The way is now open

ITER site, 5:25 a.m. on Friday 20 September. The moon is high and, despite a sleepless night, so are the spirits. The huge trailer with its load of concrete blocks that replicates the size and weight of ITER’s most exceptional components—800 tons in all—has rolled to a stop.

Among those present at that early hour there’s a feeling of relief and a deep sense of accomplishment: the operation was a complete success.

Arriving on schedule and with only one minor incident the test-convoy has demonstrated the conformity of the ITER Itinerary with the rigorous technical specifications of ITER’s most exceptional loads. The way is now open for the delivery of the actual components of the ITER Tokamak.

The journey had begun four nights earlier on the shores of the Étang de Berre, a small inland sea connected by a narrow channel to the Mediterranean. The self-propelled trailer, accompanied by a large escort of support personnel, vehicles, technical experts and gendarmerie motorcyclists got off to a start at around 9:45 p.m.

_To_60_Tx_The setting in Berre was reminiscent of a village fair: complete with lights piercing the night, an exhibition tent (set up by Agence Iter France, the organizers), a large crowd of onlookers of all ages and the feeling of excitement that exceptional events generate.

Although local inhabitants are accustomed to the passage of exceptional convoys for the steelworks and refineries of the region, they had never seen such a monster: 46 metres long, 9 metres wide and 10 metres high, as heavy as two fully loaded Boeing 747s.

Combined with its escort of men and vehicles, the convoy formed a „sealed pocket” more than one hundred metres long, slowly progressing along public roads and some stretches of dedicated track and crossing the A7 and A51 motorways in four different locations. Measurements were made all along the 104-kilometre journey to verify that the stresses caused to the roads, bridges and roundabouts agreed with engineering calculations.

Parked in a secure area during the day, the convoy progressed night after night at speeds varying from 5-15 km/hour. It crossed three times over every bridge (backing up and going over them again) in order to take the required measurements. It is estimated that some 2,000 people came out along the different stages of the Itinerary to watch the passage of the ITER test convoy.

_To_62_Tx_Although it will take several weeks to process and analyze all of the data that was collected over four nights, it was already clear on Friday morning that the reality was in near sync with the calculations—all measurements fell to within a few percentage points of what had been predicted.

The fourth and last leg of the journey was by far the most spectacular: the convoy had to negotiate the narrow main street of Peyrolles, cross the A51 motorway in order to bypass the tunnel of Mirabeau, weave along the road through Saint-Paul-lez-Durance and, last but not least, climb the steep incline of the heavy-duty track leading to the ITER platform (A tractor was attached to the trailer, adding 500 hp of pulling power).

At 4:45 a.m. on Friday 20 September, the convoy arrived at the last roundabout at the entrance of the ITER site. It took another 40 minutes to reach the parking area between the on-site concrete batching plant and the Cryostat Workshop worksite.

_To_61_Tx_As soon as the ignition key was turned off, two large cranes took position at its side to prepare for dismantling operations. By the following Monday, all 360 concrete blocks had been unloaded and the disassembly of the 88-axle vehicle was well advanced.

The successful conclusion of the test convoy operations bring to a close some eight years of preparation, from the first Itinerary feasibility studies to the final adjustments last year.

More images on the arrival of the ITER test convoy.

Read the Press Releases in English and French.

Watching from above

Anyone travelling in France on vacation or long weekends has heard of Bison futé, a name inspired by American Indian culture that translates as „Cunning Buffalo.”

Bison futé is the national gendarmerie-run service that provides real-time information on traffic conditions, road safety and driving restrictions in France.

Last week, the Bison futé command centre for the southeast quarter of French territory, located in Marseille, was busy with a very special mission: monitoring the ITER test convoy as it slowing progressed along the ITER Itinerary.

Every night, as the convoy was readied for yet another leg of the journey to the ITER site, a group of five to six people representing the French authorities (Préfecture), the gendarmerie forces and Agence Iter France prepared for another sleepless night.

As they sat in front of an array of computer screens and radio equipment, the members of this small „ITER cell” had a unique and privileged view on the ongoing operation, some 60 kilometres away.

„Actually, we are the only ones who have a global vision,” says Colonel Geneau of the gendarmerie. „We are connected by radio and telephone with all parties involved. Geolocalization devices on the convoy vehicles provide us with real-time information on convoy progression and we even have infrared images from a helicopter hovering high above the convoy…”

Watching the video stream from the helicopter is particularly impressive: it’s like viewing the negative of a black-and-white movie, where people appear as greyish silhouettes and the hot engines of the trailer as intense white. (The helicopter’s usual routine is to track offenders or missing persons).

In case of an incident, the ITER cell’s „global view” would enable Colonel Geneau to activate the proper response. „We, too, are testing our organization in advance of the actual transport of ITER components,” he says.

A peep into the future

Last week, 16-20 September, the fusion community convened in Barcelona, Spain for the International Symposium on Fusion Nuclear Technology (ISFNT). More than 750 participants gathered at the Palau de Congressos to be brought up to date on developments in the field of fusion technology and materials and on the construction of ITER—the „symbol and example of global cooperation to tackle a global energy problem,” according to Pere Torres, Secretary of Enterprise and Competitiveness of the Generalitat de Catalunya, as he opened the symposium.

