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ITER NEWSLINE 264
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 tonnes—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 trivial when considering the enormous electromagnetic forces.
The first wall is made out of shaped "fingers." These fingers are individually attached to a poloidal beam, the structural backbone of each first wall panel through which the cooling water will be distributed. Depending on their position inside the vacuum vessel, these panels are subject to different heat fluxes. Two different kinds of panels have been developed: a normal heat flux panel designed for heat fluxes of up to 2 MW/m² and an enhanced heat flux panel designed for heat fluxes of up to 4.7 MW/m².
The enhanced heat flux panels are located in areas of the vacuum vessel with greater plasma-wall interaction and they make use of the hyper-vapotron technology which is similar to that used for the divertor dome elements. All panels are designed for up to 15,000 full power cycles and are planned to be replaced at least once during ITER's lifetime. A sophisticated R&D program is currently under way in Japan for the development of remote handling tools to dismantle and precisely re-position the panels.
Due to the high heat deposition expected during plasma operation—the blanket is designed to take a maximum thermal load of 736 MW—ITER will be the first fusion device with an actively cooled blanket. The cooling water is fed to and from the shield blocks through manifolds and branch pipes. Furthermore, the modules have to provide passage for the multiple plasma diagnostic technologies, for the viewing systems, and for the plasma heating systems.
Because of its low plasma-contamination properties, beryllium has been chosen as the element to cover the first wall. Other materials used for the blanket system are CuCrZr for the heat sink, ITER-grade steel 316L(N)-IG for the steel structure, Inconel 718 for the bolts and cartridges, an aluminium-bronze alloy for the pads that will buffer the electromechanical loads acting on the segments, and alumina for the insulating layer.
The procurement of the 440 shield blocks is equally shared between China and Korea. The first wall panels will be manufactured by Europe (50%), Russia (40%) and China (10%). Russia will, in addition, provide the flexible supports, the key pads and the electrical straps. The assembly of the blanket is scheduled for the second assembly phase of the ITER machine starting in May 2021 and lasting until August 2022. The work will be performed with the help of two in-vessel transporters working in parallel.
In assessing the work presented at the Final Design Review, Andre Grosman, deputy head of Magnetic Fusion Research Institute at CEA and chair of the review panel, enthusiastically commended the BIPT for its achievements since the Preliminary Design Review in December 2011 which were "beyond the expectation of the panel." He added: "We have singled out the continuity and benefit of the work done by the ITER Organization and the Domestic Agencies within the BIPT framework with a sharing of risk and information among all stakeholders."
The panel nevertheless pointed out some remaining issues, including a few challenging issues that need to be addressed at the project level. But thanks to the excellent quality of work performed by the BIPT, the ITER blanket design can today be called "approved." The BIPT can now turn its focus to addressing the feedback received at the Final Design Review, applying the final touches to the design, and preparing for the Procurement Arrangements, where fabrication is handed over to the Domestic Agencies, starting at the end of 2013.
ITER owes a lot to a few individuals who, at decisive moments in the project's history, made decisions that changed the course of events.
Philippe Busquin is one of them. In 2001, as European Commissioner for Energy (1999-2004), he played a key role in pressing the Commission to commit itself to actually realizing ITER.
"I took the responsibility to launch ITER," he recalls. "At the time, the European effort to develop fusion was quite diluted amongst several associations. ITER was still a paper project and I felt it was high time to get on to the experimental phase."
2001 was a defining year for ITER. A new design for the Fusion Energy Advanced Reactor ("ITER-FEAT") had been approved by the ITER Council; Canada had proposed to host the installation; local governments in Provence were mobilizing to promote the Cadarache site... For Busquin, the time was ripe to take action.
"As a nuclear physicist, I could measure what was at stake with fusion; as a politician, I knew Europe had to be daring. And I was optimistic..."
Two years later, in 2003, Europe had two sites to offer to ITER—one in Vandellòs, Spain; one in Cadarache, France. Busquin considered at the time that this "double offer" was proof of Europe's determination to host the project.
As he stood above the Tokamak Seismic Pit, one decade later, the former European Commissioner felt profound satisfaction and a sense of pride.
"I was standing close to where we are now, with French Research Minister Claudie Haigneré and all the people who worked so hard to make ITER happen here—of course the landscape was quite different but I can still recognize the place."
Philippe Busquin, now retired from public affairs (but still active in promoting collaboration between industry and the academic world) took some time from a vacation with his wife and son to meet ITER Director-General Osamu Motojima and visit the ITER site last week.
As for the future of ITER, he is as optimistic in 2013 as he was in 2001. "With ITER we are working at the limits of about every available technology," he says. "We cannot begin to imagine the benefits of such a venture. But the project is also a first in terms of international governance and management. In this respect also, what we are learning will have huge consequences for the future."
French law requires that a local commission for information (CLI) be established every time a nuclear installation is created. A CLI is an independent body that acts as an interface between the installation's operator and the public. It is composed of representatives from local government, environmental groups, trade unions, businesses and health professionals.
A CLI can request from the operator any documents it deems necessary, or call on independent laboratories to proceed with environmental and health investigations. The CLI must be consulted on any new project undertaken in the scope of the installation's evolution.
The ITER CLI was established in December 2009. Last Thursday 11 April, its 42 members held their biannual general assembly—for the first time in the Council Chamber on the 5th floor of the ITER Headquarters.
The general assembly of the CLI provides an opportunity to discuss the present status of the project and its expected developments, which are traditionally presented in French by ITER Deputy Director-General Carlos Alejaldre.
