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Open Doors Day | An intense and unforgettable experience

ma, 20/05/2019 - 20:07

Saturday was Jacques's birthday. At age 90, the long-retired engineer from Aix-en-Provence had only one item on his wish list: to visit ITER for a third time and "see the progress of the Tokamak." Jacques was lucky: his birthday this year coincided with the 14th edition of the ITER Open Doors Day—a twice-a-year opportunity for the public to take the full measure of the ongoing works on the ITER construction site in Saint-Paul-lez-Durance, southern France.
The Open Doors Day has come a long way since the event's inception in October 2011. The first edition had little to show: a "near-finished" Poloidal Field Coils Winding Facility, a "forest of pylons" in the electrical switchyard, and a 17-metre-deep excavation where installation work had just begun on the anti-seismic system of the Tokamak Complex.
Eight-and-a-half years later, the ITER installation is a massive presence. More than 70 percent of civil work to First Plasma has been completed, spectacular assembly tools are in place, and giant components are taking shape on site.
For the 800 visitors who passed through the worksite gates on Saturday, the experience was intense and unforgettable. As they walked from the Cryostat Workshop, where the base section of the cryostat is in the last stages of fabrication ... past the lower cylinder (now cocooned on site) ... through the lofty Assembly Hall ... and finally into the depths of the Tokamak Complex, they were able to take the full measure of ITER in both its scientific and industrial dimensions.
The success of an Open Doors Day rests on faultless organization¹, the dedication of dozens of volunteers, and a collective enthusiasm for explaining and sharing what ITER is about. All these pre-requisites and more were fulfilled by the participants in the 14th edition on 18 May.
Scientists traded the complex equations of plasma physics they are familiar with for simple and concrete explanations and examples accessible to the lay public; engineers discarded their technical jargon to convey the challenges of ITER construction.
For everyone involved the reward was in the eyes of the children exploring a 3D rendition of the ITER machine, or in the eyes of their parents gasping at the sheer size of the sub-assembly tools and the unique strangeness of the Tokamak Pit.
¹Open Doors Day is organized by the ITER Organization in close collaboration with the European Domestic Agency, Fusion for Energy, and its contractors Engage, Apave, Energhia, etc. Close to 50 volunteers participated in the 14th edition. Representatives of "Les petits débrouillards," a national network that promotes scientific and technical education, were also present to provide hands-on experiments on magnetism and electricity.

ITER physics school | Ten years of lectures now available

ma, 13/05/2019 - 18:58

The lectures from ten ITER International Schools held since 2007 have been collected and are now available through a dedicated webpage on the ITER website.
In anticipation of the beginning of ITER's construction, the Aix-Marseille University and the French National Centre for Scientific Research (CNRS) together with ITER Organization launched a series of "ITER International Schools," whose main goal is to offer advanced graduate students, recent PhDs, and young researchers a complete picture of both the theoretical and experimental aspects of tokamak physics. The school aims at preparing young researchers to tackle the current and anticipated challenges at magnetic fusion devices, and spreading the global knowledge required for the effective exploitation of ITER's scientific potential.
The ITER International School (IIS) is jointly hosted and organized every two years by the Aix-Marseille University and the ITER Organization and alternates between Aix-en-Provence, France, and sites within the ITER Members. The first ITER school—in July 2007 in Aix-en-Provence, France—was organized on the topic of turbulent transport in fusion plasmas. Nine different editions have followed: Fukuoka, Japan, on magnetic confinement (2008); Aix-en-Provence on plasma-surface interactions (2009); Austin, Texas (US) on magneto-hydro-dynamics (2010); Aix-en-Provence on energetic particles (2011); Ahmedabad, India, on radio-frequency heating (2012); Aix-en-Provence on high performance computing in fusion science (2014); Hefei, China, on transport and pedestal physics in tokamaks (2015); Aix-en-Provence on the physics of disruptions and control (2017); and, finally, Daejeon (Korea) on physics and technology of power flux handling in tokamaks (2019). The next ITER International School is planned in Aix-en-Provence, France, in 2020.
Over the last decade, the school has covered a very wide range of topics in the areas of experimental and modelling fusion physics and engineering. The choice of ''school format'' for IIS was adopted due to the need to prepare future scientists/engineers on a range of different topics and to provide them with a wide overview of the interdisciplinary skills required by the ITER Project.
The lecturers at the schools are leading specialists from research organizations within the ITER Members and from the ITER Organization. Their lectures, together with the proceedings published for some school editions, represent a wealth of knowledge on fusion and ITER. The ITER Organization and Aix-Marseille University, supported by the organizers and lecturers at the past schools, have thus taken action to collect this priceless knowledge and make it accessible for future generations of fusion scientists and engineers, particularly for post-graduate students and young researchers who are the primary attendants of the schools.
The ITER Organization and Aix Marseille University would like to warmly thank the school organizers and lecturers at the ten ITER International Schools for making the lectures available.
Please see the new resource on the ITER website here.

