Through a technical collaboration established between the ITER Organization and the UK Atomic Energy Authority (UKAEA) in 2017, the UKAEA's centre for Remote Applications in Challenging Environments (RACE) is designing and planning mockup trials that will allow ITER's remote handling team and system owners to verify that component designs are well matched with the maintenance capabilities of the project.  Remote handling has an essential role to play in the ITER Tokamak. When nuclear operation begins, it will be impossible to make changes, conduct inspections, or repair any of the machine components in the activated areas other than by remote handling.   Components requiring maintenance or replacement will be removed through the cask and plug remote handling system and transferred to the Hot Cell Complex, where an array of bespoke, multipurpose tools will be in place to perform the required handling operations, such as lifting, rotating, tilting, fastening/unfastening, and cutting/welding of pipes.   However, the complexity of maintenance operations over a wide array of systems and components—coupled with the risk that even a small hitch can have grave consequences for the continuity of machine operations—increases the importance of testing the maintenance solutions foreseen in the system designs before the components are tendered out for manufacturing. The ITER Organization is planning a mockup facility on site—the ITER Maintenance Test Facility—from 2022 onward, but what about the next five years?   That's where the UKAEA's RACE facility lines up as a strong match for ITER's needs.   Created in 2014 by the UKAEA at the Culham Centre for Fusion Energy (also home to the JET tokamak), RACE is already supporting a number of industry-led partnerships that are developing specific remote maintenance tasks for ITER. Teams there have the experience that comes from years of designing and operating JET's remote handling systems, and they are already thinking ahead to the remote handling challenges that will have to be overcome in the step after ITER, DEMO.   Equipment is already on order for the first task: verifying the maintainability of ITER diagnostic port plugs. The generic equatorial port plug (GEPP) test stand will allow operators to simulate basic vertical insertion operations (pictured) as well as more complex cooling pipe and fastening operations. "There are real advantages to having a single facility with advanced capabilities and extensive experience to run a series of mockup tests for us over the next five years," stresses Spencer Pitcher, head of ITER's Remote Handling & Radioactive Materials Division. "Sharing best practice across a number of tasks, reusing common equipment for multiple mockups, and finally migrating specific structures and hardware back to ITER's on-site test facility at the end of activities makes this an efficient and cost-effective solution for all stakeholders."   According to the terms of the collaboration, RACE will test and evaluate remote handling system designs, and conduct remote handling trials of generic and specific maintenance tasks in order to demonstrate the feasibility of remote handling tasks and provide operational feedback to the system designers.   The first task is already underway: verifying the maintainability of the ITER diagnostic port plugs. These stainless steel plugs—measuring 3 metres in length and weighing up to 50 tonnes—will seal the openings (or ports) of the vacuum vessel. Port plug maintenance in the Hot Cell Facility will require the vertical handling of heavy loads, tilting, and the removal/insertion of diagnostic shield modules to tight tolerances—all operations that will be tested on a specific mockup in the RACE experiment hall.   Since early this year, the design of the mockup stand has been advancing in close collaboration with ITER experts in diagnostic port plugs and remote handling. The detailed design of a generic equatorial port plug (GEPP) mockup and remote handling tooling has now been transferred to industry for fabrication and the first trial tests are expected in approximately four months. RACE will provide the handling capabilities that are representative of the ITER Hot Cell refurbishment cell assembly/disassembly zone, including overhead crane, telemanipulator arms and other tools.   "When it comes to perfecting a remote handling process, fine details can make the difference between success and failure," explains remote handling engineer David Hamilton, who coordinates the collaboration with RACE. "And even with today's powerful computing techniques, in the end only physical modelling can give that final verification."   Implementation agreements are already at an advanced state of preparation for two other tasks, relating to planned maintenance activities for the neutral beam cell and port cell interspaces (vacuum flanges), and the feasibility of cutting and welding the small bore pipes that provide cooling to the diagnostic first wall.  

They work like tailors, carefully taking measurements and cutting immaculate fabric with large pairs of scissors. But they're not making a white three-piece suit. The workers are busy insulating turns of conductors for the first ring magnet to be produced on site.   The ITER Tokamak comprises six ring magnets (poloidal field coils) ranging from 8 to 24 metres in diameter and weighing between 200 and 400 tonnes. Four of them are too big to be manufactured off site and shipped and will be produced by Europe in the Poloidal Field Coils Winding Facility—the largest facility on the ITER platform.   Poloidal field coils are made of six to nine circular conductor arrangements (called "double pancakes") that are insulated, resin-impregnated, stacked together and compressed.   Following the fabrication of a real-size dummy, workers have now wound and insulated the first of the eight double pancakes needed for poloidal field coil #5 (PF5), a coil that measures 17 metres in diameter and that—when finished—will weigh 340 tonnes.   Prior to the manual insertion of fiberglass material between the turns, a large tape dispenser automatically wraps the conductor with five layers of insulating material. The first production double pancake has been placed in a staging area so that additional activities can be carried out (the addition of terminations, the brasing of the intra-pancake joint, and additional insulation) before it passes on to the resin-impregnation phase. In the meantime, back at the winding table, the fabrication of a second double pancake has already started. Before being wound into turns with specific dimensions, the conductor is wrapped with insulating tape.   It takes five layers of fiberglass-kepton bonded tape and a last layer of glass tape at first go; later on, an extra layer of fiberglass will be inserted in between the turns to ensure the "primary insulation" of the double pancake. Resin-impregnation under vacuum (the next fabrication stage) will guarantee the perfect electrical insulation and mechanical resistance of the pancakes and hence, of the whole coil.   In November, a dummy winding will be used to qualify the impregnation tooling and processes before the first impregnation operation is carried out on a "real" double pancake. Elements of twin impregnation stations are being assembled and welded now.   The beams for the new gantry crane, capable of lifting the final coils, have been assembled. Equipped with powerful hydraulic towers, they will be installed inside the facility in the coming weeks. Further down the manufacturing line, workers are also preparing the final stacking station, where the eight double pancakes of PF5 will be placed one on top of the other and joined, and the station where the full coil assembly will undergo impregnation.   Finally, four bright red hydraulic towers and dozens of crates filled with lifting equipment await assembly at the far end of the building. These elements are part of a powerful new gantry crane, capable of lifting the final coils, which will be installed in the coming weeks.