The ISFNT is recognized as one of the main international gatherings on fusion energy with a clear focus on reactor-relevant technology. In its 11th edition last week, the symposium took a close look not only on the current state-of-the-art technology related to ITER, but also dared to look forward to the possible design, requirements and safety aspects of future DEMO reactors and power plants.

The road forward, it seems, is not yet clearly delineated. Different concepts were presented; some countries, like China, seem to even have more than one iron in the fire. Complementing these discussions, a special fusion Roadmap Panel—moderated by prominent fusion representatives—tried to narrow down the key issues on the way to a fusion reactor.

Dedicated workshops addressed future reactor-relevant technologies such as ceramic breeder blankets or the treatment of beryllium; a half-day industrial workshop was set up to provide companies with updated information on the current procurement status of ITER and forthcoming opportunities; no less than 161 posters gave lots of opportunity to exchange and connect. And this is what the ISFNT is all about. In the words of Pere Torres, „This event contributes to the collaboration amongst researchers and allows for the sharing of knowledge.” 

The conference closed with a presentation by South Korea as host to the next ISFNT from 14-18 September 2015 on the island of Jeju.

The Spanish contribution to ITER

Spain’s relationship with ITER is especially close as the city of Barcelona hosts the European agency Fusion for Energy, which manages the European contribution to the Project.

Spanish research centres—led by CIEMAT and in cooperation with other European partners—play a crucial role in ITER by contributing to the development of diagnostic systems, plasma heating components, test blanket modules, and control and data acquisition systems.

The Centre for the Industrial and Technological Development (CDTI) promotes the participation of Spanish industry and acts as a focal point between companies and ITER. For Spanish industry, ITER is a unique opportunity to develop cutting-edge technologies, but also an occasion to foster commercial products in industrial areas outside fusion energy. This cross-fertilization will contribute to the scientific and technological progress in the coming decades.

Since 2008, Spanish companies have earned an increasing number of contracts for ITER, with a peak in 2012. According to the latest estimates, Spanish industry has won over EUR 400 million in contracts in a highly competitive market, with many opportunities for participation ongoing. Spanish industrial capabilities cover a wide range of technological areas, making it possible to participate in the fabrication of many ITER components such as the vacuum vessel, magnets, buildings, test blankets modules, plant systems, in-vessel components, remote handling, safety, instrumentation and control and CODAC, to name but a few.

Spanish companies have also won important contracts in other fusion facilities such as the European tokamak JET, TJ-II (CIEMAT) and W7X (Germany) and have taken on significant challenges in the supply of components for the Spanish in-kind contributions to the Broader Approach projects IFMIF-EVEDA and JT-60.

Many of the developments for ITER and fusion projects have been made in collaboration with other European industries either through consortia or through the supplier chain, showing that the effort for fusion is really framed inside a wide European dimension.

Work begins to extend ITER Headquarters

In less than one year the capacity of ITER Headquarters will have increased to about 900 desks, from 550 currently, following the award of the extension construction contract signed in July with a French consortium (Vinci). Drilling to investigate the soil and rock of the land parcel near the west end of the ITER Headquarters, where the 35-metre extension will be added, began last week.

The extension will provide much-needed additional space for the ITER Project team: projections show that during the peak of construction there will be more demand for offices than can be accommodated in the current ITER Headquarters building or existing pre-fabricated structures.

Work should progress rapidly on the extension once the worksite has been secured and temporary contractor offices are in place. During the month of October, excavation and levelling operations will begin. Foundation pouring will be carried out in November and December and—beginning early in the new year—the structure of the five-storey building will rise at the rate of approximately one level every three weeks. The entire building will be standing in May 2014.

The design and plans for the 3,500 m² extension were provided by the firm of local architect Rudy Ricciotti, who was the principle in the team that conceived the original project—the 20,000-square-metre Headquarters that was handed over to the ITER Organization in October 2012. The tender offer launched in March by the ITER Organization was concluded on 26 July with the award of the contract to Travaux du Midi/Dumez Méditerranée (Vinci).

From the exterior, the extension will look like a carbon copy of the original, although important cost-saving measures were put into place to respect the strict budget. Employees with desks in the new extension will take the last elevator in the main building to arrive at their offices (there will be no elevator in the extension, although the space for an elevator shaft will be maintained on the exterior of the building in case it becomes necessary to add this feature in the future). Choices were also made on the finishing materials that resulted in important cost savings.

The priority during the tendering and negotiation phase for this contract was to respect the budget and the schedule. The EUR 7.5 million budget for the extension (which includes the design, construction and the addition of an extra parking level in the main ITER lot) will be offset by charging existing and future contractors who use office space in the ITER buildings. 

Employees will notice changes to their work environment in the weeks and months to come. The tall fence that will be erected around the extension building site will reduce the road in front of Headquarters to one lane, with alternating traffic lights for the shuttle buses that travel between office buildings. Also, the large bay windows that terminate the west-end corridors in the main Headquarters building will soon be replaced by solid walls, with soundproofing to reduce construction noise.