DDG Alejaldre's presentation featured the important events that have occurred since the last general assembly on 3 December 2012 such as the inauguration of the ITER Headquarters and the signature of a convention with URSSAF, significant progress in construction including the beginning of foundation works for the Tokamak Complex, Procurement Arrangement signatures (representing at this stage 82 percent of the total project value), and contracts and fabrication.
Of special interest to the CLI members were the figures of the economic benefits that ITER has already generated: as of the end of December 2012, companies based in the PACA region have benefitted from almost one billion euros (EUR 927 million) in contracts awarded by the ITER Organization, the European Domestic Agency Fusion for Energy, and Agence Iter France.
Although more difficult to calculate, the economic benefits to neighbouring towns and villages resulting from the presence of 452 ITER staff (as of February 2013) and a similar number of direct contractors, experts and consultants, are also considerable.
Since the ninth of April, GÉANT, the world's leading high-speed research and education network managed and operated by DANTE in Cambridge, UK, has been providing data links to the International Fusion Energy Research Centre (IFERC) in Rokkasho, Japan.
IFERC hosts the Helios supercomputer, a system with a compute power exceeding 1 PFlops attached to a storage capacity of 50 PB. The Helios supercomputer is provided and operated by the French Alternative Energies and Atomic Energy Commission (CEA) and is a European Domestic Agency resource.
GÉANT is supplying a 10 Gbps (10 Gigabits per second) link to connect Helios with scientists involved in ITER and DEMO, the demonstration fusion reactor considered as the follow-up to ITER.
It is hoped that, after the first fusion plasmas of ITER planned for 2020 and beyond, DEMO, an industrial demonstration fusion reactor, will lead to full-scale fusion energy reaching the commercial market in the second half of this century.
Read more on the European Domestic Agency website.
cryostat will be assembled from 54 smaller segments manufactured by India.
Like the largest poloidal field coils, the size and weight of the main cryostat segments makes travel along the ITER Itinerary impossible. The cryostat base section—1,250 tonnes—is the single largest load of ITER Tokamak assembly; the other three cryostat sections (lower cylinder, upper cylinder and top lid) weigh in the range of 600-800 tonnes each.
Within the on-site Cryostat Workshop, assembly activities will take place on two huge steel platforms built to support the weight of the components, jigs and fixtures.
"The 30 x 30 metre assembly platforms will also act as transporters," explains Bharat Doshi, Leader of the Cryostat Section. "The Cryostat Workshop will be linked by rail to the Assembly cleaning facility and building. Once completed, the cryostat sections can be moved on their assembly platforms by rails/rollers to the Assembly cleaning facility and from there transported to the Tokamak Pit by main bridge crane."
Planned along the fence on the northeast corner of the ITER platform, the football field-size (50 x 100 m) Cryostat Workshop will be approximately 100 metres from the Assembly Building. It will be equipped with equipment for machining, welding and testing, and a large "goliath" crane capable of travelling the facility's full length. "Assembling the four main sections, each 30 metres in diameter, will require several kilometres of joint welding in total," specifies Bharat.
As a high vacuum component, the cryostat is subject to strict quality requirements. Two types of testing will be carried out in the Workshop: an examination of each weld through non-destructive means (ultrasonics or radiography) and the vacuum leak testing of each joint (helium mass spectrometer leak detection). Dimensions and tolerance control will be achieved using sophisticated alignment and metrology equipment. Approximately 50 people are expected to manage the machining, alignment, welding and testing operations during assembly of the cryostat segments.
"The ITER cryostat will have the privilege of beginning and ending the assembly of the ITER Tokamak," says Bharat. "The base section of the cryostat will be the first large component installed in the Tokamak Pit and the top lid of the cryostat will be the last large component, set into place after the installation of the vacuum vessel, magnets, thermal shielding and central solenoid."
As soon as the Tokamak and Assembly buildings (and their heavy-lift crane) are available, the cryostat base must be ready ... and the lower cryostat cylinder soon after that. The Indian Domestic Agency is procuring two transporter platforms so that work can be carried out in the Cryostat Workshop on the two sections simultaneously. A gap of about two years will then follow before the upper cylinder and top lid can be assembled in the pit.
The contract for the design, fabrication and assembly of the cryostat was awarded in August 2012 by the Indian Domestic Agency to Larsen & Toubro Ltd—this contract also includes the set-up of the Cryostat Workshop, workshop assembly activities, and in-pit assembly (integration of cryostat main sections, welding, etc.). In the autumn, Larsen & Toubro awarded the construction of the Workshop to the French company SPIE Batignolles TPCI (part of the consortium that built the ITER Poloidal Field Coils Winding Facility).
Work on the steel-framed structure is scheduled to last 18 months.
The Japanese people have a long history of creating ceramics of great beauty and elegance. Now they are putting their skills towards the search for materials for future fusion plants — in this case not crafting elegant forms, but elegant solutions: ceramics are nearly impervious to tritium.
In a colloquium delivered at JET last week, Assistant Professor Takumi Chikada from the University of Tokyo outlined promising progress in research into the ceramic coating, erbium oxide, which may prove to be a vital coating for use in tritium-carrying pipework. "Without solving this problem it will be impossible to operate a fusion reactor," he stated.
Because of its very small size, tritium tends to permeate through materials readily — an undesirable characteristic in a tritium processing plant, where tritium would be exposed to a large surface area as it passes through cooling, ducting and processing pipework.
Assistant Professor Chikada's results showed that a layer of erbium oxide only tens of microns thick on a steel surface could reduce permeation of tritium by 100 000 times.
Erbium oxide was originally chosen as an insulation coating because it has a high thermodynamic stability and is resistant to liquid lithium-lead — a proposed blanket material for fusion plants, which is corrosive to many materials.
Read more on the EFDA website.