20 Sep 2021 to 27 Sep 2021
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R&D | Diagnostic shielding material qualified in India
Subsequent to the full validation of material production and machining feasibility, 'Made in India' boron carbide (B4C) blocks are now qualified for use as radiation shielding material for India's plasma-facing diagnostic systems. Indian industry has demonstrated that it can manufacture the boron carbide (B4C) blocks that will protect diagnostic equipment installed near the plasma. B4C is an extremely hard, synthetically produced material whose chemical composition and vacuum and thermal properties make it an excellent choice for the neutron protection of equipment in the ITER diagnostic ports. To validate the material production process and demonstrate manufacturing feasibility, the Indian Domestic Agency and its supplier M/s Bhukhanvala Industries developed full-scale samples of B4C blocks and tested them to rigorous ITER specifications. Diagnostic port plugs: shielded 'containers' for diagnostic systems In order for ITER's plasma measurement diagnostics to be close enough to "see" deep within the plasma, yet far enough away to avoid the full brunt of heat and neutron radiation, they are integrated into port plugs. Twenty-five of these box-like structures, which seal off all vacuum vessel ports, host the diagnostic systems procured by seven Domestic Agencies. Working from a generic port plug structure, each Domestic Agency performs the integration engineering to adapt plugs under their responsibility to 'embark,' or host, a specific set of diagnostic equipment. Shielding is particularly important on the plasma-facing end of the port plug. There, inside the drawer-like diagnostic shield modules that host front-end equipment, B4C in ceramic form is used to block or limit the neutron flux. Shaped into blocks of varying density and organized in modular assemblies around the diagnostic equipment, B4C represents a critical line of protection. 'With responsibility for the design, manufacturing, supply and commissioning of all diagnostic equipment integrated into upper port #9, the Indian Domestic Agency required a 'Made in India' source of B4C ceramics,' says Hitesh Pandya, project manager at the Indian Domestic Agency. 'The material will be also be used in shielding applications in other Indian-procured systems for ITER, so the successful development and qualification of B4C per ITER requirements was particularly important for us.' Qualifying Indian-made boron carbide blocks Studies carried out to determine the optimal shielding material for diagnostic port plugs—with neutron-blocking capacity and machine weight limits as primary considerations—identified B4C as the best material. The presence of boron isotopes makes it an excellent neutron blocker, characterized by a high neutron absorption cross section; it also can absorb neutrons without forming long-lived radio nuclides. Other properties—including low density (2.45-2.52 g/cm3), high melting point (~2445-2450 °C), high hardness (up to 9.75 on Mohs hardness scale), toughness, chemical stability, and thermal stability at elevated temperatures—contribute to its suitability for ITER's diagnostic shielding needs. B4C is readily available in powder form in the Indian market; however, because of vacuum requirements at ITER, powder could not be used. Instead, the material has to be converted into dense blocks. 'The manufacturing challenge of obtaining the required density is very great,' says Bhoomi Gajjar, scientific officer at ITER India. 'The results from pressure-less sintering were not good enough, so we chose vacuum hot pressing. A high temperature (2050-2100 °C) and high pressure (~30MPa) hot press facility was developed for this purpose by the Bhabha Atomic Research Centre (BARC)—technology which can now serve other applications in the nuclear, defence and aerospace industries.' To validate the material production process and to check the manufacturing feasibility as per ITER requirements, full-size samples were produced and tested. The chemical composition of the samples, as well as their mechanical, thermal and physical properties, were studied and validated. The out-gassing rate of the final product—which multiplied by the B4C surface area gives the total B4C outgassing per port plug—was also determined to be within requirements during testing conducted at the vacuum calibration laboratory at the Institute for Plasma Research (IPR). With the achievement of these important test and qualification steps, 'Made in India' B4C material has been qualified for use as radiation shielding material in India's diagnostic port.