„Clauses were negotiated into the contract to make noise reduction a priority on this worksite,” says Erwan Duval, Facility Management Officer. „We have some latitude—for example the loudest operations can be scheduled before the arrival of employees in the morning. We are also fortunate that the heaviest works will be over by the time windows are opened again next spring.”

The completed extension is planned for delivery in July 2014.

Pellet injection advances to next stage in the US

Researchers at the Oak Ridge National Laboratory (ORNL) have developed a continuous extruder for fusion fuel and are advancing state-of-the-art fuelling and plasma control for ITER. Reliable, high-speed continuous fuelling is essential for ITER to meet its goal of operating at 500 MW for several minutes at a time.

The latest pellet injection experiments using US ITER prototype designs were performed during the week of 22 July at the DIII-D Tokamak operated by General Atomics in San Diego, California. The conceptual design review for the ITER pellet injection system was completed earlier this year, and preparations are now underway for full-scale prototype testing.

The task of the pellet injection system is to provide plasma fuelling, while also lessening the impact of plasma instabilities due to large transient heat loads. The ITER pellet injectors must operate continuously, which is very different from most existing tokamak pellet injectors. The ITER machine also requires a higher rate of pellet fuelling throughput.

According to Dave Rasmussen, team leader for the US ITER pellet injection and disruption mitigation systems, „The ITER pellet injectors will require an increase in the deuterium-tritium mass flow and duration by a factor of 1,000 compared to present systems.”

To produce the pellets, researchers developed a twin-screw extruder which shapes a continuous ice stream of deuterium-tritium fuel into specific diameters and lengths.

„There are existing extruders used on tokamaks today, but they cannot meet the requirements of ITER. On most current installations, extruders have only needed to supply a few seconds of fuel pellets at a time, but the ITER Tokamak will require almost an hour of a continuous ice stream for pellet injection. The ORNL twin-screw extruder is designed to meet the requirements of ITER,” notes Mark Lyttle, a project engineer for the US ITER pellet injection and disruption mitigation systems.

Multiple pellet injectors will be installed on the ITER Tokamak, with up to two injectors at each of three locations on the machine. Some locations will be used more for fuelling while others will be deployed for lessening the impact of plasma instabilities known as edge localized modes (ELMs) by a technique called pellet ELM pacing. The pellet injector can also insert impurity pellets made of argon, neon, or nitrogen into the Tokamak for plasma impurity studies. The pellet injectors must also be able to handle tritium, a radioactive isotope of hydrogen with a half-life of about 12 years, safely.

„There is a 30-year technology development history at ORNL behind the ITER pellet injection design,” says Lyttle.

Under testing now is a 1:5 scale pellet twin-screw extruder. „We do plan to build a full-scale prototype and test it at the Spallation Neutron Source cryogenic facility at ORNL, where we have access to a supply of supercritical helium. Supercritical helium at only 5 degrees above absolute zero is used as the coolant to form the pellet ice and we are lucky to have one of the few facilities in the world that can supply our needs here at ORNL,” says Lyttle.

Other key upcoming activities for researchers and engineers are tests of a propellant gas recirculation loop for the pellet injection system using a tritium-compatible vacuum pump. The recirculation loop supplies the pressurized propellant gas and assures that the gas used to accelerate the pellets is not injected into the vacuum chamber of the ITER Tokamak during the fuelling process.

„Initial tests on the pumping speed look promising,” observes Lyttle. This pump has been tested with helium gas and soon will be tested with hydrogen gas. Ultimately, the pump and loop will undergo a multi-year „lifetime” test to assure its readiness for the ITER pellet injection system, where 99.9% availability is required.

For the original article and more news from US ITER, click here.

Successful test of the ITER Itinerary

The ITER Itinerary test convoy, featuring an 800-metric-ton trailer replicating the weight and dimensions of ITER’s most exceptional loads, has successfully completed its four-night journey, arriving at the ITER construction site at 4:45 a.m. on Friday 20 September.

The 46-metre-long trailer, with its dummy load of 360 concrete blocks, was escorted by a large squadron of police officers and followed by support vehicles and technical personnel. It had completed the journey from Berre L’Etang near the Mediterranean Sea to the ITER site over four nights.

Large-scale public works were carried out by France as Host to the ITER Project along the 104 kilometres of the ITER Itinerary between 2008 and 2011 to widen roads, replace or reinforce bridges and modify intersections in preparation for the exceptional size and weight of some of the ITER components.

The test campaign was conceived to monitor key points along the Itinerary. Measurements collected as the convoy passed over bridges and negotiated its way through towns and intersections will be carefully analyzed in the weeks to come. But already, the Itinerary has demonstrated its conformity with the rigorous technical specifications of ITER’s most exceptional loads.

Organized by Agence Iter France in close collaboration with French authorities; implemented by ITER’s global logistics service provider DAHER; and financed by the European Domestic Agency for ITER, Fusion for Energy, the test mockup simultaneously replicates the largest and the heaviest of the actual loads that will be transported for ITER: 600 metric tons (plus the 185-metric-ton trailer), 33 metres long, 9 metres wide and 10 metres tall.

