Plan is to generate first ultra-hot plasma at €20bn facility in 2025 The €20bn project will replicate the reactions that power the sun and is intended to demonstrate fusion power can be generated on a commercial scale. Photo courtesy Iter. The world’s largest nuclear fusion project began its five-year assembly phase on Tuesday in southern France, with the first ultra-hot plasma expected to be generated in late 2025.

The €20bn Iter (International Thermonuclear Experimental Reactor) project will replicate the reactions that power the sun and is intended to demonstrate fusion power can be generated on a commercial scale.

The steel and concrete superstructures nestled in the hills of southern France will house a 23,000-tonne machine, known as a tokamak, capable of creating what is essentially an earthbound star.

Millions of components will be used to assemble the giant reactor, which will weigh 23,000 tonnes and the project is the most complex engineering endeavour in history. Almost 3,000 tonnes of superconducting magnets, some heavier than a jumbo jet, will be connected by 200km of superconducting cables, all kept at -269C by the world’s largest cryogenic plant.

Iter said “massive and complex” first-of-a-kind components have been arriving at the construction near Cadarache site in recent months from all over the world. The tokamak building and assembly hall are complete and the cryostat base has been installed. “The requisite assembly tools are largely in place,” Iter said.

The French president, Emmanuel Macron, launched the assembly phase, alongside senior figures from Iter members, the EU, UK, China, India, Japan, Korea, Russia and the US. Shinzo Abe, the Japanese prime minister, said: “I believe disruptive innovation will play a key role in addressing global issues including climate change and realising a sustainable carbon-free society.”

“Enabling the exclusive use of clean energy will be a miracle for our planet,” said Bernard Bigot, Iter director-general. He said fusion, alongside renewable energy, would allow transport, buildings and industry to run on electricity.

But Mr Bigot said: “Constructing the machine piece-by-piece will be like assembling a three-dimensional puzzle on an intricate timeline [and] with the precision of a Swiss watch.” The Iter project was conceived in 1985 but has suffered delays.

Europe is contributing almost half of the cost of Iter’s construction. The other members of the venture – the UK, China, India, Japan, South Korea, Russia and the US – are contributing equally to the rest.

What is nuclear fusion?

Fusion is the same process involved in powering the sun and other stars in our universe. Energy is produced by fusing together light atoms, such as hydrogen, at the extremely high pressures and temperatures. These particular conditions are present in the sun’s core, delivering temperatures of up to 15 million ºC.

The extremely high temperatures can transfer a gas into a state of plasma, which is essentially an electrically-charged gas. Although plasma is rarely found on Earth, it is thought that more than 99% of the universe exists as plasma.

To replicate this process on Earth, gases need to be heated to extremely high temperatures of about 150 million degrees Celsius at which point atoms become completely ionised.

The easiest method for this type of fusion reaction is with two hydrogen isotopes: deuterium, extracted from water, and tritium, produced during the fusion reaction through contact with lithium.

When deuterium and tritium nuclei fuse, they form a helium nucleus, a neutron and a lot of energy.

The Iter tokamak

The Iter tokamak will weigh 23,000 tonnes and be 60m in height. In a tokamak the plasma is held in the looping structure. Using coils, a magnetic field is created that causes the plasma particles to oribit in spirals, without making contact with the chamber walls.

The neutron has no electrical charge and is unaffected by the magnetic fields, allowing them to move away from the bond of the plasma.

The neutrons are then absorbed by the surrounding walls transferring their energy into heat and generating steam from pools of water.

How much power will the Iter tokamak provide?

The plant at Iter will produce about 500 MW of thermal power. If operated continuously and connected to the electric grid, that would translate to about 200 MW of electric power, enough for about 200,000 homes.

A commercial fusion plant will be designed with a slightly larger plasma chamber, for 10-15 times more electrical power. A 2,000 MW fusion power plant, for example, would supply electricity for two million homes.

Date: Wednesday, 29 July 2020
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