Central solenoid | First of 7 modules completed

ma, 06/05/2019 - 18:58


When ITER begins operations in 2025, its plasma will be initiated by the largest stacked pulsed superconducting magnet ever built—the ITER central solenoid. The US ITER magnets team, based at Oak Ridge National Laboratory, is overseeing the fabrication of the central solenoid modules, support structures, and assembly tooling. A major milestone was reached this spring when vendor General Atomics completed fabrication of the first of seven modules.
"General Atomics has done an outstanding job to reach the difficult and important milestone of completing module 1 fabrication," said Wayne Reiersen, US ITER Central Solenoid Magnets Team Leader. "This is the culmination of an eight-year effort involving concurrent engineering of the module design, the creation of a facility in which these powerful superconducting magnets could be built and tested, the qualification of the manufacturing processes, and the building of this first-of-a-kind module."
The next step for the module is intensive testing to ensure that the component is ready to perform in the ITER Tokamak. The module has already completed the first Paschen voltage test as well as a global leak test.
The central solenoid will be installed in the centre of the ITER machine, and will drive up to 45,000 amps of current in each module during plasma operation. Six modules will be stacked to form the 17-metre-tall solenoid, while the seventh module will serve as a spare.
Fabrication of each module requires multiple fabrication steps spread out over 24 months. 
For a detailed view of the module manufacturing process, see "Building the Heart of ITER" on the Oak Ridge National Laboratory YouTube channel.

Disruption mitigation | JET gets an injection

ma, 29/04/2019 - 22:15


A shattered pellet injector using the same technology as that planned for disruption mitigation on ITER will be tested soon on the JET tokamak at the Culham Centre for Fusion Energy (UK). Technical commissioning of the components is underway.
At the Culham Centre for Fusion Energy in the UK, a global team has been working together to install and commission a shattered pellet injector on the European tokamak JET.
Contributors from US ITER, EUROfusion, the ITER Organization, Culham Centre for Fusion Energy, and Oak Ridge National Laboratory (with support from the US Department of Energy, Fusion Energy Sciences) are interested in testing the shattered pellet technique for disruption mitigation on the world's largest operating tokamak, after performing similar experiments at General Atomic's DIII-D machine (US), which has a plasma volume four times smaller.
"We are very excited to start testing the new shattered pellet injector on JET—it is a core part of EUROfusion's upcoming program," said Joe Milnes, JET Operating Contract Senior Manager for the UK Atomic Energy Authority. "The dedication shown by the project team to get the equipment installed and commissioned has been vital, and I'm sure they will feel immensely proud when the first shattered pellets are injected and the first results are published."
In order to produce a self-heated, burning plasma on ITER, a disruption mitigation system is essential. Plasma disruptions can produce large heat loads, electromagnetic forces, and runaway electron beams. After investigating different designs, ITER partners concluded in a 2017 international workshop that the injection of frozen pellets of deuterium, neon, and/or argon will be the baseline method for the ITER system. Experiments on the DIII-D tokamak in San Diego, California, produced findings that shattered pellet injection leads to more effective thermal mitigation than another technique that was investigated—massive gas injection—with deeper penetration of the fragment spray. 
"The extrapolation of shattered pellet injection performance to ITER is greatly enhanced by employing an injector on JET to see how the mitigation metrics scale with plasma size and energy. This will give us higher confidence in the predicted mitigation outcome on ITER," said Larry Baylor, distinguished scientist at Oak Ridge National Laboratory's Fusion Energy Division. "A unique feature of JET is that it has an ITER-like wall of beryllium and tungsten, which influences disruption behavior."
Shattered pellet injection involves cryogenically freezing pellets of deuterium, neon, argon, or some combination in a specially designed cryogenic "pipe gun." The pellet is injected into the plasma at speeds of 500-1800 km per hour when a disruption is detected. By shattering the pellets in a curved tube before the material enters the vacuum vessel, it is possible to form collimated sprays of pellet material that penetrate deeply and rapidly into the plasma. For ITER, a sufficient quantity of material must be delivered to the plasma when a disruption is detected, as the ITER plasma volume is ten times greater than JET's. This quantity will be achieved with multiple shattered pellets and multiple injectors.
The shattered pellet injector installed on JET is similar to those planned for use on ITER, but scaled to JET plasma parameters. The injector will utilize three distinct pellets, sized from 4.5 mm to 12.5 mm, depending on the experiment.
"The experiments will help answer questions about whether shattered pellet injection will remove energy from the plasma fast enough and uniformly enough to effectively mitigate disruptions in a large tokamak," said Baylor. "We'll also learn how the physics of shattered pellet injector disruption mitigation scales to larger, more energetic plasmas."
Planning is already underway for other injector experiments on the KSTAR tokamak in Korea. In the KSTAR experiments, two identical 3-barrel shattered pellet injector systems will be deployed to mimic the planned multi-injector approach at ITER. These experiments are part of the efforts of the ITER Disruption Mitigation Task Force to validate design choices for the ITER system and to develop the technology to an industrial level to face the challenges in the ITER environment.

