Nuclear fusion: what is it?

Sometimes two or more light atomic nuclei unite to form a heavier nucleus. We then speak of merger nuclear. The merger nuclear is in a way the opposite of nuclear fission – the phenomenon physical operated at the heart of nuclear center – which consists in breaking a heavy nucleus into two lighter nuclei.

To trigger a nuclear fusion reaction, it is necessary to bring a large amount ofenergy. Up to some 200 million degrees! For such a coming together of nuclei can only take place if the intense forces of repulsion which exist between these charged entities can be overcome.

A natural and artificial phenomenon

The phenomenon of nuclear fusion occurs quite naturally in the heart of stars. So our Sun does it transform at every moment and according to stages, colossal quantities of hydrogen into helium. The whole, by releasing, as ordered by the famous formula ofEinstein, a large amount of energy. L’energy from stars therefore comes from cycles of nuclear fusion reactions. It is this that makes shine the sun.

Furthermore, the phenomenon of nuclear fusion – and the energy it produces – has been used since the 1950s to manufacture H-bombs, hydrogen bombs, as they are still called. In this type of thermonuclear bomb, the A-bombs – which exploit the phenomenon of nuclear fission – serve asmatches. Indeed, their explosion makes it possible to reach the temperatures necessary to trigger fusion.

Nuclear fusion and energy production

What makes the phenomenon of nuclear fusion interesting when it comes to produce energyis first of all that it does not emit greenhouse gas. Second, that it inherently allows the production of large amounts of energy from small amounts of matter first. And that all this is done potentially without the production of Radioactive waste to long duration of life.

It is still necessary to manage to control the process. The main difficulty comes from the fact that it is necessary for this to heat cores to temperatures beyond comprehension while keeping them confined. Two techniques – inertial confinement and magnetic confinement – are currently being explored, among others by the Megajoule Laser and by Iter.

Melting of a nuclear reactor core

The term nuclear fusion is sometimes misused whenaccidents nuclear. It would then be better to speak of fusion of the core of the nuclear reactor. Because at that moment, it is not the atomic nuclei that fuse, but the combustible materials and fission products inside the reactor that overheat and melt. Such an accident can occur when the reactor is no longer properly cooled.