ICONE23-1713 WELDING JOINT DESIGN OF ITER TOROIDAL FIELD COIL STRUCTURE UNDER CRYOGENIC ENVIRONMENT

Abstract

Application of partial penetration welding (PPW) to ITER Toroidal Field Coil structure has been proposed because of limited access for weld due to complex shape and low stress components. In order to obtain fatigue crack growth (FCG) behavior of PPW joint in cryogenic environment, Japan Atomic Energy Agency performed FCG test at 4K by using Compact Tension (CT) specimens having as-weld notch of PPW. These CT specimens were sampled from mockups having one of actual joint shape of PPW, double J-groove. As the result of these tests, it was observed that crack propagated in weld metal having inclination from as-weld notch. Moreover it was shown that as-weld CT specimens had high FCG rate region in early stage of crack propagation due to residual stress distribution. In addition, it was proposed and verified application method of this FCG rate to designing of PPW joint.