MAM has a word to say


There is a procedure for everything…and certainly more than one when it comes to building the world’s largest fusion device. One of the procedures established within the ITER Organization is the Model Approval Meeting (MAM), in which the design descriptions for critical components pass the final check before they are turned into hardware.

The 3D-viewer room on the neighbouring premises of CEA Cadarache has become a regular meeting spot for ITER engineers over the last weeks and months. On one morning in late August, about a dozen ITER staff working on the central solenoid, the centrepiece of ITER’s magnet system, have come together to review the compatibility of the detailed 3D CAD model provided by US Domestic Agency with the rest of the Tokamak. This model, developed by US ITER at Oak Ridge National Laboratory on the basis of the functional specifications provided by the ITER Organization, reflects the final design proposed by the US after feedback from industry and manufacturing trials.

The turn-to-turn spacing of the solenoid conductor had apparently been too tight to be guaranteed by the industrial manufacturer. The solution on the table, proposed by US ITER, is to extend the winding gaps by reducing the inner radius. The impact of this solution is the focus of the discussion.

Jens Reich, coordinator of Tokamak design integration and leader of the meeting, asks the 3D-room operators to overlay the original Configuration Model developed by the ITER Organization with the detailed model they have received back from the US.

A few seconds later, through their 3D-glasses, observers saw a real-size, down-to-the-detail central solenoid unfold on the screen in front of them. What impact would the changes have? And what about the margins at the perimeter—would they still allow for the assembly of this supersized magnet? The central solenoid will be lowered into the machine at the very end of the assembly process, a procedure that doesn’t leave much flexibility for manoeuvring.

The last word about the design of the central solenoid will have to wait until the Final Design Review planned for 18-20 November this year. „But this 3D-check is a very helpful tool to verify the details of a component and to identify any potential interface issues to be solved,” explains Jean-Jacques Cordier, leader of the ITER Design Integration team, before he and his colleagues put their glasses on again to look at the next client, the support structures for the poloidal field coils. 

Resisting the thrust of two Space Shuttles

US ITER is building one of the world’s largest and most powerful electromagnets to energize the ITER Tokamak; the 13-metre-tall central solenoid will be located in the heart of the machine. In order to maintain structural integrity in the face of thousands of tons of force, the solenoid requires a specially designed support structure to hold the electromagnet in place.

„With a typical solenoid, the electromagnetic forces pull the magnet together. But the ITER central solenoid is made of six different modules which are not all pulling together at the same time. They can be opposing each other with large magnetic forces,” notes Bob Hussung, the lead mechanical engineer for central solenoid structures at the US ITER project managed by Oak Ridge National Laboratory.

The forces affecting the central solenoid can be very large, in the range of 60 meganewtons, or over 6,000 tons of force. „For perspective, the Space Shuttle at lift-off had about 30 meganewtons of thrust. So we are handling about two Space Shuttles' worth of magnetic thrust,” says Hussung. „With ITER, we’re avoiding a launch! We’re dealing with all of these magnetic forces, and we have to hold the solenoid in a very accurate position.”

To prevent movement of the modules in the solenoid during tokamak operations, the support structure is designed like a large cage, with 18 tie-plates outside the modules and 9 inside, plus lower and upper key blocks which connect to the tie-plates and attach the entire structure to the ITER tokamak. The complete central solenoid assembly weighs 1,000 tons.

Two approaches are being studied to determine the best way to fabricate the long tie-plate structures. A welded tie-plate, manufactured by Major Tool, Inc. in Indianapolis, Ind., has performed well in initial testing, with results within the ITER requirement margin. A single piece tie-plate, forged by Kind, LLC in Gummersbach, Germany and machined by G&G Steel, Inc. in Russellville, Ala., is also being fabricated; testing will begin in May.

Hussung observes, „The big question for the one-piece tie-plate was 'can you fabricate it.' The answer is clearly yes, it is forgeable. Now the mechanical properties need to be confirmed through testing at liquid helium temperatures.”

Read more on the US ITER website.

Let there be light!

Once the components of the ITER Tokamak are assembled and individually verified, a delicate and complex series of operations will be necessary before lighting the fire of First Plasma.

Commissioning, as this phase is called, means that all the different systems of the machine—vacuum, cryoplant, magnets—will be tested together in order to verify that the whole installation behaves as expected.

