Superconducting Magnets

3,000 sensors for detecting the quench

A robust detection system is under development to protect the ITER magnets in case of quenches—those events in a magnet’s lifetime when superconductivity is lost and the conductors return to a resistive state. When cooled to the temperature of 4.5 Kelvin (around minus 269 degrees Celsius), ITER’s magnets will become powerful superconductors. The electrical current surging through a superconductor encounters no electrical resistance, allowing superconducting magnets to carry the high current and produce the strong magnetic fields that are essential for ITER experiments. Superconductivity can be maintained as long as certain thresholds conditions are respected (cryogenic temperatures, current density, magnetic field). Outside of these boundary conditions a magnet will return to its normal resistive state and the high current will produce high heat and voltage. This transition from superconducting to resistive is referred to as a quench. During a quench, temperature, voltage and mechanical stresses increase—not only on the coil itself, but also in the magnet feeders and the magnet structures. A quench that begins in one part of a superconducting coil can propagate, causing other areas to lose their superconductivity. As this phenomenon builds, it is essential to discharge the huge energy accumulated in the magnet to the exterior of the Tokamak Building. _To_57_Tx_Magnet quenches aren’t expected often during the lifetime of ITER, but it is necessary to plan for them. „Quenches aren’t an accident, failure or defect—they are part of the life of a superconducting magnet and the latter must be designed to withstand them,” says Felix Rodriguez-Mateos, the quench detection responsible engineer in the Magnet Division. „It is our job to equip ITER with a de Czytaj dalej...

Korean contract advances neutral beam ports

The Korean Domestic Agency signed an important contract in July for the fabrication of neutral beam port in-wall shielding with Korean supplier Hyundai Heavy Industries Co., LTD (HHI). Through this contract, installation of the in-wall shielding into the port stub extensions will begin in mid-2015 with fabrication completed by early 2016. Hyundai Heavy Industries is also manufacturing two sectors of ITER vacuum vessel as contractor to the Korean Domestic Agency, as well as seventeen equatorial ports and the nine lower ports The vacuum vessel’s neutral beam ports are composed of a connecting duct, port extension, and port stub extension. The spaces between the inner and outer shells of the port extension and port stub extension are filled with preassembled blocks called in-wall shielding. The main purpose of in-wall shielding is to provide neutron shielding for the superconducting magnets, the thermal shield and the cryostat. In order to provide effective neutron shielding capability with the cooling water, 40-millimetre-thick flat plates (steel type 304B4) are used in almost all areas of the volume between port shells. In-wall shielding is composed of shield plates, upper/lower brackets and bolt/nut/washers. Pre-assembled 368 in-wall shielding blocks will be assembled into the neutral beam port extension and port stub extension during port fabrication, while 160 field joint in-wall shielding blocks will be assembled after field joint welding on the ITER site. The total net weight of all neutral beam in-wall shielding approximates 100 tons. Ki-jung Jung, Director-General of the Korean Domestic Agency, commented during the signature: „ITER Korea takes very seriously the demands of the vacuum vessel schedule and quality requirements by ITER.” Czytaj dalej...

Green light for ITER’s blanket design

After three days and 29 presentations, a comprehensive design review with probably the largest participation in the history of the ITER project was completed last week. More than 80 experts from the ITER Organization, Domestic Agencies and industry attended the Final Design Review of the ITER blanket system. „The development and validation of the final design of the blanket system is a major achievement on our way to deuterium-tritium operation—the main goal of the ITER project,” Blanket Integrated Product Team Leader (BIPT) and Section Leader Rene Raffray concluded at the end of the meeting, obviously relieved at the success of this tremendous endeavour. „We are looking at a first-of-a-kind fusion blanket which will operate in a first-of-a-kind fusion experimental reactor.” The ITER blanket system provides the physical boundary for the plasma and contributes to the thermal and nuclear shielding of the vacuum vessel and the external machine components such as the superconducting magnets operating in the range of 4 Kelvin (-269°C). Directly facing the ultra-hot plasma and having to cope with large electromagnetic forces, while interacting with major systems and other components, the blanket is arguably the most critical and technically challenging component in ITER. The blanket consists of 440 individual modules covering a surface of 600 m2, with more than 180 design variants depending on the segments’ position inside the vacuum vessel and their functionality. Each module consists of a shield block and first wall, together measuring 1 x 1.5 metres and weighing up to 4.5 tons—dimensions  that not only demand sophisticated remote handling in view of maintenance requirements during deuterium-tritium operation, but also an approach to attaching the modules which is far from trivi Czytaj dalej...

