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.

Two things are infinite: the universe and human stupidity; and I'm not sure about the universe

– Albert Einstein -