Photos: Building the World’s Largest Fusion Reactor

Each of the nine wedge-shaped modules stands 13 meters (42.65 feet) tall and weighs approximately 1,200 tons. They are designed to contain a huge volume of intensely-hot plasma inside a torus-shaped vacuum vessel, confined by powerful magnetic fields.Science Photo Library / Reuters Reinforcing bars are laid in place across the facility’s foundation, before a 1.5-meter-thick concrete foundation slab will be poured over. The building will house the tokamak of the ITER experimental fusion reactor. The acronym ITER is also a word in Latin, meaning “journey,” or “path.”Science Photo Library / ReutersThe 300,000-ton tokamak complex will rest on top of 493 anti-seismic bearings that are mounted on concrete plinths rising up from the foundation.© ITER Organization / EJF RicheAn aerial view of the 100-acre central platform of the ITER Complex, seen in early 2026 in Saint-Paul-lès-Durance, France. The largest buildings, seen at the center, are the Tokamak Complex and its assembly building. Surrounding it are more than 35 support buildings that house workshops, diagnostic centers, heating, cooling, power handling, and more. Construction continues, with a target date of 2033 for its first successful generation of plasma.© ITER OrganizationA snapshot of construction progress on the assembly building and the Tokamak Complex, seen on April 7, 2025© ITER OrganizationThe first 110-ton module of the central solenoid, seen from below on December 6, 2023. When complete, the central solenoid will form an 18-meter-tall column at the heart of the tokamak, acting as an incredibly powerful superconducting magnet, driving current into the plasma. Teams from the United States fabricated the central solenoid, then shipped the modules to France. Thirty-five nations around the world are collaborating on the ITER project, building and con