On Wednesday 25 June, ITER awarded one of the most pivotal responsibilities of tokamak assembly to Westinghouse Electric Company. For the American powerhouse, better known for its decades of nuclear fission plant design and construction, this will be a key opportunity to bring its world-class capabilities and expertise to fusion plant construction.It is no small step. The vacuum vessel is ITER’s most critical component: a hermetically sealed, double-walled steel container that will house the fusion plasma. Nine vacuum vessel sectors, each comprising 40 degrees of the doughnut-shaped chamber, are being contributed by Korea and Europe. Two have already been installed in the tokamak pit. When all the sectors are in place, Westinghouse will commence the most delicate and intensive stage of ITER assembly: simultaneously welding the nine sectors to form a single, circular torus.  The ITER tokamak will provide an unprecedented experimental platform for fusion physicists. The interior volume of the vacuum vessel will be about 1400 m³, enabling a plasma volume of around 840 m³ at its centre. At 19.4 metres across, 11.4 metres high, and—with the blanket and divertor installed—weighing 8,500 tonnes (for reference, that’s more than half the weight of the Brooklyn Bridge!), it will be six times larger than any previous tokamak, reaching industrial scale.Assembling this remarkable fusion chamber will require equally remarkable skill. Welding causes deformation; welding at this scale and volume will require extraordinary strategy and execution to control the deformation to achieve a perfect result.ITER’s original plan was to first weld the sectors to each other in groups of three, and then to weld the three triplexes together. Under Director-General Pietro Barabaschi that approach was rejected, considering the risks of generating unpredictable and uncontrollable deformations. Instead, with the new strategy, welding will only commence once all sectors are in place and firmly clamped to each other. This approach will ensure better control and a more uniform distribution of the deformation across the whole vacuum vessel, achieving in this way a regular plasma chamber, essential for the proper operation of the tokamak.  Side by side in the pit: two complete sector modules (vacuum vessel sectors assembled with thermal shielding and a pair of toroidal field coils) are now in place; a third is expected in the pit before the end of the year. The first stage will be the welding of the outer wall of the vacuum vessel. With wedge-shaped splice plates in place in each field joint, each weld will be approximately 60 millimetres thick and 35 metres long. For each welding step, three groups—each comprised of four robotic welders—will work simultaneously on specific portions of three field joints, spaced 120 degrees apart. Once the required batch of welds is completed, the welding process will shift 40 degrees to the three adjacent field joints, and then finally to the remaining three field joints, completing the circle. The process will then start again on the initial set of field joints, this time focused on a different portion of the joints. This sequential process will continue until the full welding has been completed.  Once the outer wall is fully welded, the entire operation will move inside the chamber to repeat the welding process on the inner vacuum vessel wall. In total, more than 10 tonnes of filler material will be used.Operations will start in 2027 with the assembly and preparation of all the needed equipment.  Once the welding process starts, it will proceed 24 hours per day, in three shifts, 6 days per week, with pauses only for radiographic and ultrasonic tests to confirm the quality and precision of the welds. Approximately 60 Westinghouse experts per shift, 180 in total, will be involved from the start of welding operations for the 30-month duration of the work.Alessandro Bonito-Oliva, who leads ITER Tokamak Delivery, remarked on the herculean nature of the welding project: “Even at ITER, where we are accustomed to singular, first-of-a-kind activities, this welding of the vacuum vessel will be quite unique. To sustain such a level of intensity, at the required level of quality and precision, will be a challenge. In order to be ready for the challenge an intensive R&D and qualification program is presently being carried out. The goal is to arrive at the start of the operation with fully qualified equipment, processes and personnel.” See the press release published by Westinghouse here.