Experiments in the Korean tokamak KSTAR in 2017 achieved record-length periods of ELM suppression by the application of three-dimensional magnetic fields with internal coils, which is the same approach for ELM control in ITER.   Edge localized modes (ELMs), which can occur during high-performance operation mode (H-mode), expel bursts of energy and particles from the plasma. The energy released can cause erosion in surrounding material, with potential impact on the lifetime of plasma-facing materials.   The new KSTAR results demonstrate the robustness of the ELM control scheme adopted for ITER. They have also provided interesting information regarding the influence of the effects of the plasma shape on the robustness of this scheme for its practical application in ITER.   In addition, robust ELM suppression has been obtained in KSTAR with 3D magnetic fields with one and two symmetry periods  in the toroidal direction (n = 1, 2) over a range of plasma currents and toroidal fields, whose ratios corresponds to the expected range for long-pulse operation in ITER (burns of 1,000 to 3,000 seconds). This indicates that there might be more flexibility regarding the shape of the 3D magnetic field that needs to be applied for ELM control in the ITER long-pulse scenarios than previously considered.

The cryostat vessel body of the JT-60SA tokamak has been successfully manufactured and pre-assembled at a factory in Spain, and will soon be transferred to the JT-60SA site in Naka, Japan, for final installation.   This large containment vessel, formed from 12 sectors, will provide thermal insulation and a vacuum environment around the machine's magnet components.   The JT-60SA tokamak is part of the Broader Approach agreement signed between Japan and Euratom, and implemented by QST Japan and the European Domestic Agency for ITER. It represents an upgrade of a previous tokamak at the Naka facility, designed to support the operation of ITER and to investigate how best to optimize the design and operation of fusion power plants built after ITER. First Plasma is planned for 2020, at the end of a six-year assembly and commissioning period.   The cryostat vessel body has been procured as a voluntary contribution to the Broader Approach Agreement by Spain (through its national fusion research centre CIEMAT) and manufactured by Asturfeito, S.A. Once assembled in Japan, it will be capped by a top lid procured by QST.

Just a short distance from the ITER site, the Institute for Magnetic Fusion Research (IRFM) is modifying the Tore Supra plasma facility which, once transformed, will become a test platform open to all ITER partners—the WEST project (acronym derived from W Environment in Steady-state Tokamak.) This summer, WEST's high frequency antenna spent one month in Titan's punishing environment—the last and most severe of its trials before being integrated into the refurbished CEA-Euratom tokamak Tore Supra.   The component is one of three identical antennas that will deposit an ITER-relevant heat load of 10 MW per square metre on WEST's tungsten divertor.   Titan (Testbed for ITer ANtenna) is a 17.5-cubic-metre vacuum vessel that can be heated to temperatures up to 250 °C. It is equipped with a water loop capable of providing pressurized water (44 bars, also at 250 °C) and can be connected to a high power radiofrequency generator for electrical tests.   Looking strangely like a giant squid, the antenna is positioned in front of its dedicated 60 x 80 cm port. In the high-vacuum atmosphere of Titan, the 4.5-metre-long, 3-tonne component was submitted to three temperature cycles in order to induce dilatations and reveal possible leaks in its high pressure cooling circuit and vacuum volumes.   The antenna's capacity to withstand high voltage was also tested and the parameters for its optimal performance determined.   All tests were completed successfully and on 7 September, the spectacular and delicate operation of inserting the component into its port was performed.   One man inside the machine, another outside; a bit of pushing a bit of pulling and the antenna is in. Carefully balanced with lead counterweights, the antenna—looking strangely like a giant squid—was lifted by crane, pulled by ropes and guided by hand all the way into its dedicated port in WEST. (The port measures approximately 60 x 80 centimetres and is about four times smaller than ITER's average port).   By October, when all the ancillary systems are installed (cabling, hydraulic positioning devices, heat insulators, diagnostics ...) the antenna will be ready to face another punishing environment—the actual plasmas of an ITER-like tokamak.