Helium-cooled pebble bed test blanket module: Alternative design and fabrication routes

This paper describes two design options of the EU-helium-cooled pebble bed (HCPB)-test blanket module (TBM) and indicates the main differences between the two designs with regard to fabrication routes and general features. The TBM reference design (TBM Ref.) was developed in 2006 and is mainly based on the assumption that fabrication of the cooling channels inside the TBM sub-components (e.g. first wall (FW), caps, stiffening grid (SG)) is based on diffusion-welding processes (DWP). In contrast to that proposal another TBM concept (TBM alt) was developed in 2007 in parallel, where DWP alone was taken into account only for fabrication of the cooling channel structure inside of the TBM FW, where DWP is mandatory with regard to the TBM requirement that plasma-facing surfaces must not include welding seams. The other TBM sub-components equipped with cooling channels were designed to be manufactured by technologies that are already state-of-the-art (e.g. combination of electron beam (EB) welding and spark erosion (SE)). Additionally the design of the manifold system for coolant distribution inside of the TBM is different for both design options.