What is nuclear fission?
The process nuclear power plants use today.
1 pastilha de urânio (~7g) ≈ 1 tonelada de carvão ou 150 galões de petróleo. Fonte: NEI / DOE.
Nuclear fission is the process that nuclear power plants use today. Unlike fusion — which joins atoms — fission splits heavy, unstable atoms into two or more smaller fragments, releasing energy.
The process: a neutron collides with an atom of uranium-235. The atom absorbs the neutron, becomes unstable, and splits into two smaller atoms, releasing energy and 2 to 3 free neutrons. Those neutrons strike other atoms — creating a chain reaction.
In a nuclear power plant, this reaction is controlled by control rods that absorb neutrons. The heat generated heats water, produces steam and drives turbines to generate electricity.
Fission produces around 200 MeV of energy per nucleus — an enormous amount compared to any chemical fuel. But it is approximately 7 times less efficient than D-T fusion per gram of fuel.
Source: article by Olívia Omagari, STEAM 2025; LIRA, J.C.L. Reação em cadeia. InfoEscola.
Quick comparison
- Fission: splits uranium/plutonium → today's power plants → long-lived waste.
- Fusion: joins deuterium/tritium → still experimental → minimal waste.