For the ITER Organization—responsible for the construction and operation of ITER—the successful arrival of the Itinerary test convoy is a major milestone.

Read the full Press Release in English and in French.

A flying "squirrel" over the ITER worksite

Over the past few years, the ITER worksite has been photographed from a helium balloon, a glider, a small airplane, a crane…

Last Friday, the French gendarmerie helicopter that took the ITER Director-General on a flyover of the ITER Itinerary (an Ecureuil AS 350 B, or Squirrel) provided another opportunity to capture the spectacular vista of the ongoing construction works.

The monster that pulled people out of their homes

The passage of an exceptional convoy is a common sight for the inhabitants of the villages of Berre, Rognac, La Fare-les-Oliviers or Lambesc. The area, close to the harbour in Marseille, is heavily industrialized: steelworks, refineries, the aircraft industry … all depend on the delivery and expedition of large-size loads that travel the roads to the general indifference of the local population.

It takes something really exceptional to pull people out of their homes, old and young alike, and bring them to the roadside to ogle and gawk.

On Monday night, 16 September, the 352-wheel, 800-ton trailer mimicking an actual ITER convoy did just that. As it commenced its four-night journey between Berre and the ITER site in Saint Paul-lez-Durance, hundreds of people were lined up along the roads, some of them in nightshirts and pyjamas, to watch the long procession of men and vehicles slowly advance along the first stage of the 104-kilometre ITER Itinerary.

The event, which aims to monitor the behaviour of roads and bridges under the extreme ITER loads, was the culmination of five years of hard work and complex calculations by the French public roads administration and the technical services of the Bouches-du-Rhône département. As ITER Deputy Director-General Rem Haange explained prior to the departure of the convoy, „The ITER Itinerary is essential to the project. It is the indispensable link between component fabrication in the factories of the ITER Members and the assembly of the machine by the ITER Organization.”

It was around 10:00 p.m. when the convoy, organized by logistics service provider DAHER, left its parking area in Berre. Night had fallen one hour earlier and the headlights of the trailer, accompanying vehicles and gendarmerie motorcycles contributed to the eerie atmosphere—the monster had awakened and was ready to take to the road.

Its first stop, two hours and five kilometres later, was at the railroad bridge in Rognac, the first of the 35 bridges that dot the Itinerary. The bridge had been equipped with a whole array of sensors to measure the deflexion of the structure under the strain of the convoy. Calculations had anticipated some 32 mm of deflexion, measurements yielded 30 mm.

The test convoy will continue another three nights to the ITER site. As it progresses along the Itinerary, the measurement operations will be repeated at every bridge. Manoeuvring space and operational margins will also be checked at every turn and roundabout. Processing the accumulated data will take about one month and a half, but early on Tuesday morning, Pierre-Marie Delplanque, the man in charge of overseeing operations for Agence Iter France, was satisfied … and relieved.

„We had a couple of very small issues,” he said, „and in two or three places we can still make small improvements. However we did not identify any major obstacle and I do not anticipate any issue when the actual convoys are organized.”

The convoy arrived in a secure zone in the village of Lambesc at 5:45 a.m. Tuesday, 16 September. Operations resume on Tuesday night at 9:30 p.m., when the convoy will take to the road again and—following the same pattern of measurements—will proceed another 15 to 20 kilometres.

The test convoy is expected to arrive at ITER in the wee hours of the morning on Friday 20 September.

View more photos here.
View local (LCM-Marseille) and regional (France 3) public TV coverage in French.

A 30-minute flyover of the Itinerary

Last Friday, under a transparent late-summer Provençal sky, ITER Director-General Osamu Motojima boarded a French gendarmerie Ecureuil helicopter and flew south to reconnoitre the ITER Itinerary.

After a few minutes of stationary flight over the ITER platform for photographs (see this issue’s Images), the three-passenger craft headed along the Durance River Valley to the Pont de Mirabeau, where heavy works were carried out to widen the road and replace the retaining wall dating from 1934 in advance of the passage of ITER convoys.

The helicopter then travelled on to the village of La Roque d’Antheron, before turning south towards Berre L’Etang, point of departure for the test convoy.

And there it was! As the helicopter flew over the salt marshes that surround Berre, the passengers got a quick glimpse of the 352-wheel vehicle loaded with concrete blocks that was being readied for its maiden voyage.

The invitation to flyover the ITER Itinerary was courteously extended by General David Galtier, head of the PACA region gendarmerie. It enabled the Director-General to take in the concrete reality of the Itinerary and the striking beauty of the Provençal landscape in the last days of summer—a half-hour flight that included a vision of the snowy peaks of the Alps, the bald summit of Mont Ventoux, the sparkling Mediterranean coast, and the urban sprawl of Marseille.

MAM has a word to say

There is a procedure for everything…and certainly more than one when it comes to building the world’s largest fusion device. One of the procedures established within the ITER Organization is the Model Approval Meeting (MAM), in which the design descriptions for critical components pass the final check before they are turned into hardware.

