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Of Interest

See archived entries

On the context of CS conductor testing

Following the publication this week of an article in Science Insider the Director-General of the ITER Organization, Osamu Motojima, has issued a letter to the author of the article to provide more detailed and accurate background information related to the ITER central solenoid conductor tests carried out recently at the SULTAN Test Facility in Switzerland.

A shortened version of the letter has also been posted on the Science Insider website.

                                                                         1st March 2012
Dear Mr. Clery,
Science Insider

I had a chance to read your article dated 27 February 2012 ("ITER Dodges Trouble With Superconducting Cables"). I appreciate your positive evaluation that the ITER Project is dodging trouble with its central solenoid coil conductor. However, I got the impression — and I'm not the only one — that this article does not really reflect the real situation of ITER's conductor development, achievements and history up to now. I believe that Neil Mitchell tried to do his best explaining the present situation to you, however your recap does not give the full picture. 

Therefore, I am writing this letter in order to ask you for the possibility of a "correction" or a "follow-up" to your most recent article. The article implies that the Japanese Domestic Agency (JA-DA) and its industrial suppliers have failed to deliver a central solenoid conductor sample that works. This is not correct, since there is neither technical mistake nor fault and the JA-DA and its supplier did their best to develop a central solenoid conductor sample as defined by the ITER baseline requirements.

The recent test conductor design reflects one episode of a long story that began with the successful testing of a central solenoid model coil in NAKA, Japan, which was implemented during the ITER Engineering Design Activity (EDA) phase that finished in 2001. A major change of the central solenoid conductor design was then decided in 2003-2004 done by the ITER team before the official establishment of the ITER Organization. After that, the tests performed at SULTAN were reviewed in 2006, which led to significant improvements in SULTAN sample preparation and instrumentation. 

Waiting for the official foundation of the ITER Organization in 2007, the Organization started to take responsibility to perform the SULTAN tests with Domestic Agencies under the authority of the Science and Technology Advisory Committee (STAC), the Management Advisory Committee (MAC) and the ITER Council.

This above-described history was a common effort endorsed by all ITER partners and the JA-DA implemented the recommended changes. The responsibility is thus not within the Japanese Domestic Agency nor its industrial suppliers. Japanese industrial suppliers have world-class capability which has been demonstrated by many superconducting projects up to now.

Therefore, the statements in your article: "The cables that failed last year ...." and: "Last year's sample, manufactured in Japan ..." do not reflect the situation. It is the failure of all of us not only Japan. However, as Neil Mitchell mentioned, "This demonstrates clearly that there is a solution that works."

With ITER, we are breaking new ground in many ways, especially with the design and manufacturing of its large and powerful superconducting coils. As it is difficult to extrapolate the performance of a new conductor design from the performance of its individual strands, all ITER Domestic Agencies and their suppliers are required to produce full-size conductor samples that are tested at the SULTAN test facility. At SULTAN, the samples have to undergo a comprehensive quality control program, which, for the central solenoid conductor, involves load cycling and warm up/cool down cycles. The recently performed tests are part of the performance qualification program of the central solenoid conductor. 

However, we have to bear in mind that at SULTAN only short samples can be tested in conditions that are not fully representative of the in-situ configuration in a real coil. Therefore, the SULTAN test results have to be carefully analyzed in order to draw conclusions that are relevant for in-coil performance.

As you correctly mentioned at the end of your article, we are now looking into options that could enable our Japanese colleagues to move forward and implement the results of the top-performing sample, CSIO1. In particular, the ITER Organization has already procured and prepared a conductor sample made from existing Japanese strands that adopt the cabling pattern of the best leg of CSIO1, where the inner triplet is made of (3 x superconducting strands) with a Cu-to-non-Cu-ratio 1.5:1. Also, based on the results of CSIO1, Japanese industry is presently developing a new generation of 1.5:1 strand that could potentially surpass the results of CSIO1 (given the lead time, this new conductor sample is expected to be tested by the end of the year). 

ITER is a challenging international collaboration, a kind of United Nations of Research, and all ITER partners are striving to achieve excellence and to demonstrate that developed nations regrouping more than half of the world's population are able to work together and address the main problems of the planet. Our Japanese colleagues are as eager as any of the other ITER Members to get the project to succeed and we expect that faced with unprecedented challenges (no other superconducting magnet coils in the world has ever been subjected to as many cycles as what is foreseen for the ITER central solenoid coil) the dedicated team of the Japanese Domestic Agency and the proactive Japanese suppliers will come up with a solution that meets the project requirements.

To conclude, if your article provides the very wrong impression that Japan had failed in demonstrating the performance because of the Japanese conductor design, you are sending a wrong message to the public. At present nothing is decided. The SULTAN tests will be continued using the Japanese sample and we will make the final decision based on more data and technical understanding. I would be very happy to ask you to continue to watch our action.

Best regards,
Osamu Motojima
Director-General, ITER Organization

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