Lower cylinder | A transfer that felt like art

di, 16/04/2019 - 21:52

Art has little to do with the transfer of a giant component. On Monday however, as ITER was preparing to celebrate Leonardo da Vinci's 500th anniversary, science, technology and industry conspired to provide a strikingly spectacular and beautiful event. As the set of trailers carrying the lower cylinder of the ITER cryostat slowly crawled out of the Cryostat Workshop, everything combined to create an awesome view: the minimalist architecture of the workshop; the cylindrical component all draped in white, and the shimmering steel of the Assembly Hall ... all against the backdrop of the intense blue of a spring sky in Provence.
The lower cylinder of the ITER cryostat is but one section of the giant thermos that will envelop the ITER Tokamak. Standing 12 metres high, it represents one-third of the total height of the ITER machine. As operators stood close to it, carrying out the highly delicate transfer operation, one could measure how tall, large and massive ITER will be.
Transferring the near-500-tonne load from its assembly site to the storage area a few dozen metres away required no less than four self-propelled modular transporters arranged in a square and moving in perfect coordination. Particularly impressive was the sharp 90-degree turn that the trailers had to take in order to reach the storage area—192 independent wheels slowing rotating at different angles, like small appendages of a powerful living organism.
To date, the lower cylinder is the heaviest load to be moved on the ITER platform. Solidly encased in its steel frame and carefully cocooned in air-tight material, it will remain in storage until the time comes to move it into the assembly pit.
The operation on Monday was a key milestone involving a dozen stakeholders—the cryostat team; heavy load transport specialist Sarens; metrology experts from ITER; global logistics provider DAHER, and many others (see box).
Transferring the lower cylinder to the storage area has freed a large working space inside the Cryostat Workshop. Soon, this space will be occupied by the assembly and welding operations for the upper cylinder whose segments are already on their way from their manufacturing location in India.
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Neutral beam | The system that makes the Tokamak feel small

ma, 08/04/2019 - 23:10


ITER is a big machine—by far the largest fusion device ever built. But there is a system just a few metres away that makes it look like a mere appendage to something much larger. The neutral beam system, with its three, possibly four, massive injectors is the real beast at the heart of the ITER installation.
Construction work underway in the Tokamak Building already gives a sense of how big the equipment for the neutral beam system will be. Giant circular cut-outs in the rebar at level 3 (L3) of the building—more than 3 metres in diameter each—will provide the passageway for high-voltage "bushings," which allow electrical power, cooling, and other services such as diagnostics to reach the neutral beam injectors hosted below.
Just below the bushings, a vast, cavernous space has been reserved for the neutral beam cell where the beam injectors will be located. The largest devices (the heating neutral beam injectors) are sized like steam locomotives—25 metres long, 5 metres high and 5 metres wide—with a chimney-like bushing reaching up 9 metres to connect to the openings on the third floor. The injectors will be connected to the Tokamak at L1 level—exactly across from the Tokamak's mid-plane and the equatorial port openings.
A neutral beam injector is essentially a particle accelerator. Its function is to deliver high-energy particles to the heart of the plasma. ITER is planning two one-million-volt (MV), 40A heating neutral beam injectors (and is making a space reservation for a possible third) as well as a smaller neutral beam line (100 kV, 60A) for diagnostic purposes
The heating neutral beam injectors will each contribute 16.5 MW of heating power to the plasma; the diagnostics neutral beam will provide information on the helium ash density produced by the D-T fusion reactions in the fusion plasma.
At the entry end of the heating neutral beam, a beam source generates the electrically charged deuterium ions that are accelerated through a succession of five grids (each separated by a 200 kV electrical potential) to the required energy of 1 MV at the exit end of the beam source, a "neutralizer" rips them of their electrical charges to become "neutrals," allowing them to penetrate the Tokamak's magnetic cage and, by way of multiple collisions with the particles inside the plasma, raise plasma temperature to the point where fusion reactions can occur. The heating neutral beams are designed to be able to operate during the entire plasma duration, up to 3,600 seconds.
Neutral beams are routinely used in tokamak devices as the workhorses of auxiliary heating. In ITER however they will be considerably larger and more powerful than in any previous fusion device.
Generating a 1 MV beam that will deliver 16.5 MW to the plasma requires a unique power infrastructure. Located just outside the Tokamak Complex, two large buildings will host the transformers, the AC/DC converters and the vast high-voltage hall that will feed power to the neutral beam system by way of transmission lines entering the Tokamak Building through the "north wall" at the L3 level.
There is only one example of a high-voltage installation more powerful than ITER's. In China, where high-voltage DC current is used to deliver electrical power to populations far away from the productions sites, a 1.2 MV system was recently established to push power from Xinjiang, in the northeast corner of the country, to the megacities in the east—1.2 MV in China for a 3,000-kilometre distance; 1 MV in ITER for slightly more than one hundred metres ...