The 3D-viewer room on the neighbouring premises of CEA Cadarache has become a regular meeting spot for ITER engineers over the last weeks and months. On one morning in late August, about a dozen ITER staff working on the central solenoid, the centrepiece of ITER’s magnet system, have come together to review the compatibility of the detailed 3D CAD model provided by US Domestic Agency with the rest of the Tokamak. This model, developed by US ITER at Oak Ridge National Laboratory on the basis of the functional specifications provided by the ITER Organization, reflects the final design proposed by the US after feedback from industry and manufacturing trials.

The turn-to-turn spacing of the solenoid conductor had apparently been too tight to be guaranteed by the industrial manufacturer. The solution on the table, proposed by US ITER, is to extend the winding gaps by reducing the inner radius. The impact of this solution is the focus of the discussion.

Jens Reich, coordinator of Tokamak design integration and leader of the meeting, asks the 3D-room operators to overlay the original Configuration Model developed by the ITER Organization with the detailed model they have received back from the US.

A few seconds later, through their 3D-glasses, observers saw a real-size, down-to-the-detail central solenoid unfold on the screen in front of them. What impact would the changes have? And what about the margins at the perimeter—would they still allow for the assembly of this supersized magnet? The central solenoid will be lowered into the machine at the very end of the assembly process, a procedure that doesn’t leave much flexibility for manoeuvring.

The last word about the design of the central solenoid will have to wait until the Final Design Review planned for 18-20 November this year. „But this 3D-check is a very helpful tool to verify the details of a component and to identify any potential interface issues to be solved,” explains Jean-Jacques Cordier, leader of the ITER Design Integration team, before he and his colleagues put their glasses on again to look at the next client, the support structures for the poloidal field coils. 

Ministerial representatives reaffirm the importance of ITER

Convening on 6 September for a meeting at ministerial level in Saint Paul-lez-Durance, France, high-level representatives of the seven ITER Members acknowledged the progress achieved in the construction of one of the most complex scientific and engineering projects in the world today, the ITER international collaboration for fusion.

Ministerial representatives reaffirmed the importance of fusion for the world’s energy future and stressed the importance of the ITER experimental device as an indispensable step on the path to the development of fusion energy—a virtually limitless and environmentally benign energy source. The participants also emphasized the role played by the ITER international partnership in defining a new model of worldwide scientific collaboration.

Read the full press release in English and in French.
See the first photos from the meeting here.

Who’s got the biggest?

At ITER, we don’t brag. But we do like to mention the exceptional dimensions of the machine we are building: the ITER Tokamak will indeed include components that, in their category, are by far the largest in the world.

In talks and presentations to the public it has become routine, for instance, to assert that the ITER cryostat will be the largest high-vacuum chamber ever built.

But recently, a young postdoc attending a presentation on ITER at the Institute of Plasma Physics in Prague took issue with this claim. It’s NASA’s Space Power Facility, the student said, that holds the blue ribbon for the largest high-vacuum chamber.

Located in Sandusky, Ohio (USA), the Space Power Facility was built in 1969 to create an environment comparable to that encountered in deep space, on the Moon or on planet Mars. It comes complete with high-vacuum, extreme cold (down to minus 195°C) and solar radiation simulation.

NASA has been using the facility for more than four decades to expose rocket components, space capsules, landing vehicles and satellite hardware to the harsh conditions of outer space. Its futuristic setting has also inspired movie makers: in 2012 the opening sequences of the blockbuster The Avengers were filmed there.

The cylindrical vacuum chamber is 30 metres in diameter and 37 metres in height—bigger, it’s true, than the 29.4 x 29 metre ITER cryostat. There is however an important difference between the two: while the aluminium Space Power Facility’s test chamber is spectacularly empty (after all, rocket stages have to fit in) the steel ITER cryostat is a very crowded place.

In ITER, because of the volume occupied by components such as magnets, support structures, the thermal shield and the vacuum vessel itself, the pump volume inside the cryostat—that is, the total volume of the chamber minus that of the components—is reduced to 8,500 cubic metres. At the NASA facility, it is almost three times larger (23,500 cubic metres).

In order to achieve high vacuum up to 10-6 Torr, one millionth time more tenuous than the Earth’s atmosphere, both installations use mechanical roughing pumps to go down to ~ 0.1 Torr, and then cryopumps to achieve the required high vacuum. While NASA’s installation can achieve high vacuum in 8 to 12 hours, the ITER cryostat will require about twice this time.

„However, the two systems are quite different," notes Matthias Dremel, an engineer in the ITER Vacuum Section. „The ITER cryostat contains thermal shields cooled to 80 K that act as pumps by condensation of the gases. What’s more, the magnets behind the thermal shield, cooled to ~4K, also act as pumps by condensation.”

Because these components are extremely cold, they significantly contribute to removing the impurities that remain in the chamber. Atoms, molecules and particles are all captured by cold surfaces: the more intense the cold … the more irresistible its holding power.

In the ITER cryostat and in NASA’s Space Power Facility we have two high vacuum chambers of approximately the same size but the latter, however spectacular, is but a big empty aluminium cylinder. The ITER cryostat, on the other hand, is a highly complex structure that must remain absolutely leak-tight despite the thousands of lines and feed-throughs that penetrate it for cryo, water, electricity, sensors, etc.

