Development of in-pipe laser welding technology applicable to narrow spaces -Advancement of piping joining technology in fusion experimental equipment -

The authors expanded a technique for the laser-welding of cooling water pipes for the equipment inside a nuclear fusion reactor, from the inside of the pipes, and developed a technology to adjust the laser irradiation position with an accuracy of 0.1 mm or under, while applying a follow-up control technique. For this purpose, it was necessary to measure the details of the joints in advance, even if the position adjustment of the joints was incomplete. By this method, reliable welding became possible with an allowable gap of nearly 1 mm, even under complicated situations where there was axial misalignment or inclination. When removing and installing the JT-60SA divertor cassette, piping welding is performed so that the cooling water piping on the vacuum vessel side and the cooling water piping on the divertor cassette side are separated and reconnected. This paper described the results of the following welding tests: (1) in-pipe laser welding test, where prior to welding using the actual divertor cassette, the pipes were fixed in a state where there was axial misalignment or inclination, (2) butt welding of the inner target unit of the actual divertor cassette, and (3) lap welding of the closing plug. (A.O.)