 

ITER Research Plan | The 400-page scenario

wo, 03/04/2019 - 11:47


The ITER Organization has just made publically available the most recent version of the ITER Research Plan, a 400-page document that describes the present vision for operating the ITER Tokamak from First Plasma through high-fusion-gain deuterium-tritium operation.
The ITER Research Plan was initially developed during the ITER Design Review in 2007-2008 in order to analyze the experimental program towards high-fusion-gain deuterium-tritium operation. In the ensuing years it was further elaborated to identify the main lines of physics R&D required to support preparation for ITER operation, and to incorporate elements of the testing program for tritium breeding technology in the fusion environment.
Since 2017—with the collaboration of fusion science experts from the ITER Members' physics communities—the ITER Research Plan has been undergoing revision in order to reflect the revised baseline cost and schedule for the project—Baseline 2016.
Baseline 2016 identifies the date of First Plasma as December 2025 and lays out a multi-phase approach to full deuterium-tritium operation in 2035, in which periods of machine operation alternate with shutdown periods for further assembly. This "staged approach" to assembly is considered to represent the best compromise between the desire of all partners to advance quickly, technical constraints (including risk), and the financial constraints of the Members. _To_143_Tx_With the acceptance of the revised ITER Baseline by the ITER Council in November 2016¹, a study was launched to bring major elements of the Research Plan in line with the framework of the staged approach to ITER construction to ensure that the operation of ITER required to commission ancillary systems was consistent with the phased installation of these systems. Also taken into account were the most recent advances in physics research.

In the staged approach, two main phases are foreseen following First Plasma:

  • Pre-Fusion Plasma Operation — in which the basic controls and protection systems are demonstrated, and the auxiliary heating systems and diagnostics are fully commissioned. (Two operational campaigns are expected.)
  • Fusion Power Operation — in which ITER fusion performance goals are demonstrated. ITER fusion power production goals are the production of 500 MW of fusion power with an energy gain (Q) of Q=10 for >300 s, and in-principle steady-state operation with Q=5. The development of long-pulse inductive plasmas² for fusion technology development is also envisioned. (The ITER Research Plan anticipates at least three operating campaigns to be required to achieve these goals.)
The revision of the ITER Research Plan has involved a re-analysis of ITER plasma scenarios in each phase and the identification of open issues that need to be resolved by physics R&D with support of the ITER Members' fusion communities.
"This revision of the ITER Research Plan was a major effort, spearheaded by my predecessor, David Campbell," said Tim Luce, Director of the Science & Operations Department. "It combines the detailed knowledge of the ITER Organization staff about the ITER facility with expertise from the Members' fusion research programs. We are especially grateful for the delegates who were appointed by the Members to help revise this document. This release is the first time the ITER Research Plan has been publicly available, which we hope will enable a stronger partnership between the fusion community and the ITER Organization to realize the ITER goals."
The Plan will continue to be updated over the years to reflect the results of continuing fusion R&D and the detailed implementation of the staged approach to ITER assembly.
Click here to view/download the "ITER Research Plan within the Staged Approach" from the ITER Technical Reports page of the website.
¹ The overall project schedule was approved by all ITER Members at the Nineteenth ITER Council in November 2016; the overall project cost was approved "ad referendum," meaning that each Member is seeking approval of project costs through respective governmental budget processes.
² An inductive plasma is a tokamak plasma in which the circulating current is sustained using the central solenoid, as opposed to a steady-state plasma in which the plasma current is sustained by heating and current drive sources and plasma-driven processes.
 

