Is nuclear fusion the energy of the future?

Imagine clean, almost unlimited energy that can produce electricity without emitting CO₂ or generating highly radioactive waste. This promise is that of nuclear fusion. Since the end of the Second World War, scientists have been trying to replicate on Earth the process at work at the heart of the Sun.

Faced with the climate and energy emergency, research has been accelerating for 20 years. Where are we today? Is nuclear fusion within reach or is it a technological pipe dream that is still out of reach?

Operation, challenges, recent advances, technical challenges, and international projects such as ITER: dive into the heart of this scientific quest with Sirenergies.

Nuclear fusion: what is it?

Nuclear fusion is a technical process that makes it possible to produce a large quantity of thermal energy thanks to fusion of several radioactive elements. The heat is then converted into electricity. The manufacturing process is based on the condensation of two atomic nuclei which, when assembled, form a heavier nucleus.

The fusion or energy of the Sun and the stars

Nuclear fusion on Earth attempts to replicate the fusion reaction observed at Heart of the Sun and stars. The latter are essentially composed of a “plasma” in which hydrogen atoms fuse to produce helium.

How is this process possible? Aren't hydrogen atoms supposed to repel each other?

In theory, yes. But plasma is a very hot ionized gas. In addition, the center of a star is distinguished by a high gravitational force and very high temperatures (around 15 million degrees Celsius for our Sun). Particles have no choice but tocollide and merge.

How does nuclear fusion work?

When hydrogen atoms fuse, they form a heavier but very unstable nucleus... The neutron is expelled, causing a tiny loss of mass. La Quantity of energy released by this expulsion is huge!

This small step for the core is a big step for humans. But the process is far from over. Other particles meet as condensation occurs, producing increasing energy. The fusion reaction continues as long as there are resources to consume.

Is reproducing nuclear fusion on Earth a utopia?

Nuclear fusion is possible on Earth, at least in theory. It could allow a considerable production of electricity thanks to adapted turbines.

The system to be put in place does not differ in any way from current technology: the Nuclear fission. The heat resulting from the reaction increases the temperature of the water contained in a primary circuit.
The latter in turn heats the water stock in the secondary circuit. At this point, water vapor causes the turbine connected to the alternator to rotate to produce electricity.

Why use nuclear fusion?

Thermonuclear fusion is in principle an inexhaustible source of energy. To better understand its potential and its place in the energy future, let's explore its advantages and disadvantages.

The benefits of nuclear fusion

Measuring the benefits of nuclear fusion is only possible by comparing it to a similar process: fission. The latter is often criticized because of the technical risks it presents.

In theory, fusion can avoid these risks while offering greater energy production. Among the advantages of this process, we can mention:

• One increased energy power, with a production four times more powerful than fission.
• One reduced risk of nuclear accident, thanks to the absence of a chain reaction.
• One carbon-free energy with almost zero greenhouse gas emissions and with limited consequences for the environment and populations.

One of the major challenges ofnuclear energy resides in the waste management. Although fusion generates waste, it is not highly radioactive. The most problematic residues should be able to be recycled in less than 100 years, while waste from nuclear fission has a lifespan of 300 years to several thousand years.

The limits of thermonuclear fusion

Although promising, nuclear fusion is not without risks. The Institute for Radiation Protection and Nuclear Safety (IRSN) warns against the formation of residues due toerosion of materials composing the internal cover of reactors (tungsten or beryllium).

OFother forms of pollution could arise from the dismantling of future nuclear reactors or from existing merger projects. The risk is all the more real as the materials and infrastructures are irradiated during the operation of nuclear power plants. However, this problem remains less significant than the consequences of fission.

ITER or the promise of a nuclear revolution

Since the end of the Second World War, projects around nuclear fusion have multiplied. Each is a veritable mine of information to give life to the international ITER (International Thermonuclear Experimental Reactor) project, launched in 2006.

A global interest in nuclear fusion

To create and confine fusion plasma, researchers designed a Experimental reactor: the tokamak. Since 1950, more than 200 models have been built around the world in the hope of reaching the holy grail: nuclear fusion.

The Tokamak — Source: © US ITER

Scientists are making full-scale tests to better understand and control the energy of nuclear fusion.

The best known projects are :

• The KSTAR (Korea) — Korea Superconducting Tokamak Advanced Research
• The EAST (China) — Experimental Advanced Superconducting Tokamak
• The WEST (France) — Tungsten Environment in Steady-state Tokamak, operated by the Atomic Energy Commission (CEA).
• The JET (Europe) — Joint European Torus
• The JT-60 SA (Japanese-European collaboration)

The KSTAR (Korea) — Photography: National Research Council of Science & Technology

ITER, an ambitious international project

Since 2006, the International thermonuclear experimental reactor ITER benefits from the collaboration of 33 countries.

