Design improvements and R&D achievements for vacuum vessel and in-vessel components towards ITER construction

Abstract

During the preparation of the procurement specifications of ITER for long lead-time items, several detailed vacuum vessel (VV) design improvements are being pursued, such as elimination of the inboard triangular support, adding a separate interspace between inner and outer shells for independent leak detection of field joints, and revising the VV support system to gain more structural performance margin. Improvements to the blanket design are also under investigation, an inter-modular key instead of two prismatic keys and a co-axial inlet–outlet cooling connection instead of two parallel pipes. One of the most important achievements in the VV R&D has been demonstration of the necessary assembly tolerances. Further development of cutting, welding and non-destructive tests for the VV has been continued, and thermal and hydraulic tests have been performed to simulate the VV cooling conditions. In FW/blanket and divertor, full-scale prototypical mock-ups of the FW panel, the blanket shield block, and the divertor components, have been successfully fabricated. These results make us confident in the validity of our design and give us possibilities of alternate fabrication methods.

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

“…Design progress of the ITER vacuum vessel (VV) and first wall (FW)/blanket has been reported in previous papers [1,2], and selection of design solutions is more clearly described in this paper. The VV structure is shown in Fig.…”

Thick SS316 materials TIG welding development activities towards advanced fusion reactor vacuum vessel applications

“…In this regard, the fabrication of majority of the components are to be developed with different weld processes in both thin and thick plates SS materials of various grades. The double wall supporting structures, thick plates, joining ribs, shells and key components are fabricated with variety of joint configurations like plane plates, curved plates like D shape or near to D shapes and T type butt welds [5][6][7]. VV components are directly in contact with high pressure water circulation to remove heat loads on vessel and in addition to thermalization of high energy neutrons and shielding them to protect other subsystems.…”

“…In this regard, the fabrication of vacuum vessel and its associated sub systems materials selection is a challenging task in terms of their mechanical and irradiation properties compatability. The fabrication of vacuum vessel sector components will be carried out with different type of welding processes for joining of SS materials in various forms of shells, ribs and key components to make final sector modules [6,7]. TIG welding is one of the major technique used for joining of the stainless steel plates for fabrication of different vacuum vessel components [8,9].…”

Design finalization and start of construction of ITER vacuum vessel

“…port housings (FSHs) and keys are welded to the vessel shells, since the blanket modules are directly supported by the VV [1]. The layout of welds on the inner and outer shells is tight considering numerous welds, code requirements regarding the minimum distance between welds for welding and the non-destructive examination requirements.…”