IBF/19 | ITER and industry speak a common language

ma, 01/04/2019 - 19:53


There is more to the French Riviera than sunny beaches, skimpy bathing suits, oversized yachts, and a world-class film festival. The stretch of coastline that extends from Saint Tropez to the Italian border also stands for scientific research and high technology. Located a few kilometres north of Antibes, Sophia Antipolis—a French equivalent of California's Silicon Valley—is home to more than 2,000 companies, most of them high-tech, and scores of laboratories, research institutes, public universities and engineering schools. Last week, as Sophia Antipolis celebrated the 50th anniversary of its creation, more than one thousand industry representatives gathered in nearby Antibes to meet with ITER stakeholders and hear updates on the project's progress, needs and upcoming tenders.
Since its first edition in 2007 in Nice, France, the ITER Business Forum (IBF) has grown dramatically in scope and attendance. IBF/19, organized in Antibes on 27-28 March by Agence Iter France¹, was attended by the representatives of close to 500 companies and research institutes from 25 countries (1,110 people in all). The ever-increasing number of participants is not the only measure of success, however. What was palpable during the two days of presentations and business meetings was the intensity of the interactions—ITER and the world industry have now found a common language.
"When they see the pictures of worksite and manufacturing progress, industry representatives gets a clear message: ITER has now entered a very decisive phase and industry has a key role to play," says ITER Divertor Section leader Frédéric Escourbiac, his pockets filled with the business cards collected during the two-day forum. "What we have seen in the successive editions of IBF is a virtual community that has progressively acquired flesh and bone. The body is now strong and fit. We can talk face to face and it makes interaction much easier and much more productive."
As at all previous editions, IBF-19 began with a series of introductory presentations that highlighted progress accomplished and challenges to come. Following a general introduction by Jacques Vayron, the director of Agence Iter France, ITER Director-General Bernard Bigot compared ITER to an extremely complex Lego construction, saying that "if one single piece, however small, is missing the whole project will suffer." Gerassimos Thomas, the Deputy Director-General for Energy at the European Commission, acknowledged that, "thanks to Director-General Bigot and with the help of the Domestic Agencies and all stakeholders, the project has dramatically turned around. [...] We now have an impeccable case to support ITER."
_To_155_Tx_In a passionate demonstration of how ITER was "making history," ITER Chief Operating Officer and Deputy-Director General Gyung-Su Lee described the inevitable "uncertainties and unknowns" of a first-of-a-kind machine but promised the audience that they would soon be "listening to the beautiful sound of neutrons"—the heavenly music of fusion "tamed and utilized to generate energy."
Representatives of each of the seven ITER Domestic Agencies took the stage in quick succession describing, sometimes with humour (and always with precision and conviction) the challenges faced and the accomplishments achieved.
"The future will be painted by you," Gerassimos Thomas told the hundreds of industry representatives gathered in the amphitheatre on the first day of IBF-19. Through technical presentations, workshops and one-to-one meetings, it was soon clear that the "future" was reaching far beyond ITER.
"We need to have as small a gap as possible between the end of ITER assembly and the engineering phase of DEMO," stressed Tony Donné, Programme Manager for EUROfusion. "Too large a gap would lead to the loss of industrial interest and expertise that is critical for the next-step machine and the future of fusion."
What IBF-19 demonstrated is that the relationship between ITER (and more broadly fusion) and industry has now reached a turning point. Beyond the experimental machine that is ITER, a whole new field of activity and innovation—encompassing hundreds of different technologies—is now opening before hundreds of companies throughout the world as the steps after ITER are being planned.
And at the same time, the very role of industry is being redefined—graduating from "supplier" to "partner." In Europe, dozens of companies are already involved in the conception of DEMO; in China 30 different entities, both industrial and academic, are at work on the China Fusion Engineering Test Reactor (CFETR)—a "super ITER" that will evolve into a fusion reactor near-prototype, and whose engineering design is set to be completed in 2020.
Since its relatively humble beginnings in 2007, the ITER Business Forum has been a key facilitator in this process.
Click here to view a video walkthrough of IBF-19. 
¹With the participation of ITER Organization, Fusion for Energy and other Domestic Agencies, and with the financial support of local authorities.  
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Cryostat | Lower cylinder revealed

