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Nuclear fusion: the energy of the future?

Photograph of the interior of the National Ignition Facility (NIF) Inertial Fusion System at Lawrence Livermore National Laboratory in Livermore, California.

© Damien Jemison/Lawrence Livermore National Laboratory/AFP

Text by: Nenad Tomic

5 mins

When, in the 1930s, British scientists from the University of Cambridge succeeded in demonstrating the principle of nuclear fusion, a real hope of abundant, clean and inexpensive energy loomed for the future of humanity.

It took until the beginning of December 2022 to see this hope take a first step: an American laboratory produced more energy through fusion reactions than that necessary to cause it. 

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What is nuclear fusion? 

Nuclear fusion is a natural phenomenon that occurs in the heart of stars and especially inside our Sun.

The process is continuous and releases a gigantic energy.

For example, the sun fuses about 600 million tons of hydrogen per second and, in a single second, produces as much energy as all of humanity consumes in a year.  

For the theoretical part, nuclear fusion consists of bringing together two light atomic nuclei to form a heavier nucleus.

It therefore differs from nuclear fission, the phenomenon that occurs in the reactors of nuclear power plants, where it is a question of separating nuclei from heavy atoms.  

To reproduce the reaction that takes place in the heart of the sun, the scientists succeeded in the laboratory in bringing together two hydrogen atoms at a temperature exceeding 150 million degrees Celsius.

When these light nuclei merge, the created nucleus tries to find a stable state and ejects a helium atom and a neutron.

It is this phenomenon that releases a large amount of energy.      

But the problem is significant: to be able to produce these quantities of energy, it must be possible to do so in a controlled manner, in other words that the entire process be contained within the reactor.

However, man has already succeeded in producing fusion and seeing its devastating effects when he designed the thermonuclear bomb (the H-bomb).

In this specific case, it is an uncontrolled merger.

So the whole problem lies in how to control the merging process. 

How to produce energy through fusion? 

This is a great challenge for the scientific community.

The conditions that the fusion process requires, and such as exist inside the celestial bodies, do not exist on Earth.

The temperature of several hundred million degrees and a strong magnetic field necessary for fusion must therefore be produced artificially.

However, no material existing in terrestrial nature resists such temperatures which make it possible to trigger fusion.  

So the researchers are working on the principle of "magnetic confinement", in other words producing a very high temperature in a ring-shaped reactor which keeps the atoms ready to merge with the help of powerful magnetic fields.

And in order to facilitate the process, it is necessary to resort to the isotopes of hydrogen.

Isotopes are atoms that have the same number of protons, but not the same number of neutrons.

Scientists have concluded that the two-neutron isotope of hydrogen, deuterium, which is heavier and easier to fuse, is also very easy to extract from seawater. the environment.

The other possibility is also to use tritium, which is produced by the irradiation of lithium.

The researchers calculated that it only takes a few grams of deuterium or tritium to produce one terajoule of energy (2,777.8 MWh).

This corresponds to the consumption of a person from a developed country for more than sixty years.  

Two ways to create energy through fusion 

In California, the Lawrence Livermore National Laboratory (LLNL), which carried out this revolutionary experiment in early December 2022 by producing more energy than that necessary for fusion, uses the so-called “ignition” method.

Indeed, the ignition threshold of nuclear fusion is reached when it crosses the point at which it is self-sufficient and begins to release more energy than it needed to reach this threshold.

And precisely, to obtain the ignition point, the reaction needs a constant supply of energy.

So that the fuel (hydrogen isotopes) can pass into the "plasma" state (the electrons are detached from the nucleus), the heat supply is done by powerful lasers which simultaneously target the capsule containing the hydrogen to increase its temperature and density.  

The Californian laboratory has certainly produced energy by merging atoms, but the yield remains derisory to be able to envisage an industrial application at this stage.

Moreover, the California facility is designed to demonstrate the principle of laser fusion and is therefore not a prototype fusion power plant. 

Unlike the American installation, the experimental fusion reactor installed in Cadarache, in the south of France, can one day be used to produce electricity.

Its name is Iter (

) and the atoms are held in a powerful magnetic field (50,000 times stronger than the Earth's magnetic field) and at a very high temperature in order to force the atoms to fuse together.

This circular-shaped reactor is the result of an international collaboration of 35 countries which have now invested more than 20 billion euros.

But we are still very far from the stage of producing cheap and clean energy.

The construction of Iter in France is experiencing some delays due to cracks which have recently appeared on the walls of the reactor.

And construction requires new funding.

The first experiments in Cadarache are expected for 2035. And only if the experiments are conclusive, the production of electricity through fusion could be possible towards the end of the century.

Cheap and clean energy  

Our selection on the subject:

• To listen : 

→ Historic breakthrough in nuclear fusion: "It's carbon-free and above all clean energy" 

→ A "portable" nuclear fusion reactor 

→ South Korea: visit to KSTAR, the research center for the energy of the future 

→ How does science infuse and spread?

Scientific press review of the month of February 2020 

• To read : 

→ [France 24] Nuclear fusion: the "net energy gain", a "historic" step that has just been taken? 

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