Recently, ASIPP successfully accomplished the qualification of CTB&SBB, the largest component of ITER FEEDER both in the size and weight.
CTB&SBB, one of the most important components in ITER FEEDER System, weighs 18 tons, 8000×1300×1500mm large. It will house thousands of components, including HTSCL（high temperature superconducting current lead）, supercondutor Busbar, 80K TS, various cryogenic valves, pipe system, high&low voltage instrumentation and various supports. The total weight will be up to 27 tons after the final assembly.
Many key technical processing of the CTB&SBB prototype have been qualified. The special welding groove and tooling were designed for the double torch automatic MIG welding of the 8m length 35mm depth(full penetration welding) main welding seam to control the welding deformation. The results showed that the deformation of the side plates was about 3mm, the top and bottom plates were about 1mm, which meets the requirements of qualification. The precision of all the interfaces and datum reference on this prototype was ensured by using the large high-precision CNC machine equipment to do the postweld overall machining. Many kinds of inspections were used, such as laser measurement, VT, PT, UT, leak testing etc. to confirm that all the dimensions and welding quality can meet the qualification requirements. The final total leak testing showed that the total leak rate of the box was 6×10-8Pa·m3/s, which satisfies the requirement of less than 1×10-7Pa·m3/s raised by IO.
In order to meet the high requirements in quality and safety regulated by ITER Organization, the manufacturers conducted a series of welding assessments and test. Besides, they also submitted as many as 82 technological documents to IO. In some key manufacturing sections and tests, many distinguished experts and the certification agencies were invited by IO to witness the process of vacuum, measuring, welding and nondestructive testing.
The successful accomplishment of CTB&SBB box manufacturing qualification is an remarkable milestone in ITER FEEDER qualification, which may provide necessary vacuum environment for the qualification tests of 80K TS, HTSCL, S-bending superconduct busbar. It definitely paves the way for the remaining qualification work.