So it’s a NASA win (but not by much) when it comes to size, but when it comes to complexity—the ITER cryostat remains unchallenged by far.

Three cities, two Procurement Arrangements

During the week of 26 August, ITER Director-General Motojima travelled to Russia, visiting three cities and signing two Procurement Arrangements in four days.

Accompanied by Deputy Director-General Alexander Alekseev, head of the Tokamak Directorate, the ITER Director-General began his trip at the Institute of Nuclear Physics in Novosibirsk, where he signed the Procurement Arrangement for Equatorial Port 11 Engineering, for the engineering of diagnostic systems into vacuum vessel Port 11. The Budker Institute will be responsible for the scope of work.

The Budker Institute already plays a key part in the development of high-tech electron equipment, engineering of diagnostic systems into the vacuum vessel ports, and research into the investigation of high-temperature plasma impact on reactor’s first wall materials as well as developing, manufacturing, and testing equipment for the ITER machine.

According to the Head of the Russian ITER Domestic Agency, Anatoly Krasilnikov, equipment development for ITER’s plasma diagnostics engineering will take five to seven years and will require constant interaction with the ITER Project’s other partners. In all, the Budker Institute will develop five engineering systems for ITER’s vacuum vessel ports.

The delegation from ITER also visited the Institute of Applied Physics and the enterprise GYCOM in Nizhniy Novgorod, where gyrotron component manufacturing and assembly are conducted as well as the development of infrastructure equipment such as cryomagnetic systems, measurement and technological devices, and part of the energy sources required for the gyrotrons. Procurement of the ITER gyrotrons is a matter of special pride to the Institute of Applied Physics, because it was here that this device was invented. More than half of existing experimental fusion facilities in the world currently use gyrotrons from Nizhniy Novgorod.

The final destination stop was in Moscow. At Project Center ITER (the Russian Domestic Agency for ITER), Director-General Motojima signed the Procurement Arrangement for the Thomson Scattering diagnostic system, one of 21 systems that Russia will deliver to ITER before 2024.

Manufacturing milestone achieved in Europe

The first step in the fabrication of the full-size, superconducting prototype of a toroidal field coil double pancake has been successfully carried out in Europe. Winding was completed at the beginning of August at the ASG premises in La Spezia, Italy.

The European Domestic Agency, Fusion for Energy, is responsible for procuring ten toroidal field coils (and Japan, nine). These D-shaped coils will be operated with an electrical current of 68,000 amps in order to produce the magnetic field that confines and holds the plasma in place. Toroidal field coils will weigh approximately 300 tons, and measure 16.5 m in height and 9.5 m in width.

Each one of ITER’s toroidal field coils will contain seven double pancakes. These double pancakes are composed of a length of superconductor, which carries the electrical current, and a stainless steel D-shaped plate called a radial plate, which holds and mechanically supports the conductor through groves machined on both sides along a spiral trajectory.

The first stage of toroidal field coil manufacturing—the winding of the double pancakes—is the most challenging. It consists of bending the conductor length along a D-shaped double spiral trajectory. As the conductor must fit precisely inside the radial plate groove, it is vital to control its trajectory in the double pancake and in the groove of the radial plate with extremely high accuracy. The trajectory of the conductor, in particular, must be controlled with an accuracy as high as 0.01 percent.

For this reason, the winding line employs a numerically controlled bending unit as well as laser-based technology to measure the position and the dimensions of the conductor. The winding takes place in an environment with a controlled temperature of 20 °C +/-1 C, at an average speed of 5 m of conductor per hour.

For the European commitments to ITER, a consortium made up of ASG (Italy), Iberdrola (Spain) and Elytt (Spain) will manufacture the full-size, superconducting prototype as well as the production toroidal field coil double pancakes in the future.

The next steps in the manufacturing process are: heat-treatment of the double pancakes at 650 °C in a specially constructed inert atmosphere oven, electrical insulation; and finally the transfer of the double pancakes into the grooves of the stainless steel radial plates. After assembly and the application of electrical insulation on the outside of the radial plate, the module is finally impregnated with special radiation-resistant epoxy resin to form the prototype double pancake module.

Work on the module is scheduled to be completed by the beginning of next year, in time to allow for the prototype to be tested at -77 K in order to assess the effect of the low temperature. The module will then be cut in sections in order to analyze the impregnation of the insulation.

Read the detailed article on the F4E website here.

Burning the candle at both ends

A significant Procurement Arrangement was concluded recently between the ITER Organization and the Japanese Domestic Agency for four key diagnostic systems for ITER.

The Divertor Impurity Monitor is a window to the operation of the divertor, monitoring impurity flows and allowing the optimization of operation. Divertor Thermography gives a detailed view of the heat load profile of the divertor targets—a key diagnostic for the protection of divertor components. Edge Thomson Scattering is used to measure the temperature and density profile of the edge of the ITER plasma, providing useful information in the study of the confinement properties of the plasma edge and for the optimization of fusion performance.

And finally, the Poloidal Polarimeter will measure the plasma current density across the plasma cross-section (the current profile). The details of this profile affect stability and heat transport in the core and must be carefully measured and adjusted to achieve ITER’s long pulses.

