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A one-piece tie plate was forged and heat treated by Kind, LLC in Gummersbach, Germany.© US ITER
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 tonnes.

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.

The "massive" Procurement Arrangement signed with the US Domestic Agency covers the manufacturing of several hundred pumps of different sizes and technologies, valves, supporting structures and connections.
The presence of representatives from the ITER Members for meetings of the Management Advisory Committee last week was also the occasion to advance the ITER Organization's procurement agenda: during "MAC week" Procurement Arrangements were successfully finalized with the United States, China and Korea.

In order to conclude the Procurement Arrangement for Standard Components, Vacuum Auxiliary Systems with the United States, a "massive" amount of work was accomplished by the vacuum team comprising ten people from the ITER Organization and five from the US Domestic Agency, according to ITER Vacuum Section Leader Robert Pearce. This Procurement Arrangement—the first to be signed with the US Domestic Agency this year—covers the manufacturing of several hundred pumps of different sizes and technologies, valves, supporting structures and connections.

"It is massive in terms of complexity—it is a highly distributed system that interfaces with about every part of the machine," says Pearce. "And it is also massive due to the sheer number of individual components that have to be produced, assembled, tested and delivered."

This brings to 85 the number of Procurement Arrangements signed by the ITER Organization to date out of a total of 140 planned work packages, not including about 45 Complementary Diagnostic Procurement Arrangements. Each Procurement Arrangement represents the transfer of work from the ITER Organization to the Domestic Agencies.

Three Complementary Diagnostic Procurement Arrangements were signed last week, two with the Chinese Domestic Agency and one with the Korean Domestic Agency.

China will supply equatorial port number 12 and a radial X-ray camera diagnostic for monitoring x-ray emission on ITER. Korea will supply upper port number 18. These Procurement Arrangements comprise complete port integration, including port plug, post interspace and port cell structures, diagnostics and services. The integration is a very important and challenging task which is required to ensure the proper functionality of all integrated systems, and diagnostics in particular, as well as to fulfil demands of safety, maintenance and handling.

The x-ray camera installed in equatorial port plug 12 consists of in-port and ex-port modules that are based on similar cameras on other machines, particularly JET. The hot plasma core is a strong source of x-rays. These x-rays carry information about the radiated power, electron temperature, plasma position, and plasma internal motion. Upper port 18 contains the vacuum ultra violet spectroscopy system already undertaken by the Korean Domestic Agency and completes the Korean diagnostic scope.

Re-solidified tungsten melt after high heat-flux exposures in the TEXTOR edge-plasma (power density: 20 MW/m2, exposure time: 5 s)
During the 14th International Conference on Plasma Facing Materials and Components (PFMC-14, 13-17 May) in Jülich, Germany, the focus was directed towards solving the issues related to wall materials and components in a future fusion reactor. Basic material and physics issues were linked with engineering activities related to fusion materials, producing synergistic results for future research.

Prior to the main conference, a tutorial course was given by experts; these introductory lectures were dedicated to PhD students, postdocs and newcomers in the field. Surprisingly, roughly three-fourths of all participants used the chance to update their knowledge and get an inside view into other research areas by attending these tutorial lectures.

More than 200 international scientists from 28 nations attended the conference in Jülich to discuss the viability of existing and future material options—in particular the plasma-facing materials for the first wall (beryllium) and the divertor (tungsten, carbon) in ITER, but also future material options including tungsten alloys, steels and even liquid metals. Results obtained to-date related to materials and components under extreme conditions are influencing upcoming decisions on ITER operation.

One important decision to be made is the selection between carbon and tungsten as material for the strike point area of the first ITER divertor—a decision scheduled for later this year. Furthermore, solving issues related to the highly demanding operational requirements of a future power plant such as the combination of steady state operation, high neutron loading, material erosion and component lifetime under the high particle and heat fluxes, is the next step to affordable and safe fusion power.

As a special highlight at this year's PFMC conference, the first results of the ITER-like wall at JET were discussed in a special session. Operating since 2011 with a beryllium main wall and an all-tungsten divertor, JET is a direct test bed for a better understanding of the plasma operation within the environment of the ITER-specific plasma-facing materials mix. It becomes even more relevant as carbon may be completely ruled out for use in ITER from the first day of operation. Results related to beryllium material migration, fuel retention, and material morphology are now available from JET and investigations are ongoing to transfer the obtained data directly to ITER.

The PFMC-14 Young Scientists Poster Prize was awarded to Rianne 't Hoen (FOM Institute DIFFER—Dutch Institute for Fundamental Energy Research, Association EURATOM-FOM, the Netherlands) for her contributions to the "High Flux and Fluence Exposures of Pre-Irradiated Tungsten to Deuterium Plasmas."

The next PFMC-15 conference will be held in Aix-en-Provence, France from 18-22 May 2015.

