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Assembly | Zero-gravity in a cramped place

The volume of the Tokamak pit may be huge, but so are the components that need to be installed. As a result, assembly operators will have very little room to manoeuvre. One tool is under development that will aid in the assembly—in a crowded environment—of the steel elements that interlink the massive toroidal field coil cases at top and bottom. The assembly of ITER's steel vacuum vessel will be one of the most technically challenging operations of the machine assembly phase. One by one, nine vacuum vessel 'sub-assemblies'—weighing 1,200 tonnes each, will be lowered by crane onto temporary supports in the Tokamak Pit. These sub-assemblies, created on massive tools in the Assembly Hall, associate one vacuum vessel sector, its associated thermal shield panels, and two vertical toroidal field coils. Once in place inside the assembly pit, and before vacuum vessel sector welding operations begin, each of the toroidal field coils will be connected to the next by way of 'intercoil structures' located at different levels of the 17-metre-tall toroidal field coil structures. At the top and bottom of each coil, box-type 'outer intercoil structures' will link one coil case to the next. The structures are formed from large brackets welded to the coil cases, with six cylindrical pins connecting one bracket to the next (see photo, above). The 35-kilogram pins are designed to withstand the tremendous shear forces that will be exerted by the magnetic field and to compensate for minute misalignments, inevitable with such tall and massive components. Creating a tool that would fit into the cramped space (especially at the bottom of the coil) and allow operators to precisely handle and position each of the 35-kilogram stainless steel pins has required a year-and-half of development at the Magnet Infrastructure Facilities for ITER (MIFI)—a set of workshops and laboratories jointly operated by ITER and the French Alternative Energies and Atomic Energy Commission (CEA). 'CEA, and specifically the Institute for Magnetic Fusion Research (IRFM) here in Cadarache, has the engineering know-how and the 'tokamak culture' that was indispensable to developing this assembly tool,' explains Bertrand Peluso, the MIFI technical coordinator on CEA side. Fabien Ferlay, the CEA mechanical engineer who led the development team at MIFI, says that the tool was 'inspired by robotic arms and telemanipulators.' Manually operated, it uses a zero-gravity 'mass compensation' system¹ that enables the operators to exert minimal effort as they move the heavy pins into position. And it is 'as compact as possible' to fit and operate within the confined space below the vertical coils. The handling and positioning tool has been successfully demonstrated on a mockup of the box-type outer intercoil structure at MIFI. And it comes with an option, which the team presented last week to the ITER Organization and assembly contractor representatives (TAC2 contract)—an 'augmented reality' setting that superimposes a virtual 3D rendition of the coil and workspace environment on the steel reality of the mockup. The mockup and tool have now left Cadarache for the SIMIC facility in Italy. As a partner in the TAC2 machine assembly consortium, SIMIC will finalize the equipment, add functionalities for extra actions such as inserting custom shims or tightening the 'superbolt' nuts, and test how the assembly sequence unfolds. When all this is done, the mockup and tool will return to a workshop close to ITER, where future operators will train in the art of connecting, by hand, components as high as a six-storey building and weighing several hundred tonnes. ¹In a "zero-gravity" device, a system of counterweights, cogwheels and a synchronization shaft balances the mass that needs to be handled.

CODAC | The "invisible system" that makes all things possible

It is easy to spot all the big equipment going into ITER; what is not so visible is the underlying software that makes the equipment come alive. Local control software manages each of the big ITER systems—everything from electricity and cooling water to all the critical systems inside the Tokamak Complex. It also manages some of the smaller systems—right down to the one that regulates the flow of potable water in buildings. 'Each of these local control systems has to interface with central conventional control, CODAC (Control, Data Access and Communication),' says Anders Wallander, Head of the Controls Division. 'We have 170 local control systems delivered by 101 suppliers —plus the CODAC itself, which makes a total of 171 control systems. It is a major undertaking to get all this software to work together.' How control systems fit into the commissioning process The Controls Division is responsible for designing and delivering the CODAC system and for making sure all the local control systems—many of which are delivered with a major system as an in-kind contribution—interface correctly with CODAC. Integrating the software takes place during the commissioning process, when equipment and software are handed over from suppliers and Domestic Agencies to the ITER Organization. CODAC is based on the open source system EPICS, which is the standard in the field of control systems engineering. The local control systems also follow this protocol, and are designed and developed to conform to a number of standards, including the interface definition for how the systems integrate with CODAC. But within those boundaries there is a lot of flexibility in how the different suppliers design and implement the control software. 'The control system requirements are generic enough to be open to some interpretation,' says Wallander. The Controls Division inherits the local systems once they are handed off. They have to get it to work with the CODAC, and they have to maintain it. This means analyzing the source code, and running tests at the various test facilities set up specifically for that purpose. Based on what they see in the source code and what they find in the tests, the Controls Division makes a decision on whether or not to accept the software during commissioning. 'The best case handoff process is when we are in close communication with whoever developed the software,' says Wallander. 'When it doesn't work right away, we have to ask the software engineers a lot of questions. This is where personal relationships really make a difference.' First three systems commissioned Before the first local system commissioning could begin, infrastructure had to be in place. 'We depend on building structures and network infrastructure to connect the 170 systems that are spread around the site,' says Wallander. 'We use a dual star architecture, with a central point—the control room—that links to all the other places, very roughly in the shape of a star. We call it 'dual' because the network is redundant to provide fault tolerance.' However, the main control room will not be in place until 2022. To overcome this challenge, a temporary control room had to be put into place. (The temporary control room is really a 'virtual control room' in the sense that it is several different rooms connected together.) Once the infrastructure was in place, the electricity was switched on and the first commissioning project—electrical distribution, along with its local control system—could begin. This was in June 2018. 'Commissioning starts when you switch things on and nothing works exactly as planned,' says Wallander. 'We all had to put in a lot of effort during the second half of 2018. But we were successful after six months.' Since January 2019, CODAC has been running 24/7, interfacing with the local control system to manage the electrical system. 'It often comes down to engineers and other people who just want to get the systems to work together,' says Wallander. 'You put all these people in a building. They don't know each other, but they have a common goal to work towards. Very quickly, and very naturally, a team spirit develops. It was a long effort, with a lot of challenges. But that team spirit was a major factor in our success.' CODAC has now reached several major milestones, including the integration of 3 out of 170 local control systems. The next project, underway now, is the commissioning of the cooling water system.