The signature represents a key milestone for both the Japanese Domestic Agency and the ITER Organization, and an important milestone for the project schedule. The long-distance coordination of the Procurement Arrangement signature went smoothly—the document was first signed by ITER Director-General Motojima, before being transported half way around the world by courier to be signed by T. Oikawa, the Director of International Affairs, Japan Atomic Energy Agency (JAEA).

There were several late nights and early mornings for the teams in both France and Japan. „It’s true that the candle had to be burned at both ends in order to achieve the tight schedule,” commented Diagnostic Division Head Mike Walsh, „but it was worth all the effort in the end.”

Kiyoshi  Itami, the Plasma Diagnostics Group Leader in Naka, added, „I am very pleased to get this critical phase in the project completed and I thank everyone involved for the good collaborative approach to get to this stage.”

Now the Japanese Domestic Agency is busy with the next stages in cooperation with the ITER Organization and in further involvement with industry.

A huge caterpillar of men and machinery

It’s a short ride for an automobile, but it’s a long, slow haul for a 352-wheel vehicle carrying an 800-ton load.

It is also a very complex and delicate journey. Organizing the test convoy that will travel the 104 kilometres of the ITER Itinerary during the nights of 16-20 September has required a tremendous amount of planning and coordination.

The Itinerary is a EUR 112 million contribution from France to the ITER Project.

In order to bring about the test convoy, an „enormous technical, administrative and regulatory machine” had to be fine-tuned, according to Pierre-Marie Delplanque, a former French navy Admiral , who is in charge of overseeing operations along the ITER Itinerary for Agence Iter France.

In addition to the two main actors—Agence Iter France and logistic services provider DAHER—planning has involved coordinating dozens of authorities representing four départements, government agencies, specialized technical services and local governments.

This four-night campaign of tests and measurements aims at verifying that the loads—and the stresses they cause to the roads, bridges and roundabouts of the ITER Itinerary—agree with engineering calculations. Such a test operation merges the rigor of methodical scientific survey with the challenges of the Highly Exceptional Load (HEL) convoys that will deliver the largest and heaviest ITER components to the site.

As the test convoy progresses from the shores of the Étang de Berre towards the ITER site in Saint Paul-lez-Durance, hundreds of measurements will be taken: manoeuvring space and operational margins will be assessed, stress on the bridges will be appraised and triple-checked, and behaviour of the transport trailer will be closely monitored.

The test convoy has been sized to mimic the most taxing parameters of the most exceptional ITER convoys: heaviest (it will be made of 360 concrete blocks, for a total of 800 tons), longest (33 metres), largest (9 metres) and highest (10.4 metres). (Of course, during the delivery of ITER components no single load will cumulate these dimensions.)

Although a „dress rehearsal” will be organized in the coming months, the convoy will also provide an opportunity to test part of the logistics that will be involved in the actual HEL convoys.

The September convoy, like the 230 convoys that will be spaced over five years for ITER, will travel in a „bubble” containing some 20 vehicles and stretching more than 100 metres along the road.

The 46-metre-long trailer carrying the dummy load will be preceded by French gendarmerie motorcycles, a pedestrian gendarmerie escort leader, guiding motorcycles, a pilot car transporting the Head of Convoy and an emergency tractor to pull the trailer in case of engine breakdown. The transport trailer will be followed by a rear-escort as well as an assistance van and further gendarmerie motorcycles. Additional personnel and vehicles will be mobilized to remove the traffic signs before and after the passage of the convoy.

When actual operations begin, in June 2014, the elite Garde Républicaine motorcyclist, flown down from Paris, will seal the „bubble” that encapsulates and protects the convoy—exactly as it does every summer when the Tour de France travels some 3,500 kilometres throughout the French provinces…

The passage of such a huge caterpillar of men and machinery, hauling a load whose weight is equivalent to two Boeing 747s filled to capacity, will certainly attract large crowds of onlookers. Two dedicated areas have been organized along the Itinerary to accommodate the public.

For the local residents, it will be the first, spectacular, contact with ITER. But as roads are closed, albeit temporarily and only at night, this first convoy may also be perceived by some as a nuisance.

Some 86,000 people live in the small towns and villages located along the ITER Itinerary. And because approximately 200 kilometres of detours will have to be organized to divert regular road traffic (not mentioning the temporary closing of the thruway on two locations), several thousands more will be impacted.

This is the challenge within the challenge: the operation will also be a test of how the local population reacts to the convoys that will become a regular (almost weekly!) fixture for the five years to come.

Melting tungsten for a good cause

Over the past two years ITER physicists and engineers, along with many scientific colleagues within the fusion research community, have been working to establish the design and physics basis for a modified divertor—the component located at the bottom of the huge ITER vacuum vessel responsible for exhausting most of the heat and all of the particles which will continuously flow out of ITER’s fusion plasmas. 

Our current Baseline begins plasma operations with divertor targets armoured with carbon fibre composite (CFC) material in the regions that will be subject to the highest heat flux densities. After the initial years of ITER exploitation, in which only hydrogen or helium will be used as plasma fuel producing no nuclear activation, this divertor is to be replaced. The replacement—a variant of the first component but fully armoured with tungsten—would be the heat and particle flux exhaust workhorse once the nuclear phase, using deuterium and then deuterium/tritium fuel, begins.

