Selection of design solutions and fabrication methods and supporting R&D for procurement of ITER vessel and FW/blanket

Abstract The vacuum vessel (VV) design has progressed by selecting design options, such as an independent cooling configuration in the VV field joint regions, 9 lower ports instead of 18, a single-wall structure for the upper and equatorial ports, and the vacuum vessel gravity support located below the lower ports. Double curvature pressing is now selected instead of facet shape welding for inner and outer shells in the upper and lower inboard regions. Regarding the first wall (FW)/blanket system, the plasma-facing surface of the FW has been redefined to avoid protruding leading edges in the inboard area. FW panels are supported with a central leg, and selection of a race-track shape cross-section for the central leg provides a more robust structure against halo current loads and also leads to a new cooling configuration in the shield block, where the pressure drop is significantly reduced to ∼0.1 MPa. Detailed EM analysis has been performed by using a newly defined plasma current quench scenario (40 ms linear decay and 18 ms exponential decay), and EM loads due to eddy currents are reduced in the current design with deeper slits. R&D results confirm the basis for the selected design solutions and fabrication methods.