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What are the differences between fission and nuclear fusion?
Mis à jour le
March 6, 2026
6
Min reading
Nuclear fission and fusion are reactions that release significant quantities of energy, including in the form of heat that can be exploited to produce electricity. They both transform the nuclei of atoms that are “unstable” because they are either too heavy or too light.
2021 was the year of all records when it came to Nuclear fusion. This technology, which is still unknown to the general public, nevertheless concentrates a lot of hope for our energy future.
The Tokamak EAST (machine in the shape of a hollow metal ring, used by scientists to create nuclear fusion reactions, to produce energy) located in Hefei in China reached the temperature of 100 million degrees for 17 minutes and 36 seconds. It is a world record for nuclear fusion reactions.
The climate emergency is pushing us to find new ways of producing electricity. Nuclear fusion seems to be the most promising today. It is an experimental technology that remains highly unstable today.
For its part, Nuclear fission has amply proved its worth over half a century. But this technology, as we all know, also comes with risks.
Renewable energies are developing around the world, but the pace does not allow today to happen Fossil fuels.
Together, we will try to understand the current state of research in order to understand the advantages and disadvantages of these two technologies.
What are the differences between fission and nuclear fusion?
Nuclear fission, a mature technology that has proven its worth
The vast majority of nuclear power plants in operation today are equipped with a nuclear fission reactor. Excluding the few experimental nuclear reactors, Nuclear fission has proven itself from the middle of the 20th century to the present day.
Source: International Atomic Energy Agency
This technology consists in projecting a neutron onto an unstable heavy atom. The latter will then explode into 2 lighter atoms.
This nuclear fission reaction will release a significant amount of energy which will cause new atom fissions and so on. It is a chain reaction which follows.
This phenomenon makes it possible to produce a large and stable quantity of energy. The fuel used in this operation is uranium-235. It turns out that the composition and physical properties of uranium correspond perfectly to this need.
Uranium atoms have a nucleus capable of breaking into two smaller nuclei under the impact of the famous neutron. This is called nuclear fission.
Nuclear fusion, a disruptive technology in an experimental state
La Nuclear fusion is the process that allows merge two nuclei to form one heavier single core. It is important to note that this phenomenon is present all the time on most stars such as the Sun.
Deuterium and tritium are very light atoms, both derived from hydrogen.
Source: Nuclear Voice
They have the ability to fuse their nuclei to form a single helium nucleus. This reaction releases a very large amount of energy.
To fuse, they must be confined in a plasma at a very high temperature.
You should know that under very high temperature conditions, matter is transformed into plasma: neither solid nor liquid, matter is comparable to a mixture in which atoms and nuclei are no longer necessarily all linked in the same way.
To achieve this, you need to be able to raise temperatures to absolutely gigantic levels. We are talking here about 150 million degrees Celsius, which is about ten times the temperature of the Sun's surface.
When the two light nuclei collide in this space, they fuse to form a single heavy nucleus.
Today, no kWh has yet been supplied through nuclear fusion processes. The first research dates back to the years 1950-1960, however since then, there have been only a few international initiatives that are seriously addressing the subject.
As such, we can cite the project ITER : International Thermonuclear Experiment Reactor. It brings together more than 35 different countries. The first plasma is planned for 2025. There are a number of tokamaks around the world that regularly carry out tests.
Source: ITER
What is the advantage of fusion over fission?
Energy that is present in abundance
Nuclear fusion is a renewable energy that is extremely powerful. It makes it possible to develop much more energy than it consumes.
It should also be noted that it is an almost unlimited source of energy. Deuterium is a natural and stable derivative of Hydrogen that can be extracted from running water. This energy source is therefore not subject to the same constraints as more conventional thermal or nuclear energies.
The amount of energy required is also much less than the current quantities. Only a few grams of fuel are needed to trigger the reaction and then maintain it.
The fusion of one gram of deuterium tritium would release 4 times more energy than the fission of one gram of uranium.
Clean energy
In addition, It does not emit CO2 or air pollutants. The only product resulting from this reaction is helium. The issue of waste is also crucial in the discussion about nuclear energy. Waste management is one of the most important obstacles to nuclear fission.
It is currently necessary to bury this waste in order to avoid any risk of contamination. With the merger, this question no longer arises.
However, it should be noted that the installations used for the fusion must be stored for about a hundred years in order to avoid any risk of contamination. This is out of all proportion to the thousands of years required today.
The promise of safer energy
Nuclear fission has its share of risks that the 20th century may have experienced. This is the case for every large-scale industrial process, a degree of risk is accepted as long as the risk/benefit balance remains largely positive.
Nuclear fusion, for its part, makes it possible to avoid any risk of industrial explosion. If a major problem occurs, the plasma may have time to return to a very low temperature before a serious incident occurs. If the reaction stops, the plasma then makes contact with the surrounding matter (in this case air) and cools.
For more information on nuclear safety, go to This article.
In summary, nuclear fusion is an experiment Full of future which requires passing an important technological milestone. The promises are numerous; it remains to be seen whether the course of large-scale implementation can work.
