What are the four main practical principles of radiation protection?

The following four principles are valid for ionising radiation (although not all will apply for individual cases as this will depend on the type of radiation source involved).

Time - Minimise the time of exposure.

Distance - Maximise the distance from the source of radiation.

Shielding - Use radiation shielding where practicable.

Containment - For unsealed radioactive materials use containment to minimise risk of contamination spread and avoid inhalation of ingestion hazards.

Atoms are very special: they like certain particular partners, certain particular directions, and so on. It is the job of physics to analyze why each one wants what it wants.

– Richard P. Feynman -