Speaker
Yatinkumar Sarvaiya
(Quality Assurance)
Description
ITER Vacuum Vessel (VV) is made of double walls connected by ribs structure and flexible housings, space between these walls is filled up with In Wall Shielding (IWS) blocks to (1) reduce neutrons streaming out of plasma and (2) reduce toroidal magnetic field ripple. These blocks will be connected to the VV through a supporting structure of Support Rib (SR) and Lower Bracket (LB) assembly. SR and LB are two independent components manufactured from SS316L (N)-IG material. Two horizontal lower brackets will be welded with one vertical support rib to make an assembly. These are welded by Tungsten Inert Gas (TIG) and Shielded Metal Arc Welding (SMAW) as full penetration joint and tested using various NDT methods such as Liquid Penetrant testing (LPT) and Ultrasonic Testing (UT), etc.
There were many challenges while qualifying UT technique such as, 1) Interpretation due to Coarse Grain Structure of the material and weld 2) The limitation of scanning distance which required special probes for testing. There are two shapes of plates, (i) rectangular (ii) trapezium welded with rectangular plate with straight weld line. All essential requirement related to qualification of personnel, calibration of instruments, probes and design of mock-up calibration blocks were identified prior to establishment of the UT procedure.
Two calibration blocks are manufactured based on the geometry of the weld joints. Artificial defects (2mm and 3mm diameter side drilled holes and 0.7mm width notch) were inserted into the blocks so as to correlate the same with the actual defects. The validation of procedures was carried on calibration blocks using Radiography testing and Macro Analysis Test. Approximately 170 Nos of such welded assembly have been tested successfully. This paper detailed the work that has been carried out to establish ultrasonic technique for weld joints of Support Rib and Lower Bracket Assembly.
Co-authors
C. H. Choi
(ITER Organization, Route de Vinon-sur-Verdon – CS 90046, 13067 St Paul-lez-Durance Cedex, France)
Haresh Pathak
(In-Walled Shield, ITER-India, Institute for Plasma Research, Gandhinagar, India)
Jigar Raval
(ITER Organization, Route de Vinon-sur-Verdon – CS 90046, 13067 St Paul-lez-Durance Cedex, France)
Rahul Laad
(In-Walled Shield, ITER-India, Institute for Plasma Research, Gandhinagar, India)
Yatinkumar Sarvaiya
(Quality Assurance, ITER-India, Institute for Plasma Research, Gandhinagar, India)
