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ITER Science | The towering importance of data

The most important product of ITER is data, which will be used to produce the information needed to build models for DEMO and commercial reactors—and much more. But ITER is also a consumer of data. Raw data and extrapolations from previous fusion experiments help scientists and engineers develop simulators that play a crucial role in design phases, and raw and processed data feed into analytical tools that will serve the equally important role of interpreting events within the plasma during operation. The Science, Controls & Operation Department is ultimately responsible for all scientific data at ITER. Within that department, Simon Pinches leads the Plasma Modelling & Analysis Section—a team that develops tools to maximize the value of information. Collecting input to simulate critical systems 'As an example, we have started to simulate diagnostics,' says Pinches. 'These simulations will grow into synthetic diagnostics that can be used to predict what will be seen on the real sensors, which will in turn help with the design of the diagnostic systems and in building the analytic tools that will interpret measurements. Because these simulators are so important to the project, we aim to have good models for all the diagnostics about five years before they're needed.' To make sure they do not miss important features, the Plasma Modeling & Analysis Section has been soliciting input. Within the ITER Tokamak Physics Activity, for example, is a Diagnostics Topical Group with a specific subgroup on synthetic diagnostics. Scientists from within the ITER Members have joined and have already provided useful ideas. One area of special interest is understanding what sensors will detect at the approach of high-confinement mode (H-mode) in the plasma. 'We have a Monaco Postdoctoral Fellow, Anna Medvedeva, who is looking into this,' says Pinches. 'We want to achieve high-confinement mode as soon as possible, since the plasma retains its heat much better once it has reached this state. To help us know when we are close to high-confinement mode, Medvedeva is modelling what we can expect the sensors to tell us.' In addition to simulating diagnostics, the Section is developing simulators of the different external heating systems because they strongly influence what goes on in the plasma. But there is one potential showstopper: whether they serve as a foundation for diagnostic or heating systems simulators, very detailed models suffer from the same downside—they take time to develop and can take an excruciatingly long time to run. The challenge is not unique to nuclear fusion; meteorologists face the same problem. The sheer number of variables in traditional weather models and the complexity of their interactions are too great for even the latest processing technology to overcome. Fortunately, artificial intelligence is providing a new path to speed and efficiency—given the right training data, artificial neural networks can learn to spot patterns of input data that produce a given output. The Plasma Modelling & Analysis Section intends to use this approach to transform input into output several orders of magnitude faster. 'Our Monte Carlo models take quite a lot of time to run,' says Pinches. 'So we're examining all the different input data for all the different cases we think some of the systems will experience in the lifetime of ITER and looking at the data that comes out. We'll use this to train a neural network equivalent that can do the same thing incredibly quickly. This will allow us to run our simulations without having to wait for these complex calculations.' Producing the right data to train analytical tools The team will apply the same thinking to the analytical tools. Using models that take into account not only direct measurements, but also the uncertainties of the measurements, analytic software will determine the state of the plasma. Examples of uncertainties include the angle of a mirror being slightly off, or a minute error in the position of a sensor. 'We will need a lot of data to create the neural network in the beginning,' says Pinches. 'This data will essentially 'teach' the systems to be able to assess the state of the plasma during operations. We plan to generate synthetic data, artificially produced, to train our network to behave like our complicated processing tools. We have to be careful to select the right data to train our neural networks. If we want to be able to spot a certain event in the plasma, we have to show it lots of examples of 'this is what it looks like, now can you go off and find it?'' Inspiring the future through data and insight These are just a few examples that illustrate the colossal importance of data in getting ITER off the ground. But while the project relies heavily on output from previous experiments, on balance it will produce more bits and bytes than it takes in—and that is where ITER is expected to have its most lasting impact.

