Currently, nuclear energy represents more than 10% of global electricity production. France is a pioneer with almost 70% of its electricity comes from this energy sourcethe State having played a central role in the development of this technology. In particular thanks to significant investments in research and by creating public companies like EDF in 1946.
In reality, when we talk aboutnuclear energythis is a generic term, behind which two distinct processes are hidden. Fission, mastered and exploited industrially by nuclear power plants, and fusion, still confined to the field of research (or in the bedroom of certain DIY enthusiasts, but this is an exception).
The delicate art of fission: proven technology
Nuclear fission is based on a principle: the division of heavy uranium atoms under the impact of neutrons (a small particle). When a neutron hits a uranium atom, it “splits” it into two smaller pieces. When it breaks, it releases a phenomenal amount of energy and sends other neutrons around it. These neutrons will then strike other atoms, which in turn divide and release even more energy. This chain reaction is the basis of the production of the enormous amount of energy used in nuclear power plants.
The fission of a uranium 235 nucleus (the type of uranium most used in power plants) releases more than 6 million times the energy of a combustion reaction of the purest coal. All this power is great, but what do we do with it? In power plants, this power is tamed thanks to a complex system where thermal energy is converted into electricity via heat exchangers transforming water into steam.
This steam is then directed towards turbines, large wheels which rotate under the force of it; the rotation of these turbines then drives generators that produce electricity. It is this steam that we see coming out of the large cooling towers that we often see above power plants. However, this vapor is not radioactive; it was simply water vapor that was used to cool the entire system, a bit like a large radiator.
Fusion: the energy of the stars
Fusion is the exact opposite of fission. : instead of dividing heavy atoms, it fuses light atoms (atoms whose nuclei contain a small number of nucleons, protons and neutrons), reproducing the process that powers stars like our Sun. When these small atoms come close enough, they “fuse” into a single, heavier atom, and this fusion releases a colossal amount of energy, in the form of heat and light.
This reaction, mainly studied with deuterium and tritium (hydrogen isotopes), promises spectacular energy yields, almost four times higher than those of the fission of uranium 235. This is why it is often described as the Holy Grail of energy sources and why projects like JET (UK) or ITER (France) exist. To demonstrate that controlled fusion is workable.
Fusion is a very complex phenomenon to replicate on Earth; it requires extreme conditions, like those which reign in the heart of the Sun : temperatures of several million degrees so that light atoms can come close enough to fuse. At these temperatures, the material becomes a plasma (a type of superheated gas), very difficult to contain without it touching the walls of a reactor, because any direct contact would immediately drop the temperature and stop the reaction.
Therefore, to overcome this problem, researchers must createe powerful magnetic fields to keep this plasma in suspension ; which requires very advanced technologies, still under development. This year, a record was set on a reactor at the ITER site in Bouches-du-Rhône. In May, plasma was confined for 364 seconds at a constant temperature of 50 million degrees Celsius, hotter than that at the center of the Sun.
This record, as impressive as it is, does not mean that we can turn on a switch and produce electricity through fusion tomorrow, we are still far from it. Research in this area is progressing very steadily, and the scientific community believes that in 2050, fusion will be able to be exploited to produce almost infinite quantities of energy. The latter presents considerable advantages: abundant fuel (deuterium is present in immense quantities in the oceans), less production of radioactive waste and above all, the impossibility of possible military use.
- Nuclear fission, which splits heavy atoms like uranium, is mastered and used in power plants to produce electricity.
- Fusion, still in development, promises abundant energy with yields four times greater than those permitted by fission.
- Projects like ITER aim to make fusion exploitable by 2050.
