ITER superconductor production nears completion

The single largest superconductor procurement in industrial history is drawing to a successful close. An eight-year campaign to produce the superconductors for ITER’s powerful magnet systems is in its final stages, with nearly 70 percent of the conductor units lengths accepted by the ITER Organization. Six of the seven ITER members—China, Europe, Japan, Korea, Russia and the United States—have been responsible for the production of 200 kilometers (2,800 metric tons) of cable-in-conduit conductors, worth an estimated EUR 610 million.

Superconductivity is vital to ITER’s construction, as without it, the pursuit of fusion energy would be impossible. Superconductors consume less power and are cheaper to operate than conventional counterparts, while carrying higher current and producing stronger magnetic fields. In ITER, an array of superconducting magnet systems with a combined stored magnetic energy of 51 Gigajoules (GJ) will produce the magnetic fields that will initiate, confine, shape and control the plasma at temperatures reaching 170,000,000°C. The building blocks of the magnet system are high performance, internally cooled superconductors called cable-in-conduit conductors, made up of bundled superconducting and copper strands that are cabled together and contained in a structural jacket. ITER’s technical requirements and the sheer amount of material needed—200 kilometers—resulted in a worldwide collaborative procurement effort.

Beginning in 2007, the ITER Organization pioneered a global procurement strategy to establish the processes and systems to ensure the standardization of conductor production and testing around the world. Eleven conductor Procurement Arrangements were signed with the ITER Domestic Agencies between 2007 and 2010, covering the procurement of conductors for the large toroidal field, poloidal field and central solenoid magnets as well as correction coils and feeders. The Procurement Agreements define technical and quality control requirements such as the qualification of suppliers, the qualification of manufacturing processes, control points at critical manufacturing steps and the testing of representative full-size conductor samples.

Production has been underway since 2008, with oversight from the ITER Organization and the Domestic Agencies. Outside reference laboratories have also contributed their expertise, performing third-party verification on critical acceptance tests.

The most technically challenging raw material was the niobium-tin (Nb3Sn) superconducting strands used in ITER’s toroidal field and central solenoid magnet systems. 500 metric tons, or more than 100,000 km, of strand were produced by nine suppliers. This large-scale industrial effort demanded a ramp-up of global production capacity from 15 metric tons per year to 100 metric tons per year, as well as the introduction of three new strand suppliers.

To date, nearly 70 percent of the produced conductor unit lengths have been accepted by the ITER Organization.

Representatives from the applied superconductivity community, members of the ITER Organization and Domestic Agency magnet teams, and suppliers convened for the last time from September 15-17, 2015, to celebrate the wind-down phase of an eight-year campaign to procure ITER’s superconductors. The “band,” as Superconductor Section Leader Arnaud Devred calls them, has met twice yearly since 2008 to facilitate the exchange of information and share experience. With the manufacturing of the ITER superconductors drawing to a close, it was time to look back and celebrate.

ITER Director-General Bernard Bigot unveils a plaque that lists all of the contributing partners to ITER's longest-lead procurement package. Image: ITER

ITER Director-General Bernard Bigot unveils a plaque that lists all of the contributing partners to ITER's longest-lead procurement package. Image: ITER

At a ceremony on September 17, a plaque was unveiled at the ITER Headquarters at Saint-Paul-lez-Durance, France, to acknowledge the contribution of many different partners in the success of ITER’s longest-lead procurement campaign.

“It has been a long and winding road,” said Devred at the close of the fourteenth and final Conductor Meeting. “Our band will soon break up but, today, let’s remember that together we have overcome many technical challenges. This has been an amazing human adventure.”

ITER Director-General Bernard Bigot said that “perhaps the project’s greatest achievement is reflected in the successful multinational collaboration on design attributes, production standards, quality assurance measures and testing protocols for a project of this technical complexity. We will continue to build on this success.”

Celebration chairman Robert Aymar, former director of both CERN and the ITER Project, wrote in a final email to participants, “The final meeting on ITER conductor procurement has given us all the opportunity to understand the status of production and conductor performances. We are now reassured that the conductors will be available on time to satisfy the needs of the coil manufacturers and that the conductors have margins in their performance to allow the magnets to satisfy their requirements. These are two very important results—bravo!!”

The next stage in the fabrication of ITER magnets is the integration of the superconductors into the final coil assemblies.