Authorization to Proceed for Korean jacket sections
20 Jul 2012
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Soo-Hyeon Park, Superconductivity Technology Team, ITER Korea
Jacket sections wait for final inspection at POSCO Specialty Steel.
The ITER toroidal field conductor is a cable-in-conduit conductor (CICC); in this type of conductor a cable is contained inside a metal conduit that is assembled through the "butt welding" of individual jacket sections.
ITER Korea, which is responsible for 20.18 percent of ITER toroidal field conductor, has completed the procurement of the necessary quantity (approximately 20 km) of jacket sections from POSCO Specialty Steel company. The production was completed officially on 14 July 2012 with the approval from the ITER Organization of the authorization to proceed point (ATPP) for the last batch of jacket sections.
A jacket section is a seamless stainless steel tube with special characteristics. For higher strength, the material is very low in cobalt and carbon for lower neutron activation, and relatively high in nitrogen content compared to standard 316LN-grade stainless steel. The jacket sections produced by POSCO Specialty Steel have an outer diameter of 48 mm, a thickness of 1.9±0.1 mm, and a unit length of 13 m.
A short sample of the ITER toroidal field conductor.
The thickness/tolerance is only a half of that of conventional seamless tubes, so a series of high-precision drawing processes are required. The most important and toughest requirement is the low temperature (< 7 K) mechanical property for which the elongation at break must exceed 20 percent. Among the six Domestic Agencies procuring ITER toroidal field conductor, only three companies have been qualified to supply the jacket sections.
POSCO Specialty Steel, the largest seamless tube supplier in Korea, was awarded the contract from ITER Korea in August 2009. The Italian Consortium for Applied Superconductivity (ICAS), conductor supplier for the European and Korean Domestic Agencies, also awarded POSCO Specialty Steel a contract for the same item. To date, POSCO Specialty Steel has completed production for ITER Korea; the production for F4E/ICAS is ongoing.