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From the source to the dosimetric impact assessment

Exposure to ionizing radiation

​Exposure to ionizing radiation can result from external irradiation or internal contamination. In the workforce, the type of exposure determines the protection and monitoring of potentially exposed personnel.

Published on 17 March 2015

Exposure to ionizing radiation can be:

  • external: the radiation source is not in direct contact with the person. The received dose is based on the duration of exposure, the distance from the source, and the protective screens in place. Exposure may be brief (e.g. during a radiography) or prolonged (e.g. in the case of natural exposure).
  • internal: radionuclides penetrate the interior of the body (internal contamination) most frequently by inhalation or ingestion, or after passage through the skin. The distribution through the body depends on the nature of the radionuclide. Exposure continues after incorporation, but decreases as a function of the radionuclide’s half-life and its physiological elimination.
Radioactivity panel, photo credit: CEA
Different panels indicate the presence of radioactivity. The ascending order of risk is: blue, green, yellow, orange, and red.
The small points symbolize the risk of contamination, while the spikes at the extremities represent the risk of irradiation.
Each zone is regulated: each one is linked with equivalent dose rates (in microSievert/hour), the maximum permitted dose equivalents (in mSv/year), access requirements, and categories of authorized personnel.
The workplaces analysis assembles all of the elements required to understand exposure, in order to evaluate the occupational risks incurred by personnel. It is therefore possible to implement preventive measures to avoid acute exposures, so as to control abnormal events and decrease chronic exposures. A form that assembles information regarding the workplace characteristics and its identified hazards allows delimiting work zones (controlled are and monitored are), as well as dividing exposed personnel into categories depending on their estimated level of exposure. This also helps to optimize biological or physical protections, and to define the nature and frequency of exams prescribed for exposed workers.