Where do iodine-129 and iodine-131 come from?Both iodine-129 and iodine-131 are produced by the fission of uranium atoms during operation of nuclear reactors and by plutonium (or uranium) in the detonation of nuclear weapons.
What are the properties of iodine-129 and iodine-131?Radioactive iodines have the same physical properties as stable iodine. However, radioactive iodines decay with time
Iodine reacts easily with other chemicals, and isotopes of iodine are found as compounds rather than as a pure elemental nuclide. Thus, iodine-129 and -131 found in nuclear facilities and waste treatment plants quickly form compounds with the mixture of chemicals present. However, iodine released to the environment from nuclear power plants is usually a gas.
Iodine-129 has a half-life of 15.7 million years; iodine-131 has a half-life of about 8 days. Both emit beta particles upon radioactive decay.
What are iodine radioisotopes used for?Iodines are among the most widely used radionuclides, mostly in the medical field. Because of its short half-life and useful beta emission, iodine-131 is used extensively in nuclear medicine.
* Its tendency to collect in the thyroid gland makes iodine especially useful for diagnosing and treating thyroid problems. Iodine-123 is widely used in medical imaging, and I-124 is useful in immunotherapy.
* Iodine's chemical properties make it easy to attach to molecules for imaging studies. It is useful in tracking the metabolism of drugs or compounds, or for viewing structural defects in various organs, such as the heart.
* A less common isotope, iodine-125, is sometimes used to treat cancerous tissue.
Iodine-129 has little practical use, but may be used to check some radioactivity counters in diagnostic testing laboratories.
http://www.epa.gov/radiation/radionuclides/iodine.html