The 31st IEEE Symposium on Fusion Engineering (SOFE) in Boston from 23 to 26 June was the occasion to measure just how fast the fusion ecosystem is changing. Technical Chair Sehila M. Gonzalez de Vicente of the Clean Air Task Force described this year's SOFE as by far the largest to date, noting that the biennial conference has doubled in size over the past decade. Not even the unprecedented heat dome—bringing extreme temperatures and humidity to the host city—could dampen the enthusiasm of the 700 attendees. Participants engaged with enthusiasm in presentations, poster sessions, networking events, and side activities, including a visit to the Devens, Massachusetts campus of the private firm Commonwealth Fusion Systems (CFS).SOFE 2025 General Chair Greg Wallace, from MIT’s Plasma Science and Fusion Center (PSFC), opened the conference by describing the field of fusion as being on the brink of major breakthroughs. “It’s incredible to see how many companies are jumping feet first into fusion,” he said. “But it is also a time of caution—we haven’t yet solved all the challenges we face.” “Fusion can’t thrive in a vacuum,” said Shira Tabachnikoff, Communications Manager at ITER, at the Women in Fusion @SOFE2025 roundtable sponsored by AtkinsRéalis, as she challenged the notion that leadership in fusion will simply evolve on its own and spotlighted the urgent need to build a more intentional pipeline for future talent. "As fusion moves from research to deployment, global collaboration to prepare and educate the workforce is no longer optional—it’s essential." The roundtable brought together a panel of actors in the fusion sphere: Susana Reyes (Xcimer), Alex Mozdzanowska (Commonwealth Fusion Systems), Amani Zalzali (General Atomics), Carlos Paz-Soldan (Columbia University), and Agnes Auledas (AtkinsRéalis) in addition to Tabachnikoff. In a context of intense competition for positions currently, yet a predicted strong increase in the need for well-trained professionals in the future, how do we attract the next generation to the field of fusion? A future with fusion, the panelists argued, will also require communicators, lawyers, advocates, project managers, educators, and public engagement specialists in addition to physicists and engineers. Andrew Holland, CEO of the Fusion Industry Association, echoed the sense of momentum, describing a “sea change” underway. To date, at least USD 8 billion in private investment has been directed toward 45 fusion companies across 14 countries, most of it in the last five years. (The Association’s full 2025 report on the state of the industry is expected in late July.) Holland attributes the rapid growth to increasing supply-side readiness—fusion is edging closer to commercial viability—and to the emergence of a “venture-capital mindset” that is reshaping the business model. “No longer do we have to solve all the problems before moving forward,” he said. He likens the proliferation of startups to “shots on goal.” “These are companies that are moving fast. No one can know in advance who is going to get there first.” Commonwealth Fusion Systems co-founder and director Bob Mumgaard predicts that recent advances in fusion technology, especially high-temperature superconducting magnets, mean that “fusion is the solution that scales.”Jean Paul Allain, Associate Director of the US Office of Fusion Energy Sciences, agrees that the private sector is moving fast, but says that there is still a need to derisk some technology gaps. “Free markets will dictate who wins and loses,” he said in a talk on public/private partnerships. “But as we think about what it will take to realize fusion energy, it is important to recognize that foundational science is the engine of innovation. Decades of investment from the public sector has created an ecosystem of national labs and universities that are nurturing other efforts today. Through this publicly enabled knowledge base we are looking at many different approaches to fusion and looking for multiple demonstrators.” Deputy Director-General for Science & Technology Yutaka Kamada gave a plenary talk that emphasized how ITER created a fusion supply chain over the last decade by bringing fusion from science to industry. He also shared the latest news from the project, where major assembly and installation milestones are being achieved ahead of schedule. The ITER project was represented at SOFE 2025 through a number of presentations and poster sessions. Deputy Director-General for Science & Technology Yutaka Kamada gave a plenary talk that emphasized how ITER is driving the availability of key fusion technologies. “Anywhere between 100 and 500 companies in each of the ITER Members have been involved in the successful fabrication of high-precision components for ITER,” he said. “That translates to thousands of companies working for fusion. ITER has created a fusion supply