Welding and cutting characteristics of blanket/first wall module to back plate for fusion experimental reactor

A modular blanket/first wall has been proposed for a fusion experimental reactor, e.g. International Thermonuclear Experimental Reactor (ITER), with support ribs connecting to a strong back plate. For the connection method, a welding approach has been investigated. Welding and cutting tests of the support ribs have been performed with three types of test specimens; flat plate (200 mm/spl times/400 mm), partial model (700 mm/spl times/200 mm), and full-box model (600 mm/spl times/1000 mm/spl times/430 mm). The support ribs were made of type 316L austenitic stainless steel with the thickness of 50 mm in all these tests. The welding method applied to these tests was narrow gap TIG, and water jet for cutting. Through these tests, engineering data including optimum welding conditions, welding distortion, and welding/cutting speeds have been obtained. Transverse shrinkage was about 10 mm for the welding of 50 mm thick rib. However, the difference in distortion at the first wall surface was within 1-2 mm. Therefore, the blanket/first wall module can be installed with quite a high accuracy by taking into account the module moving to the back plate during the welding.