Manufacturing | Like a fire-breathing dragon
With the precision of a surgical tool, the plasma jet cuts through the thickness of the steel plate. As sparks fly, the large circular opening at the centre of the cryostat lid is bathed in pinkish-mauve light—the colour of the ultra hot (30 000 °C) hydrogen-nitrogen-argon plasma. Towering above the operator, the computer-controlled 10-tonne robot slowly moves its cutting head up one of the component's ribs, slicing through steel like a thread through butter. One by one, the ribs are machined in order to align perfectly with the edge of the opening. The plasma machining underway on the central part of the top lid, where a central cylinder will soon be fitted and welded, is the most spectacular of the ongoing works in the Cryostat Workshop. While the dragon-like robot breathes its fire through the steel, a dozen welders from contractor MAN Energy Solutions are busy finalizing the radial joints between the component's segments, and an operator from the Indian manufacturer Larsen & Toubro Ltd, under the constant supervision of a quality inspector, performs ultrasonic tests on the completed welds. 'At this point, approximately 50 percent of the welding is done and 4 out of 12 radial joints have been checked by ultrasound,' explains Anil Bhardwaj, ITER Cryostat Advisor. The operation is long and delicate: every radial joint must be leak-tested on both surfaces (top and underside) of the steel plate and the process takes about two days. After all welds have passed this first round of testing, helium leak tests, scheduled in mid-October, will demonstrate that the top lid, like the three other sections of the 8,500 m³ cryostat, is leak-tight as can be. At 665 tonnes, the cryostat top lid is the second heaviest single component of tokamak assembly. 'With the base, it is also the most critical part of the cryostat,' adds Anil. 'Its shape is particularly complex, the amount of welding is considerable and access is not always easy.' Like a roof on a house, the installation of the cryostat top lid will mark the completion of core machine assembly.
Control buildings | A question of balance
Construction on the main ITER Control Building is now underway. Scientists, engineers and operators will work from this building on the platform to monitor machine operation and analyze the data they receive from each pulse. 'If the tokamak is the heart of the ITER worksite, then the control building is the brain,' says Paul Stewart, a civil engineer in the Building & Civil Works Section. Inside of the main Control Building, which is a non-nuclear structure directly accessible from ITER Headquarters, experts will operate the machine from the control room, and a server room will store data for future reference. But the control building will also serve as a primary workspace for these experts, and this is where the non-nuclear distinction becomes necessary. While working through plans and designs for a control building, the ITER Organization sought to balance two important requirements—the need to protect the critical function of the building through safety-important-class construction (by definition, windowless and drab), and the desire to create an optimum work environment. The solution? To build two buildings instead of one. The first is designed as a comfortable and efficient workspace, while the other is an emergency fallback. One of the first steps of construction back in March was to create an access point to the non-nuclear building. This meant digging a tunnel from the control building to the pre-existing bridge that connects ITER Headquarters with the platform. The first concrete pour for the basement took place in April, and now the construction crew is working on foundation slabs, walls, infrastructure and drainage. The principal contractor and supplier for this project is Demathieu Bard Construction (DBC), through a contract with the European Domestic Agency, Fusion for Energy. As part of this contract, DBC will also work on the buildings housing the neutral beam power supply installation and the fast discharge and switching networks resistor building, along with the busbar and cryogenic bridges. The main Control Building itself will sit on the northern end of the worksite, adjacent to the cooling towers. The 3,500 m2 structure will have three floors: a basement, ground floor and mezzanine. Inside will be housed the main control room and server room, along with individual offices and areas for refreshments and other support facilities. Once the civil engineering phase is complete at the end of the year, the next step for the non-nuclear control building is steel work. The steel elements should begin to arrive soon; in the meantime, building systems such as HVAC are under manufacturing review and will be constructed once they have been approved. Ultimately, the goal is to complete construction of the building and services in summer 2022 with commissioning activities finished later in the year. Though the control building is not a physical component of the machine, its completion will be another step toward the start of operation. Without its brain, the pulsing heart of ITER cannot function.
On site | Co-locating port plug assembly and testing
For about 20 of the ITER ports that house diagnostics elements, the path to installation in the tokamak passes through a Port Integration Facility on site. Side by side, the port plugs will be equipped with their tenant systems and tested at operating temperature prior to transfer to the assembly arena. The Port Integration Facility will host two important activities—port integration, where tenant system hardware is mounted on the port plugs and on the interspace and port cell support structures, and port plug testing, where environmental and functional tests are performed to ensure the availability of diagnostics and heating port plugs is as high as 99.5 percent. Port integration is a responsibility shared by all seven Domestic Agencies as well as the ITER Organization, which is procuring a certain number of diagnostics directly. While Domestic Agencies will handle integration of their port plugs domestically, port plugs procured directly by the ITER Organization, and all support structures (except those procured by the European Domestic Agency), will be assembled in the on-site Port Integration Facility. Port assembly activities include the assembly not only of the diagnostic equipment that sits inside a port plug, but also of the equipment behind the plug, which includes the interspace support structure and the port