chain over the last decade by bringing fusion from science to industry.”And ITER is contributing value to the ecosystem in other ways too, he said. By operating deuterium-tritium plasmas at a scale not experienceable in other devices, the project will provide important knowledge on disruption control, on the diagnostics critical to operating a fusion plasma, on maintainability, on fuel cycle and on fusion codes and standards ... among other valuable lessons from operation. “ITER will deliver the scientific basis for practical fusion energy,” agreed Kathy McCarthy, director of the US ITER Project Office, in her session on the value of ITER. Reflecting one of the top priorities of the new fusion startups, the conference opened with a talk by MIT Professor of Finance Andrew Lo. He proposed acting as a “fresh pair of eyes” and telling the audience how fusion looks to an outsider—especially an outside investor. He considers fusion energy as part of a group of transformational technologies (think quantum computing, drug development, climate tech…) that involve complex engineering or scientific challenges, that are deeply risky, but that potentially offer huge returns on investment. He describes investors are willing to take risks, but deeply suspicious of uncertainty. His advice to private firms? “If you can measure what you are doing and show how uncertainty will be resolved progressively, you’ll be better at raising money.” ITER's "Fuse Baby Fuse" T-shirts, distributed on the last morning of the conference, disappeared in minutes. In approximately 100 technical talks, experts in practically every fusion engineering domain—magnets, cryogenic systems, fuelling, exhaust, vacuum, diagnostics, control, power supply, blankets, materials, tritium breeding, heating and current drive, remote handling, safety and regulation—shared the latest progress and the challenges they are facing. Many of the talks will be published in an upcoming special issue of IEEE Transactions on Plasma Science (TPS), a peer-reviewed journal.The conference closed with the recognition of the IEEE Fusion Technology Award winners Fernanda Rimini (2024), for her leadership in JET’s deuterium-tritium operations, and Zach Hartwig (2025), MIT professor (Department of Nuclear Science and Engineering) and co-founder of Commonwealth Fusion Systems. The awards celebrate outstanding contributions to research and development in the field of fusion technology.Photos courtesy of Tamás Szabolics, EUROfusion

A new cold test facility for ITER magnets is taking shape on site, with testing on the first toroidal field coil expected to begin at the end of the year. Components for the facility continue to arrive on schedule.  On 22 June, the first batch of equipment and materials for the facility's customized 68 kA power supply system reached ITER. Two other batches have been shipped from Shanghai harbour, and their delivery is expected in August.In May 2024, a consortium formed by Rongxin Huike Electric Co., Ltd (RXHK), the Institute of Plasma Physics/Chinese Academy of Sciences (ASIPP), and Hefei Rongke Hengyang Power Technology Co., Ltd (RHR) was awarded a contract for the design, manufacturing, installation and commissioning of the test facility’s power supply system. Despite an extremely tight schedule and several challenges, the overall project team for this procurement, composed of representatives of the Chinese consortium and ITER specialists, successfully achieved this key milestone within thirteen months, demonstrating the power of collaboration and persistence using their efforts in days and nights. Two other batches have left China and are expected in August. Commissioning on the magnet cold test facility will start in the autumn, when all components have been installed. Located in the former Poloidal Field Coils Winding Facility, the magnet cold test facility will have its own cryostat and power system to cool magnets to 4 K (minus 269 °C) and energize them up to 68 kA—offering a real-scale test of a diverse set of toroidal field coils, from multiple coil and conductor manufacturers, as well as a general rehearsal for auxiliary systems (feeders, cryogenics, control-command…) to derisk that portion of the machine’s integrated commissioning.

It took approximately one month for this central solenoid module to travel from the port of Houston, Texas, to the ITER site in southern France. A fifth and penultimate central solenoid module travelled along the ITER itinerary during the last week of June, arriving on the worksite early in the morning on Friday 27 June. Only one more module is necessary to complete the central solenoid stack at ITER, and it is already en route after tests were completed at US ITER supplier General Atomics. The 110-tonne module arrives at ITER outside of the warehouse where it will be stored until needed by the central solenoid assembly team.