Nuclear power plants use energy released by the decay of certain radioactive isotopes to produce electricity. Additional radioactive isotopes are produced during this process. In nuclear power plants, specially designed fuel rods and containment structures enclose the radioactive materials to prevent them, and the ionizing radiation they produce, from contaminating the environment. If the fuel and surrounding containment structures are severely damaged, radioactive materials and ionizing radiation may be released, potentially posing a health risk for people. The actual risk depends on
the specific types and quantities of radioactive materials, or isotopes, released
how much radiation someone is exposed to and for how long
how a person comes in contact with the released radioactive materials (such as through contaminated food, water, air, or on the skin)
the person’s age (with those exposed at younger ages generally at higher risk of cancer)
The radioactive isotopes released in nuclear power plant accidents include iodine-131 (I-131), cesium-134 (Cs-134), and Cs-137. In the most severe kinds of accidents, such as the Chernobyl accident in 1986, other dangerous radioactive isotopes, such as strontium-90 (Sr-90) and plutonium-239, may also be released.
Human exposure to I-131 released from nuclear power plant accidents comes mainly from consuming contaminated water, milk, or foods. People may also be exposed by breathing dust particles in the air that are contaminated with I-131.
Inside the body, I-131 accumulates in the thyroid gland, which is an organ in the neck. The thyroid gland uses iodine to produce hormones that control how quickly the body uses energy. Because the thyroid does not distinguish between I-131 and nonradioactive iodine, the thyroid gland will accumulate either form. Exposure to radioactive iodine may increase the risk of thyroid cancer for many years, especially for children and adolescents.
Exposure to Cs-134 and Cs-137 can be external to the body or internal. External exposure comes from walking on contaminated soil or coming into contact with contaminated materials at nuclear accident sites. Internal exposure can come from breathing particles in the air that contain Cs-134 and Cs-137, such as dust originating from contaminated soil, or ingesting contaminated water or foods. Because Cs-134 and Cs-137 do not become concentrated in a particular tissue, the ionizing radiation that it releases can expose all tissues and organs of the body.