Piece by piece, engineers are building a machine designed to bottle star fire. The latest step came with the delicate installation of a new, several-hundred-ton component at the heart of ITER, the world’s largest fusion experiment.
Module no. 5 slips into place in the south of France
On 25 November 2025, at Cadarache in Provence, a massive sector of ITER’s vacuum vessel, known as module no. 5, was lowered into the tokamak pit. The operation took hours, with operators guiding the load at a glacial pace as it descended between reinforced concrete walls.
This new module joined modules no. 6 and no. 7, which were installed earlier in April and June. With three of the nine vessel sectors now in position, ITER’s torus — the doughnut-shaped chamber that will one day host a 150‑million‑degree plasma — has passed a psychological and technical milestone.
Three out of nine vacuum vessel sectors are now in place, forming a continuous 120‑degree arc of the future fusion chamber.
The stakes go far beyond construction bragging rights. Every correctly placed sector inches ITER closer to its core goal: showing that fusion power can generate more energy than it consumes while emitting no CO₂ during operation.
How do you install a 400-tonne “slice” of a star machine?
A choreography with millimetre tolerances
Each vacuum vessel module is a towering, curved chunk of steel integrating multiple subsystems. Before it reaches the tokamak pit, the component goes through a decontamination-like ritual in a dedicated cleaning building. There it is meticulously dusted and prepared for entry into the controlled assembly hall.
From there, overhead gantry cranes take over. Operators manoeuvre the module along rails and lift points, shifting it in three dimensions inside a clearance that, in some places, barely exceeds a few centimetres.
Alignment tolerances are unforgiving. Engineers must keep positional errors to fractions of a millimetre. That means constant laser measurements, real-time adjustments, and teams communicating continuously as the load swings gently between supports.
A misalignment of a few tenths of a millimetre could ripple through the entire structure and compromise magnetic performance.
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Once in the pit, the sector is slowly rotated and brought up against its neighbours. Temporary supports and massive jigs hold it in place so that welders and fitters can prepare future joints and connections without disturbing the modules already installed.
Inside a single vacuum vessel sector
These modules are not just thick steel shells. Each includes:
- Two large superconducting coils integrated into the structure
- A thermal shield to keep the supercooled magnets insulated from surrounding heat
- A segment of the double-walled vessel where the plasma will be confined
- Dozens of ports and penetrations for diagnostics, heating systems and maintenance
When all nine modules are installed and welded together, they will form a closed torus almost 30 metres in diameter and roughly as tall as a 10‑storey building.
An industrial symphony spanning three continents
Shared build, shared risk
ITER is often described as the energy equivalent of the International Space Station: no single country could afford or deliver it alone. The installation of module no. 5 is the tip of an industrial iceberg that stretches from Asia to Europe and North America.
A China–France consortium, grouped under the name CNPE and involving companies such as ASIPP and Framatome, oversees the assembly of the cryostat, the central solenoid supports, and some of the magnet feeds. These structures will keep ITER’s magnetic “cage” at superconducting temperatures just a few degrees above absolute zero.
Italian firm SIMIC S.p.A. shares responsibility for positioning and mechanically joining the vacuum vessel modules. Meanwhile, Indian engineering giant Larsen & Toubro handles ultra-precise welding for vessel openings, where future instruments, heating lines and maintenance equipment will pass through.
US-based Westinghouse is tasked with the final structural welds that will permanently lock the nine sectors into a continuous pressure boundary.
Every vacuum vessel module is effectively custom-built, with tolerances measured in microns and logistics that resemble a space programme more than a standard power plant.
Where the schedule stands
| Module | Installation date | Status |
|---|---|---|
| Module no. 7 | April 2025 | Installed |
| Module no. 6 | June 2025 | Installed |
| Module no. 5 | 25 November 2025 | Installed |
| Modules no. 1–4, 8–9 | 2026 (planned) | Pending installation |
The team aims to place a new sector roughly every two to three months through 2026, a pace that leaves little room for surprises.
From steel ring to artificial star
What happens after the nine modules are in
Once the full ring is closed, work will shift to the painstaking phase of final welding and leak testing. The vacuum vessel must hold ultra-high vacuum conditions while enduring huge thermal and magnetic stresses.
Engineers then begin installing internal components: the divertor that exhausts helium “ash”; shielding blocks that protect the structure from neutron bombardment; and a network of diagnostics that will watch the plasma in real time.
High-frequency heating systems, including radio-frequency antennas and neutral beam injectors, will follow. These tools will push the plasma temperature well beyond that of the Sun’s core.
Current plans foresee ITER starting vacuum tests towards 2028–2029, leading to the first hydrogen plasma around 2030. That initial plasma will be relatively low power, aimed at checking that magnets, cooling systems and controls all work together as designed.
The big prize is a deuterium–tritium plasma, expected later in the 2030s. In that phase, ITER is supposed to show a power amplification factor where fusion output significantly exceeds the heating power supplied.
A race against engineering limits and the calendar
ITER’s construction has already slipped years beyond its original schedule. The first plasma was once advertised for 2025; pandemic delays, supply chain issues and design refinements have all pushed that date back.
The budget has climbed north of €22 billion, with Europe, China, India, Japan, South Korea, Russia and the United States sharing the bill. For supporters, the cost is comparable to a large space mission, yet targeted at a technology that could reshape global energy for centuries.
ITER is not designed to feed the grid itself, but to prove that sustained, net‑energy fusion can be engineered and controlled.
Why this matters beyond the ITER site fence
Fusion basics in plain language
Nuclear fusion joins light atomic nuclei — typically forms of hydrogen — into heavier ones, releasing energy in the process. Stars do this naturally under crushing gravitational pressure. On Earth, devices like tokamaks use powerful magnets to squeeze and heat a thin gas until it becomes plasma.
Unlike nuclear fission, which splits heavy atoms and generates long-lived radioactive waste, fusion reactions can be designed to produce smaller volumes of shorter‑lived waste. Fusion reactions also stop if conditions deteriorate, which limits the risk of runaway accidents.
That said, fusion plants will still be nuclear facilities. Components close to the plasma will become activated by neutrons and will require careful handling and long-term planning.
What success at ITER would unlock
If ITER hits its targets in the 2030s, the next step would be demonstration plants, often called DEMO reactors. These would connect to the grid and trial technologies for continuous operation, fuel recycling and commercial maintenance strategies.
Progress at ITER is already feeding into other fusion efforts. Private companies in the UK, US and elsewhere are testing high‑temperature superconducting magnets, alternative geometries and advanced digital control systems. Some of these tools could be combined with lessons from ITER to shrink reactor size or speed up construction for second‑generation plants.
For people living far from Cadarache, the installation of “module no. 5” sounds obscure. Yet each of these industrial moves is part of a slow turning of the dial: from idealised physics to concrete hardware. If that dial keeps turning, the energy mix of the late twenty-first century could look very different from today’s gas- and coal-heavy landscape.
Originally posted 2026-03-04 02:34:41.