Inside the World's Biggest Bet on Fusion Energy

A machine designed to bottle a star is being built in southern France—and it might just save civilization as we know it.

In a remote corner of Provence, 35 nations are spending more than $20 billion on a single bet: that they can replicate the nuclear fusion that powers the Sun and bring it to Earth. The ITER fusion project (International Thermonuclear Experimental Reactor) is the largest and most ambitious energy experiment ever conceived. If it works, it will produce a near-limitless source of clean, safe power. If it fails, the energy world may have to wait decades for a plan B.

The ITER fusion project is not a power plant. It's a physics experiment on a gargantuan scale. Its core is a tokamak — a donut-shaped magnetic cage designed to hold plasma hotter than the core of the Sun. For a few minutes at a time, scientists will try to fuse deuterium and tritium, two isotopes of hydrogen, releasing energy in the form of heat. The goal: produce 500 megawatts of fusion power from only 50 megawatts of input — a tenfold energy gain. No commercial reactor has ever come close.

Why now? The world's climate clock is ticking. Renewable energy alone cannot decarbonize heavy industry, aviation, or baseload electricity. Nuclear fission carries baggage — waste, meltdown risk, proliferation. Fusion offers the upsides of fission without the downsides: no chain reaction, no long-lived radioactive waste, no CO₂ emissions, and abundant fuel from seawater and lithium. The ITER fusion project is the test bed that could prove fusion's viability.

ITER's history is as much a story of international politics as engineering. Conceived in 1985 by Ronald Reagan and Mikhail Gorbachev, it survived the Cold War, multiple budget crises, and a decade-long site selection battle. Construction began in 2010 in Saint-Paul-lès-Durance, France. The European Union funds 45% of the cost; the other six members (US, China, India, Japan, South Korea, Russia) each contribute roughly 9%. To date, the price tag has ballooned past $22 billion — three times the original estimate — and the timeline has slipped repeatedly.

Key details: First plasma was originally slated for 2020, then 2025. Current official target is 2027–2028. The full power demonstration may not happen until 2035. The device is 30 meters tall, 30 meters in diameter, and weighs as much as three Eiffel Towers. The magnets, made of niobium-tin and niobium-titanium, will generate a magnetic field 250,000 times stronger than Earth's. Over one million components are being manufactured in factories across 35 countries and shipped to France for assembly. It is the most complex supply chain ever assembled for a scientific instrument.

Analysis: The ITER fusion project is not without critics. Some argue the money would be better spent on solar, wind, batteries, and next-generation fission. Others point to smaller, private fusion ventures — Commonwealth Fusion Systems, TAE Technologies, Helion Energy — that are moving faster and spending less. But ITER's defenders say the big machine is the only way to study the physics of burning plasma at reactor scale. “You cannot simulate a star in a spreadsheet,” one particle physicist told CNET. The knowledge gained at ITER will inform all future fusion designs, public or private.

Outlook: The next few years are critical. Mechanical assembly is ongoing; the first vacuum vessel sectors are being welded. The magnet system will be tested in 2026. If ITER meets its milestones, it will set the stage for DEMO — a prototype fusion power plant — by the 2040s. Even so, commercial fusion is unlikely before 2050. But the wheels of the world's biggest bet are turning, and the countdown to the first burning plasma has begun. Whether ITER delivers on its promise or becomes a cautionary tale, it is shaping the future of energy science.