The construction of the 830 m³ tokamak was carried out in Cadarache in the south of France. This project aims to generate “burning plasmas” and to analyze their behavior. Plasma production should start in 2033. The first deuterium/tritium fusion is expected to start in 2039. This preparatory period will make it possible to progressively increase the power of the ITER reactor, while guaranteeing its stability and limiting additional costs.

If ITER succeeds in achieving and maintaining nuclear fusion, it will prove the technical feasibility of the process. This advance would pave the way for an even more ambitious project: the Tokamak DEMO. Its objective? Demonstrate the possibility of producing large quantities of electricity through thermonuclear fusion, in the second half of the 21st century^E century.

What is the future for nuclear fusion?

The future of nuclear fusion depends on the ability of researchers to overcome the obstacles to its exploitation. To answer this question, let's analyze the challenges and results achieved so far.

Fusion energy is a utopia. Many might be tempted to reach this conclusion, as there are so many challenges ahead. This ambitious project aims to reproduce the conditions of plasma formation in the heart of the Sun.

However, the gravitational force is not at all the same on Earth...

Numerous technical challenges to nuclear fusion

To harness the energy of nuclear fusion, scientists must combine four elements :

• A basic resource composed oflight atoms.
• One superpowered reactor to create plasma.
• One containment device to contain the plasma.
• A solution for densifying plasma in order to promote atomic collisions.

To date, two ingredients seem suitable for simmering in plasma soup: deuterium (D) and tritium (T), two isotopes of hydrogen. They offer good energy efficiency at relatively low temperatures. However, D-T fusion requires a temperature of 150 million degrees, which is 10 times more than the temperature at the center of the Sun!

With regard to plasma, two confinement techniques are being studied: inertial confinement And the magnetic confinement. The first solution requires heating a metal capsule of about 2 mm in size with laser beams and a power of 300 billion watts! This technique has not yet made it possible to reach the expected ignition threshold (production of thermal energy).

Principle of fusion by inertial confinement — Source: Veinhard, Matthieu. (2019). Surface damage to silica with LMJ laser beams.

Nuclear fusion: results still partial

Since the first tokamaks, nuclear fusion has oscillated between excessive hype and technological stagnation. Even though progress is significant, the technology is still a long way from being exploited on a large scale. However, the records keep coming, bringing hope:

• In December 2021, the Chinese TOKAMAK EAST maintained a fusion plasma at nearly 70 million degrees Celsius for 17 minutes and 36 seconds.
• In 2022, the JET reactor located in the United Kingdom produced nearly 11 MW for 5 seconds, a significant advance but barely enough to power an LED bulb for 2 hours.
• In 2022, the United States announced a net gain in energy, marking a world first in which the quantity of energy produced exceeded that consumed.
• In 2023, the Japanese-European JT-60SA project generated plasma in a record volume of 160 m³ at over 15 million degrees Celsius.
• In February 2025, the WEST tokamak maintained a plasma for 22 minutes, surpassing the record set a few weeks earlier by the EAST tokamak.

All eyes are now on ITER, which aims to produce 500 MW for 400 seconds using only 50 MW of power to carry out the D-T deuterium-tritium fusion.

A renewed interest in nuclear energy

Nuclear fusion research could continue to accelerate in the coming years, with support from new countries. After years of skepticism, several European states have just taken major decisions in favor of nuclear power.

In Belgium, the repeal in May 2025 of the law to abolish nuclear power allows the maintenance of the five nuclear power plants in operation, two of which see their extended lifespan of ten years. Belgium is also considering the construction of new nuclear production capacities, in particular via small reactors (SMR).

A fervent defender of renewable energies, Denmark passed a law exploring the possibility of using nuclear power to cover electricity demand and reduce its dependence on gas and coal. Focusing on SMRs, the impact study should last one year.

Even anti-nuclear Germany seems to be softening its position. Although the last German power plants were shut down in 2023, Germany nevertheless remains a stakeholder in the ITER project and plans to invest more than one billion euros to develop its first fusion reactor.

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To conclude...

Clean, powerful and abundant, nuclear fusion embodies the energy ideal. But this seductive image hides a complex reality. Many states rely on nuclear power to meet energy and climate challenges. Every year, tokamak projects push the envelope. However, uncertainty remains: while experts hope for the first concrete results from 2050, large-scale energy production seems far from reaching. There is still a long way to go to transform nuclear fusion into the key to the energy future... but it is being traced by international research and cooperation.