These commissioning operations all converge toward one point: the breakdown of the gas inside the vacuum vessel.

It happens in the following way: Initially, the toroidal field coils are electrically charged. Then the varying electrical current in the central solenoid and poloidal field coils generates an electric field around the torus of the tokamak causing the atoms in the gas to collide with the accelerated electrons. The gas in the vacuum vessel becomes ionized (electrons are stripped from the atoms) and reaches the state of plasma.

„At this moment,” explains Woong Chae Kim who joined ITER two months ago as Section Leader for Commissioning and Operations, „First Plasma will be achieved and the commissioning process will be over.”

ITER commissioning is expected to last more than two years and every step—from vacuum vessel leak-testing to the electrical charging of the magnets—will bring its own challenges. Woong Chae, however, is confident. „In the long history of tokamaks, start-up operations have never failed. Technically, I am not afraid. I’ve done it before …”

„Before” was five years ago, when Woong Chae was in charge of plasma commissioning at KSTAR. On 13 June 2008, following six months of commissioning operations, the large Korean tokamak (and the first to implement superconducting niobium-tin coils) achieved a First Plasma that surpassed the original target parameters.

From a technical perspective, commissioning KSTAR was close to what it will be at ITER. The difference lies in the regulatory status of the two devices—ITER is a nuclear installation, KSTAR is not—and in the inner workings of the organization.

„I participated in several design reviews for ITER components over the past four years and have had many opportunities to experience the complexity of the decision-making process within the ITER Organization. It is indeed a very complex machinery, even more than I had anticipated …”

KSTAR, which he joined in 1995 when the project was launched, taught something essential to Woong Chae: „While doing your own job on your own system or component, it is essential to have an overview of the whole device. If you don’t, coordination and interfacing becomes very, very difficult …”

Woong Chae chose to train as a fusion physicist/engineer because he felt fusion was „cool.” „It’s ideal as an energy-producing source, fascinating in terms of physics and technology and so different from the things one comes across in daily life.”

The first fusion device he encountered at graduate school in Seoul was the small tokamak SNUT-79 that Korea had developed in the late 1970s—the country’s first significant step onto the fusion stage. At the time, says Woong Chae, „the device was already a museum piece standing at the centre of the laboratory.” He then worked on the mirror machine HANBIT („Great Light”) in Daejeon, a partial reincarnation of the MIT’s 25-metre-long TARA, where he „learned how to manage big projects.”

After spending 18 years at KSTAR, Woong Chae felt that ITER was the „natural playground" for people like him—people who thrill at the challenge of „organizing men and procedures in order to make things happen.” Several ITER colleagues like Chief Engineer Joo Shik Bak or CODAC Section Leader Mikyung Park made a similar choice.

Woong Chae has moved to Aix-en-Provence with his wife, who spent a year in France as a graduate student, and their 16 year old son. They live near „Painters Ground” and have a beautiful view of Mount Sainte-Victoire. „Although I do not speak much French and am not what you would call a specialist in impressionism, I’m on familiar ground. In the early days of my marriage, we lived in Daejeon, close to restaurant named … Cézanne.”

Team work celebrated at last Conductors Meeting


In pre-ITER times, the world production of niobium-tin (Nb3Sn) strands did not exceed 15 tons per year. Discovered in 1954, this intermetallic compound that exhibits a critical temperature of ~18 K and is able to withstand intense magnetic fields was used mainly in high field coils and nuclear magnetic resonance equipment.

To match the needs of ITER’s 19 toroidal field coils (18 plus one spare), the world production capacity of Nb3Sn strand had to be ramped up by one order of magnitude. As of today, 400 tons of Nb3Sn have been produced by the industry of the six ITER Domestic Agencies involved in conductor procurement, representing 85 percent of toroidal field coil needs.

Nb3Sn conductors will also form the core of the central solenoid, the backbone of the ITER magnet system. Strand production has been launched in Japan for the lower module (CS3L) and conductor lengths will be shipped at a later time to the US where the central solenoid will be manufactured.

For ITER’s third major magnet system—the poloidal field coils—because the magnetic field they produce is less intense, they can be manufactured from the metallic alloy niobium-titanium (NbTi), which is cheaper and easier to produce than the brittle Nb3Sn.

