Testing for radiation, Australia. During the 1950s, the UK carried out a number of atom-bomb experiments in the Nullarbor Desert of southern Western Australia. Fallout was detected across the country while service personnel in the immediate area were exposed to high levels of radiation. Radiation levels at the test-sites are still very high.

Atomic radiation may be in the form of alpha particles, beta particles, or gamma radiation. Alpha particles are fast-moving and consist of two protons and two neutrons. Because they have a relatively large mass, alpha particles have a range of up to 10 cm in air and can be stopped by skin or thin paper. Beta particles are electrons created and then instantly ejected from a radioactive atom. They have a greater range in air than alpha particles and can be stopped by a thin sheet of metal, such as aluminium. Gamma radiation is high-frequency, high-energy electromagnetic radiation. It is very penetrating and can only be blocked by thick lead or very thick concrete.