Chain Reaction

Key Stage 5

A chain reaction is a series of reactions in which each reaction causes a further reaction.

In a nuclear reactor, each fission event caused by a neutron produces additional neutrons that cause further fission events.
A steady chain reaction occurs when one fission neutron on average from each fission event produces another fission event.
Nuclear chain reactions require a critical mass of the fissionable material.
Chain reactions can be controlled or uncontrolled.
Controlled chain reactions are used in nuclear reactors to generate power.
Uncontrolled chain reactions occur in nuclear weapons.
The ability to control the chain reaction is crucial for the safe operation of nuclear reactors.

Uranium-235 and Plutonium-239 are materials capable of sustaining a chain reaction.
Chain reactions are controlled in nuclear reactors to produce energy and uncontrolled in nuclear weapons for explosive effects.