Nuclear Chain Reaction

Key Stage 4

Meaning

A nuclear chain reaction is when the neutrons released from one nuclear fission event triggers one or more other nuclear fission event.

About Nuclear Chain Reactions

For a nuclear chain reaction to occur each nuclear fission event must cause the release of at least 1 neutron which can go on to cause a second fission event.

In a nuclear reactor on average 1 neutron from each fission event goes on to cause one more fission event. This results in a constant release of energy.

During nuclear fission the neutrons produced usually have too much energy to be captured by the nucleus of another atom, so they must be slowed down by a moderator to a lower energy in order for a chain reaction to occur.

Neutrons with the right amount of energy to be captured are called thermal neutrons because they have a similar energy to molecules in the air at room temperature.

A nuclear chain reaction can only happen if enough thermal neutrons are produced from the fission events.

The neutrons released from one fission event go on to cause at least one other fission event in a chain reaction.