Radiation in Perspective

Ionizing radiation is energy particles given off by unstable atoms as they undergo radioactive decay to stabilize.

The radiation given off by the radioactive materials in commercial nuclear power plants is called ionizing radiation. That means that it causes ion pairs (positively and negatively charged particles) to form in the cells that the radiation encounters.

It is important to understand that ionizing radiation from nuclear power plants is the same as ionizing radiation from other possible sources, such as cosmic radiation, medical treatments and the naturally occurring background radiation from the soil and building materials around us.

Low-level ionizing radiation is measured in units called millirem (1/1000 of a REM). The average exposure to people living in the US is approximately 620 millirem per year, (NCRP Report 160, "Ionizing Radiation Exposure of the Population of the U.S." Most people in the U.S. receive about 250-310 millirem per year from natural background radiation. The sun and stars give off radiation called cosmic radiation and most of us receive about 31 millirem a year from this source. We get another 28 millirem from the naturally occurring radioactive materials in building materials (usually bricks, stone and mortar) and the soil. There is an additional 229 millirem from the air we breathe, largely from radon.

Medical treatments and examinations are another source of radiation exposure for many people and contribute more than 50% of the average person's exposure. The majority of medical exposures are from Computerized Axial Tomography, (CAT Scan) and Nuclear Medicine procedures. A chest X-ray is generally about 10 millirem, while a dental X-ray is usually about 9 millirem.

The average person living within 50 miles of a commercial nuclear power plant will receive about .001 millirem of additional radiation exposure on an annual basis. Even people living within a few miles of a plant rarely get as much as 1 millirem per year.