The testing of the ITER central solenoid conductors last November in the SULTAN facility produced some puzzling results. In an article that appeared in March, 2011, Nature viewed these results as proof of a "potentially serious problem" that could "further delay" the project.
For Neil Mitchell, Head of the ITER Magnet Division, some of the SULTAN data simply "does not fit with our existing database of conductor behaviour." The issue, he says, may not be about "real quality" but rather the consequence "of an artefact of the samples and of the test arrangement."
Conductor samples tested in SULTAN are exposed to magnetic field, current intensity and temperature conditions that are very close to those of the actual ITER environment—with one important difference. "SULTAN's configuration prevents us from mimicking the strain that magnetic forces exert on the conductor in a coil," explains Neil.
For the niobium-tin (Nb3Sn) superconducting compound used in central solenoid conductors, strain simulation is a crucial parameter in the qualification process. In the SULTAN tests, however, ITER-like magnetic forces can only be applied to a 45-centimetre section of the three-metre-long straight sample. In Neil's opinion, this is what causes "a local unrepresentative strain pattern" and is the artefact that distorts the results of the tests. This supposition has been confirmed by strain gauges placed on the sample.
The SULTAN tests consist of submitting the central solenoid conductor samples to several thousand cycles in order to verify that they will withstand the 60,000 or so current pulses that are anticipated during ITER's lifetime. Neil explains: "We cycled two conductor samples 7,000 times. Results were getting better through the first 100 cycles, then went down to the original level over the following 900 and then continued down. It doesn't make sense to ignore the increase and focus on the decrease. The combination shows that this is not just an irreversible degrading of the conductor under the magnetic forces."
While a program is being implemented to definitively confirm the cause of the SULTAN sample behaviour and also to improve the sample design and data interpretation, another solution exists for discriminating between the probable deficiency in testing methodology and a possible quality issue: the central solenoid insert. This solution consists in inserting a new conductor sample into the central solenoid model coil that was built during the ITER Engineering Design Activities (EDA) in the mid-1990s.
"As we know from the first successful model coil test, the central solenoid insert option would provide conditions that are much closer to reality," says Neil. "The central solenoid insert should be manufactured and tested as soon as possible to confirm the actual conductor performance, benchmarking the SULTAN samples."
It has been agreed that the US Domestic Agency will manufacture the central solenoid insert for testing in Naka, Japan, beginning 2013.
The ITER Organization now faces a difficult decision: since toroidal field conductors face some of the same testing issues as central solenoid conductors, should toroidal field manufacturing be delayed until a reliable quality test is available? And should ITER also wait to initiate central solenoid conductor manufacturing?
"In view of the data already available," says Neil, "which show that the toroidal field conductors have sufficient margin to meet the requirements despite the uncertainty of the test results, ITER believes that it is an acceptable risk to continue with toroidal field production and initiate central solenoid production as soon as we have a sample test where we can separate artefacts from real degradation."
The Legal Affairs Office at the ITER Organization may be only a small shop, but it's a busy one. Any legal issue that arises during the course of ITER activities falls within its responsibility: the Office advises the Director-General, departments and staff members; and represents the ITER Organization for all legal matters.
For Assistant Legal Advisor Anna Tyler, who joined Legal Advisor Harry Tuinder last October, the challenge lies both in the specific legal status of the ITER Organization and in the scientific nature of the project. "As the ITER Organization is a public international organization, it enjoys privileges and immunities in order to ensure its independence. As a result, national laws and regulations do not apply. However, the ITER Organization is committed to observing French laws and regulations in certain cases as provided in Article 14 of the ITER Agreement related to the nature of the project," she explains.
"From a legal perspective," Anna adds, "ITER is a very challenging environment. It is necessary to know all of the basic agreements establishing the ITER Organization in depth, as well as the rules of public international law, and the French laws and regulations that the organization is committed to observe pursuant to Article 14 of the ITER Agreement (see Textbox). It is also necessary to have an overview and understanding of all of its activities."
A typical day for Anna might include a morning spent poring over public international law as she researches a memo on a staff matter, and an afternoon spent in a solicitor's office on issues relating to site access for the company charged with installing electricity on the platform. She concentrates particularly on legal issues relating to the construction site and the implementation of the ITER Organization's Privileges and Immunities.
She enjoys her job because of the diversity of subjects that the Legal Affairs Office is called upon to deal with. "I'm fortunate to work with Harry, who is the encyclopedia for any legal matters relating to the ITER Organization. I feel I'm learning a lot," says Anna. A third Office team member, Maria Mena, is now assisting Harry and Anna with the archiving of documents dating from the early days of the project.