The Russian-European collaboration that procures NbTi strands for ITER has already produced 80 tons of Strand 1, destined for poloidal field 1 and 6. China, responsible for the procurement of conductors for poloidal field coils 2 to 5, has registered nearly 50 tons of of NbTi Strand 2 into the Conductor Database (this essential tool monitors the strand, cable, jacket and conductor production of each Domestic Agency). China will send its first poloidal field conductor shipment to the ITER site within the next two months.

Altogether, conductors for the magnet systems account for 13 percent of the total ITER project credits.

_To_45_Tx_These figures and other information relating to correction coils, feeder conductors, manufacturing issues, quality control, test results and technical issues were presented and discussed at last week’s meeting on conductor production status at the Château de Cadarache.

The Conductor Meeting, which has been held twice a year since 2008 (at ITER in the spring and in one of the „Conductor Domestic Agencies” in the fall), gathers representatives of the ITER Organization, the Domestic Agencies and their suppliers.

„It is an opportunity to share and benefit from each other’s experience,” says ITER Superconductor Systems and Auxiliaries Section Leader Arnaud Devred who traditionally chairs the meeting. „As all conductors are now in the production phase, the feeling in our community is definitely optimistic. Everything is moving ahead and the collaborative spirit, not only between the ITER Organization and the Domestic Agencies but between the Domestic Agencies themselves, is truly excellent.”

Corrective actions in place to accelerate construction

Last Wednesday, ITER Director-General Osamu Motojima called for an all-hands meeting in the Headquarters' brand-new amphitheatre in order to brief the ITER Organization staff on the outcome of the recent meetings of the projects scientific and managerial advisory committees. To this memorable event, Director-General Motojima had invited both the present and former chairmen of the Management Advisory Committee, Ranjay Sharan and Bob Iotti.

At the outset, the Director-General presented the conclusions of the 14th meeting of the project’s Management Advisory Committee (MAC) that had taken place on 29-31 October. The MAC had acknowledged the intensive work done by the ITER Organization in collaboration with the seven Domestic Agencies since the special MAC meeting held in August. Required schedule recovery actions have been taken and the collaboration between the ITER Organization and the Domestic Agencies has been intensified through the establishment of the Unique ITER Team.

„However, the MAC recognized that further and intensive efforts are necessary,” MAC Chair Ranjay Sharan explained. „The variances will have to be minimized by parallel working approaches and innovative methods. The MAC will closely monitor these approaches.”

„Yes, there are issues,” Iotti admitted, „but we are working closely together to resolve them.” Of great concern: the delays related to six super-critical items—the buildings, the vacuum vessel, the poloidal field coils, the toroidal field coils, the central solenoid conductor and the cryostat.

Two other essential issues were the focus of this 14th MAC meeting: the rules for further distribution of credits amongst the ITER Members as proposed in the „MAC-10 Guidelines,” and the proposal for a simplified assembly plan with the intention to recover some of the time slippages. „Based on the different feedback we received to this plan, the MAC suggests that the project remain focused on the normal step-by-step assembly strategy, but that it evaluate options to reduce risks and the time required for the assembly and the transport of components in order to provide more confidence in the dates for First Plasma and Deuterium-Tritium operation,” Sharan said.

As for the technical assessment, the Science and Technology Advisory Committee (STAC) commended the ITER Organization and the ITER Domestic Agencies on significant progress made, especially in the manufacturing of ITER magnets. More than 350 tons (73,000 km) of niobium-tin (Nb3Sn) strand for the toroidal field conductor have been produced so far, corresponding to approximately 75 percent of total amount needed. Also, approximately 65 tons of poloidal field conductor strand (25 percent of supply) have been produced.

The STAC noted that—with the exception of the poloidal field coils—there are currently no new major delays in the critical path due to magnets. The STAC further complimented the ITER Organization’s comprehensive report on remote handling and the good progress that has been made in developing a strategy for the installation, maintenance and potential repair of the first wall and the divertor.

„Take pride in what you have accomplished so far,” and, „Work in cooperation with others as team,” were the final comments from Bob Iotti and Ranjay Sharan respectively.