ma, 18/03/2019 - 18:16

They were all there: those who designed it, those who forged it, those who assembled and welded it, and those who closely monitored the requirements and procedures connected with a "safety important" component. Two years after an array of segments were delivered to ITER, the cryostat lower cylinder—one of the four sections that form the giant thermos that will enclose the machine — had been fully assembled. With scaffolding removed and just a thin translucent film to protect it, the massive structure was at last revealed, both delicate and mighty.
"This is the largest component that will go into the machine assembly pit," said Patrick Petit, ITER In-Cryostat Assembly Section leader. "It is also an example of broad and exemplary collaboration."
Like the other sections of the cryostat, the realization of the lower cylinder epitomizes the larger collaborative nature of ITER: designed by the ITER Organization, forged in India, it was assembled and welded by a German company under contract to India on international territory conceded by France.
"The realization of this component was not a single person's job," said Anil Bhardwaj, ITER Cryostat Group leader. "It has been quite a serious task for all of us, with a large variety of challenges, particularly regarding fitment and welding quality" added Vikas Dube, a mechanical engineer in his team, "and although there were lots of lessons learned, we will face them again when we commence the assembly and welding of the upper cylinder in the coming months."
Read more about the fabrication of the ITER cryostat here.

Divertor cassette bodies | Four years from prototypes to series

ma, 11/03/2019 - 17:21


Hell is a balmy place when compared to the environment of a divertor cassette body. In the vicinity of this ITER component, heat loads will be comparable to those at the surface of the Sun, and radiation will be almost as intense as in the neighbourhood of a neutron star. Cassette bodies will also have to resist the huge mechanical forces that will be exerted for a few tens of milliseconds in the event of a severe plasma disruption. Rarely—even in the space or nuclear industries—has a component posed so many fabrication challenges.
From its strategic position at the bottom of the vacuum vessel, the ITER divertor is the component that will extract the heat and the helium ash from the burning plasma. The divertor is made up of 54 individual "cassette assemblies" arranged in a circle—each one formed from a structural backbone (the cassette body), actively cooled plasma-facing elements (the "targets" and the "dome"), and diagnostic systems.
Cassette bodies are massive and contorted structures that weigh close to 5 tonnes. Prototype manufacturing began in 2013 under two contracts awarded by the European Domestic Agency, Fusion for Energy; five years later the Italian company Walter Tosto and the Italian-French consortium CNIM-SIMIC had each finalized a real-size, fully functional prototype, opening the way for series production to begin.
Under fabrication contracts signed in November last year with Fusion for Energy for the first 19 divertor cassette bodies, Walter Tosto will manufacture 15 cassette bodies and CNIM-SIMIC another 4—all for delivery by 2024. The order for the remaining 39 cassettes (including 4 spares) will be awarded at a later stage, as the divertor is not needed for the initial stages of ITER operation.
"Going from prototype to series manufacturing is a highly symbolic and rather moving moment for us," says Frédéric Escourbiac, ITER Divertor Section leader. "It is the culmination of seven years of hard work on detailed design development and on the demonstration of manufacturing feasibility. These actions were particularly demanding in terms of collaborative efforts with Fusion for Energy and their industrial partners."
"Series," however, does not mean "uniform": the 19 cassette bodies in the first production batch are of the "standard" type. The remaining 39 will present some added complexity, such as specific cooling for diagnostic systems or operational instrumentation, or specialized "cut-outs" for open lines of sight for neutron cameras.
"At ITER, we are used to dealing with systems that do not fit in the typical categories of industrial equipment," explains Laurent Ferrand, the ITER Technical Responsible Officer for the cassette bodies Procurement Arrangement. "When you first look at the technical specifications, what you see is a massive, complex stainless steel structure with lots of welds and very stringent welding and inspection requirements. But of course, it's much more than that ..."
Tolerances on the cassette bodies are sub-millimetric, which is quite standard for ITER but a huge challenge for such a massive component with moving parts. Leak-tightness is an even bigger challenge: "The prototypes were leak-tested at dedicated satellite facilities in Cannes, France, and Pisa, Italy. The engineers there were quite impressed by the 'ITER leak-tight' requirements—our criteria for a component like a cassette body are several orders of magnitude tighter than those for a satellite's fuel tank, for example."
Despite these considerable constraints and difficulties, Walter Tosto and CNIM-SIMIC took up the challenge, worked their way faultlessly through the prototyping phase, and produced fully functional components. The (numerous) lessons learned will be of great value for the series manufacturing phase.
Plasma-facing components and auxiliary systems will eventually be attached to the cassette body to form an 8-tonne cassette assembly that will be positioned within tenth-of-millimetre tolerances in order to be perfectly aligned with the machine's magnetic axis.
As minute variances during the manufacturing process and assembly of the vacuum vessel are inevitable, the positioning of the cassette assemblies, and hence of the whole divertor, will need to "recover" these slight departures from nominal dimensions and positions—a feat that will be achieved by custom machining the rail sections to which the cassette assemblies will be attached as well as all the interfacing elements between the divertor and the vacuum vessel structure.

