Moderator

Key Stage 4

Meaning

A moderator is a substance used in nuclear fission reactors to slow fast moving neutrons to become thermal neutrons.

About Moderators

Moderators absorb some of the energy of fast moving neutrons which slows them down to a speed where they are called thermal neutrons which are able to be captured by fissionable isotopes.

Without a moderator in a nuclear reactor the neutrons released from each fission event would be moving too fast to cause a second fission event so a chain reaction would not be possible.