielding blanket and reports the rationale for the selection of each design characteristic.