ITER Newsline / 13 January 2018


 
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First toroidal field coil structure
Submillimetric tolerances achieved

In major news for the ITER superconducting magnet program, the first toroidal field coil case has passed all fitting tests. The two sides of the huge component—as tall as a four-storey building and machined from 20-centimetre-thick steel—were matched within gap tolerances of 0.25 mm to 0.75 mm, an accuracy of more than one order of magnitude in relation to conventional high-precision welded structures of comparable size. On 18 and 19 December 2017, precision laser trackers were used to measure the alignment of inboard and outboard legs of the first toroidal field coil case as well as the precise position and orientation of the heavy steel segments. The measurement results were sent electronically to the ITER Organization for detailed analysis, where it was confirmed that giant steel structures matched at all welding grooves with gaps ranging from 0.25 mm to 0.75 mm, fully respecting specified tolerances. 'This is a technological achievement of the highest order,' declared Eisuke Tada, ITER Deputy Director-General, as he attended a ceremony on 26 December at the testing site. 'A component that is 16 metres in height, weighing 190 tonnes, has been successfully pre-assembled to within sub-millimetre tolerances by multiple manufacturers. The international nature of this achievement makes it all the more remarkable.' The toroidal field coils cases provide protective covers for the toroidal field winding packs, the superconducting core of the magnets wound from approximately 5.5 kilometres of niobium-tin conductor. The thick steel cases also have a structural role to play, anchoring the poloidal field coils, the central solenoid and the correction coils and withstanding huge electromagnetic loads inside the machine. Japan* is responsible for producing 19 toroidal field coil structures (for ITER's 18 toroidal field coils plus one spare). Nine of the structures will encase the toroidal field coil winding packs produced in Japan, while ten—including this first unit—will be shipped to Italy for the insertion of winding packs produced in Europe. The inboard leg of the first coil case was manufactured at Mitsubishi Heavy Industries, Ltd. (Kobe, Japan). During fitting tests in July 2017 the two sections of the inboard leg—the U-shaped sub-assembly ('AU') that will contain the superconducting core plus a cover plate ('AP')—were successfully paired with gap tolerances of 0.25 mm to 0.75 along the entire 14-metre-long weld groove. The outboard leg was contracted by Japan to Hyundai Heavy Industries in Ulsan, Korea. The ultimate test was then to verify that structures manufactured in two locations following stringent ITER Organization specifications would fit together perfectly. 'Ultimately, the story of the toroidal field coil cases is the occasion to showcase the spirit that underlies the ITER Project in its entirety—the 'One-ITER' spirit of teamwork that unites us around one design, one schedule and one mission,' stressed Deputy Director-General Tada. At Hyundai, the outboard leg sub-assemblies ('BU' and 'BP') were first fitted together to verify manufacturing precision. Then, on 18 and 19 December the principal segments of the coil case ('AU,' manufactured in Japan and shipped to Korea, and 'BU' manufactured in Korea) were positioned and measured. (Please see the photo gallery below for further explanations.) The required tolerances of bevels at the welding grooves were respected across the board at less than 1 millimetre—with gap variations ranging from 0.25 mm to 0.75 mm. Witnesses on hand during the fitting tests included representatives of the ITER Organization, the Japanese and Korean Domestic Agencies, the European Domestic Agency (which will be receiving the component), and manufacturers Mitsubishi Heavy Industries and Hyundai Heavy Industries. The successful fitting trials of the first toroidal field coil case demonstrates that the final assembly—the insertion of the superconducting winding pack followed by closure welding—can be achieved within the tight tolerances required. This is excellent news, as work proceeds on the fabrication and precision machining of elements for the other 18 cases. The first case is now on its way to SIMIC (Italy), where the first European winding pack has been delivered for insertion. *QST—Japan's National Institutes for Quantum and Radiological Science and Technology—is responsible for the procurement of all components allocated to Japan by the ITER Organization.

Load tests
Lifting and moving four Boeing 747s

It's almost midnight and everything is still on the ITER worksite. Everything? Not quite. In the Assembly Hall, a small group of people are craning their necks to carefully monitor the nearly imperceptible movements of a large mass of steel suspended some 50 metres above the floor. High in the rafters, electrical motors are whirring, pulling with all their strength at the thick cables that hold the 1,650-tonne load—the equivalent of 1,500 average-sized cars, 300 African elephants or five fully loaded Boeing 747s. The date is 18 December and this is the second-to-last of the 'load tests' for the main cranes in the Assembly Hall. A few days earlier, in order to prove the resistance of the crane's structural elements, the slings had been put into tension with an even heavier load (1,875 tonnes). These 'static' tests had confirmed that the double overhead crane could withstand, without difficulty, a load 25 percent heavier than the nominal lifting capacity of 1,500 tonnes. Now, with a load 10 percent heavier than nominal, the crane system is being tested 'dynamically,' performing all the movements that will be required for the handling of the actual machine components. What needs to be observed and measured this time is the building's 'behaviour.' As the load slowly moves along the width of the Assembly Hall—and then along its length—the building's structure is submitted to considerable forces, causing the steel pillars of its frame to compress and flex. The building is designed to accommodate these transient millimetric deformations that laser measurements closely monitor. 'The steel structure is elastic,' explains a surveyor from the architect-engineer Engage. 'We know precisely, from computer models, what the expected values are. We're just making sure that what we are observing tonight remains within the anticipated numbers.' One last test needs to be performed before the crane system can be fully commissioned. Called the 'DCHLB test,' for Dual Crane Heavy Lifting Beam, it will consist in attaching the four crane hooks to a single connection point in the form of a massive clevis. Such a configuration is required to interface with the dedicated tools that will lift vacuum vessel sectors and the central solenoid. In about a year, the crane system in the Assembly Hall will begin handling actual machine components—massive steel pieces (or pre-assemblies) that will be delicately moved and deposited inside the 'well' formed by the bioshield to be assembled and integrated. Like a giant hand performing a watchmaker's job.

