you're currently reading the news digest published from 05 Jun 2023 to 12 Jun 2023



Fusion world | Data from WEST to optimize ITER's divertor

In 2013, a quarter-century-old tokamak decided to reinvent itself and, under a new name, head for new horizons and objectives. Tore Supra—a CEA/Euratom device located one kilometre from ITER in the CEA-Cadarache research centre—was the first tokamak to implement superconducting magnets and actively cooled plasma-facing components. For close to two decades the machine held the record for plasma pulse duration with a 6.5-minute shot achieved in December 2003. The lessons learned constructing and operating Tore Supra largely contributed to the definition of ITER. The realization that a reinvented Tore Supra could contribute even more led to the WEST project; under this new identity, the machine has become a test bench for its big neighbour still under construction. Last week, WEST donned a suit of lights to celebrate the finalization of 14 weeks of an 'intense experimental campaign' with its full ITER-like tungsten divertor. The divertor is a crucial component whose role in a tokamak is to control the exhaust of waste gas and impurities from the plasma. During operation, the heat loads on the divertor's plasma-facing elements can be as high as 10-20 MW per square metre, equivalent to those that a space shuttle or capsule encounter when re-entering the Earth's atmosphere. The manufacturing of a divertor is in itself a major industrial challenge: in WEST's case, the divertor comprises 456 actively cooled elements that are not all identical—some equipped with instrumentation, others not. Combining tungsten and copper, two metals that are particularly difficult to weld together, the elements need to be positioned within tolerances of 0.3 millimetres. In September 2020, WEST's Chinese partners within the SIFFER collaboration delivered the last batch of plasma-facing units that, once assembled in 30-degree sectors, form the WEST divertor. By December 2022, WEST had a fully operational, ITER-like divertor and launched its 'Phase II' campaign centred on a succession of high-fluence pulses reaching or exceeding 100 seconds. The combined duration of the hundreds of plasmas produced in 14 weeks exceeded that of all plasmas produced since the device first started operating in 2016. Close to 30 fusion experts from nine different countries (Europe, the United States and Korea) participated in the campaign, confirming WEST's international dimension and scope. The lessons learned from Phase II experimentation are many. From an industrial point of view, the series manufacturing of 456 divertor elements was a successful first¹. The five-month-long assembly process, within extremely tight tolerances, has generated hands-on experience that will prove precious when assembling the ITER divertor. The focus of Phase II, however, was science: subjected to a punishing ITER-like environment, how did the ITER-like divertor behave? Although the accumulated data is still being analyzed, the ITER-like divertor has demonstrated its resistance and performance. Following the current shutdown, a new experimental campaign will start in the autumn in close collaboration with the ITER Organization and the European Domestic Agency Fusion for Energy. A small proportion (4%) of WEST's Chinese-procured divertor elements will be replaced with European² equivalents and exposed to the same long-duration pulses as in Phase II. 'With the first part of the Phase II campaign now over—and with the second planned this autumn—we will have accumulated a considerable amount of data to model and optimize the lifespan of the divertor in ITER and in future industrial power plants,' says Jérôme Bucalossi, head of the CEA institute IRFM (Institute for Magnetic Fusion Research) that operates WEST. ¹The divertor in China's EAST tokamak uses a different technology; the divertor elements for KSTAR (Korea) were manufactured after WEST's; and the JT60-SA team in Japan hasn't launched the fabrication of tungsten-coated elements for its replacement divertor yet. ²Russia, Japan and Europe are procuring the plasma-facing targets for the ITER divertor. Target units from Japan were tested during WEST's Phase I, but with a partially cooled divertor.

