On a quiet plateau in southern France, the world’s most ambitious energy experiment has entered a new phase. Engineers at ITER have begun assembling the heart of the reactor, a 64-foot-wide steel chamber designed to recreate the same fusion reactions that power the Sun, according to Earth.com.
It marks a turning point for the multibillion-dollar international megaproject, shifting it from planning to hands-on construction as crews prepare to contain a plasma hotter than the solar core.
The work centers on ITER’s vacuum vessel, a double-walled steel chamber weighing about 5,700 tons. Once complete, it will form the doughnut-shaped space where hydrogen isotopes are heated into super-hot plasma. Keeping that plasma suspended and away from the walls is crucial. Even a brief touch can end an experiment or damage hardware, which is why alignment tolerances for each steel sector are being tightened to a fraction of an inch.
Europe and South Korea are providing all nine massive vessel sectors. A U.S. contractor will weld them into a perfect ring on site, using robotic tools and an extremely slow welding sequence to keep the structure from warping as thousands of degrees of heat cool.
ITER recently adopted a revised baseline plan that gives engineers more time to test systems before using full fusion fuel. Early experiments will use hydrogen and deuterium to validate hardware, magnets, cryogenics, and safety systems. The staged approach runs through 2036 and 2039 with a milestone called Start of Research Operations, a 27-month test period for initial plasmas.
The ultimate goal is Q?10, meaning 50 megawatts of input heating generating 500 megawatts of fusion output. ITER itself will not produce electricity for the grid; instead, it is designed to prove that long-lasting, high-power plasmas using deuterium-tritium fuel are scientifically achievable.
One major change in the new plan is replacing beryllium with tungsten on the reactor’s inner wall. Tungsten’s extreme heat resistance and lower risk during off-normal events make it better suited for future commercial fusion systems. Operators will also coat surfaces with boron to keep plasma free from impurities.
ITER now involves 35 nations, each contributing parts, money, and expertise. Progress has been slowed by repairs and delivery delays, but the result is a more refined machine entering operations with fewer unknowns.
If successful, ITER will offer the strongest real-world proof yet that fusion energy could eventually become a clean, virtually unlimited power source for the planet.
