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ITER NEWSLINE 179
The 1970s were years of great achievements, both scientific and technological. Men were routinely landing on the Moon, the Concorde had introduced supersonic transatlantic service, and microprocessors would soon trigger one of the major revolutions of the 20th century.
In fusion, too, big things were brewing. The success of the Russians with the tokamak concept in the previous decade had opened new and exciting perspectives.
In the Soviet Union, the US, Japan, and France, plasma physicists were all coming to the same conclusion: they needed far bigger machines, machines that—due precisely to their size and energy-confinement capacity—would reach the threshold of fusion power production.
Results obtained in the Soviet T3, the French TFR, the American Symmetric Tokamak (converted from the C-stellarator) and ORMAC had convinced the fusion community that now was the time to take the Big Leap.
"Going toward a much larger machine was the next natural evolutionary step," recalls ITER Deputy Director-General Rich Hawryluk, a post-doctoral researcher at the Princeton Plasma Physics Laboratory (PPPL) at the time. "There was a great deal of optimism about how quickly we would develop fusion. We didn't know at that time how many outstanding scientific and technical issues remained."
On all continents, in every lab, a similar mood prevailed. Soon giant tokamak projects were sprouting in the Euratom organization, at PPPL, at the Kurchatov Institute in Moscow and at Japan's Atomic Energy Agency.
"We needed to achieve a gigantic leap in scale," recalls Jean Jacquinot, a veteran physicist who joined the CEA fusion program in 1961 and later headed Europe's JET. "We were fascinated with the possibility of building a machine that would actually produce fusion power ... ."
Thinking back on the potential and the challenges of the endeavour, Rich Hawryluk comments: "The machine we were about to design and build was an incredible extrapolation, arguably even greater than the one we are presently facing with ITER."
Fusion machines, throughout the 1960s and 1970s, had been relatively small installations. The size and complexity of the giant tokamaks, however, would require an industrial approach that was not familiar to the fusion community.
It took six years (1976-1982) to build the Tokamak Test Fusion Reactor (TFTR) at PPPL and about the same time (1978—1983) to complete Europe's Joint European Torus (JET) in Culham, near Oxford (UK). In Japan, the boldly named "Breakeven Plasma Test Facility" (later renamed JT-60) began operations in 1985, three years before the Soviet T-15 obtained first plasma. Among these four machines of comparable size, only TFTR and JET were designed to perform deuterium-tritium (DT) operations.
The physicists and engineers who operated these new tokamaks were like 15th century navigators sailing the vast, unchartered seas. "In terms of power, pulse duration, energy confinement time, and confinement of energetic particles, JET, JT-60U and TFTR were opening new territory that had been until then inaccessible," says Jacquinot.
The Columbuses and Magellans of fusion competed as much as they collaborated. "Sure, as you would expect, there was competition," acknowledges Hawryluk, "but it was based on respect for each other."
Personnel would move from one machine to the other. Paul Thomas, now Head of the Heating & Current Drive Division at ITER, arrived at JET in 1980 and was sent to Princeton the following year to take "driving lessons" on the Poloidal Divertor Experiment (PDX) Tokamak. He would later sit on the TFTR Program Committee to review the progress of that American machine.
JET and TFTR routinely exchanged data and feedback. "We kept no secrets from each other. However cultures, philosophies and technical approaches were different," says Jacquinot. "More than anything, what each team brought to the other was a different and stimulating intellectual environment."
Collaboration with the Japanese JT-60 team in Naka was also intense. In 1988, Paul Thomas spent nine months there, sharing his tokamak driving experience with such colleagues as Ryuiji Yoshino, the machine's physics operator, and divertor physics expert Michiya Shimada. Years later at ITER, they would all work side by side again.
JET was first to achieve fusion power on Saturday, 9 November 1991. "Today's experiment," read the official press release, "was the first occasion in which the correct fusion fuels, deuterium and tritium, have been used in any magnetic confinement fusion experiment." Close to 2 MW of fusion power had been obtained in a two-second pulse. "This demonstration," continued the press release, "fully confirms that [...] we will be able to design the experimental fusion reactor ITER."
