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ITER NEWSLINE 273
Remote handling is never easy, but in the ITER machine it will be particularly difficult. Narrow entry ports, space constraints, poor visual contrast between the different components, limited options for camera placement ... all will combine in ITER to create an exceptionally demanding environment.
"In remote handling, lighting and viewing are vital ingredients," explains David Hamilton, the engineer in charge of the remote handling control systems at ITER. "And yet during ITER machine maintenance, camera placement will be very limited and visual obstacles will be everywhere. As for lighting, we will have to bring in our own sources, which will also be quite limiting."
Although ITER will not be the first tokamak to rely on remote handling, the machine's characteristics generate some unique challenges. "In JET for instance, a 300-kilo antenna is considered an exceptional load to handle. In ITER, we go up to 40 tonnes ..."
3D models and virtual reality can help solve some of the difficulties—both are quite useful for having an overview of the environment. "But there's always an error margin," says David. "You can't trust them for the last 20 or 50 millimetres because, after a certain period of operation, the machine's components will have moved and shifted slightly from the position recorded in the model."
A new innovative technique called "synthetic viewing," although not completely mature, looks like a promising alternative. "Synthetic viewing is based on the combination of data from the model and of data acquired and updated in real time by sensors, like cameras. It allows you to generate your own version of the view from an optimal angle and with optimal contrast and lighting. Based on the data stored in the model, you can 'see through' the obstacles that are blocking the camera."
In Holland, ITER NL—a consortium of Dutch laboratories and industry established in 2007 to promote participation in ITER—had done some exploration in this direction. In August 2012, the consortium was commissioned by the ITER Organization to assess the feasibility of synthetic viewing and to develop a system prototype. In February, this prototype was successfully demonstrated at the Petten nuclear research centre (see video).
"Synthetic viewing is still a speculative technology," warns Hamilton. "For the moment, ITER is an end-consumer with an interest in the area... However, it is important to stimulate research because we will need such a system in ten years' time."
The largest obstacle that stands on the way to a perfectly efficient synthetic viewing system is computer power. "The problem is data calculation. A one-tenth of a second delay between what you capture on the viewing system and what is actually happening with the remote-handling device is the maximum tolerable. For the moment, computer systems are too slow to do object recognition and accurate localization within this time delay. But I'm confident these possibilities will evolve along with the calculation algorithms..."
Synthetic viewing systems of the future could also support more radiation-tolerant and lower cost acquisition devices, such as ultrasonic sensors.
Now that a prototype and an impressive self-explanatory video have been produced, the next step for Hamilton and the remote handling specialists at ITER is to "stir up interest in synthetic viewing" amongst the ITER European and Japanese Domestic Agencies who will procure the machine's remote-handling systems and components. "I'd like to think," says Hamilton, "that by acting together we'll be able to fund more research. There's a huge market there ..."
For ITER, the stakes are considerable. A swift, precise and reliable remote-handling system will reduce the length of the machine shut-down phases and largely contribute to optimizing overall operation costs.
Watch the ITER NL video on synthetic viewing here.
Across the river from Philadelphia, in the industrial suburb of Camden, New Jersey (US), manufacturing of the ITER drain tanks has begun at the Joseph Oat Corporation. Thick stainless steel plates are being welded and will soon be formed into cylinders—the largest nine and a half metres high and more than six metres in diameter, capable of holding over 227,000 litres of water.
Procured by the US Domestic Agency, the drain tanks will be installed in the "basement" (level B2) of the Tokamak Building, ready to collect the water from the cooling circuits in case of leaks or accidental situations.
Because the ITER drain tanks fall into the category of "Safety Important Components" (SIC), the ITER Organization must ascertain that manufacturing processes and procedures meet the safety requirements established by French nuclear safety regulations and, specifically, the August 1984 Quality Order (Arrêté Qualité).
"As nuclear operator, it is our responsibility to control that this set of regulations is applied throughout our whole chain of contractors and suppliers," explains Joëlle Elbez-Uzan, acting division head for Nuclear Safety, Licensing & Environmental Protection at ITER.
An important point at this stage in the manufacturing process is to make sure that the tanks' stainless steel is not exposed to pollution from carbon. Exposure to carbon could cause corrosion, which would put at risk the required leak-tightness of the tanks.
In Camden, Joëlle and Safety Control Section Leader Lina Rodriguez-Rodrigo noted with satisfaction that a specific "ITER zone," clearly separated from other production and using specific tooling, had been organized within the factory.
Joëlle and Lina's sojourn at Camden was short (two days) but fruitful. "The 1984 Quality Order is well implemented," says Joëlle. "US ITER has done a great job in propagating its requirements down the whole chain of contractors and they have a permanent representative in the factory we visited. For us, it is a very strong guarantee."
The Camden inspection was part of the annual audit program that ITER Safety, Quality & Security Department submits for approval to the ITER Director-General. One other inspection has already been performed this year on vacuum-vessel manufacturing in Korea; next on the agenda are the fast-discharge units, whose fabrication has begun at the Efremov Institute in Russia.
Thirty years ago, on 25 June 1983, the Joint European Torus (JET) came to life with a flash of plasma. "There was an air of hushed expectancy as the countdown for the first plasma attempt progressed," remembers Phil Morgan, then an optical spectroscopy specialist who had joined the project the year before. "A suppressed gasp was heard as on one of the TV screens the machine appeared to tilt when the magnetic field was switched on—then loud laughter as people realized that the field was distorting the image recorded by the TV camera."
This anecdote and many others were shared on 24-25 June as JET and ITER personnel, connected by video link, assembled to commemorate the event that, 30 years ago, opened a new era in the history of fusion.
In the ITER Council Room, where some 25 former members of JET's staff had gathered around the head of ITER's CODAC, Heating & Diagnostics Directorate, Paul Thomas, and at Culham, where participants were hosted under a tent, participants remembered with equal emotion the intensity of the peak plasma current that was achieved on that day and the taste of the minestrone soup prepared by the wife of Franco Bombi, then head of JET's Control and Data Acquisition System.
To Paul, and many others who now are part of the ITER team, JET provided "invaluable experience." Thirty years after its first plasma and two decades after its first burst of fusion power on 9 November 1991, "JET is the key device to resolve many of the challenges that we are facing," (Mike Walsh, head of Diagnostics); "Its input is critical for our commissioning plan," (Ken Blackler, head of Assembly & Operations); "It continues to deliver important results that provide direct input, even today, in our design decisions," (Günther Janeschitz, Engineering Officer).
The posters decorating the conference room at Culham for this two-day celebration read: "30 years of JET — Paving the way to ITER's take-off." ITER Director of Plasma Operation David Campbell, who made the trip to JET, stressed this important mission in his speech, broadcast live: "JET provides substantial training for those who will operate ITER."
More coverage on the EFDA website.