Nuclear fission is the form of energy used to generate electricity in nuclear power stations.
In a nuclear reactor, a neutronUncharged subatomic particle, with a mass of 1 relative to a proton. The relative charge of a neutron is 0. is absorbed by a uranium nucleus (typically uranium-235).
This causes the nucleusThe central part of an atom. It contains protons and neutrons, and has most of the mass of the atom. The plural of nucleus is nuclei. to become uranium-236, which is violently unstable.
The entire nucleus splits into two smaller fragments called 'daughter nuclei' and energy is released.
In addition, two or three neutrons also explode out of the fission reaction.
These can collide with other uranium nuclei to cause further fission reactions.
This is known as a chain reaction.
The fast moving neutrons carry most of the energy from the reaction with them (99%) but before the neutrons can collide with fresh uranium nuclei, they need to be slowed down.
This energy is passed on to other components in the nuclear reactor, which can then be used to heat water to drive the turbines that turn the generators to generate electricity.