HTS current leads | China launches series production

ma, 04/03/2019 - 18:52


Because they reduce the input power requirement for plant operation, high-temperature superconducting (HTS) current leads are one of the enabling technologies (together with superconducting magnets) for large-scale fusion power plants. First driven by the high-energy physics accelerator community, the development of high-current HTS leads is now being pushed by magnetic confinement fusion towards larger currents. At 68 kA, the ITER toroidal-field type HTS current leads will be the largest ever operated.
HTS current leads are key components of the ITER magnet system, transferring the large currents from room-temperature power supplies to very low-temperature superconducting coils at a minimal heat load to the cryogenic system. Although HTS current leads represent an additional cost over conventional current leads, this additional cost is quickly amortized due to savings in cryoplant operation.
ITER's largest magnets—18 toroidal  field coils, 6 central solenoid modules, 6 poloidal field coils, and 18 correction coils—will be supplied with 60 current leads, ranging from very large (68 kA for the toroidal-field type) to medium (10 kA for the correction-coil type), transferring up to 2.6 MA into and out of the cryogenic environment of the machine. Located at the far end of the magnet feeder relative to the machine (see diagram below) the current leads operate in much lower magnetic field than the magnet coils themselves.
The largest toroidal-field type of current lead is over 3 metres long and weighs 600 kgs.
The HTS current leads for the ITER Tokamak are procured by the Chinese Domestic Agency through the Institute of Plasma Physics (ASIPP) in Hefei. The Procurement Arrangement signed between the ITER Organization and the Chinese Domestic Agency for magnet feeders laid out a multi-year plan to develop the designs and to qualify the HTS lead manufacturing technology in ASIPP and its sub-suppliers Juneng and Keye.
Following the development of critical manufacturing technologies through targeted trials in mockups, Chinese contractors recorded a string of qualification milestones¹:
  • The successful testing of a pair of correction coil 10 kA current lead prototypes in March 2015;
  • The successful testing of a pair of toroidal-field type 68 kA current lead prototypes in July 2015;
  • The successful testing of a pair of poloidal-field/central-solenoid type current leads in 2016;
  • The completion of a Manufacturing Readiness Review in August 2016 (marking the end of the qualification phase).
Series manufacturing is now underway, and the first-of-series for all three types of HTS lead have been completed (see gallery). The fact that manufacturing is proceeding strongly, with only a small number of non-conformities, is a tribute to the thorough qualification efforts as well as the Chinese manufacturers' high level of expertise.

It should also be noted that the Chinese Domestic Agency and the ITER Organization put a supervision framework into place allowing local inspectors to witness critical manufacturing steps. Erwu Niu of the ITER China office now manages at least two inspectors who are permanently stationed at the suppliers' sites in Hefei.

Thousands of documents have already been uploaded to the ITER Organization Manufacturing Database—from material certificates, to personnel certificates and test reports. Documents attesting to the components' performance during testing—for example the final factory acceptance cold test in near-to operational conditions under full current—can be fully verified through the database before the final ITER Organization hold point is released.

At ASIPP, lead engineers Quan Han and Qingxiang Ran are now turning their attention to ramping up the pace of production to meet the ITER schedule. A number of additional pieces of large-scale manufacturing equipment—such as another electron-beam welding machine, insulation curing autoclaves and a third cold test station—are being commissioned to handle the extra load.

This year and next, up to 20 current lead pairs will be manufactured in parallel in by Juneng and Keye for shipment to ITER.

¹The qualification of the HTS current leads in China is summarized in an ITER Technical Report (Reference: ITR-18-001). You can download it on this page.