Image of the week | A closer look at KSTAR

Over its twelve years of operation, the KSTAR tokamak (for Korea Superconducting Tokamak Advanced Research) has built an extremely valuable database for the future operation of ITER as well as for the design basis of a next-step DEMO machine. KSTAR is considerably smaller than ITER (with a 1.8-metre major radius as compared to 6.2 metres) and it differs in many design details. The machine achieved high-performance operation mode (H-mode) in 2010 and reached an ion temperature of 100 million °C in 2018. KSTAR has proved especially efficient in suppressing edge localized modes (ELMs), a phenomenon that can occur during H-mode during which bursts of energy and particles are expelled from the plasma. Along with the European JET, KSTAR has been at the core of an extensive international program to validate the design of an effective disruption mitigation system based on shattered pellets injection—the very system that will be installed in ITER. Let's take a guided tour of the pristine KSTAR hall at the National Fusion Research Institute in Daejeon, Korea. 1-2: Neutral beam injectors #1 and #2 KSTAR is presently equipped with two 110 kV positive-ion-based neutral beam injectors. A third is optional. 3: Power sources Whereas the power source for neutral beam injector #1 is located in an adjacent building, the three modules of the power source for injector #2 are installed in the KSTAR hall proper. 4: ECEI diagnostics systemThe electron cyclotron emission imaging (ECEI) diagnostic is designed to visualize the electron temperature profile and fluctuations in 2D and 3D. In case a third neutral beam injector is installed, the system would be relocated. 6: Vacuum UV diagnostics systemThis prototype vacuum ultraviolet diagnostics system uses spectroscopy to monitor transport and accumulation of the tungsten particles in the plasma. 7: Pellet injectorPart of the international program of R&D on ITER disruption mitigation, two shattered pellet injectors were installed in 2019 (one is visible in the inserted image, the other is in a diametrically opposed location).The equipment was provided by US ITER through Oak Ridge National Laboratory. 8: Cryovalves boxConnected to the cryoplant outside the hall, the valves are activated to control the flux of supercritical helium circulating in the magnet system.

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Exploring the Sun's uncharted regions

Led by the European Space Agency (ESA) with strong NASA participation, the Solar Orbiter mission, which lifted off from Cape Canaveral on 10 February, will provide the first views of the Sun's uncharted polar regions, giving unprecedented insight into the workings of our familiar star. Solar Orbiter will also investigate how intense radiation and energetic particles being blasted out from the Sun and carried by the solar wind impact our home planet, to better understand and predict periods of stormy "space weather." Find out more at ESA or NASA.

Fusion's hot moment

In a context of new momentum in fusion research—as the ITER Organization begins assembling its machine, a number of upgraded tokamaks return to operation, and private investors fund fusion startups—what does the near future hold for the development of fusion energy? This was the question the Andlinger Center for Energy and Environment at Princeton University asked Steve Cowley (left), director of the US Department of Energy's Princeton Plasma Physics Laboratory (PPPL) and Princeton University professor of astrophysical sciences, and Egemen Kolemen (right), a PPPL physicist and assistant professor of mechanical and aerospace engineering at the Andlinger Center, during a Highlight Seminar event in January. You can read their replies here. Princeton University's Andlinger Center for Energy and the Environment is a multidisciplinary research and education centre, whose mission is to the develop technologies and solutions of the future.

Calling for nominations: 2020 Fusion Technology Award

During the next Symposium on Fusion Engineering (SOFE April 2021), Fusion Technology Awards will be presented for the years 2020 and 2021 to individuals who have made outstanding and widely recognized contributions to research and development in the field of fusion technology, or for technical contributions that have had a major impact in fusion technology and/or leadership and service within the community. The Awards each consist of a USD 3,000 cash prize and a plaque. Any person, regardless of nationality or Society affiliation, is eligible for the award, with the exception that no current member of the IEEE/NPSS Standing Committee on Fusion Technology may be nominated. The nomination package should be sent to the Fusion Technology Committee Awards Chair, Carl Pawley (drcpawley@ieee.org), and it should consist of a nomination letter describing the technical and/or leadership contributions on which the nomination is recommended and a resume of the candidate. The nomination period for the 2020 Fusion Technology Award is 4 February to 10 March 2020. For more detailed information on eligibility, basis for judging, nomination process and a list of past Award recipients, please visit the IEEE-NPSS website and go to the "Fusion Technology Awards" section.

video

ITER NOW 1.2: The Monaco Post-Docs

press

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Fusion energy can power us to a greener world

After decades of decline, the U.S. national fusion lab seeks a rebirth

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SNC-Lavalin has contract extended on ITER project

DIII-D Researchers Use Machine Learning to Steer Fusion Plasmas Near Operational Limits

Japan completes its first superconducting coil for ITER

Assystem wins ITER contract

Italian companies support DTT fusion project