cell support structure (see diagram below). The diagnostics include sensors, and also the reflectors and mirrors that collect signals. In some cases, sensors are placed behind the plug for extra protection from radiation. The Port Integration Facility will include four different assembly lines to allow parallel work on all of these elements. The port plugs are the most difficult to assemble; an equatorial port plug, for example, weighs up to 48 tonnes and has three drawer-like diagnostic shield modules close to the plasma with one to three diagnostic systems hosted in each module. Because the diagnostic shield modules are inserted into the plugs vertically, tooling is needed to tilt the port plug and the diagnostic shield modules to the vertical position, and cranes are needed to maneuver the load. The upper port plugs present their own set of challenges, requiring a different set of tools and cranes. While each upper port plug will contain only one diagnostic shield module, both the port plug structures and the modules are longer (6 metres and 5.5 metres, respectively compared to only 3 and 2.6 for the equatorial plugs). A total of 14 metres are needed in a vertical direction to insert a diagnostic shield module into an upper port plug. Once assembled, the port plugs have only a short distance to travel to be tested. Three separate test stands—called port plug test facilities—are planned, with a fourth delivered directly to the European Domestic Agency for the testing of port plugs under its responsibility. Environmental (leak tightness, vacuum and thermo-hydraulic performances) and functional tests (radio frequency acceptance tests, behavior of the plugs' steering mechanism and calibration of diagnostics) will be performed on all upper and equatorial port plugs, driven by the high machine availability requirement for the diagnostics port plugs. 'The advantage of having the assembly tools next to the test facility is that if a port plug fails the test, we will have the tools to un-mount it and to disassemble and reassemble it,' says port plug test facility engineer Thierry Cerisier. 'In the worst case, we will only need to ship back a part of the port plug.' The Port Integration Facility will be installed in the current Poloidal Field Coils Winding Facility on site, taking over space that is progressively vacated as winding activities come to an end. The space meets Port Integration Facility requirements for physical dimensions and access—and very importantly, for cleanliness and cranes. The first installation activities are planned for January 2024. ***The ITER Organization is organizing a virtual information meeting on the general procurement strategy for the package "Engineering Design of the Port Integration Facility and Tooling" on Tuesday 5 October. All interested industrial actors from the ITER Members are invited to register for the event here. (Please note: Registration closes at the end of business on Tuesday 28 September.)
Image of the week | Two coils in a boat
Sailing ten thousand miles alone in a ship's hold can be a very lonely experience. Fortunately for them, toroidal fields #2 and 10 will be able to keep each other company all the way from Japan to the ITER site. Both D-shaped magnets were finalized at about the same time (although in different facilities) and were loaded at a few days apart on the same ship. The coils are travelling together for two main reasons: one is cost, and the other has to do with the availability of a suitable ship in the tense context of COVID-impacted maritime transport. The general cargo that transports the coils can be fitted with a removable twin-deck that can accommodate two large and massive loads. TF10, manufactured by Toshiba Energy Systems & Solutions, was loaded onto the ship and positioned in the hold on 20 August in Yokohama harbour. The removable twin deck was then installed and the ship sailed to Kobe to load TF2, manufactured at the Futami facility of Mistubishi Heavy Industries. Both coils are now en route and are expected at Fos-sur-Mer harbour in late October. Once delivered to ITER and equipped, each coil will go its own way, TF10 to be assembled with TF11 on vacuum vessel sector #8, and TF2 with TF3 on vacuum vessel sector #4.
ITER @ IAEA 2021
Each year, the International Atomic Energy Agency (IAEA) holds a General Conference to discuss topics of nuclear science and technology as well as budgetary and administrative issues. The 65th annual conference took place from 20-24 September 2021 at the Vienna International Centre in Austria, where a number of projects and organizations, including ITER, joined to share their progress with the world. ITER was represented by Laban Coblentz, head of Communication. In his statement, delivered on behalf of ITER Director-General Bernard Bigot, he emphasized the benefits of the relationship between ITER and the IAEA. As ITER creates the first reactor-scale fusion device, the IAEA has the opportunity to take this blueprint and develop guidelines for fusion around the world. He also reported on ITER's assembly progress and the project's impact on the fusion community. 'Above all, the ITER Project is a tangible demonstration that multinational collaboration is possible at a practical level with countries that are not always aligned on all items," Coblentz said. "But at ITER we are working hand-in-hand toward a common goal: to leave a better legacy with regard to clean energy supply for our children and future generations.' For more information on the 2021 General Conference, see the IAEA site here.
Apply now: SOFT Innovation Prize
The pursuit of fusion has led to many promising advancements in physics and technology. To highlight excellence in fusion research and innovation, and to stimulate the fusion research community to strengthen innovation and foster an entrepreneurial culture, the European Commission is offering to reward three fusion innovation proposals. The SOFT Innovation Prize is open to researchers, research teams and industry players who would like to propose devices or methods that have been developed in magnetic confinement fusion research. Each proposal will be judged on its market potential and replicability as well as its originality. The contest opened on 15 September 2021 and will close on 18 January 2022 at 17:00 CEST. After the proposals have been reviewed, prizes will be awarded at the 32nd Symposium on Fusion Technology (SOFT) in September 2022. To learn more or submit a proposal, see the original announcement here.
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