Public dose in a nuclear accident
If there were to be an accidental release of radioactivity to the air then the radioactivity would be expected to drift downwind, spreading out as
it goes and maybe sticking to surfaces such as the ground, walls, trees and so on. In this situation there are several ways in which people downwind
can be exposed to radiation. These tend to be called "exposure routes" (see diagram).
Figure ©IAEA 1991 - from the International Chernobyl Project Technical Report ISBN 92-0-12191-4 printed by the IAEA in 1991.
In an emergency the dose routes of initial concern are
- Direct inhalation dose - Resulting from the person being within the radioactive plume and breathing in the radioactive dust or gas, some of
which remains in the lungs when they breath out
- Cloud dose or external irradiation - Resulting from being in or near a cloud of radioactive material and being irradiated by it (some of the radiation that the cloud is giving off hitting
the person)
.
These two dose routes tend to give most of the radiation dose to people during the time that the radioactive plume is near them and are,
therefore, the dose routes that the initial countermeasures are designed to reduce.
The other dose routes that can become important after the plume has gone by are:
- Ground gamma dose or external irradiation Resulting from the person being near radioactivity that has stuck to nearby surfaces (the ground, walls,
vegatation etc) and being irradiated by it.
- Ingestion dose Resulting from eating or drinking contaminated materials (note this is contaminated i.e. radioactive food and drink and
not food and drink which has itself been irradiated in the past)
- Resuspension dose Resulting from breathing in radioactive dust that had settled on the ground and other surfaces and then been pushed back into
the air by something such as the wind or something touching the surface
- Skin contamination dose Resulting from radioactive dust settling on the skin and continuing to irradiate the skin until it is removed
.
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