This giant magnet could unlock zero-carbon electricity from nuclear fusion

Imagine almost limitless clean, carbon-free electricity. That’s the dream that’s driving scientists to build the world’s biggest magnet.

The ITER project in southern France is pushing the boundaries of nuclear fusion, a reaction in which atoms are fused releasing enormous amounts of heat. It's the process that powers the sun, but so far it's only been achieved on Earth in very short bursts in experimental reactors.

The hope is that, by using a powerful magnetic field to control the plasma created by the fusion reaction, it can be sustained long enough to heat water to produce steam to drive a turbine generator.

Not that ITER is due to power the grid any time soon. What they’re building is a Tokamak - an experimental machine designed to harness the energy produced by fusion. If this stage of the project is successful, the next step will be to build a prototype power plant.

Unlike conventional fission nuclear power plants, fusion produces virtually no harmful waste and emits zero carbon dioxide. A fusion reaction creates helium gas. It’s also renewable - the fuel sources, deuterium and tritium, are derived from hydrogen and can be extracted from seawater.

"Fusion is one of the few potential options for large-scale carbon-free energy production,” John Smith, director of engineering and projects at General Atomics, the company building the magnet, told Live Science.

“It offers a safe, clean, always-on resource that produces no emissions or long-lived waste products," he added.

Starting a fusion reaction is very energy intensive. The fuel must be pressurised and heated to extremely high temperatures to create a plasma - similar to a gas but nearly one million times less dense than air.

So a big challenge is to ensure that the new fusion reactor creates more energy than it uses. The current world record for fusion power is held by the European experimental Tokamak called JET which needed 24 megawatts of heating power to produce 16 megawatts of fusion power.

But the ITER scientists are optimistic that their new doughnut-shaped reactor will do better. Once the reaction is started, they say fusion will generate intense heat - 150 million degrees Centigrade - 10 times hotter than the core of the Sun.

The 18 metre tall magnet, known as the central solenoid, will weigh in at 907 tonnes when its complete and will generate a magnetic field 280,000 times stronger than the Earth’s magnetic field - strong enough to lift an aircraft carrier into the air.

The magnet is already on the move from the factory in San Diego, California, where it was built to Houston, Texas, from where it will be taken by ship to Marseille for its final road journey to the ITER site near Aix-en-Provence.

It will be joined there by another giant component, the world’s largest superconducting coil which will wrap around the reactor core, being manufactured in Japan by Mitsubishi Heavy Industries, a World Economic Forum strategic partner.

In all, the project involves 35 countries including the US, France, China, the European Union, India, Japan, Korea, Russia and the UK, who between them have manufactured more than one million components for the new plant.

ITER scientists say that more than 99% of the Universe exists as plasma, including interstellar matter, stars and the Sun. On Earth, plasmas are used in neon tubes, for lightning and in plasma televisions. In nature they create the northern lights (aurora borealis).

If all goes well, the Tokamak at ITER should be ready to generate it’s first plasma in December 2025.