Principles of Radiation ProtectionTo prevent deterministic (detrimental) tissue effects
To limit the probability of stochastic effects to levels deemed to be acceptable
Guidelines are established for radiation exposure have had two principle objectives:
- To prevent acute exposure; and
- to limit chronic exposure to "acceptable" levels.
Radiation Protection Standards*For Radiation Protection Purposes there is no threshold for Stochastic Effects.
Americans receive a radiation dose of about 0.62 rem (620 millirem) each year. Half of this dose comes from Natural Background radiation. Radiation is all around us and comes from the earth and outer. Most of this background exposure comes from radon in the air, with smaller amounts from cosmic rays and the Earth itself.
In the context of Occupational Exposure the intent is to keep exposure at zero or below the minimum acceptable dose or:
As Low As Reasonably Achievable
Basic Principles of ALARATime limits – Keep time as short as possible (amount of exposure time limited).
Distance – Maintain maximum distance from radiation source.
(Inverse square law (ISL) – distance effects the amount of radiation reaching the skin; the intensity of the radiation from a point source varies inversely as the of the distance from the source.)
Shielding – Thickness of walls in concrete lead equivalent to reduce dose rate to outside *controlled areas to absolute minimum. Stay behind wall or shield to block transmission of x-rays.
Radiation Protection Primary Rule
Time (keep exposure as short as possible)
Distance ( stay as far away as possible)
Shielding (walls, shields, aprons)
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