ITER is well underway

The Eleventh ITER Council convened last week at the ITER site for a two-day meeting that brought together the high-level representatives of the seven ITER Members. As approximately 100 people took their places in the solemn setting of the new Council Room, Director-General Osamu Motojima welcomed the participants, adding, „I would like to take this opportunity to thank the Members, in particular Europe, the Host Party, and Agence ITER France for providing the project with the ITER Organization Headquarters building where staff is nearly fully installed.”  The Council noted the strong measures that have been taken by the ITER Organization and the Domestic Agencies to realize strategic schedule milestones and to develop new corrective measures for critical systems such as buildings, the vacuum vessel, the cryostat, and the superconducting magnets. Delegates urged further corrective actions to improve schedule execution and to seek additional savings. Delegates welcomed the integrated project management approach proposed by the ITER Organization to enhance collaboration between the ITER Organization and the Domestic Agencies, an approach, according to Director-General Motojima, to „cooperate even more closely for the implementation of ITER.” The ITER Council also celebrated the recent major licensing milestone for ITER, the strong pace of construction activities at the ITER site, and the manufacturing activities well underway in all ITER Members. The next ITER Council meeting is scheduled to take place in Japan in June 2013. Click here to view the photo gallery of the Eleventh ITER Council   Read the Press Releases in English and in French. Czytaj dalej...

"ITER is well underway"

The Eleventh ITER Council convened last week at the ITER site for a two-day meeting that brought together the high-level representatives of the seven ITER Members. As approximately 100 people took their places in the solemn setting of the new Council Room, Director-General Osamu Motojima welcomed the participants, adding, „I would like to take this opportunity to thank the Members, in particular Europe, the Host Party, and Agence ITER France for providing the project with the ITER Organization Headquarters building where staff is nearly fully installed.”  The Council noted the strong measures that have been taken by the ITER Organization and the Domestic Agencies to realize strategic schedule milestones and to develop new corrective measures for critical systems such as buildings, the vacuum vessel, the cryostat, and the superconducting magnets. Delegates urged further corrective actions to improve schedule execution and to seek additional savings. Delegates welcomed the integrated project management approach proposed by the ITER Organization to enhance collaboration between the ITER Organization and the Domestic Agencies, an approach, according to Director-General Motojima, to „cooperate even more closely for the implementation of ITER.” The ITER Council also celebrated the recent major licensing milestone for ITER, the strong pace of construction activities at the ITER site, and the manufacturing activities well underway in all ITER Members. The next ITER Council meeting is scheduled to take place in Japan in June 2013. Click here to view the photo gallery of the Eleventh ITER Council   Read the Press Releases in English and in French. Czytaj dalej...

