In order to climb the face of steep cliffs, mountain climbers use a clever device, invented in the 1950s, called a "rope ascender." Also known by its brand name Jumar, the device can be compared to a mechanical hand that can slide up a rope but that is prevented from sliding down by a locking clamp.   A similar mechanical principle was used, last Thursday 10 September, to lift the steel roof structure of the ITER Assembly Building. Since April, construction contractors had been assembling the 730-tonne structure on the ground to be lifted as one piece.   Centimetre by centimetre, over the course of 14 hours, 22 hydraulic jacks hoisted the huge structure along thick steel cables that hung from support structures fixed temporarily to the top of the pillars, 60 metres above the surface of the building's basemat.   The operation had to be carried out with extreme care. The structure, measuring 60 metres long and 25 metres wide, had to be precisely positioned between two rows of vertical pillars, with a tolerance of only a few centimetres on each side.   It began with a mere 20 cm lift in the morning of Wednesday 9 September, followed by precise laser metrology to measure potential deformation of the steel structure. By Thursday morning, all systems were go, the wind below the 11 metre per second safety limit and the 50-metre lift could commence.   The successful lift operation had a high symbolic value for the ITER Project. "It is here, in the antechamber of the Tokamak Complex, that the main components of the ITER Tokamak will be prepared and pre-assembled," explained ITER Director-General Bernard Bigot in the short speech he gave prior to cutting the ribbon. "Without this building there would be no assembly, and without assembly there would be no machine and no project..."   The ceremony was broadcast live to the ITER staff assembled in the Headquarters amphitheatre and by video feed to the ITER community throughout the world.   The construction milestone demonstrated, once again, the value of close collaboration between all project stakeholders. Under the authority of the European agency for ITER (Fusion for Energy), more than a hundred workers, engineers and technicians worked in shifts for the success of the operation.   "The months and years to come will continue to demand effort and dedication from all of us," said Director-General Bigot, "but we are all conscious of working for one of the greatest ventures in the history of mankind, one that could change the course of our civilization..."   As the ribbon was cut, 500 ITER-yellow and European-blue balloons slowly ascended to the top of the structure and out to the clear sky. The "house" now has a roof and the ITER family is impatient to move in.

When it's up and running, the ITER fusion reactor will be very big and very hot, with more than 800 m³ of hydrogen plasma reaching 170 million °C. The systems that fuel and control it, on the other hand, will be small and very cold. Pellets of frozen gas will be shot into the plasma—some to keep it fuelled, some to manage plasma activity, and some to extinguish the plasma as needed. The idea of using frozen pellets to fuel a magnetic fusion reactor is not new. Researchers with the Fusion Materials and Nuclear Systems Division at Oak Ridge National Lab (ORNL) have been working on the technology for 35 years. Their handiwork helps run fusion experiments across the world, including America's largest fusion reactor, the DIII-D tokamak operated by General Atomics in San Diego, California. Their expertise also made them the right choice to take on the much more challenging job of controlling ITER, which is more than eight times larger than the largest fusion reactor now in existence. "The pellets are much more efficient at fuelling the fusion plasma because they can penetrate fairly deep into the hot plasma before being ablated and ionized into additional plasma," explained Larry Baylor of ORNL's Plasma Technology and Applications Group. "The alternative method of injecting gas that is primarily used in today's smaller devices will not add fuel efficiently in ITER because of its large size and high magnetic field." Baylor said his group is working on three types of pellet, which he refers to as fuellers, ticklers, and terminators. Continue reading the article on the ORNL website.

The plasma-facing components of the ITER divertor will be exposed to a heat load that is ten times higher than that of a spacecraft re-entering Earth's atmosphere (10-20 MW per square metre). To ensure the performance and manufacturability of these critical components, qualification activities on the ITER divertor targets (inner vertical target, outer vertical target, and dome) have been underway for years.   The European Domestic Agency, responsible for procuring the divertor inner vertical target, has concluded multiple framework contracts for the fabrication of qualification prototypes. Work will be conducted in two phases: the pre-qualification phase, during which small-scale prototypes will be manufactured and tested in order to validate manufacturing technologies, and a second qualification phase (for those companies whose mockups pass the first phase) for the fabrication of full-scale inner vertical target prototypes.   Two French consortiums (ALCEN-ATMOSTAT and CNIM-TPI) and the German firm Research Instruments have joined the already approved contractor Ansaldo Nucleare (Italy) in a bid to pre-qualify as European Domestic Agency suppliers.   For the European Domestic Agency, contracting with different suppliers not only ensures competition, but also contributes toward mitigating technical risks through the development of different technologies. "We are working to find the right compromise," says Patrick Lorenzetto, project manager for Europe's in-vessel team. "We need enough companies for the pre-qualification stage in order to have enough competition when we then get to the qualification stage."   With the framework contract signatures now in place, the companies will have approximately 18 months for the manufacturing of the small-scale inner vertical target mockups.   Read the full story on the European Domestic Agency website.