"We did it 'live', with TV crews present in the control room, which was quite daring," recalls Jacquinot. "The event had a tremendous knock-on effect on the whole fusion community. Its psychological and communication value were exceptional."
JET had achieved fusion with 10 percent tritium only. Two years later, on 9 December 1993, also with massive media coverage and amidst "a great sense of excitement," it was TFTR's turn to make headlines. A 50/50 mix of deuterium and tritium enabled the PPPL machine to produce shots that culminated with 6.2 MW of fusion power produced. Eleven months later, on 2 November 1994, the symbolic 10 MW threshold was crossed.
The "friendly competition" was not over. In 1997, JET launched a campaign of what Jacquinot calls "actual DT plasmas" whose most spectacular achievement was not the one that is most often mentioned. "The 16 MW shot of 1997 was spectacular indeed, however we did it mainly to beat TFTR's 1994 results. What really mattered in the 1997 campaign were the 5-second 4 MW stationary shots we did in H mode, because these shots are the basis for extrapolation to ITER."
If 1997 was a great year for JET, it was a sad one for TFTR. "From mid-1993 to 1997 we ran continuously, night and day," recalls Hawryluk. "People were publishing at a wonderful rate." However due to budgetary constraints, in 1997 the machine was stopped.
Hawryluk remembers, "We took it apart as part of decommissioning and examined it. After 15 years of intense operation at and above design requirements, everything still looked very good."
TFTR personnel went on to work for DIII-D in California, C-Mod, JET and JT-60U or stayed at PPPL to develop the National Spherical Torus Experiment (NSTX), a fusion installation that reused part of TFTR's hardware.
"What we set out to do in the 1970s was largely accomplished," says Hawryluk today. "The machine had been unbelievably successful. Not only did we produce significant fusion power and demonstrate that we could conduct tritium experiments safely, but more importantly we extended our understanding of fusion plasmas including the confinement of alpha-particles from the D-T reactions."
At JET, by the end of the 1990s, "the identification of alpha-particle heating and the studies of alpha-particle plasma interactions completed the program," recalls Paul Thomas. "It was then admissible to move on to activities that had not been anticipated in the Design Document of 1975."
The European tokamak, upgraded with a new divertor, now pursues what remains as its principal mission: being a test bench for ITER, particularly in the realm of ELMs, plasma disruptions and—thanks to a new ITER-like wall—plasma-surface interactions. A year and a half ago, JET Director Francesco Romanelli confided to Newsline that "a deuterium-tritium experiment is envisaged to allow extrapolation of the scenarios to ITER-relevant conditions."
Lighting the fusion fire in both TFTR and JET had required more power than the fire eventually returned. With an input/output energy ratio (the famed Q) of respectively 0.27 and 0.67, the two machines remained below the breakeven threshold. (Progress in fusion science, technology and materials now enable the fusion community to aim for Q=10 in ITER.)
Q, however, was not the only measure of success: two decades ago, JET and TFTR demonstrated that fusion energy could become a reality within the foreseeable future. Both machines had opened the way to ITER and future industrial fusion installations.
On 26-27 May, over 60 scientists met at the Karlsruhe Institute of Technology (KIT) in Germany to discuss the use of high temperature superconductors (HTS) in future fusion magnets, for example those that will be needed for DEMO. In a series of presentations, the status and prospects of HTS materials for future fusion magnets was reviewed.
Gianfranco Federici, head of the recently formed EFDA Department on Power Plant Physics & Technology (PPP&T) gave an overview of technical challenges on the path to DEMO and the strategy of EFDA on power plant physics and technology, followed by a talk that targeted the challenge for superconducting magnets in fusion.
In dedicated sessions the basics of HTS, the status of highly optimized HTS material fabricated by industry, and details of HTS materials at 50 K in the field range up to 20 Tesla were presented. Ideas and first demonstrators of scalable fusion conductor designs and possibilities for joint formation were shown and issues like mechanical and electrical stability, AC loss optimization and influence of neutron radiation on HTS were discussed.
