Critical infrastructure components are routed through ITER’s thick concrete bioshield with the help of a little human ingenuity and bespoke construction solutions.   In an elaborate nine-month operation that has involved laying temporary rail lines and setting up aerial buckets to avoid concrete drips, 18 openings in the bioshield reserved for tokamak cooling water system piping have been “plugged” ahead of schedule. Achieved in September 2025, this critical milestone opens the way for the start of work on the water piping infrastructure known as the “jungle gym.”A three-metre-thick concrete bioshield around the ITER machine provides essential nuclear safety functions such as confinement, fire sectorization and radiation shielding. However, openings, or “penetrations,” are needed in the wall so everything from busbars to magnet feeders can feed into the tokamak. Once these critical infrastructure components are routed through, the penetrations need to be backfilled with concrete to meet the same safety standards as the rest of the wall structure.Among the most important openings are the 18 located at Level 3 of the Tokamak Building that are for the massive tokamak cooling water system pipes. Each opening requires a 6.5-tonne “penetration assembly” designed to fit snugly into the bioshield opening and serve as a connecting point for the inlets and outlets that travel from the cooling plant, through the Tokamak Building, and into the tokamak. â€œWe had to find solutions to optimize the penetrations sequence and to overcome an exceptionally demanding schedule so we could move ahead with assembly as quickly as possible, and we achieved this,” says Raphael Hernandez, the Construction Coordination Manager who oversaw the project. “We found the right synergies and managed the co-activity well.” The penetration assemblies inside the concrete bioshield serve as the interfaces that connect the cooling pipes as they travel between the cooling plant and into the tokamak pit. The penetration assemblies are composed of outer sleeves maintained within support plates and separators. The sleeves will allow two families of pipes bundles to cross through the bioshield—one providing cooling for the blanket, divertor and plasma-facing components (called the IBED set); and the other for the vacuum vessel sectors. The penetration assemblies also have bellows to deal with the movements of the cryostat and the pipes due to thermal expansion, as those pipes will carry pressurized water that can reach temperatures as high as 250 °C. Originally, the schedule provided a two-year installation window for the completion of tokamak cooling water bioshield penetrations, but in the end this schedule was accelerated. From the arrival of the first components in August 2024 to the completion of all 18 openings in September 2025, the work took just over one year.Two strategies were adopted that permitted the acceleration. First, instead of waiting for each penetration assembly to be fully complete, including pipe bundles, some were inserted with only the outer sleeves or just one of the two pipe families. The remaining components were installed while work was underway on other penetrations, which reduced the overall project time because the work was being done concurrently rather than sequentially. To speed up installation, some of the penetration assemblies were inserted into the bioshield without their pipe bundles. Here, a pipe bundle is being carefully manoeuvred into the waiting sleeve. The second time-saving strategy was to install the penetration assemblies based on other work being carried out in the tokamak pit. This required extensive logistics and resources—as the scaffolding had to be assembled and disassembled in different places around the tokamak pit—but allowed for greater flexibility in scheduling than if the entire pit needed to be closed for bioshield penetration activities.Besides the schedule, the biggest challenge was how to safely and cleanly slide the 6.5-tonne penetration assemblies into place. Instead of lowering them by crane into the pit and placing them in the openings, it was decided to insert them from the other side of the bioshield, working from inside the Tokamak Building. The team installed a temporary rail system in the galleries around the bioshield to move the penetration assemblies and glide them into place. However, safeguards were required to avoid an accidental and uncontrolled trajectory that could cause damage.The penetration designer Pascal De Boe and his team came up with three levels of protection. First, there were chains and metal blocks to stop the penetration assemblies if they began to slide too quickly. Second, wedges would deploy so they would jam against the bioshield wall and not fall into the pit. As a final defence measure, a crush pipe at the end of the track would act as a bumper.“We had to sharpen our pencils several times in order to optimize the installation strategy,” says De Boe, project leader for the In-Field Engineering team. “That’s why we had so many precautions, but thankfully none were required because the operation was very well prepared.” In this picture from May 2025, the progress on the penetration assemblies is visible. The first penetrations to be completed are situated where one vacuum vessel sector is installed and another is expected imminently. In the other areas of the pit, work continues behind the protective tents that hide the scaffolding from view. Once placed in the waiting openings, the penetration assemblies had to be aligned with a positioning tolerance of only five millimetres. Each one had fiducial markers for laser guidance and the engineers used trigonometry to make calculations against references in the building to ensure they were a perfect fit.After that, the backfilling of the openings with concrete was carried out to maintain the security requirements of the bioshield. Special formwork was built with Teflon and aluminium, and aerial buckets were rigged on cranes on the machine side of the bioshield to be sure no concrete spilled out and caused contamination. The coating of the pit-facing sides of the penetration assemblies with multi-fibre protective material and the removal of the scaffolding were completed in September.“Finishing the civil works on the penetrations clears the scaffolding in the tokamak pit and allows for the installation of the piping infrastructure on the other side of the bioshield,” says Jonathan Baker, the construction engineer for the tokamak cooling water system who managed the pipe assembly. “This is a significant step forward.”Watch how penetration assemblies get (carefully) inserted into waiting openings in the time-lapse video below. (Video courtesy of 4TCC1.)  