Anna has worked in Paris with the French Atomic Energy Commission (CEA) and with AREVA as a corporate lawyer specializing in nuclear and environmental law. At the ITER Organization, she is pursuing both of those interests, as well as working on other areas of law and enjoying a return to the south of France where she grew up. Raised in a bilingual family—her mother is French and her father, English—and with law degrees earned in France and in Great Britain, she is particularly well suited to the legal challenges faced by the ITER Organization.
In the Legal Affairs Office, files are treated according to urgency, "although, we are also available for consultation before the problem needs urgent attention," Anna stresses. "Our door is always open!"
As a veteran fusion physicist Professor Michael Tendler, who just joined ITER on an "expert" mission, is familiar with the worldwide fusion community; as a professor at the famed Alfvén Laboratory
of the Swedish Royal Institute of Technology and one of the former leaders of the Erasmus Mundus
program, he is concerned with the training of the future generations of fusion scientists.
"I'm a long-timer in fusion," he explains. "I began working in plasma physics in the then-Soviet Union in the late 1960s! After moving to Sweden in 1975, I had the privilege to benefit from the ideas and advice of Hannes Alfvén
, who pioneered fusion research and who was awarded the Nobel Prize in Physics in 1970. At heart, however, I am a professor."
His mission at ITER will be to strengthen the communication channels between the project and the large and scattered family of fusion scientists. "ITER," he stresses, "has been the goal of the fusion community for the past thirty years. The project is like the ultimate crescendo of a symphony that several generations of scientists have built up. Communicating its high notes is important for the spirits of our colleagues throughout the world."
What is important also—and has been clearly stated as part of professor Tendler's mission—is attracting young, talented scientists to participate in ITER activities, and sowing the seeds of the fusion community of tomorrow.
"We have a Master's program in fusion within Erasmus Mundus," he explains, "and over the past six years, we have been able to produce some 20 graduates every year. Now, we're extending this program to the doctoral level. This is an experience that perfectly fits ITER's goals and infrastructure."
A foreign member of the Russian Academy of Sciences since 2003, the Saint-Petersburg-born physicist was elected in 2005 to the Royal Swedish Academy of Engineering Sciences and is now a member of its Executive Committee. Professor Tendler also sits, or has sat, on the Boards of several committees and institutions in countries as different and distant as Australia and Israel, Estonia and China, Belgium and Russia...
To ITER, he brings his expertise of the worldwide fusion community, both in its human and scientific dimensions, and also his long experience in the challenges of science education. His visits to Cadarache will bring him back to a place he is familiar with: in 1990, Professor Tendler spent several months working at the brand-new Tore Supra fusion installation.
Students of the École Internationale de Provence-Alpes-Côte d'Azur are likely to know something about fusion energy. Half of them have parents who work for the ITER Organization and probably grew up thinking that words like divertor, tokamak, cryostat or vacuum vessel were part of everyday speech.
There is a world of difference, however, between "knowing something" about fusion and producing posters and a presentation capable of impressing the jury of a science festival—especially one presided by Bernard Bigot, CEA Administrator General and High Representative for the implementation of the ITER Project in France.
As challenging as it may appear, this is exactly what students of classe de première (11th grade) and of the European section S3 (7th grade) achieved last Friday at the 9th Science and Technology Festival in Marseille.
Their project featured a very detailed and professional presentation on ITER and Tore Supra and explained how fusion would fit into the energy mix of tomorrow.
The jury, composed of prominent scientists awarded them the first prize in the high school category...and a check for 300 euros.
Lycée Georges-Duby of Aix-en-Provence, the other international school in the Aix-Marseille académie; and Lycée Thiers in Marseille, one of the most prestigious high schools in the region, respectively won second and third prize.
One of the students' teachers was quoted in the regional daily La Provence as saying: "The questions asked by the jury were extremely difficult and precise. Some of them, I would have had a hard time answering..."
The pre-compression rings will be one of the most challenging composite structures ever manufactured. Weighing more than 3 tonnes each, they will tightly hold the ITER toroidal field coils from the top and bottom with a radial load of 7,000 tonnes per coil and withstanding hoop stress of 350 MPa per ring.
Ten years of successful R&D performed by the Italian laboratory ENEA near Frascati, under Task Agreements with the European Fusion Development Agency (EFDA), the European Domestic Agency, and direct contracts with the ITER Organization, have recently been brought to a close. The work performed at ENEA by the team of Paolo Rossi identified two suitable fabrication processes for the rings, and developed applicable non-destructive examination methods by x-ray and ultrasound. The Italian team further completed the full mechanical characterization of the glass-fibre/epoxy composite at room and operating temperatures, allowing a final optimization of the ring design, and determined the ultimate tensile stress (UTS) of six mock-up rings (in average over 1500 MPa) in a purpose-designed machine that, with 18 independent hydraulic pullers, simulates the configuration of the 18 toroidal field coils (see related article
The last challenge was to achieve the prediction of the long-term performance of the mock-up rings: this challenge has also been met. Tests on specimens at different constant loads during long periods had allowed the definition of the creep behaviour, however the correlation with long-term tests on the mock-up rings was pending. Early last year a ring was loaded at 950 MPa (65 percent of UTS) with no measurable degradation rate after 210 days maintained at such stress. A new ring was loaded last month at 1100 MPa (77 percent of UTS) and maintained under constant load until rupturing after 140 hours, right between the breaking times of two specimens loaded equivalently.