Tritium Plant Summit | Taking stock, midway through plant procurement

Fuelling the fusion reactions in ITER is not a 'once-through' process; instead, fuel that is not consumed gets pumped out as part of torus plasma exhaust, together with helium ash and impurity gases, and recycled through the Tritium Plant for reuse. This 'closed loop' fuel cycle requires a wide variety of advanced technologies that are under the procurement responsibility of four ITER Domestic Agencies plus the ITER Organization. A recent Tritium Plant Summit at ITER Headquarters was the occasion for all of the involved parties to share the status of their designs, suggest areas for standardization, and create a unified timeline. The fusion reactions in ITER will be fuelled with two isotopes of hydrogen—deuterium and tritium. Although the effective 'burn rate' in the plasma chamber is estimated at only 1%, that's enough for helium ash to begin accumulating and the core plasma to dilute. To avoid this, powerful torus cryopumps in the divertor region are designed to continuously exhaust helium ash, along with unconsumed fuel and impurities. The gas streams from the pumps go to the Tritium Plant (integrated in the Tokamak Complex), where the fusion fuels are extracted for reinjection into the fuelling cycle. Multiple technologies are involved in the extraction and separation process in the Tritium Plant, grouped into six sub-systems: * Tokamak Exhaust Processing — receives reactor exhaust and separates out impurities from the hydrogen isotopes. (Procured by the United States.) * Isotope Separation — receives the purified hydrogen isotope steam and separates deuterium from tritium. (Procured by Europe.) * Storage and Delivery — stores ITER fuel, whether recycled or new. (Procured by Korea.) * Atmospheric Detritiation — recovers tritium from impurity gases as water. (Procured by Japan and the ITER Organization.) * Water Detritiation — recovers tritium from tritiated water and returns it to the fuelling stream. (Procured by Europe.) * Analytics — chemical and isotopic analysis in support of other five sub-systems. (Procured by the ITER Organization.) These sub-systems are, in general, currently in the preliminary design stage; only a small number of 'captive' components have already been manufactured and installed in areas of the Tokamak Complex that will no longer be accessible later. (See some examples, here.) 'As contributors to the ITER Tritium Plant work toward the final design of the process systems under their responsibility, we thought the time was right to compare notes, hear about progress and challenges, and discuss ways to save cost and accelerate the project,' says Ian Bonnett, head of the Tritium Plant Section. From 5 to 9 June 2023, he organized a Tritium Plant Summit at ITER, with 65 people present on site and several dozen dial-in participants. 'It had been at least 15 years since the last comprehensive meeting on the Tritium Plant. We wanted to gather the procuring agencies together with technical responsible officers for interfacing systems, integration officers, and safety specialists, and bring everyone to the same level of understanding about the status of procurement.' On the first day of the Summit, each procuring agency presented its system design efforts and future milestones, leaving all participants with a broad overview of program status. In 31 breakout sessions throughout the week, the focus was on ways to integrate and mutualize the efforts underway by the different parties. Are there opportunities for standardization that can result in manufacturing savings across multiple packages? Can a common approach to operation and maintenance be adopted so that Tritium Plant tools can be standard? Can a common calibration approach be decided on for process equipment? 'There is a lot of commonality behind the technology of the Tritium Plant systems,' says Bonnett. 'If one party's qualified solution for a common component like an isolation valve can be standardized, as a project we save money and time.' Working from Tritium Plant status as defined during the Tritium Plant Summit, the next challenge will be to build an integrated schedule that merges the construction and building services milestones in the Tritium Building with process equipment milestones planned by the Domestic Agencies and the ITER Organization. 'We hope to have an integrated schedule by the end of this year,' says Bonnett. As part of this forward-looking work, the teams will be taking into account the re-baselining work that is underway project wide, and incorporating any changes to the plan for machine operation that emerge as a result. In the end, the main objective of the Tritium Plant Summit—a shared sense of ownership in the Tritium Plant project—was achieved. A 2024 Summit is planned. For detailed information about the ITER Tritium Plant, see this recent ITER Talks video.

Image of the week | A long-awaited shot

What makes a great photograph? Sometimes it's just seizing the moment—what Magnum photo agency founder Henri Cartier-Bresson called the 'decisive instant' when people, shapes, light or movement can be frozen into a pattern that is both graphic and poetic. But sometimes it can be exactly the opposite, like in this 'Image of the week' by Donato Lioce, head of the ITER Tokamak Cooling Water System Section. 'For three years I tried to get precisely this image,' he says. Whereas the moon's position could be exactly anticipated, the worksite lights, the position of the cranes and, above all, weather conditions were critical elements. At 9:17 p.m. on Saturday 3 June, everything came together and magic was made. In order to obtain the striking effect of the moon's 'closeness,' Donato used a powerful telephoto lens mounted on his Fujifilm XT-3 APS-C camera and shot from a location 4.5 kilometres away from the ITER site, on the other side of the Durance River. 'As it had been raining heavily for the most of the afternoon, the atmospheric dust was washed to the ground and the air was almost perfectly transparent.' The result: awesome. Donato's pictures, which he calls 'astrolandscapes,' can be viewed on his Instagram page.

Future energy | Fusion on the agenda in Berlin

A day devoted to fusion is organized in Germany, with the presence of government officials, fusion researchers, and business leaders. Fusion energy has not been on the agenda of the political debate in Germany—until now. The recent experimental milestone achieved at the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory in California at the end of last year, the promising performance of the German stellarator Wendelstein 7-X, and the growing number of private fusion startups is attracting the attention of politicians. And so on a Monday in early June, the Federal Ministry of Education and Research together with the Federation of German Industries (BDI) held an event in to Berlin on 'The new dynamic in fusion research—opportunities and perspectives for German industry.' 'In view of the challenges ahead we have to be open to all technologies,' the Federal Minister for Research Bettina Stark-Watzinger said. 'Fusion has to be part of the agenda.' Together with Siegfried Russwurm, BDI President, Sibylle Guenter, the Director of the Max Planck Institute for Plasma Physics (IPP), Frank Laukien, the executive chairman of the newly formed private startup Gauss Fusion, and leading representatives from Siemens Energy and the provider for industrial laser technology Trumpf SE, the Minister spoke about the state of fusion research in Germany and the options to move forward—whether with publicly funded projects or through a growing number of private initiatives. As fusion startups thrive in the United States, the United Kingdom, and elsewhere, 'Europe risks falling behind,' Laukien said. 'We have to jump onto the train now.' Gauss Fusion was also part of an industry-focused fusion forum taking place that same morning. Around one hundred representatives of industry had responded to the invitation from Germany's Fusion Industrial Liaison Office to participate. They heard IPP physicist Hartmut Zohm sketch out the fusion landscape, and ITER engineer Jens Reich summarize the status and lessons learned of the ITER Project. 'We cannot do without science,' was the consensus of the morning. 'But in the end industry will have to build it.' Two private projects received special applause for their presentations: Proxima Fusion, a spin-out of the Wendelstein 7-X experiment, and the US-German laser-based initiative Focused Energy. Late May, an expert commission appointed by the Federal Ministry had handed over a 150-page Memorandum on Laser Fusion after the experimental success of Lawrence Livermore. In a few more days, on 22 June, the Ministry is expected to publish an official strategy paper on the development of fusion energy. Stark-Watzinger seems to be committed: 'Fusion has the potential to revolutionize our energy supply.'


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