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

  • Top management | ITER Council appoints new Director-General

    Convening in an extraordinary session in Paris, the ITER Council has appointed Pietro Barabaschi as the next Director-General of the ITER Organization. Mr Barab [...]

    Read more

  • On site | Open Doors for ITER families

    In a first at ITER, the gates of the monumental worksite opened on Saturday 17 September for a family-only Open Doors Day event, reserved for the families of st [...]

    Read more

  • Manufacturing | Russia ships four gyrotron sets

    Twenty-four electromagnetic wave generators called gyrotrons are at the heart of electron cyclotron resonance heating—the system on ITER that will ini [...]

    Read more

  • Fusion world | Science to resume at Wendelstein 7-X

    Improved equipment on Wendelstein 7-X will permit the stellarator device to achieve new scientific heights in a campaign planned to begin this autumn. Science a [...]

    Read more

  • ITER International School | On operation scenarios and control

    The 11th ITER International School concluded successfully in San Diego, USA, on 29 July after five days of lectures and discussions on the development of tokama [...]

    Read more

Of Interest

See archived entries

In-pit machine welding

Filling the gap

Inside the Tokamak assembly pit, two small machines are entrusted with a formidable task: faultlessly and seamlessly welding the first two sections of the cryostat. Following the manual welding of feeder stubs and "manways," and the initial manual passes on both sides of the weld joint between the base and the lower cylinder, the time has now come to join both components. The delicate operation, which began on 26 October, will take approximately five months to fully complete.

Closely observed by an operator, the welding machine slowly progresses along the gap between the base and lower cylinder sections of the cryostat. The gap is 40 millimetres deep and it takes approximately 80 passes to fill a predefined 6-metre-long weld section. (Click to view larger version...)
Closely observed by an operator, the welding machine slowly progresses along the gap between the base and lower cylinder sections of the cryostat. The gap is 40 millimetres deep and it takes approximately 80 passes to fill a predefined 6-metre-long weld section.
The two machines have been positioned across from one another, on opposite sides of the 30-metre-in-diametre cryostat base. Closely monitored by operators—one observing the weld's quality and progression from a distance of a few centimetres, another monitoring the process on a video screen nearby—each machine covers 8 centimetres per minute.  A pass inside the six-metre-long predefined sections is approximately one millimetre thick ... and it takes close to 80 passes to fill the gap between the two components.

Equipped with a flat head that is half-inserted into the gap, the machine uses a welding technique called "gas tungsten welding". A tungsten electrode creates an electrical arc that melts the filler material, which is deposited, pass after pass, inside the gap. All in all, the welding process will require close to one tonne of filler material.

To prevent the oxidation of its tungsten electrode, the welding head operates under a local atmosphere of argon. A mere draft in the assembly pit could disrupt the protective cloud and alter the quality of the weld. (Click to view larger version...)
To prevent the oxidation of its tungsten electrode, the welding head operates under a local atmosphere of argon. A mere draft in the assembly pit could disrupt the protective cloud and alter the quality of the weld.
The weld area and the electrode are protected by a local atmosphere of argon to prevent oxidation. It is therefore essential that no air currents occur within the pit while welding is in progress. A mere draft caused by the opening of a port cell door could dissipate the local argon atmosphere and alter the quality of the weld.

As soon as two six-metre-long sections are completed, the quality of the weld is tested using non-destructive ultrasonic test examination. As for helium tests, they will be performed when the whole 90-metre circumference is finalized.

With the planned addition of a third welding machine, the operation should take approximately 65 workdays, which amounts to approximatively three-and-a-half months. An additional month-and-a-half will be necessary for tests and documentation after the welding is complete.

 



return to the latest published articles