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By Roger Highfield on

Can Fusion Power Cut Fossil Emissions?

Roger Highfield, Science Director, visits ITER in southern France, the world’s largest fusion project, to assess whether it will mark a milestone in averting harmful climate change.

We are gazing down into a circular well, almost 30 metres across, where a grey totem – an assembly crane – looms over us. Around it boxes wrapped in pink plastic sit like supplicants anxiously awaiting the arrival of vast supercooled magnets that will confine the superhot heart of this extraordinary nuclear reactor.

With my curatorial colleagues, Oliver Carpenter and Laura Joy Pieters, I am on a tour of the International Thermonuclear Experimental Reactor (ITER is ‘the way’ in Latin) which is taking shape on a sprawling construction site among the limestone ridges of Saint Paul-lez-Durance in Provence.

This is the world’s biggest and most advanced fusion project, where the nuclear reactions that make the Sun shine, and explode hydrogen bombs, will be tamed to turn gram quantities of fusion fuel into energy.

‘Within this pit we will generate the hottest temperatures in the universe, hotter than the core of our Sun,’ says Sabina Griffith, our guide who has worked on the project since it began in 2006. ‘Where the magnets sit will see the coldest temperatures, similar to those on the dark side of the moon,’ she adds.

If ITER succeeds in generating more energy than it consumes – they hope to get 500 megawatts of fusion power for 50 megawatts put in (albeit for ten minutes) – this international venture could be a game-changer when it comes to cutting the planet’s dependence on fossil fuels.

The UN’s Intergovernmental Panel on Climate Change (IPCC) gave a stark warning this week that computer models suggest that global carbon emissions need to peak, at the latest, by 2025 and then decline rapidly for the world to have a 50-50 chance of limiting warming to 1.5°C. That is a very tall order given that current commitments will only limit the rise to more than 3.2°C this century, more than double the 1.5°C limit set by the 2015 Paris climate agreement, which would see the planet ‘hit by unprecedented heatwaves, terrifying storms and widespread water shortages’, says UN Secretary General, Antonio Guterres.

ITER. Exterior view.


This could well be the most complex machine being built on the planet. The last time I saw engineering of this complexity, scale and ambition – where scientific demands are at the bleeding edge of what engineering can deliver – was while visiting Atlas, one of the huge ‘eyes’ of the Large Hadron Collider, the atom smasher near Geneva.

Vast cranes are assembling ITER, which weighs 23,000 tons (the equivalent of three Eiffel towers). Of its million or so components, the heaviest will weigh nearly 900 tons including the transport vehicle; the largest will be approximately four storeys—or 10.6 metres—high.

Strangely enough, among the myriad smaller components, ITER will also rely on coconuts—tons and tons from one particular harvest from one particular Indonesian island —to make the charcoal lining of the reactor’s vacuum pumps. ‘The coconuts are all in boxes under the terrace of the headquarters’, said Sabina Griffith.

Coconut next to a jar of the resulting carbon destined for use in the vacuum pumps.

ITER offers the world the tantalising hope that there might be a way to generate the extraordinary amounts of energy required to live a modern lifestyle without the excessive carbon emissions that are pushing the planet relentlessly towards extreme weather, rising sea levels and ecosystem collapse.


Politics made this vast venture possible, a collaboration that was first discussed in the mid-1980s. Today, the European Union has a 45% stake, with India, Japan, Korea, Russia, China and the United States each holding 9%.

In a vast warehouse in the docks near Marseille, we see bus-sized wooden crates, metal spars and other multi-ton components that have been shipped from around the world. An hour’s drive away in Saint Paul-lez-Durance, the flags of the member nations flutter in the sunshine.

Wander around the construction site and you can see components from South Korea, Japan, Russia, the UK (incongruously, most visible in the form of sleeping policemen) and eavesdrop on many languages, from a group of Bavarians who have been working on the vacuum chamber – cryostat – around the tokamak to the Chinese construction workers in the pit.

But politics has also proved ITER’s worst enemy. When it was launched in 2006, the project was estimated to cost €5 billion and begin operation within five or six years.

