[en] Two breeding blanket concepts, the Helium-Cooled Lithium-Lead (HCLL) and the Helium-Cooled Pebble-Bed (HCPB), developed in Europe in the frame of DEMO and relevant TBM studies, present many similarities in terms of design and manufacturing. As an example, all structure sub-components are internally cooled by helium circulating in meandering squared section channels. Several technologies have been investigated in the frame of EU fusion research programme for the manufacturing, including a specialized machining, fusion and diffusion welding and joints inspection, of DEMO breeding blanket and TBM sub-components (Cooling Plates (CP), Side Caps (SCs), Stiffening Plates (SPs), First Wall (FW)) and their assembly, main of which are discussed in this paper. The manufacturability of DEMO blanket modules Back Supporting Structure (BSS), a big structure located behind blanket modules and supporting them, is also discussed. The applicability of technologies takes into account specificities of EUROFER97 steel, foreseen as structural material. For each assessed technology, main results, e.g. in terms of mechanical properties and microstructure of weld joints, are presented and main advantages and drawbacks are summed up, in order to identify most promising technology/ies and to propose manufacturing scenarios. It should be noted that these developments are performed according to standards and professional codes (RCC-MRx). Further development strategies are also briefly discussed in the paper. (authors)

[en] Within the framework of the European fusion strategy, two tritium Breeder Blankets concepts are developed to be tested in ITER as Test Blanket Modules (TBM): the Water-Cooled Lithium-Lead (WCLL) which uses the liquid Pb-16Li as a breeder, neutron multiplier and tritium carrier, and the Helium-Cooled Pebble-Bed (HCPB) with lithiated ceramic and beryllium pebbles as breeder and neutron multiplier, respectively, and helium purge gas as tritium carrier. Both concepts consider as structural material reduced activation ferritic martensitic steel, the EUROFER97 (X10CrWVTa9-1). Pressurized water (15.5 MPa, 295−328 °C for WCLL) and pressurized helium (8 MPa, 300−500 °C for HCPB) are foreseen for heat removal. The TBM is constituted of a BOX (side caps, first wall), stiffened by stiffening plates (SP) and closed on its back, in the manifold area, with back plates with passing-through elements, like stiffening/tie rods, SP nozzles and inlet/outlet water/He pipes. Internally, breeder units, delimited by SP, are cooled-down by cooling plates for the HCPB and double-wall tubes for the WCLL. This paper describes manufacturing technologies for the TBM and deals with the definition of the preliminary Welding Procedure Specifications (pWPS) and feasibility mock-ups for the manifold area and TBM BOX assembly. The transfer and validation of the pWPS developed for the TBM, from P91 to EUROFER97 steel, is demonstrated. Consolidation of the pWPS for the TBM BOX assembly made with HIP process and development for the HCPB TBM manifold area elements, based on GTAW technique, are discussed. Manufacturing tests are performed using the EUROFER97 steel (RCC-MRx, AFCEN Code rules [1]). As part of the WCLL conceptual design development activities, an assembly and manufacturing welding sequence is detailed, focusing on design changes and the impact on the selection of manufacturing technologies. The article will present as well the future fabrication developments and the associated design proposals envisaged on TBM.

[en] Highlights: • Significant progress on the development of welding procedures for European TBM achieved. • Fabrication processes feasibility based on diffusion and fusion welding demonstrated. • An optimized welding scenario/sequence for TBM box assembly identified. • Future qualification of pF/WPS proposed through realization of a number of QMUs. - Abstract: The paper reviews progress achieved in development of fabrication technologies and procedures applied for manufacturing of the TBM sub-components, like, HCLL and HCPB cooling plates, HCLL/HCPB stiffening plates, and HCLL/HCPB first wall and side caps. The used technologies are based on fusion and diffusion welding techniques taking into account specificities of the EUROFER97 steel. Development of a standardized procedure complying with professional codes and standards (RCC-MRx), a preliminary fabrication/welding procedure specification (pF/WPS), is described based on fabrication and non-destructive and destructive characterization of feasibility mock-ups (FMU) aimed at assessing the suitability of a fabrication process for fulfilling the design and fabrication specifications. The main FMUs characterization results are reported (e.g. pressure resistance and helium leak tightness tests, mechanical properties and microstructure at the weld joints, geometrical characteristics of the sub-components and internal cooling channels) and the key pF/WPS steps and parameters are outlined. Also, fabrication procedures for the TBM box assembly are presently under development for the establishment of an optimized assembly sequence/scenario and development of standardized welding procedure specifications. In conclusions, further steps towards the pF/WPS qualification are briefly discussed.

[en] Highlights: • Significant progress on development of welding procedures for European TBM achieved. • Fabrication processes feasibility based on diffusion and fusion welding demonstrated. • TBM box assembly welding scenarios investigated and welding scenarios identified. • Future qualification of pF/WPS proposed through realization of a number of QMUs. - Abstract: The paper reviews fabrication technologies and procedures applied for manufacturing of the TBM sub-components, like, HCLL and HCPB cooling plates, HCLL/HCPB stiffening plates, and HCLL/HCPB first wall and side caps. The used technologies are based on fusion and diffusion welding techniques taking into account specificities of the EUROFER-97 steel. Development of a standardized procedure complying with professional codes and standards (RCC-MRx), a preliminary fabrication/welding procedure specification (pF/WPS), is described as well as a fabrication and characterization of feasibility mock-ups (FMU) aimed at assessing the suitability of a fabrication process for fulfilling the design and fabrication specifications. Also, fabrication procedures for the TBM box assembly are presently under development through collaboration between European Fusion Laboratories and Industry for the establishment of an optimized assembly sequence/scenario and development of standardized welding procedure specifications. Selection of optimized assembly scenario takes into accounts not only the design requirements and fabrication possibilities/constraints but also maximum accessibility to the welds for sound non-destructive examination in compliance with welds classification. A future approach towards qualification of the developed fabrication technologies and procedures, through a number of medium to full-size qualification mock-ups according to European standards, is outlined before construction of the first TBMs.