Development of in-pipe access welding and cutting tool using YAG laser

Abstract

In the International Thermonuclear Experimental Reactor (ITER), the blanket is categorized into the schedule maintenance component and has to be replaced by remote handling technology due to activation by the 14-MeV neutrons during DT operations. The blanket is segmented into a number of modules to facilitate remote operation and requires the welding and cutting of cooling pipes connected to each module from the inside of the pipe due to space constraints. A prototype tool fabricated for branch pipe welding/cutting demonstrates the required mobility for traveling the cooling pipe with a diameter of 102.3 mm and a bent radius of 400 mm, and for accessing to the branch pipe with a diameter of 54.5 mm. The welding and cutting performance has been also tested, including the dependency of laser power, processing speed, and gaps on weldability. In addition, a composite optical fiber composed of a number of thin fibers arranged around a core fiber is also tested for direct viewing of the edge preparation before welding and for monitoring during welding/cutting. This paper describes the test results of the prototype tool performance and of in-pipe access welding and cutting operations.