Joaquín Sánchez is Director of the CIEMAT National Fusion Laboratory in Spain and Chair of the ITER STAC.
The 14th meeting of the Science and Technology Advisory Committee (STAC) took place recently at the ITER Headquarters, from 14-16 May. We had the honour to be the first ITER Council subcommittee that met at the impressive Council chamber after it was inaugurated by the ITER Council last November.

The STAC advises the ITER Council on two areas: the monitoring of ongoing project activity and the assessment of new proposals which imply a change in the ITER Baseline. The work at every meeting is based on the "STAC charges" adopted by the ITER Council. We assess the input from the ITER Organization that replies to recommendations made by the STAC and answers questions implied in the STAC charges.

The preparation of each STAC meeting involves an important work load on key ITER Organization staff and, as Chair of the STAC, I am aware that we must be careful with the amount of work that our requirements put on ITER Organization resources. I must also recognize the high overall quality of the reports and presentations delivered to our committee.
 
One of the first agenda points since I have participated in the STAC is the review of the project schedule from a technical point of view. Essentially, we analyze the technical causes of delays, including aspects which are midway between the technical and the managerial world such as configuration control, quality control, process control, etc.

As is happened in previous meetings, STAC 14 continued to express its concern about delays in the project. A number of systems are "critical or supercritical," which means that they drive the First Plasma schedule, amongst them buildings, vacuum vessel, the poloidal field coils ... and even the toroidal field coils could come into this category if delays are not stemmed. In addition, the "microschedule" reflected in the milestone achievement index and similar management parameters also indicates delays. However my personal perception, and to some extent that of many STAC members, is that the processes are improving and that the project schedule will soon consolidate. The STAC also acknowledged the organizational efforts and the implementation of recovery plans in order to mitigate the delays.

As I explained during the meeting with the staff in the afternoon of 16 May, my personal view on the delays is that they are not dangerous per se for the project but they undermine our credibility in front of stakeholders and society and this is the actual danger. In order to rebuild credibility our best tool is to keep working hard, as everyone involved is already doing. The ITER project is not only extremely complicated technically, it is also a nuclear project, which adds complexity. It was conceived with a complicated collaborative structure and, unfortunately, an underestimated allocation of resources. The fact that it is effectively progressing and that many components are actually being constructed should encourage all of us.

In addition to the technical analysis of the schedule STAC also looked at deferrals, i.e., procurements which are proposed to be delayed in order to free resources for other items that are needed in earlier phases of the project. We were worried about the deferred implementation of some systems, in particular diagnostics, and we have requested the ITER Organization to make every possible effort to implement those systems in time in order to avoid delays to the deuterium-tritium campaign derived from a slow implementation of the research plan.

During STAC-14 we noted that the organization and the progress of neutronics analysis has improved, for which we commended the ITER Organization. We have requested further detail on the results obtained for the next meeting of the STAC, in particular in relation to the heating of toroidal field coils and shutdown dose rates near the ports.

The news presented to the STAC on the central solenoid conductor was very good: in the last tests of a new cable developed by the Japanese Domestic Agency it showed very good stability—in fact, the degradation noted in earlier samples was essentially non-existing. Thus, we are now confident that the construction of the central solenoid can go ahead while keeping ITER's performance as originally planned.

This STAC had the responsibility to make a clear recommendation on an important technical decision: whether or not to include in-vessel coils for ELM control in the Baseline. After we evaluated the specific problems that a lack of ELM control could cause, in particular when operating with a tungsten divertor, our unanimous recommendation was to include the coils in the ITER Baseline. STAC concluded that the potential benefits of the use of the coils in achieving ITER's mission outweigh the risks, which were found to be very modest taking into account the solid design of the coils and the fact that they will be thoroughly tested during the non-nuclear phase.

STAC expects to make a recommendation next October for another key technical decision: the material for the first ITER divertor (tungsten or carbon).

At STAC-14 we analyzed the input from the ITER Organization regarding progress in divertor technology and tungsten divertor physics and the preliminary report prepared by the ITPA topical groups, which provided an excellent in-depth review of what is known today concerning tokamak operation with high Z* walls. The results from JET and other devices give a positive view of the operation with tungsten divertor in ITER but impose some scenario restrictions that must be further considered for ITER. Experiments to be carried out at JET in the near future, aiming at local melting of some tungsten elements of the divertor, will provide important input for a final recommendation by the STAC on its next meeting.

A final element in the last STAC meeting was the monitoring of progress in a number of areas: remote handling, quality control, ion cyclotron, and negative neutral beam heating. On this last item STAC looks forward with interest to the recent start of activities in the ELISE facility, which will provide important input to the physics and engineering design of the neutral beam injection sources for ITER.

In summary, STAC 14 corroborated important steps in the progress in the ITER project, which we expect to see reinforced next October thanks to the continued effort of all ITER Organization staff.

* A high Z element, like tungsten, is an element with a high
atomic number—its nucleus includes a large number of protons.

Like he did at KSTAR in 2008, Woong Chae will manage the long and complex commissioning phase of the ITER Tokamak.
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."