However, people living near the Chernobyl plant were exposed to considerably more radiation. More than 30 people died and many more were injured. Radiation from that accident reached Europe, Asia, and the United States. In total, radiation exposure from reactors in the first 40 years of nuclear energy use, excluding Chernobyl, has resulted in 35 serious exposures with 10 deaths, but none was associated with power plants. In the United States, nuclear power reactors must meet stringent federal standards that limit the amount of released radioactive material to extremely low levels.
Radiation is measured in several different units.
A single, rapid dose of radiation can be fatal, but the same total dose given over a period of weeks or months may have little measurable effect. The total dose and the rate of exposure determine the immediate effects on the genetic material of cells. The dose rate is the amount of radiation a person is exposed to during a given period of time. As the dose rate or total dose increases, the likelihood of detectable effects increases. The effects of radiation also depend on how much of the body is exposed.