However, to sell the project internationally, there was a blind eye to many key details, an expensive omission. In the second year, the costs and timeline tripled in the wake of a design review. Today the price tag is officially put at €22 billion, and it seems likely to rise further.

Key appointments were made on the basis of pork barrel politics, not merit, background or experience. The first leadership team was criticised as weak, as the project limped along. The politics of Brexit have ensured that the UK, a pioneering fusion nation, will make no new commitments to the project.

Now the war in Ukraine is causing a headache when it comes to getting the people and hardware from Russia, the nation that invented the tokamak, the doughnut-shaped magnetic bottle that holds the superheated heart of the reactor and has around 80 staff on site.

It is no accident that the office that controls the logistics is among the biggest on the ITER organogram. The delays in delivering massive hardware components from Russia, which now have to avoid transport through Ukraine, will cause a chain reaction of knock-on effects on ITER’s schedule.

The current date for ITER to enter operation is 2025 but that seems likely to slip towards the end of this decade, making it unlikely that commercial fusion based on this concept will be ready in time for the current energy transition needed to avert a climate emergency.

However, there is an emerging industry of private fusion firms, backed by more than $2 billion, that hope to have commercial reactors ready in the next decade.

In the long-term, the potential of fusion power is almost limitless.


Fusion is simple – in outline, at least. Take two forms (isotopes) of hydrogen, squish them together, and you get a helium atom, and a very energetic subatomic particle called a neutron.

Like conventional ‘fission’ nuclear reactors, fusion harnesses Einstein’s famous equation, E = MC², where energy equals mass times the speed of light (a huge number, 300,000 km/sec) squared.

While fission reactors exploit how a little nuclear mass is lost to release vast amounts of energy when heavy elements such as uranium and plutonium decay, fusion reactors take advantage of how a little mass is lost when light elements fuse together.

The catch is that the nuclei of these atoms are positively-charged and repulse each other. That is why they can only be persuaded to fuse together at colossal temperatures, or under the huge gravitational forces found within our nearest star.

Within ITER, the fusion fuel breaks down to form a plasma, a soup of charged particles at temperatures which will reach 150 million °C—or ten times the temperature at the core of our Sun.

No Earthly material can withstand these temperatures and the plasma must be held away from the walls of the tokamak with extraordinarily powerful magnetic fields created with the help of superconductors, materials that lose all resistance to electricity – in this case, at liquid helium temperatures.

Understandably, one brake on progress is the constant attention of the nuclear regulator, which has imposed several hold points on the great project to ensure that ITER is subject to the same scrutiny as a nuclear power plant. During our visit, elements of the project were on hold because of concerns about the welding of the vacuum vessel that surrounds the reactor.


At the heart of ITER is the tokamak, one third of which sits under ground level within the pit. We are gazing through one of the great access ports (see top photograph), which will be sealed to form a vacuum around the core of the reactor where its magnets can be kept within a whisker of Absolute Zero.

There is a constant hustle and bustle of workers around the totemic cylindrical crane which will assemble six sections to create the core of the reactor.

These sections will form the central solenoid, a five storey, 1000-ton superconducting coil which must be strong enough to contain a force equivalent to twice the thrust of the Space Shuttle at take-off (more than 6,000 tonnes of force), or enough to lift a couple of aircraft carriers.

Like a great beating electromagnetic heart, the solenoid made by General Atomics in America will generate pulses of energy to ignite the fusion reactions.

Pass through waves of cool air and heavy plastic sheets that keep dust out of the pit, and one enters a cathedral-like space where the D-shaped sections of the tokamak are lined up in vast support structures and cleaned before installation.


Picture of one of the D shaped sections (less its ‘blanket) and support structure.

A nonchalant Frenchman, fiddling with what looks like a high-tech bum bag, is casually operating one of the overhead cranes, each of which can lift 1500 tons, the equivalent of four Boeing 747s full charged with passengers and fuel, which are used to lift each of the nine sections into place in the pit.

