Wrapping up conductor fabrication
25 Mar 2011
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Sabina Griffith
Butt welding of two toroidal field conductor jackets at Nippon Steel Engineering in Kyushu, Japan. (Photo: Peter Ginter)
This week, representatives from the ITER Organization and the six Domestic Agencies engaged in the production of ITER's magnets gathered together at the ITER Headquarters in Cadarache to assess the status of the magnet conductor production.
The conductors are a core component of the magnets and one of the longest lead-time items for the ITER Project. As summarized by Arnaud Devred, ITER's Superconducting Systems Section Leader, the production of strands for both the toroidal and the poloidal field magnets made out of Nb3Sn and NbTi, respectively, is ongoing in all six Domestic Agencies. "As of today, 40 percent of strands required for the toroidal field magnets have been produced, which equals 165 tonnes of superconducting wire. All Domestic Agencies have successfully qualified their domestic suppliers and started to register the manufactured strands into the Conductor Database."
The panel this week also reviewed the latest test results of a conductor sample for the central solenoid, which recently showed some unexpected behaviour. Required to withstand 60,000 current pulses during plasma operation, the conductor test performed in November 2010 at the SULTAN facility in Switzerland revealed unacceptable degradation after only 6,000 pulses.
As "a testimony of sympathy" for their colleagues and friends at the Japanese Domestic Agency who could not join the meeting in Cadarache due to the recent events, the members took a group photo, signed it and emailed it to Japan.
In order to assess and solve the problem, experts assembled at the Château de Cadarache this week agreed on a multiple-step approach: a series of tests will be performed over the next weeks and months aiming to find out whether the unsatisfactory performance is a result of the sample configuration, the sample preparation, or the conductor design itself. "These tests will be performed in parallel in order to save time and to enable the start of procurement," says Devred. "The SULTAN test serves as a risk mitigation strategy for launching production, but the true validation of the performance in conditions similar to the operating environment will be made by a long length of conductor." This so-called central solenoid insert test will occur during the second half of 2013, when 50 metres of central solenoid conductor will be tested in the central solenoid model coil based in Naka, Japan that provides test conditions very similar to those in ITER.