Corrective actions are now in place to accelerate ITER construction

Last Wednesday, ITER Director-General Osamu Motojima called for an all-hands meeting in the Headquarters' brand-new amphitheatre in order to brief the ITER Organization staff on the outcome of the recent meetings of the projects scientific and managerial advisory committees. To this memorable event, Director-General Motojima had invited both the present and former chairmen of the Management Advisory Committee, Ranjay Sharan and Bob Iotti.

At the outset, the Director-General presented the conclusions of the 14th meeting of the project’s Management Advisory Committee (MAC) that had taken place on 29-31 October. The MAC had acknowledged the intensive work done by the ITER Organization in collaboration with the seven Domestic Agencies since the special MAC meeting held in August. Required schedule recovery actions have been taken and the collaboration between the ITER Organization and the Domestic Agencies has been intensified through the establishment of the Unique ITER Team.

„However, the MAC recognized that further and intensive efforts are necessary,” MAC Chair Ranjay Sharan explained. „The variances will have to be minimized by parallel working approaches and innovative methods. The MAC will closely monitor these approaches.”

„Yes, there are issues,” Iotti admitted, „but we are working closely together to resolve them.” Of great concern: the delays related to six super-critical items—the buildings, the vacuum vessel, the poloidal field coils, the toroidal field coils, the central solenoid conductor and the cryostat.

Two other essential issues were the focus of this 14th MAC meeting: the rules for further distribution of credits amongst the ITER Members as proposed in the „MAC-10 Guidelines,” and the proposal for a simplified assembly plan with the intention to recover some of the time slippages. „Based on the different feedback we received to this plan, the MAC suggests that the project remain focused on the normal step-by-step assembly strategy, but that it evaluate options to reduce risks and the time required for the assembly and the transport of components in order to provide more confidence in the dates for First Plasma and Deuterium-Tritium operation,” Sharan said.

As for the technical assessment, the Science and Technology Advisory Committee (STAC) commended the ITER Organization and the ITER Domestic Agencies on significant progress made, especially in the manufacturing of ITER magnets. More than 350 tons (73,000 km) of niobium-tin (Nb3Sn) strand for the toroidal field conductor have been produced so far, corresponding to approximately 75 percent of total amount needed. Also, approximately 65 tons of poloidal field conductor strand (25 percent of supply) have been produced.

The STAC noted that—with the exception of the poloidal field coils—there are currently no new major delays in the critical path due to magnets. The STAC further complimented the ITER Organization’s comprehensive report on remote handling and the good progress that has been made in developing a strategy for the installation, maintenance and potential repair of the first wall and the divertor.

„Take pride in what you have accomplished so far,” and, „Work in cooperation with others as team,” were the final comments from Bob Iotti and Ranjay Sharan respectively.



How to assemble ITER’s backbone

Although it may appear as a faraway activity, the assembly of the ITER Central Solenoid (CS), the backbone of the machine’s magnetic system, and its installation inside the tokamak were discussed at two Preliminary Design Review meetings held in Cadarache last week.

The US Domestic Agency (US-DA) is responsible for the construction of the 6 CS modules plus one spare, and for the associated pre-compression structure. Due to its large size, the CS will not be delivered by the USDA as a single piece and thus needs to be assembled on the ITER site in Cadarache.

The US partner is in charge of the design, procurement and delivery of the special assembly tools that are necessary to assemble the 6 modules with the pre-compression structure and the current lead extensions. The assembly itself will be carried out by the ITER Organization. Once assembled, the 17metre-high CS will be lifted and transported to the tokamak where it will be lowered into its 4.4-metre diameter pit with a clearance of 42 mm.

Both reviews, assembly tooling and installation, were chaired by Michel Huguet, former Director of the ITER Naka site during the Engineering Design Activities (EDA) phase of the project. Most of the presentations were delivered by Mike Cole and Robert Hussung, both staff members of the US-DA, leading the development for the special tools.

These include: an assembly platform where the modules will be stacked; a lifting device to handle the module and to stack them on top of each other with millimetre-accuracy; a rotating fixture to turn over the three lower modules; a man lift to allow performance of operations inside the inner bore of the modules; a drill guide fixture to allow drilling holes in the interface between modules in order to insert shear pins preventing relative displacement between modules; a lead extension alignment fixture, and a lead support structure.