Cooling water system | The tanks within a tank

Deep inside the bowels of the Tokamak Building, the entrance to one of most spectacular rooms of the whole installation resembles that of a broom cupboard.  The staircase is temporary and the wooden door at the top barely wide enough to allow passage.   We once described the vast space it opens into as a 'many-mirrored room.' At the time (in January 2018), workers were busy lining the floor and the lower walls with stainless steel panels. The view was striking: an immense volume, empty, and large enough to contain a three-storey building (40 metres long, 15 metres wide, and 11 metres high).   The room was being prepared to accommodate a set of massive water storage containers: three drain tanks to support normal operation, maintenance and water collection following an accident in the machine; and four vapour suppression tanks, stacked two by two, to protect the vacuum vessel against overpressure in case of a "loss of coolant accident" in the vacuum chamber. Containing contaminated water, the tanks act as a first confinement barrier and form one of the key safety systems for the ITER machine.   The room itself was designed as a tank, ensuring that, in the event of a leak, contaminated water would remain contained within, its steel lining acting as a 'drip pan' just like the tray that collects drippings from roasting meat.   In August 2018, in one of the most spectacular activities yet performed in the Tokamak Complex, the tanks were positioned inside the room and anchored with temporary bolts pending the development of a design for an anchorage system compliant with the tight safety requirements (leak-tightness, resistance to seismic events) of the system.   By the end of 2019, the design, drawings and calculations were finalized and work began on the final installation—a particularly challenging operation considering the size and weight of the tanks and the very constricted space left for operators.   One year later, what was once a vast and shiny expanse has turned into an overcrowded cavern. Sheets of protective plywood cover the stainless steel lining of the floor and lower walls; light is scarce and focused on working areas.   In order to install and weld the final anchorage system, the tanks—more than 6 metres tall and weighing up to 180 tonnes— have been lifted some 30 centimetres by way of hydraulic jacks. In this position, standing very close together, the tanks nearly reach the concrete roof two levels above.   Welded on the embedded plates, the anchorage system (bolts, seal lids and shear pins for withstanding lateral seismic accelerations) must be absolutely leak-tight. Non-destructive tests are performed on each individual weld, including a leak tightness performed using a vacuum box specifically designed and customized to fit the geometry under the skirts of the tanks. There are 280 welds, amounting to a total weld length in excess of 400 metres.   The welding and testing of the anchorage system for the entire set of tanks was completed on 16 December 2020; however, a lot of work remains to be done. This month, the tanks will be lifted again to allow the steel liner under the skirts to be cleaned and 'passivated' (a chemical process that prevents corrosion). Also, the piping needed for First Plasma must be installed and platforms erected to allow access to all parts of the tanks and to the support equipment such as valves, heat exchangers and pumps.   Sometime in the near future, with the steel lining shining, the dark cavern will regain something of the splendour of the 'many-mirrored room' ... albeit a very crowded one.  

ITER assembly | Last major assembly contract signed

One year after finalizing two major machine assembly contracts, the ITER Organization has chosen the contractors who will carry out assembly and installation activities inside of the Tokamak Complex. Following competitive global tender campaigns managed by ITER's Procurement & Contracts Division, two international groups—one incorporated as a consortium and the other as a commercial partnership—have been awarded contracts for installation activities inside of the Tokamak Complex. These phased, long-term contracts will cover the pre-assembly and installation of the millions of components that make up the plant systems supporting the ITER machine, including fuelling, vacuum, diagnostics, cooling, power, and heating. The two assembly contractors for the Tokamak Complex will carry out similar types of installation tasks, notably mechanical and piping works (vessels, piping systems, heat exchangers, pumps, motors; cable trays and cable pulling; wave guides; piping thermal installation; pressure tests), and electrical- and instrumentation-and-control-related works (DC busbars, switching equipment, power cables, I&C cables and cabinets).  The TCC1 assembly contract—for the installation of heating and current drive, diagnostics, fuelling, secondary cooling, and vacuum components—was signed in December 2019 by the ITER Organization and the Fincantieri Consortium(Fincantieri S.p.A., Fincantieri SI S.p.A., Delta-ti Impianti S.p.A., Comes S.p.A.) The TCC2 assembly contract—for the installation of primary machine cooling water, test blanket module equipment, some vacuum pipework, vacuum vessel pressure suppression—was signed in December 2020 by the ITER Organization and the META SNC (Ponticelli Freres SAS, Cobra Instalaciones y Servicios SA, and Empresarios Agrupados Internacional SA.). These contracts are the last major assembly and installation contracts planned for first-phase ITER assembly. (Two major contracts for Tokamak assembly, as well as five 'balance of plant' contracts are already underway.)   'The Procurement & Contracts teams have worked in very close collaboration with the Legal, Finance, Project Control, Quality and Nuclear Safety teams to prepare, develop, select and negotiate the two Tokamak Complex contracts. The two partners were chosen based on excellent technical capability at a competitive price, and we now need to collectively deliver on these promises through a deep collaboration between the teams at all levels. Such effective collaboration doesn't happen overnight; it requires a common sense of purpose that's aligned with the long-term business interests of all the companies involved,' commented Christophe Dorschner, head of Procurement & Contracts Division at ITER. Within the ITER Organization, the contracts are managed by Machine Assembly Planning & Contract Management Section (part of the Machine Construction Department) in close collaboration with Tokamak Complex Division. Each contract is broken into phases, with detailed works assigned progressively to the contractors through ITER Organization work packages. The execution of assembly works will take place under the overall responsibility of the ITER Construction team and the day-to-day management of ITER's Construction Management-as-Agent, MOMENTUM. Although the works will be concentrated in the Tokamak Complex (outside of the Tokamak machine boundary), some activity will also take place under these contracts in the Radiofrequency Building and Assembly Hall. Part of the expected challenge will be the coordination on the ground between Tokamak Complex contractors, contractors to the European Domestic Agency who continue to progress the installation of building services, and other dedicated teams carrying out the installation of multi-process cryolines, busbars and magnet feeders. For more information on the ITER strategy for machine and plant assembly, see this article.

Image of the week | In my arms!

In late November, one part of the 'shell' that encloses every vacuum vessel sector—a right-hand outboard thermal shield panel—had been mounted on a giant pre-assembly tool in the Assembly Hall. The relatively lightweight, silver-coated component (10 tonnes) now has company. With the left-hand outboard panel now installed in the opposite 'arm' of the tool, thermal shield assembly trials can begin. The trials will consist in rotating the two arms of the tool, with their outboard segments, toward the centre, bringing the segments close enough to determine—through trial and error—the precise trajectory for actual assembly. The trial operations will enable operators to identify and solve potential issues before the 440-tonne vacuum vessel segment is added to the Titan's embrace.