Central solenoid
Ground insulation completed on first module

The team at General Atomics in Poway, California (US), achieved an important milestone for the ITER central solenoid: completion of ground insulation for the first of seven production modules. The massive central solenoid, known as the heartbeat of ITER, will initiate and drive plasma current in the ITER vacuum vessel. Ground insulation ensures that each module is isolated from a potential fault of up to 30,000 volts from other systems and components in the ITER cryostat. 'Completion of insulation is an important milestone in fabricating the first central solenoid module,' said John Smith, program manager for ITER central solenoid production at General Atomics. 'The complexity of the operations presented unique challenges, but the team was able to draw from previous experience and know-how to develop successful solutions.' Ground insulation is the seventh of ten steps in the module production process. Ground insulation consists of 18 layers of fiberglass, six layers of Kapton sheets totalling over 2,300 square metres, and a ground plane, which provides a ground potential surface on the outside of the coil. The fiberglass sheet insulation around the coil was precisely placed to within several millimetres' tolerance. The ground insulation was also tightly fit around complex coil features such as the helium inlets and coil leads. The first module has now moved on to the vacuum pressure impregnation station where 3,000 litres of resin will be injected to encapsulate the module for further insulation and module stability. After helium piping is connected, the module will move on to final testing and is expected to be completed in 2019. The ITER central solenoid will consist of six stacked modules, and will stand nearly 18 metres tall and weigh more than 900 tonnes. When completed, it will be the largest pulsed superconducting magnet in the world and will drive 15 million amperes of electrical current to ITER's plasma. See the full report on the website of General Atomics.

Europe
3D printing for small-size components

The European Domestic Agency is investigating the benefits of 3D printing for the fabrication of smaller size (up to metre-scale) metal components. The technique seems particularly well adapted to unconventionally shaped objects or those with complex interior geometry. The new method, known as additive manufacturing, uses computer-aided design (CAD) drawings as a starting point to directly manufacture 3D objects in a more efficient and cost-effective approach that avoids the mockups and prototypes of traditional manufacturing. The 3D printing equipment is able to read CAD data and lay down successive layers of liquid, melted powder or sheet material to form the component—a process that may be particularly well suited to some of the highly complex components required for ITER. Together with a Swedish consortium, the European Domestic Agency is studying the feasibility of different 3D printing techniques for the manufacturing of the first wall beam--a metal beam that will fix plasma-facing panels to each ITER blanket module. The component, made of ITER-grade stainless steel, has a very complex internal structure to accommodate the passage of cooling water pipes. The first feasibility studies have shown that the first wall beam components produced this way meet ITER specifications for physical properties and mechanical stress tolerances. The next step is to apply this method to the fabrication of larger components. The 3D printing techniques for stainless steel components developed as part of Europe's research and development for ITER open up spin-off opportunities for the manufacturing of complex unconventionally shaped components in other fields. Potential areas for application of the 3D manufacturing technology include power plants and car engines. Read the full article on the European Domestic Agency website here.

Image of the week
Snowy planet

On 16 December, ITER woke up under a thin layer of snow—a rather rare event in Provence. Three days later, when this drone picture was taken, just enough white remained to outline the buildings on the ITER platform-planet.

 OF INTEREST

Fusion documentary "Let there be light" available for rent/purchase

EyeSteelFilm's 90-minute documentary on fusion and ITER—Let there be light—is now available worldwide for rent or purchase on the Vimeo platform. For audiences in North America it is also available on iTunes for purchase and on Amazon Prime for rent or purchase. Subtitled ''The 100 Year Journey to Fusion,'' the documentary shows work underway around the world at both ends of the fusion spectrum—from the giant ITER Project to the warehouse-based startup. It has had success at film festivals in North America and Europe since its launch in early 2017 and major international broadcast stations are showing interest. The European culture channel Arte is set to show the documentary in the coming months. In early January 2018, "Let there be light" was listed as one of the top ten Canadian films in 2017. The documentary is now available for rent or purchase worldwide on Vimeo.com in English or French. In North America it is also available for purchase on iTunes and for purchase or rent on Amazon Prime, both in English.

Next stop: Europe-Japan tokamak in Naka

The JT-60SA tokamak is part of the Broader Approach agreement signed between Japan and Euratom to complement the ITER Project and accelerate the realization of fusion energy. The JT-60SA tokamak represents an upgrade of a previous tokamak at the Naka facility, designed to support the operation of ITER. It will investigate how best to optimize the design and operation of fusion power plants built after ITER. First Plasma is planned for 2020, at the end of a six-year assembly and commissioning period. In the latest news of progress, 12 cryostat vessel sectors manufactured in Spain are now ready for transport to Naka. Heavy frames and robust plastic and tarpaulin wrapping will ensure adequate protection during transport of the sectors, each measuring approximately 11 metres in height, and during storage in Japan. (Storage is required as the elements will arrive ahead of their scheduled assembly in the JT-60SA Torus Hall.) Along with the completed cryostat vessel sectors the shipment also includes heavy lifting equipment. In total the shipment weighs about 322 tonnes. It is scheduled to arrive at the Hitachi port in Japan by mid-January 2018. See the full article here and related information here.

 IN THE MEDIA

EUROfusion

Six postdocs connect tokamak and stellarator



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