The workshop allowed for valuable scientific exchange on the use of HTS material for future fusion magnets. The advantages of this material are numerous: HTS reaches the highest magnetic fields with a sound temperature margin and stability; it allows for savings in the investment and operation cost for cryogenics; and simplifies machine design by omitting cryogenic shielding.
The presentations of the workshop can be found under http://www.itep.kit.edu/hts4fusion2011.
On the day the ITER Tokamak realizes its first controlled deuterium-tritium (DT) burn, Ryuji Yoshino hopes to be there, hand on the helm. "It is a challenge for all mankind to get this to work," says Ryuji. "Realizing controlled DT burning for a new source of energy has been my personal target and dream for many years." As Senior Officer for Machine Operations at ITER, Ryuji will call upon tokamak expertise acquired over thirty years, first as a specialist in control systems then as physics operator, and finally as project leader.
Ryuji will coordinate machine and plasma operation issues during the construction phase, in particular central instrumentation and control (I&C), interlock and safety systems, and plasma operations. He'll begin with overseeing the development of a safety control system for ITER operation. "Creating a 'barrier' for safe operation of ITER involves interfacing with many other systems," says Ryuji. "To this task, I bring the point of view of both a plasma physicist and a machine operator."
Following a degree in electrical engineering and a PhD in plasma physics, Ryuji began his career in 1980 at the JT-60 Tokamak in Japan during its design and construction phase. He worked on the supervisory control system (the equivalent of ITER's CODAC system) for plant control, discharge control, plasma real-time control and the interlock system. Following the machine's first plasma in 1985, Ryuji concentrated on feedback control of the plasma as well as plasma equilibrium and plasma shaping.
From 1987 to 2000 he was the physics operator of JT-60 and JT-60U, operating the machines to realize a wide variety of experiments, using equipment such as poloidal field coil power supplies, gas puffing, pellet injection, neutral beam injection, and electron and ion cyclotron heating—all of which will be part of the ITER machine. "My experience is in how to drive the initial phase in order to get the best plasma. There are many techniques to do this...many parameters to manage," explains Ryuji.
He proposed machine upgrades at JT-60U to improve performance, including the installation of the electron cyclotron resonance heating system, the modification of plasma shape in order to increase its triangularity, and the adjustment of electrical connections to the poloidal field coils for increasing efficiency of the discharge cleaning. He was also able to demonstrate, for the first time in the world, a fast plasma current shutdown using impurity pellet injection (also called 'killer pellet injection).
Ryuji became skilled during this phase of his career at coordinating machine operators and researchers to identify and implement experimental targets, and forging consensus to ensure successful experimental results. "In my experience," he explains, "it is very important that the plasma physics people and the plant system people work closely together for successful operation of the machine. Constructive relationships make a lot of difference."
In 2007, he stepped naturally into the shoes of JADA Leader, taking over the implementation of Japanese in-kind procurement responsibilities to ITER. "Responsibilities of the past years have taught me that it's important to have a well-defined target that is understood by all, a common vision, and a similar spirit for a project to be successful. I hope to apply these principles in my area of expertise at ITER.
Since his arrival in early May, Ryuji has been settling—slowly—into his new life in France. "Everything is drastically different here!" he exclaims. "On my first night, without the help of a friendly restaurant owner, I may never have found my lodgings...But every day I am excited to come to work. To have seen ITER move from Conceptual Design Activities to construction is wonderful. To me, it's like a miracle!"
The knowledge and skills gained during the course of his career in Japan make him uniquely suited to the task at hand. Getting just the right parameters for plasma operation at ITER will require mastery of control systems, plasma physics operations, and leadership. Few can say, as Ryuji, that they have worn all three hats.
The communication staff from the ITER Organization and the Domestic Agencies meets twice per year in order to define ITER's communication strategy. Last week, the international team once more got together in the ITER Headquarters in Cadarache to swap ideas and to define new strategies. Exchanging information about manufacturing going in the Member states is becoming an ever-greater part of our world-spanning communication efforts, as well as the production of high quality photo and video material in order to document the project's progress.
