IB Physics E.4.2 Nuclear Reactors Key Definitions

A self-sustaining sequence of nuclear fission events in which each fission releases neutrons that trigger further fissions in neighbouring fuel nuclei.

Rods made of neutron-absorbing material (typically boron or cadmium) that are inserted into or withdrawn from a reactor core to regulate the rate of the fission chain reaction.

A material (such as water or graphite) surrounding the fuel in a nuclear reactor that slows fast fission neutrons to thermal energies, increasing their probability of causing further fission.

Radioactive material produced as a by-product of nuclear fission, classified as high-level waste (spent fuel and fission products) or low-level waste (contaminated equipment and clothing), requiring long-term containment to prevent environmental harm.