Brexit | The UK will remain part of ITER

'It was a great Christmas present,' says Ian Chapman, head of the United Kingdom Atomic Energy Authority. Many in the ITER community would agree. The Brexit negotiations of recent years have included a high-stakes element for the ITER Project: the question of whether the United Kingdom, one of the global leaders in the past five decades of fusion research, would be able to continue as an ITER contributor. For UK companies as well as UK passport holders among the ITER staff, it was a critical and sometimes deeply personal point of focus as the negotiations dragged on. On 24 December 2020, in parallel with the 1,246-page Trade and Cooperation Agreement signed by the United Kingdom and the European Union, another somewhat less high-profile deal was also signed: a Nuclear Cooperation Agreement (NCA) between the UK and Euratom (the European Atomic Energy Community), the legal entity through which Europe holds its membership in ITER. Under Article 12, 'Cooperation on nuclear research and development,' the NCA makes clear the intent for the UK to remain a part of Fusion for Energy, the European Domestic Agency for ITER. But to find the precise language agreed regarding ITER requires a bit more sleuthing. Specific citations about fusion research and ITER can be found in the 'joint declarations' issued with the EU-UK trade agreement. Under the generically worded 'Joint Declaration on Participation in Union Programmes and Access to Programme Services,' the parties to the agreement formally recognize the mutual benefit of cooperation on science R&D. And scrolling down to Article 8 uncovers the long-hoped-for language: 'The United Kingdom shall participate as a member of the Joint Undertaking for ITER and the development of Fusion Energy (F4E).' Other passages reveal more about the scope of the agreement. The UK will continue to be part of EU's Horizon 2020 research program. Collaboration on fusion research at JET, the Joint European Torus tokamak at Culham, can continue with mutual funding. As part of Fusion for Energy, the UK will remain part of the Broader Approach agreement. But for the ITER community, it is the 20 words cited above that justify a collective, heartfelt sigh of relief. UK government officials have long made clear that they hoped their country would remain in the ITER Project; but as the saying goes, the proof is in the pudding. From a legal standpoint, a bit more time will be needed for the necessary agreements to be formally approved, but in practical terms it means that we can expect the continued full involvement and participation of UK citizens and UK companies. The persistent tension that has been so troubling for UK fusion experts at ITER—and their families—has at last been resolved. The ITER team will remain intact.

of-interest

A detailed and realistic 360° MCNP model of ITER

In a paper published this month in Nature Energy, a team from the Universidad Nacional de Educación a Distancia (UNED, Spain) offers the scientific community a "full and heterogeneous model of the ITER Tokamak" for comprehensive nuclear analyses. "Nuclear analysis is a core discipline in support of the design, commissioning and operation of the machine. To date, it has been conducted with increasingly detailed partial models, which represented toroidal segments of the tokamak. However, the limitations of this methodology became evident as estimates of quantities relevant to design, safety and operation showed unquantifiable uncertainties, which is a risk. [...] Thanks to increasing high-performance computing capabilities and improvements in the memory management by the codes over the years, it is now feasible to take an important step forward. In this work, we present a 360° heterogeneous and detailed MCNP model of the ITER tokamak, which we call E-lite. It can be used to determine all the quantities relevant to the ITER's nuclear operations without the aforementioned uncertainties." The main authors—Rafael Juarez, an associate professor at UNED, and Gabriel Pedroche, a PhD student in the same research team—worked closely with colleagues from ITER and the European Domestic Agency (Fusion for Energy). Key contributions came from Michael Loughlin, Eduard Polunovskiy and Yannick Le Tonqueze from the ITER Organization, and Raul Pampin and Marco Fabbri from Fusion for Energy. Follow the link below to consult the article: Juarez, R., Pedroche, G., Loughlin, M.J. et al. A full and heterogeneous model of the ITER tokamak for comprehensive nuclear analyses. Nat Energy (2021). https://doi.org/10.1038/s41560-020-00753-x   

Fusion and the climate: webinar 13 January

On Wednesday 13 January 2021, the Stellar Energy Foundation and Pegasus Fusion Strategies are co-hosting a webinar-style workshop titled 'Energy, Environment, Innovation: Fusion's Promise for our Climate.' Join featured speakers Laban Coblentz, Head of Communication at ITER, and Dennis Whyte, Director of the MIT Plasma Science & Fusion Center and Hitachi American Professor of Engineering at MIT, for a thought-provoking discussion of the state of energy supply and demand today, the effort to mitigate atmospheric CO2, and the possible role of fusion energy. Is fusion power a realistic green energy option for combating climate change? Should private sector fusion projects be given priority over large multinational projects such as ITER? Can we rely on renewables like wind and solar to avoid climate change? The 90-minute webinar (11:30 a.m. — 1:00 p.m. US Eastern time) will be moderated by Chris Gadomski from BloombergNEF. Update 18 January 2021: The recording of the webinar can be found at this link.

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