In addition to reports given by the representatives from the Domestic Agencies on ITER-relevant matters, the head of communication at EFDA, Petra Nieckchen, joined the meeting in order to present new communication strategies within the European Fusion Associations. On the subject of EFDA's outreach activities, Tomaž Skobe from the Jožef Stefan Institute in Ljubljana, Slovenia, gave a very colorful run-through of the Fusion Expo, a travelling fusion exhibition. Another means of increasing public awareness is the Fusion Roadshow, a stage performance featuring the fascinating science of fusion. Gieljan de Vries from the FOM Institute for Plasma Physics Rijnhuizen, Netherlands, travelled to Cadarache to present this entertaining way of communicating fusion.
The construction of the winding facility for ITER's poloidal field coils is making visible progress. The insulation works and the metal sheet cladding of the outside walls is almost completed; now it is time for the utilities to be installed.
The pumps for component cooling water are already in place and in the pipework assembly area, impressive regulating valves dominate the scene. Still stored in a special unit, the air filters for the rooftop air-handling system are waiting for their installation. On Tuesday this coming week, the big crane that will move the coils and their components within the facility is scheduled to arrive on site.
The ITER vacuum vessel will have 18 upper, 17 equatorial and 9 lower ports to allow access to the plasma for diagnostic, heating, pumping systems and maintenance. Welded "lips" made out of 2 mm thick stainless steel will seal the port plugs and confine the ultra-high vacuum inside the vessel.
In order to develop the appropriate cutting and welding techniques for the lip, the ITER Organization launched an R&D project together with the Finnish company VTT called the "Lip Seal Project." This week, the first two mockups arrived at the ITER site. They were manufactured at the VTT facility using a robotic arm especially adapted to the port's high-vacuum and nuclear environment.
The laser welded mockup successfully passed the tests for qualification and leak tightness, which was a big milestone for Bruno Levesy, the responsible engineer, and the team from VTT.
Click here to watch the movie on the Lip Seal welding technology produced by VTT.
The manufacturing of ITER's toroidal field coils will require a total of 450 tonnes of superconducting niobium-tin (Nb3Sn) strands. Such a large amount has called for a significant ramp-up of the world production capacity which was estimated around 15 tonnes per year before the start of ITER. The in-kind procurement of the Nb3Sn strands for ITER's magnets is shared among six Domestic Agencies (China, Europe, Japan, Korea, Russia and the US) who have selected a total of eight different suppliers.
Sharing the manufacturing of such a critical component among so many partners is of course quite a challenge. All suppliers are required to implement similar quality assurance and quality control programs in order to ensure that the strands produced all around the world meet the same technical requirements. The web-based Conductor Database developed by the ITER Organization enables the ITER Organization and the Domestic Agencies to closely monitor the ongoing production.
Two of the six Domestic Agencies, the European Agency F4E and US ITER, have selected a common supplier. Oxford Superconducting Technology (OST), located in Carteret, New Jersey, has been awarded contracts for the production of about 60 tonnes of Nb3Sn strands for F4E and approximately 10 tonnes for the US counterpart. To facilitate the work and encourage synergies, all partners agreed to rely on a common strand design and to keep each other informed about the progress made. This synergy was further enhanced through a common meeting organized at OST where all partners reviewed the status of production.
"Our involvement with ITER has been both challenging and rewarding," says Jeff Parell, vice president at OST. "The quantity of strand required by ITER has allowed OST to create more than 60 new jobs, and we now work to produce Nb3Sn strands on an around-the-clock basis. The ITER technical and quality requirements are comprehensive and, as a result, our internal process and quality controls have been strengthened. OST and our parent company, Oxford Instruments, are both proud to be associated with a project of this importance in globally advancing the knowledge of fusion energy."
As illustrated in the picture, OST is now about to proceed with the shipment of its first deliverables to Europe.
On 27 May, a group of Chinese civil servants from Wenzhou, Yiwu, Haining and Zhejiang, who are studying public management at the University Paul Cezanne in Aix-en-Provence, visited the ITER worksite. After a presentation of the project's stakes and challenges, the acting Head of Directorate for General Administration, Shaoqi Wang, was happy to answer their questions, which dealt to a large extent with the international nature of the ITER collaboration.