Tore Supra ready to go WEST

On the other side of the CEA fence, in Cadarache, sits a large tokamak which played an important role in the definition of ITER. Tore Supra, a CEA-Euratom device which began operating in 1988, was the first tokamak to successfully implement superconducting magnets and actively-cooled plasma-facing components. Over the past twenty-four years, Tore Supra has explored the physics of long-duration plasma pulses, reaching a record of 6.5 minutes in December 2003. In 2000-2002, Tore Supra was equipped with a new carbon-carbon fibre (CFC) „limiter” — the equivalent of the divertor in ITER — capable of withstanding an ITER-relevant heat load of 10 MW per square metre. This project, named CIEL for Composants Internes Et Limiteurs, demonstrated that, while CFC performs very well in terms of power handling and compatibility with the plasma, its use results in substantial erosion caused by the physico-chemical reactions between the carbon of the limiter and the hydrogen (deuterium) in the plasma. Further experiments in JET have confirmed these observations. Now, there are not many options when it comes to choosing the material of a divertor. Fifty years of experience in tokamak technology have narrowed them to two: it’s either CFC or tungsten, their respective advantages or disadvantages depending on the plasma regimes they are exposed to. (More here). In ITER, it was originally planned to begin operations with a CFC divertor and replace it with a tungsten one before the start of nuclear operation (deuterium + tritium) in 2026. After years of discussions, panels and reviews, a new plan was established and ITER is now considering doing without the first-phase CFC divertor. Indeed, substantial cost reductions would be achieved by installing a tungsten divertor right from the start and o Czytaj dalej...

Reflecting on San Diego

A large gathering of fusion scientists such as the 24th IAEA Fusion Energy Conference held in San Diego on 8 — 13 October, offers a unique vantage point to assess the progress of fusion research worldwide. The 400 papers and posters that were presented throughout the week — some 70 being ITER-related — clearly demonstrated that, in many critical areas, researchers are reaching a much better understanding of the phenomena that control plasma behaviour — and we all know that this fundamental knowledge is essential to the success of our project and, beyond, to the future of fusion energy. One of the highlights of the meeting was the presentation of JET’s results: now equipped with an ITER-like wall, JET, together with ASDEX Upgrade, is answering critical questions on how tungsten would affect plasma performance in  ITER. The results on fuel retention on JET are encouraging and we are awaiting further results from JET on how to optimize plasma performance. The synergy between exploratory experiments on ASDEX Upgrade and follow-up experiments on JET has been valuable.  This has implications for the role of satellite experiments in the member states when ITER comes into operation.  The superconducting tokamak facilities, EAST, KSTAR and JT-60SA, clearly see how they could contribute to ITER. It was also pleasing to hear that the SST-1 tokamak at IPR has been reassembled and that commissioning of the superconducting magnets is underway. We were all very interested in the new data on disruptions and runaway electrons that the teams working at JET, Alcator C-Mod,  DIII-D and T-10, as well as other machines, have accumulated. Innovative techniques are being developed to minimize the impact of the runaway beams on the plasma-facing materials on DIII-D, which is good news for our comm Czytaj dalej...

Larsen & Toubro Ltd will manufacture ITER Cryostat

The ITER cryostat will be the world’s largest high-vacuum pressure chamber ever built. On 17 August, the contract for the manufacturing of the 3,800 ton steel-structure was signed with the Indian company Larsen & Toubro (L&T) Ltd. The cryostat forms the vacuum-tight container surrounding the ITER vacuum vessel and the superconducting magnets – essentially acting as a very large refrigerator. It will be made of stainless steel with thicknesses ranging from 50 mm to 250 mm. The structure will have to withstand a vacuum pressure of 1 x 10 -4 Pa; the pump volume is designed for 8,500 m3. Its overall dimensions will be 29.4 meters in diameter and 29 meters in height. The heavy-weight will bring more than 3,800 tons onto the scale – making it the largest vacuum vessel ever built out of stainless steel. The cryostat will have 23 penetrations allowing internal access for maintenance, as well as over 200 penetrations—some as large as four metres in size – providing access to the vacuum vessel for cooling systems, magnet feeders, auxiliary heating, diagnostics, and the removal of blanket and parts of the divertor. Large bellows are used between the cryostat and the vacuum vessel to allow for thermal contraction and expansion in the structures. India, being one of the seven Members of the ITER project, is in charge of procuring the cryostat. On 17 August, Shishir Deshpande, Project Director ofITER-India and Anil Parab, Vice President of the L&T Heavy Engineering division, signed the contract for manufacturing of the ITER cryostat. The design of the ITER cryostat represented a huge international endeavour involving engineers and technicians from both the ITER Organization and the Indian Domestic Agency. „The cryostat is an essential part of the ITER machine. Seeing this huge Czytaj dalej...