Delivery of these tools is planned to start in June 2016, matching the IO needs for the assembly of the machine’s central magnet. Manufacturing of the early delivery items, the assembly platform and the lifting tool, is expected to start in early 2015.
Once installed in the tokamak, the CS will be supported at its bottom on lower supports attached to the bottom of the TF coils and kept centred at its top by a system of rods attached to the top of the TF coils. The lower supports are thus the first components to be put in place. The CS can then be lifted by the crane and lowered into the tokamak.

The review panel was pleased with the quality of the presentations which helped everyone to  understand how the tooling is designed and the way it is planned to be used. The reports demonstrated the high involvement of the team and its capacity to address the challenge of accurately positioning heavy loads given the fact that the total weight of the assembled CS is around 1000 tons.

Nevertheless, several chits are in preparation by the review panel and will be communicated through the review report within a few weeks. This will help the design team to focus on the few remaining issues to be tackled before moving into the final design phase.



ITER "conductor community" meets in Moscow

The traditional International Conductor meeting was held in Moscow on 10-13 September, 2012. The regular meeting was attended by representatives from the ITER Organization, experts from the ITER Domestic Agencies of Europe, China, Japan, Republic of Korea, Russia and USA, as well as specialists from the DAs' suppliers.

Such meetings are particularly important since the ITER magnetic system, with conductors forming its core, is one of the ITER tokamak’s key elements. The manufactured conductors, which are designed to withstand super high current in continuous mode, have to meet the IO’s strict requirements.

At the moment, 10 out of the 11 conductor Procurement Agreements, are either well into the production phase or are completing the qualification/pre-production phase. This is particularly true for the Toroidal Field conductors, where 75 percent of the required Nb3Sn strands and one third of the cable-in-conduit conductor unit lengths have been completed. Also, a technical solution has been found for the Central Solenoid conductors that are being implemented by the ITER Japanese partner.

„This is a clear indication  that the ITER project is moving ahead and is able to keep schedule”, says the meeting’s Chair Arnaud Devred, ITER Superconductor Systems and Auxiliaries Section Leader.

In Devred’s opinion, „in spite of the difficulties of coordinating work with about 30 suppliers and six DAs around the world, the ITER conductor community has always tried to work in a cooperative and synergetic manner, and the conductor meetings have always been a great opportunity for sharing experience and tackling difficult interface issues.

The conductor meeting is also an opportunity to showcase the work done in the Russian Federation and for the DAs involved in coils procurement to visit the conductor production facility”. Russia is responsible for the procurement of 22 kilometres of conductors, destined for Toroidal field (TF) coils, and 11 kilometres destined for the Poloidal field (PF) coils of the ITER magnet system. TF coils include more than 90 tons of superconducting Nb3Sn strands; PF coils include 40 tons of Nb-Ti strands.

Arnaud Devred highly praised the progress achieved by the Russian suppliers saying that „The Russian Domestic Agency has now entered full TF conductor and PF cable production. It is a proactive partner, eager to play collectively and to assume its role within the ITER collaboration”.

The next regular meeting is planned for March 2013 in Cadarache.


Where conductors are born

Manufacturing the toroidal field conductors for the ITER magnet system is a sophisticated, multistage process. Early this year, specialists at the All-Russian Cable Scientific Research and Development Institute (VNIIKP) in Podolsk, Russia twisted semiconductor strands into a 760-metre niobium-tin (Nb3Sn) cable—the second product of this kind manufactured in Russia. 

At the end of February, at the High Energy Physics Institute in Protvino, this cable was pulled through a stainless steel jacket that had been assembled on site. The process involved the most advanced Russian technology and knowhow. The jacket itself—reaching nearly a kilometre in length and composed of more than 70 tubes welded together by gas tungsten-arc welding technology—was exposed to triple testing of the weld seams' quality and reliability.

During the next stage in the process, the jacketed cable, called a conductor, was compacted and spooled into a solenoid measuring four metres in diameter. Following vacuum and hydraulic tests at the Kurchatov Institute in Moscow, the conductor will be shipped to Europe.

Follow this link to a 10-minute video in English that will bring you inside the Russian factories involved with toroidal field conductor manufacturing for ITER.

Click here to see the video in Russian.