Radiation Protection Phylosophy..
There are three factors that control the amount, or dose, of radiation received from a source. Radiation exposure can be managed by a combination of these factors:
1. Time: Reducing the time of an exposure reduces the effective dose proportionally. An example of reducing radiation doses by reducing the time of exposures might be improving operator training to reduce the time they take to handle a source.
2. Distance: Increasing distance reduces dose due to the inverse square law. Distance can be as simple as handling a source with forceps rather than fingers.
3. Shielding: The term 'biological shield' refers to a mass of absorbing material placed around a reactor, or other radioactive source, to reduce the radiation to a level safe for humans. The shielding strength or "thickness" is conventionally measured in units of g/cm2. The radiation that manages to get through falls exponentially with the thickness of the shield.
Practical radiation protection tends to be a job of juggling the three factors to identify the most cost effective solution.