One after another, governments around the world are unveiling their strategies for national programs in fusion energy. Common themes consistently emerge: significant technical challenges remain on the road to commercialization, there is a need for a clear regulatory framework, and public-private partnerships are key to acceleration. Below is a selection of some of the most recent policy papers, announcements, and strategy documents released by the ITER Members. China: China has emphasized its fusion energy goals as part of its recently released 15th Five-Year Plan for economic development covering 2026 to 2030. This follows an announcement this summer that China is setting up a state-owned fusion energy company, China Fusion Energy Co., which will be a subsidiary of the China National Nuclear Corporation. This is part of the country’s long-term fusion strategy that includes the newly baptized China Fusion Engineering Demo Reactor that will serve as a bridge between ITER and commercial fusion plants. European Union: The new European Union strategy for fusion energy, planned for release later this year, is intended to clarify the pathway towards commercialization through increased coordination between the public and private sectors and a specific approach to regulation. Several recent reports and discussion papers are informing the debate. See Towards the EU Fusion Strategy from the European Union’s Fusion Expert Group published in April; Fusion energy: A paradigm shift in power generation for Europe? published in September by the European Parliamentary Research Service (EPRS); Regulatory Frameworks for Fusion Technologies published last month by the International Group of Legal Experts on Fusion Energy (FELEX).India: Like other ITER Members, is exploring concepts for a demonstration reactor, DEMO, that will test technologies for a fusion reactor. The country is considering a four-stage approach to establish power performance, tritium breeding, fuelling over long-pulse operations, and technology integration on the way to the pilot plant (see more details here). At a recent event at ITER (India Fusion Day), government and industry representatives cited participation in ITER as a key element in India’s fusion research plans and the foundation for an Indian nuclear fusion industry.Japan: In June 2025, Japan’s Cabinet Office updated its 2023 Fusion Energy Innovation Strategy, emphasizing the “industrialization of fusion energy” as a central component of its strategic vision (see all documents in Japanese here) and proposing a more ambitious timeline. The strategy seeks to leverage Japan’s expertise from projects such as ITER and the Europe-Japan JT-60SA tokamak, while strengthening the domestic supply chain to develop a homegrown nuclear fusion industry through coordinated public-private initiatives and an adapted regulatory framework. Also in 2025, the Japan Fusion Energy Council published a White Paper on Japan’s Fusion Energy Industry with recommendations on regulating fusion in Japan (available in Japanese and English).Korea: At the Nuclear Fusion Energy Technology Development Strategy Forum held in October by Korea’s Ministry of Science and ICT, officials unveiled a roadmap (see the Korean or English versions) to accelerate progress in eight core nuclear fusion technologies. Some of these—such as high-efficiency heating and current drive systems, superconducting magnets, and artificial intelligence applications—can be tested on the Korean Superconducting Tokamak Advanced Research (KSTAR) device, which serves as a scaled model for future reactors. Other key areas, including fusion materials, technologies for continuous long-term operation and power extraction, and the regulatory framework, will be advanced through strengthened collaboration among academia, industry, and research institutes, as well as the country’s participation in ITER. A preliminary feasibility study will be launched to select a site for advanced research infrastructure.Russian Federation: The development of fusion and plasma technologies are part of the Russian Federation’s U3 Federal Project within the broader DETSR Comprehensive Program on nuclear energy. The work scope—designed to ensure “balanced progress toward nuclear fusion power”—covers five areas: basic nuclear fusion technologies, the development of hybrid (fusion-fission) reactor technologies and systems, innovative industrial applications, laser nuclear fusion, and the development of a regulatory framework for fusion and hybrid systems. The Program runs through 2030. (More detail here.)United States: In October, the US Department of Energy (DOE) announced its Fusion Science and Technology Roadmap, a national strategy to accelerate the development and commercialization of fusion energy. It identifies the key research, materials, and technology gaps that must be closed to realize a Fusion Pilot Plant (FPP) and defines a “Build–Innovate–Grow” strategy to coordinate and align public investment with private innovation. A second paper published in October by the Special Competitive Studies Project’s (SCSP) Commission on the Scaling of Fusion Energy calls for the rapid commercialization of fusion energy as a strategic priority for the United States and suggests an investment of at least USD 10 billion.

From this angle, the object seems shaped like a mushroom cap. In reality, this lid segment of the large cryostat that recently arrived on site is oblong in shape—nearly twice as long (22 metres) as it is wide (almost 11 metres). When it arrived at ITER, the cold chamber for the magnet cold test facility at ITER was wrapped in white plastic. Upon delivery to its final destination in the former winding facility for poloidal field magnets, it was unpacked and separated in two—the deep chamber positioned just inside the wide doors of the building that will open to admit the first toroidal field coil to be tested at 4 K (minus 269 °C); the top lid, with its undercoating of shiny silver insulation (photo), positioned on temporary supports a few dozen metres to the side.We'll have a full report about magnet test bench commissioning in an upcoming edition of the ITER Newsline.  

In this episode of Behind the Science of Fusion, join ITER vacuum engineers Robert Pearce and Liam Worth for a live conversation that proves that "nothing" can be truly fascinating. Co-hosts Kruti Mawani Fayot and Julia Ponomareva explore how science fiction has inspired real-world engineering, dig deep into the everyday engineering challenges involving plasma, inspection, vacuum systems and cryogenics, and share plenty of laughs along the way.You’ll also hear surprising stories about inspection, cleaning, coconuts (yes, really, coconuts), spin-off applications, and how lessons from past experiments are shaping ITER’s vacuum engineering and paving the way for future fusion machines.Tune into Episode 5, "All About Nothing," for good humour, insights and a peek behind the curtain of one of fusion’s most fascinating challenges.  Find “All About Nothing” on the ITER website's podcast page or open it directly here. You can also find this episode and all past episodes of the ITER podcast at Spotify, Amazon Music, Apple Podcasts, and Podbean.