Today, this reaction does not last long enough to be profitable in terms of energy produced. As Joseph Schumpeter theorized, innovations are often triggered in clusters. One evolution leading to another, we can hope that this phenomenon will come to life in terms of mergers in the years to come.
Do not hesitate to read our complete article on” Nuclear energy: between innovation and energy transition ”.
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Comment l'eau est-elle transformée en électricité ?
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Le processus repose sur l'utilisation de la force de l'eau (énergie cinétique) issue des courants, des chutes d'eau ou des dénivelés. Le fonctionnement suit trois étapes clés :
- Le barrage retient l'eau et l'oriente vers des conduites.
- La pression de l'eau fait tourner une turbine, créant de l'énergie mécanique.
- Une génératrice (alternateur) transforme cette énergie mécanique en électricité, laquelle est ensuite adaptée par un transformateur pour le réseau
Pourquoi la France a-t-elle exporté un volume record d'électricité en 2025 ?
Ce record de 92,3 TWh s'explique par la conjonction de trois facteurs :
- Le redressement du parc nucléaire : Après les problèmes de corrosion sous contrainte de 2022, la production nucléaire a retrouvé une forte disponibilité (373 TWh).
- L'essor des renouvelables : Une capacité installée en hausse (solaire et éolien) et une production hydraulique solide.
- Une consommation intérieure atone : La demande française reste inférieure de 6 % à la moyenne historique, créant un surplus massif disponible pour nos voisins.
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Sourcing consists in identifying and analysing the offers of several electricity and gas suppliers. This approach makes it possible to obtain contracts adapted to the consumption profile and budgetary constraints of the company.
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C'est l'indicateur d'efficacité d'un appareil électrique ; il représente le ratio entre la puissance active (utile) et la puissance apparente (totale).
Pourquoi le kVA est-il crucial pour les entreprises ?
Parce que la puissance souscrite en kVA détermine le prix de l'abonnement et que tout dépassement peut entraîner des surcoûts importants.
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These are signals sent by RTE during periods of tension on the electrical network. The Sirenergies tool informs you in real time to anticipate your uses.
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L'abondance de production française tire les prix du marché de gros vers le bas.
En vertu du mécanisme de l'Ordre de Mérite (Merit Order), les centrales les moins coûteuses (nucléaire, renouvelables) couvrent la demande plus souvent, évinçant les centrales à gaz ou charbon plus onéreuses.
Cela multiplie les épisodes de prix bas, voire négatifs, sur le marché spot.
How do I read an electricity or gas bill?
One invoice consists of several elements: consumption, supplier share, taxes and contributions. The analysis of each line makes it possible to identify possible errors and to check the consistency with the signed contract.
Qu'est-ce qui remplace l'ARENH depuis le 1er janvier 2026 ?
Le dispositif ARENH a laissé place au VNU (Versement Nucléaire Universel).
Ce changement structurel expose davantage les entreprises aux prix de gros, rendant la gestion des risques plus complexe qu'auparavant.
Il devient alors indispensable de définir une stratégie d'achat d'électricité avec Sirenergies pour lisser l'impact de la volatilité des marchés sur votre budget.
What is the difference between €/MWh and kWh?
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What are the customer reviews on bellenergie Business's customer service?
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Is Bellenergie Business electricity really green?
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For the most demanding companies, the offer GREENVOLT+ ensures very low carbon intensity electricity, sourced exclusively from independent French producers (hydraulic, wind, solar).
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C'est le levier le plus rapide pour obtenir des résultats visibles. L'éclairage représente environ 40 % de la consommation d'électricité d'une commune.
Passer au LED avec pilotage intelligent permet de réduire la facture de 50 à 80 %, avec un retour sur investissement (ROI) rapide, souvent estimé à 2 ou 3 ans.
Pourquoi mon contrat est-il en kVA et ma consommation en kWh ?
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Quelle est la différence concrète entre le transport et la distribution d'électricité ?
Le transport (RTE) correspond aux "autoroutes" de l’électricité. Il s’agit de transporter de très grandes quantités d'énergie sur de longues distances, depuis les centrales de production (nucléaires, barrages, parcs éoliens offshore) vers les régions de consommation.
La distribution (Enedis) s'apparente aux "routes départementales" et aux rues. Elle récupère l'électricité à la sortie du réseau de transport pour la livrer directement chez le client final, en abaissant la tension pour qu'elle soit utilisable par vos appareils.
Quel est le nouveau record 2025 d'exportation d'électricité de la France ?
En 2025, la France a atteint un solde exportateur net de 92,3 TWh, battant le précédent record de 2024 (89 TWh).
L'hydroélectricité est-elle une énergie "propre" ?
Oui, elle est considérée comme une énergie renouvelable à faibles émissions de gaz à effet de serre.
De plus, l'eau ne subit aucune transformation chimique durant le cycle de production et réintègre son milieu naturel en aval.
Cependant, la construction de barrages nécessite des mesures pour protéger les écosystèmes (débit minimum, passes à poissons).
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