Common Radioactive Isotopes
The table below provides information about common radioactive isotopes. Isotopes are forms of an element that have the same number of protons (positively charged particles) but different numbers of neutrons (neutral particles) in their nuclei. The number attached to each isotope is its atomic mass (the sum of its neutrons and protons). The radioactive isotopes in the table have a variety of uses, from industrial measurement equipment to medical therapies to nuclear reactor fuel.
| Isotope | Type of radiation | Half-life | Where isotope is commonly found | For more information |
|---|---|---|---|---|
| Americium-241 (Am-241) | Alpha particles; weak gamma radiation | 432.2 years | Medical diagnostic devices; industrial devices that measure density and thickness; household and business smoke detectors | CDC Radioisotope Brief |
| Cesium-137 (Cs-137) | Beta particles and gamma radiation | 30.17 years | Medical radiation therapy devices; calibrating radiation detection equipment; industrial devices that measure density and thickness; as a byproduct of nuclear fission processes in nuclear reactors (e.g., power plants) | CDC Radioisotope Brief |
| Cobalt-60 (Co-60) | Beta particles and gamma radiation | 5.27 years | Medical radiation therapy (implants or external radiation sources); food irradiation | CDC Radioisotope Brief |
| Iodine-131 (I-131) | Beta particles and gamma radiation | 8.06 days | Medical diagnostic and radiation therapy | CDC Radioisotope Brief |
| Iriduim-192 (Ir-192) | Beta particles and gamma radiation | 73.83 days | Industrial gauges for inspecting welding seams; medicines to treat certain cancers | CDC Radioisotope Brief |
| Plutonium-238 (Pu-238) | Alpha particles | 87.7 years | Heat and power source for satellites | CDC Radioisotope Brief |
| Plutonium-239 (Pu-239) | 24,110 years | Nuclear weapons; byproduct of nuclear reactor operations and nuclear detonations | ||
| Plutonium-240 (Pu-240) | 6,564 years | Byproduct of nuclear reactor operations and nuclear detonations | ||
| Polonium-210 (Po-210) | Alpha particles | 138 days | Naturally occurring and found in small amounts in the environment, including in food, water, and the air | CDC Clinical Guidance for Polonium Exposure |
| Strontium-90 (Sr-90) | Beta particles | 29.1 years | Power source for space vehicles, remote weather stations, and navigational beacons; industrial gauges; medical radiation therapy | CDC Radioisotope Brief |
| Uranium-235 (U-235) | Alpha particles | 700 million years | Concentrated (i.e., enriched) for use as nuclear power plant or other reactor fuel; nuclear weapons; as naturally occurring material | CDC Radioisotope Brief |
| Uranium-238 (U-238) | 4.47 billion years | Radiation shielding (only weakly radioactive, much denser than lead); as naturally occurring material |