In 2011 the ITER Organization proposed to eliminate the first divertor and instead go for the full-tungsten („full-W”) version right from the start. This makes more operational sense and has the potential for substantial cost savings. By June 2013, the design was at a sufficiently advanced stage and we were confident that the necessary tungsten high heat flux handling technology was mature enough to invite external experts to examine our progress during the full-W divertor Final Design Review

But making a choice to begin operations with tungsten in the most severely loaded regions of the divertor is not just a question of having a design ready to build. 

Tungsten, a refractory metal with high melting temperature (3400 Celsius), is a much more difficult material than carbon when it comes to handling very high heat loads and running the plasmas which ITER will require to reach good fusion performance. Why? For two principal reasons: as a metal, tungsten will melt if the heat flux placed on it is high enough; also, as an element with high atomic number it can only be tolerated in minute concentrations in the burning plasma core.

Carbon, on the other hand, does not melt but sublimes (passing directly from solid to vapour) and is low atomic number, so can be tolerated in much higher quantities in the core plasma. Unfortunately, carbon is a difficult option for ITER nuclear phase operations as a result of its great capacity for swallowing up precious tritium fuel and efficiently trapping it inside the vacuum vessel. Tungsten retains fusion fuel only at comparatively low levels.

Why is melting such a problem? Because a melted metal surface is no longer the flat, pristine surface which is installed when the component is new. One of the ways the ITER divertor is able to handle the enormous power flux densities which will be carried along the magnetic field lines connecting to the target surfaces is to make the target intersect the field lines at very glancing angles, so that the power is spread over a wider surface. But a small angle means that any non-flat feature on the surface will receive a higher-than-average heat flux and can be further melted, producing a cascade effect.

The ITER full-W divertor design goes to great lengths to make sure that there is no possibility—on any of the many thousands of high heat flux handling elements—of an edge sticking up (for example, as a result of mechanical misalignment) that could overheat and begin to melt under the relentless bombardment these components receive during high power operation. However ITER’s size means that it will have the capacity to reach a value of stored energy in the plasma more than a factor of 10 higher than the largest currently operating tokamak, JET (EU). When some of this energy is released in a rapid burst (for example due to very transient magnetohydrodynamic events such as ELMs), some melting is possible—even if all edges have been hidden by clever design.

We intend to stop this happening as much as possible by applying ELM control techniques, but occasional larger events cannot always be excluded. So one of the big physics questions we have tried to answer over the past two years is: what exactly happens when a burst of energy, sufficient to melt tungsten, strikes our divertor targets?

Until recently we had only rather complex computer simulations with which to establish the physics design specifications. One of the main worries was not just that energy bursts could roughen up and damage divertor component surfaces, but that the very rapid melting induced by the burst could lead to the expulsion, or spraying, of micro-droplets of tungsten back into the plasma leading to intolerable contamination and a decrease in performance.

The computer simulations say this shouldn’t happen, but the process of melt ejection is so complex that experiment is the only sure test. But how to test the behaviour under conditions which only ITER can create? Well, as far as tokamaks are concerned, the only place where this was even conceivable was at JET, in which natural ELM energy bursts can be generated at levels similar to those expected for controlled ELMs in ITER. The problem is that these comparatively benign transients will not melt a tungsten surface!

In an experiment proposed and planned jointly between JET and the ITER Organization over the past two years, a small region of one of the full-W modules in the JET divertor was carefully modified to create a situation which every divertor designer would do anything to avoid—a deliberately misaligned edge.

The JET divertor modules are made up of about 9,000 small tungsten plates („W lamellas”), bound together by a complex spring loading system. The lamellas are only 5 mm wide and about 60 mm long with 1 mm gaps between neighbouring elements. For the experiment, a few lamellas were machined to make a single element stand up out of the crowd, presenting an edge of about 1.5 mm on average to the plasma in one of the hottest zones of the divertor.
The result: reassuringly unsurprising! Although there was some evidence suggesting the occasional ejection of very small droplets from the melted area, there was very little impact on the confined plasma. As the ELM plasma bursts repetitively melted the edge of the misaligned lamella, the molten material continuously migrated away from the heat deposition zone, accumulating harmlessly into a small mass of re-solidified tungsten (see video at left, courtesy of EFDA-JET). The JET plasmas with 3 MA of plasma current were able to produce ELM plasma pulses very similar to the lowest amplitude events we need to guarantee for 15 MA operation in ITER—a fact which makes the experiments very relevant from a plasma physics point of view.

Much more analysis is required to see how the results can be matched quantitatively by simulation, but the observations are clearly in qualitative agreement with theory. That’s the most reassuring part: that physics codes used to assist in component design for ITER tomorrow can be validated on experiments performed today. We will have to wait another year now for the damaged lamella to be retrieved from JET before the full picture of these important experiments can be completed, but this is already extremely valuable physics input for the important decisions coming up later this year with regard to our divertor strategy.