This accomplishment occurred concurrently with the end of the European Domestic Agency call for tender for the pre-compression rings. It enables our Division to wrap up the technical understanding of the rings' performance before industry enters in the game. The expertise and the purpose-design equipment available at ENEA will continue to play an essential role for industry in the years to come.
In Fantastic Voyage, a 1966 science-fiction movie starring Raquel Welch and Donald Pleasence, a medical team and their submarine are miniaturized to the size of a human cell and injected into a scientist's body in order to operate a blood clot in his brain.
The movie was a huge success, the voyage inside the human body spectacular, and a few scenes—like the attack by the blood's white cells—quite unforgettable.
Last Friday at the CEA Research Institute on Magnetic Fusion (IRFM), a few guests from ITER, Director-General Motojima among them, were treated to a comparable experience—well, almost...
Although retaining their normal size, the visitors were able to virtually enter and explore the innards of the ITER Tokamak, walk through its walls and blanket modules, stand upon the divertor's surface, and observe the machine's every nut, bolt and weld.
This was not science fiction. The virtual reality room that IRFM has just set up in its former library will be a precious tool for design and control activities, as well as a training platform for assembly and maintenance operations.
This brand-new equipment is the work of CEA/IRFM who will use it for design and engineering activities, mainly in relation with Tore Supra, and also within the framework of collaborations established with ITER and, as part of the EU/Japan Broader Approach Agreement, with the Japanese Tokamak JT-60 SA.
The virtual reality room appears as a small and rather spartan 3D theatre—no velvet seats or sophisticated sound system. What makes it special, however, is the type of "movie" it features. For the ITER machine, the 3D images that appear on screen are directly interfaced with the CAD files produced by the Design Office and Design Integration.
Once equipped with 3D glasses, the viewer becomes virtually immersed in the image, whether it be a three-dimensional rendition of a machine component or that of a burning fusion plasma.
Such techniques are not new. Virtual reality is widely used in the automobile and aerospace industries and in other fusion installations like JET or Laser Megajoule (LMJ). What has been added at CEA/IRFM is a capability to connect a physical robotic arm to the virtual objects that appear on the screen.
The robotic arm is manoeuvrable by an operator, and can be programmed to mimic existing industrial counterparts. The operator can thus prepare and rehearse actual remote handling operations.
The CEA/IRFM virtual reality room was financed by CEA through a recent French government "Recovery Plan" (Plan de relance) for research. Half a million euros were invested in the room's design and equipment.
Beginning in 1997, representatives from the ITER Members involved with the design of the ITER divertor came together once a year in order to coordinate their activities. When the divertor design was finally approved in 2008 and the procurement process launched, the need for a coordination forum was no longer felt.
This year, as the manufacturing of the first components has begun, Mario Merola, in charge of ITER's Internal Components Division, decided to revive the forum, with a focus this time on quality and manufacturing issues. Last week—after a four-year break—the divertor group finally convened again in the ITER Headquarters.
One of the issues discussed at the ITER Divertor Meeting was the Procurement Arrangement for the assembly of the divertor cassette body, scheduled to be signed in December with the European Domestic Agency. It will be the fifth Procurement Arrangement for the divertor team and—as Europe, Japan and Russia are involved in procurement—it once again represents a truly international joint venture. "We are now looking at the interfaces, at contact points and tolerances, and common policies, but also at liabilities and customs issues," Mario says.
Before being mounted onto the cassette body, the plasma-facing units of the divertor will be subject to cyclic high heat-flux tests aimed at confirming their performance capability under relevant operating conditions. A new facility, especially dedicated to such extreme heat-flux tests, is currently being built by the Russian Domestic Agency at the Efremov Institute in St. Petersburg. The first component procured by Japan is due to be tested there in October.
Another point on the agenda of the revived forum was the strategy for the design and procurement of the plasma-facing components for the second-generation ITER divertor, which will be needed when ITER moves into the deuterium-tritium phase of operations. "Although this may appear very far in the future...more than 14 years from now," Mario comments, "it is a brand-new project, with physics requirements, design solutions, manufacturing technologies, and procurement organization yet to be defined and agreed. This is a process that will take several years."