Three main factors contribute to how much radiation a person absorbs from a source. The following factors can be controlled to minimize exposure to radiation.
Increasing distance from the source of radiation
The intensity of radiation falls sharply with greater distance, as per the inverse square law. Increasing the distance of an individual from the source of radiation can therefore reduce the dose of radiation they are exposed to. For example, such distance increases can be achieved simply by using forceps to make contact with a radioactive source, rather than the fingers.
Decreasing duration of exposure
The time spent exposed to radiation should be limited as much as possible. The longer an individual is subjected to radiation, the larger the dose from the source will be. One example of how the time exposed to radiation and therefore radiation dose may be reduced is through improving training so that any operators who need to handle a radioactive source only do so for the minimum possible time.
Reducing incorporation into the human body
Potassium iodide (KI) can be given orally immediately after exposure to radiation. This helps protect the thyroid from the effects of ingesting radioactive iodine if an accident occurs at a nuclear power plant, for example. Taking KI in such an event can reduce the risk of thyroid cancer developing.
Shielding refers to the use of absorbent material to cover a reactor or other source of radiation, so that less radiation is emitted in the environment where humans may be exposed to it. These biological shields vary in effectiveness, depending on the material’s cross-section for scattering and absorption. The thickness (shielding strength) of the material is measured in g/cm2. Any amount of radiation that does penetrate the material falls exponentially with increasing thickness of the shield.
Taking X-ray rooms as an example, lead sheets may exist in the walls of the room containing the generator or barium sulphate may be incorporated into the plaster. The subject being X-rayed is viewed through a leaded glass screen and lead aprons are worn in cases where operators need to be in the same room as the subject.
Reviewed by Sally Robertson, BSc