Vacuum leaks | A whole suite of tools and technologies

ma, 25/02/2019 - 21:24



The Greek philosopher Aristotle (384-322 BC) knew nothing about tokamaks. But when he stated in his famous aphorism that "Nature abhors a vacuum,"¹ he anticipated one of the problems that tokamak designers would face 25 centuries later.
Vacuum occupies a large part of ITER, both literally and figuratively—vacuum volumes are huge and vacuum challenges daunting. Successful plasma operation rests on the quality of the vacuum in the (aptly named) vacuum vessel, but also in the cryostat, the neutral beam injection system, and many other systems.
A vessel under vacuum is submitted to pressure from the external environment ... and the higher the vacuum, the more aggressive is the attack of particles from the environment and surfaces.
Gases and liquids will find the tiniest breach in a structure under vacuum. "A crack the width of a human hair is enough to alter the vacuum quality and halt fusion performance," emphasizes ITER Vacuum Section Leader Robert Pearce. Nature not only abhors a vacuum, it conspires by all available means to destroy it ...
Close to ten years ago, an intense R&D program was started to develop risk-mitigating concepts for leak detection and localization. The Procurement Arrangement that was recently signed between the European Domestic Agency, Fusion for Energy, and the ITER Organization is a direct outcome of this decade-long effort.
Under this agreement, Fusion for Energy will deliver a whole suite of ITER-designed systems and instruments to detect and localize leaks throughout the vast volumes of the vacuum vessel and cryostat, and also in smaller areas such as the neutral beam injectors or the cryopumping systems.
"Basically it's about ensuring the integrity and leak testing the totality of the machine: the 2,000 m³ of the vacuum vessel, the 8,500 m³ cryostat (pumping volumes);  the primary vacuum for the neutral beam, not to mention the tens of kilometres of piping carrying gases and fluids that could leak into these volumes," explains ITER Vacuum Section leader Robert Pearce.
Although the risk of leakage is minimized by design as well as best practices and quality control throughout the fabrication and assembly processes, it cannot be reduced to nil. "There should be no leaks," says Vacuum team member Liam Worth, "but experience tells us that if we achieve this it will be a 'miracle.' To date, all tokamaks, stellarators, particle accelerators, and other vacuum installations of large size and complexity have experienced a certain number of leaks."
Some leaks are "tolerable" but others are not. "There are thresholds," explains Liam. "We can cope with the thermal shield or magnet system leaking a minute quantity of helium into the cryostat. But a leak into the vacuum vessel, whether of air or water, starts to affect plasma performance as the size increases and so cannot be easily tolerated."
Once detected and localized, leaks can of course be fixed, generally by cutting, replacing, bypassing, or isolating the faulty part. In some cases it is relatively easy; in others—for example in the case of a leak occurring in one of the in-cryostat helium lines—it would be a "huge job" to repair, according to Liam.
Among the systems and tools to be procured by Fusion for Energy under the recent Procurement Arrangement is a spectacular device—a self-propelled "in-pipe inspection tool" that can wiggle its way into the smallest and most contorted piping networks (see video) and find its way deep into the cryostat.
Conceptualized by the ITER Organization and developed by Doosan Babcock in Scotland, the working prototype of the articulated tool can propel itself inside pipes no larger than 40 millimetres in diameter, move forward and backward, take a 90-degree turn and, thanks to a tiny video camera and built-in lighting system, provide high-resolution images (better than 0.01 mm) of potential cracks or faulty welds. The device, which is evocative of an ultraminiaturized freight train or an oversized, segmented tapeworm, is equipped with inflatable "bladders" that can isolate and locate leaks in precise sections.
Although basic in-pipe inspection tools are standard in industry for much larger pipes, the articulated tool is unique. "Nothing in the world can do what it does," says Liam. "It's reduced size means, for instance, that 100 percent of the thermal shield manifolds² are accessible for inspection and leak localization."
"With the exception of the drive mechanism, all the prototype tool's components, including motors, are off-the-shelf or slightly modified off-the-shelf," says Liam. "The concept design has been demonstrated but the tool can be significantly improved with the use of bespoke components that are smaller and lighter." This task of improvement will now pass to Fusion for Energy as part of the Procurement Arrangement.
"In the more distant future, with advances in material and electronic technologies, such a tool could be further miniaturized by a factor of 10 and provide an even more powerful tool for leak localization and repair for fusion devices and many others," concludes Pearce.
Achieving and maintaining the required vacuum in the ITER machine is an immense task that the Vacuum Team took on more than one decade ago. As ITER is now gearing up for assembly operations, the team is moving forward with a new set of tools and technologies that potentially enable the localization and detection of leaks smaller than the width of hair divided by one million.
¹-Aristotle couldn't have known that at the atomic scale, Nature—that is, the material world—is essentially made of ... vacuum.
²-A manifold is an arrangement of interconnected pipes. In the ITER thermal shield, the manifolds supply cryogens to the shield's panels.
Read a related story on the Fusion for Energy website.

On site | Drone survey on a perfect day

ma, 18/02/2019 - 18:15

There are days in winter when the skies over Provence are perfectly transparent. Snowy peaks 200 kilometres away appear close enough to be touched and farms, country roads and villages are all revealed in sharp detail.
A drone flying over the ITER site on such days captures every single iron bar, scaffolding tower, or embedded plate in the Tokamak Complex; every insulator in the electrical switchyard; and every component carefully wrapped in green plastic in the site's storage areas.
This new harvest of images from early February also reveals the broader setting of the ITER Project, among the rolling hills and plowed fields along the Durance River valley—a futuristic enclave in an unchanging environment.