Comparative study of laser and TIG welding for application to ITER blanket hydraulic connection

The shield blanket in ITER has an active cooling structure necessitating hydraulic connections to the cooling water manifold. To maintain or replace the blanket, welding the hydraulic connection by remote handling is necessary. Access for the welding is limited in a small hole in the first wall because of spatial constraints related to neutron and heat fluxes. A bore welding tool is required. Laser and TIG welding tools have been developed, and the welding conditions have been optimized for all position welding to horizontally located pipes. Obtained parameters such as the weld heat input, allowable misalignment, the lifetime of the tools, and the amounts of spatter and fumes, are assessed comparatively. Considering additional aspects related to the remote handling compatibility, for example, the optical fiber or power cable handling, the preferable welding technique for the blanket remote maintenance is discussed.