Advanced cutting, welding and inspection methods for vacuum vessel assembly and maintenance

ITER requires a 316 1 stainless steel, double-skinned Vacuum vessel (VV), e ach shell being 60 mm thick. EFDA (European Fusion Development Agreement) i s investigating methods to be used for performing welding and NDT during VV assembly and also cutting and re-welding for remote sector replacement, in cluding the development of an Intersector Welding Robot (IWR) [Jones et al. This conference]. To reduce the welding time, distortions and residual str esses of conventional welding, previous work concentrated on CO2 laser weld ing and cutting processes [Jones et al. Proc. Symp. Fusion Technol., Marsei lles, 1998]. NdYAG laser now provides the focus for welding of the rearside root and for completing the weld for overhead positions with multipass fil ling. Electron beam (E-beam) welding with local vacuum offers a single-pass for most of the weld depth except for overhead positions. Plasma cutting h as shown the capability to contain the backside dress and preliminary work with NdYAG laser cutting has shown good results. Automated ultrasonic inspe ction of assembly welds will be improved by the use of a phased array probe system that can focus the beam for accurate flaw location and sizing. This paper describes the recent results of process investigations in this R&D p rogramme, involving five European sites and forming part of the overall VV/ blanket research effort [W. Danner et al. This conference]. (C) 2000 Elsevi er Science B.V. All rights reserved.