Basic protective measures used to minimize external dose include:
Minimizing time in radiation areas
Maximizing the distance from a source of radiation
Using shielding whenever possible
Reducing the amount of radioactive material (source reduction)
Methods for minimizing time
Reducing the time spent in a field of radiation will lower the dose received by the
Plan and discuss the task thoroughly prior to entering the area. Use only the
number of workers actually required to do the job.
Have all necessary tools present before entering the area.
Use mock-ups and practice runs that duplicate work conditions.
Take the most direct route to the job site if possible and practical.
Never loiter in an area controlled for radiological purposes.
Work efficiently and swiftly.
Do the job right the first time.
Perform as much work outside the area as possible. When practical, remove parts
or components to areas with lower dose rates to perform work.
Do not exceed stay times. In some cases, the Radiological Control Organization
may limit the amount of time a worker may stay in an area due to various reasons.
This is known as "stay time." If you have been assigned a stay time, do not exceed
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b. Methods for maximizing distance from sources of radiation
The worker should stay as far away as possible from the source of radiation.
Stay as far away from radiation sources as practical given the task assignment. For
point sources (such as valves and hot spots), the dose rate follows a principle called
the inverse square law. This law states that if you double the distance, the dose
rate falls to 1/4 of the original dose rate. If you triple the distance, the dose rate
falls to 1/9 of the original dose rate.