A few minutes’ walk away, in another yawning hangar, a team of Bavarian engineers is strolling around a great lid some 30 metres across which will complete the cryostat, the 29-metre-tall vacuum vessel that surrounds the tokamak and the largest stainless steel vacuum vessel ever made. The following day there will be beer and sausages to celebrate how, with the lid, they now have the wherewithal to build this ultracool container.

The top of the cryostat that is key to keeping ITER’s superconducting magnets cool.

But the atmosphere in another nearby hangar is quite different, like the hush of a chapel, where another team of engineers is carefully winding the vast superconducting coils that will surround the tokamak.

In all 100,000 kilometres of niobium-tin superconducting strands are necessary for ITER’s vertical D shaped toroidal field magnets. However, there are also correction coils and great horizontal hoops too – the poloidal coils. ‘The magnets are responsible for a quarter of the cost,’ said Dr Enrique Gaxiola, ITER magnet engineer.

Winding one of the vast superconducting coils.


Hanging on the wall of Sabina Griffith’s office in the site headquarters is a sign: ‘Trying to confine plasma is like trying to confine a doughnut of marmalade with duct tape’ (Emmanuelle Tsitrone of the French Alternative Energies and Atomic Energy Commission (CEA)).

It is one thing to generate the vast magnetic fields to confine the plasma, quite another to control them in an instant to confine the plasma and keep it away from the inner lining of ITER, the blanket. Such is the speed and complexity of plasma confinement that these great vertical and horizontal coils are likely to be controlled by artificial intelligence, with one advance reported recently by the UK company DeepMind.

Those who are queasy about the safety implications of this new kind of power plant, who fret about how a fusion accident would compare with a Chernobyl or Windscale, should take heart from how hard it is to tame the plasma.

Yes, an out-of-control plasma could vaporise the inner cladding of the tokamak. But such is the difficulty of nurturing and maintaining the doughnut of plasma, the fusion reaction will quickly wink off. A runaway reaction is impossible, with less than four grams (equivalent to four paper clips) of fusion fuel present at any given moment in ITER.


In one sense, ITER is the same as the power plants we have depended on since 1884 when the modern steam turbine was invented by the Anglo-Irish engineer Charles Parsons to turn steam into rotation that can be harnessed to drive a dynamo and make electricity.

The source of heat is the unique feature. The ITER tokamak will be the largest ever built, with a plasma volume of 830mᶟ, compared with 100mᶟ in the Joint European Torus, near Culham in the UK, which will enable it to produce, for the first time, a “burning plasma” in which most of the heating needed to sustain the fusion reaction is produced by the fusion process itself. The production and control of such a self-heated plasma has been the goal of magnetic fusion research for more than half a century.

In the tokamak, much of the energy created by fusion will be carried away in the form of subatomic particles called neutrons, which are neutral and thus oblivious to the powerful magnetic fields around them. These slam into the walls of the tokamak – a blanket of copper and stainless steel coated with beryllium – to create heat.

ITER will be the first fusion reactor to be cooled with water. While the resulting steam would be used in a commercial fusion plant to make electricity, in ITER it is dissipated through a huge complex of cooling towers next to the reactor to do away with the cost of building a power plant.

Once that can be done reliably, ITER will pave the way for true commercial fusion power plants where tweaks in design and efficiency should ensure that much more energy is generated than used to liberate power from the pellets of fusion fuel, fired by a ‘gun’ into the plasma. When that energy can be extracted routinely, we will have entered the age of fusion power.


There is a long running joke about fusion power: it was 50 years away when the Soviet Union first came up with the tokamak in the 1960s and it always will be.

Yet recent results reporting a record-breaking sustained fusion reaction at the Joint European Torus in Culham, offer yet more hope that ITER is indeed on the right path. Equally, even when ITER does start working it will take another eight years for the reactor to create a burning plasma of fusible fuel, in the form of the hydrogen isotopes deuterium and tritium.

Anyone who gets the chance to visit this jaw-dropping construction site near Marseilles will be left in no doubt that, if it works, it will for the first time take us beyond the receding horizon of current expectations, into a new era where a colossal low carbon energy source has the potential to transform the way we all live.