Enable Recite

Subscribe options

Select your newsletters:

Please enter your email address:

@

Your email address will only be used for the purpose of sending you the ITER Organization publication(s) that you have requested. ITER Organization will not transfer your email address or other personal data to any other party or use it for commercial purposes.

If you change your mind, you can easily unsubscribe by clicking the unsubscribe option at the bottom of an email you've received from ITER Organization.

For more information, see our Privacy policy.

News & Media

Latest ITER Newsline

  • Manufacturing | Completion of the first vacuum vessel gravity support

    The factory acceptance test on the first ITER vacuum vessel gravity support has been successfully completed at Haneul Engineering in Gunsan, Korea. Under the 8, [...]

    Read more

  • Technology | Hail showers in ASDEX Upgrade for ITER disruption mitigation

    Just before the 2021 Christmas holiday break, the team at the ASDEX Upgrade tokamak successfully fired frozen deuterium pellet fragments into a plasma as part o [...]

    Read more

  • Image of the week | Like a Meccano under the Christmas tree

    Like Erector set or Meccano parts scattered beneath the tree on Christmas morning, components for the ITER Tokamak cover the floor of the Assembly Hall, waiting [...]

    Read more

  • Poloidal field coils | 12 months saved on number two

    Whatever their size or position, the role of the ITER poloidal field coils is to shape and stabilize the plasma inside the vacuum vessel. However, as the plasma [...]

    Read more

  • Divertor dome | Russia delivers a full-scale prototype

    A multiyear qualification program in Russia has concluded with the successful manufacturing and testing of a full-scale divertor dome prototype at the Efremov I [...]

    Read more

Of Interest

See archived entries

The unique art of tokamak grounding

It was an impressive group of experts in their field that had come together for a two-day workshop to discuss the earthing policy of ITER. (Click to view larger version...)
It was an impressive group of experts in their field that had come together for a two-day workshop to discuss the earthing policy of ITER.
While the first buildings of the ITER facility are rapidly taking shape on the platform, only a few hundred meters away at the Château de Cadarache a group of very skilled and specialized engineers this week took a close look at the earthing and electromagnetic compatibility (EMC) design for ITER. Because what sounds trivial in a private household is far from trivial for what will become the world's biggest tokamak ever built.

It was an impressive group of experts in their field that had come together for a two-day workshop to discuss the earthing policy of ITER. Amongst the experts were engineers from: CERN; the Experimental Advanced Superconducting Tokamak (EAST) in Hefei, China; the National Ignition Facility (NIF) in Livermore, California (US); NSTK in Princeton, New Jersey (US); Aditya in Gujarat, India; Asdex Upgrade in Garching, Germany; JT-60 in Naka, Japan; KSTAR in Daejon, South Korea; and the Laser Megajoule Project in Bordeaux, France. And the question was, would the "business as usual" option hold for a project with the dimension of ITER?

With operating voltages up to 1 MV and currents up to 68 kA, "earthing becomes a very important issue," said Kofi Korsak, a nuclear engineer from Oak Ridge National Laboratory. "One thing that we are looking at is the shielding of the equipment against the high magnetic fields—especially the instrumentation and control systems need to be protected. There are a lot of unknowns in a fusion environment compared to the experience we have gained in building fission plants," Kofi Korsak said.

"This workshop is very important as it focuses on tokamak grounding which is a unique art," Charles Neumeyer from the Princeton Plasma Physics Lab added. "There exist lots of types of grounding techniques in the world, but a tokamak has unique characteristics such as a big stray magnetic field, plasma disruptions, fast discharges. All of those features have to be incorporated into the design of the ITER grounding which makes it so completely different than building AC power systems or accelerators."

Another feature that makes ITER unique compared to existing tokamaks such as JET or TFTR is the extended length of its plasma pulses, explains the "Engineer of the Year 2001." The biggest challenge Neumeyer and his fellow colleagues see are the large stray magnetic fields and the magnetic moment that will be much larger than in any tokamak ever built. Even outside the Tokamak hall, in the adjacent building, this stray magnetic field could have an effect on the instruments if no countermeasures are taken. Another challenge is how to shield cables and instrumentation against all the interferences generated by the heating systems, which could inject many kilo-Ampère (kA) in the earth and radiated MW at high frequency.

So what is the solution for ITER? "Many of the tokamak people are stuck with the prior practice," Charles Neumeyer says. "They have almost a religious feeling of how this was done in the past with isolating breaks. And there are some folks who are advocating a new approach which is to avoid isolating breaks and to connect the whole thing. Those two roots have not yet converged. So we are here to seek for a clear explanation, for a clear engineering justification to do it the one way or the other, to follow the traditional approach or to go for a new one."

ITER is the first large tokamak facility—around 10 times larger than the current ones. During the workshop, there were reports about large facilities where major (and expensive) upgrades were done due to earthing and EMC problems, just to apply the same principles than in previous small experiments.

For Charles Neumeyer and his fellow engineers this is new territory, "a fascinating experience." You go through a phase of confusion, uncertainty and frustration—and then you solve the problem. I have no doubt about that."


return to the latest published articles