ITER PF 52 kA HTS Current Leads Developed by ASIPP Pass 5 K Cold Test

“Everything is perfect”, said Dr. Pierre Bauer, ITER IO, witnessing the three-week full tests of 52 kA High Temperature Superconductor (HTS) current lead for the ITER Poloidal Field (PF) coil at ASIPP on June 20- July 4.  

 The ITER PF current lead was cold tested at the nominal 52 kA steady-state current and 57 kA over-current, the test results showed that its mass flow rate, joint resistance, the loss of flow accident(LOFA) time and overheating time are all above the design requirement.  

According to the experiment measurement, the 50 K mass flow rate of nominal current operation is 0.068 g/s/kA, superior to the ITER design requirement of 0.071 g/s/kA. The 5 K joint resistance of 0.5 nΩ meets the design requirement of 2 nΩ. The 65 K HTS joint resistance of 5 nΩ is better than the design requirement of the 10 nΩ. The loss of flow accident (LOFA) time and overheating time are 12 minutes and 30 seconds, which is superior to the design requirement of 400 seconds and 18 seconds. 

ITER PF 52 kA HTS current lead was designed by the feeder team and manufactured by HEFEI JU NENG. ELECTRO PHYSICS Company of ASIPP. Under the witness of the ITER international organization and its commissioned third party company BV, ASIPP spent nearly a year to complete the manufacturing and assembly. Through cooperation, technical staff of various departments finally completed CODAC interlock system and the traditional CODAC, fast control, quench protection system and multi-system integration and debugging. 

The CTB SBB prototype of ITER PF superconducting feeder is used as PF electric current lead prototype parts of vacuum and low temperature vessels. It provides a real operating environment similar to ITER, making the vacuum vessel during the experiment reach 1 E~5 Pa level, cold shield temperature below 90 K. 

This test took nearly three weeks, during which totally 9 big test tasks including 22 sub-test tasks were implemented. The major tests contain controllable cooling down, thermal cycles test, the steady-state full current 52 kA, intermediate current operation, pulse current operation, over-cooling test etc to fully validate the quality of the PF prototypes.  

The 900 W@4.5 K helium cryogenic system and the long-time-stable 80 kA power supply also made an important contribution to the test. 

The prototypes of ITER HTS current leads are categorized into three types: the 68 kA TF-types, the 52 kA PF/CS-types and 10 kA CC types. ASIPP kicked off the R&D of the prototype in 2012. The CC prototypes and TF prototypes has passed the 5 K cold test in 2014 and 2015 respectively. The recent achievement of PF 52 kA HTS current lead prototypes becomes a key milestone that paves the way to the series production for ITER HTS current leads. (WANG Kequn reports)

PF HTS current leads

Completed in CTB housing assembly

Current lead test site

ITER current leads for control system interface