As WBBM Newsradio 780's Lisa Fielding reports, the Daily Herald says Warrenville-based Exelon Nuclear has discovered trace amounts of radioiodine-131, a radioactive isotope associated with the damaged nuclear plants in Japan, were found on March 22 at the Dresden nuclear power plant in Morris.
Air test samples also picked up a small amount of radioiodine-131 at Argonne National Laboratory near Darien, the Daily Herald reported.
CBS Chicago
Per Wikipedia
Iodine-131 (I131) is a beta-emitting isotope with a half-life of eight days, and comparatively energetic (190 KeV average and 606 KeV maximum energy) beta radiation, which penetrates 0.6 to 2.0 mm from the site of uptake. This beta radiation can be used in high dose for destruction of thyroid nodules and for elimination of remaining thyroid tissue after surgery for the treatment of Grave's disease. Especially in Grave's disease, often a thyroidectomy is performed before the radiotherapy, in order to avoid side effects of epilation and radiation toxicity. The purpose of this therapy, which was first explored by Dr. Saul Hertz in 1941,[1] is to destroy the remaining thyroid tissue that was impossible to be removed by surgery. In this procedure, I131 is administered either intravenously or orally following a diagnostic scan. This procedure may also be used to treat patients with thyroid cancer or hyperfunctioning thyroid tissue.
Beta radiation consists of highly energetic electrons or positrons. Beta radiation is emitted when an atom with "too many" neutrons in the nucleus converts a neutron to a proton; the difference between a neutron and a proton is one electron, and that spare electron is ejected.
The half life of a radioactive material is the length of time required for half of the atoms in a sample to decay into some other sort of atom. In the case of I-131, converting a neutron to a proton produces Xe-131. Xe-131 is a stable isotope of Xenon, which is a noble gas similar to neon and not dangerous.
Federal agencies are monitoring more than 100 similar reports all over the country. It is important to remember that I-131 is used medically. However Wiki also notes
The high energy beta radiation from I-131 causes it to be the most carcinogenic of the iodine isotopes, and it is thought to cause the majority of the excess in thyroid cancers seen after nuclear fission contamination (such as bomb fallout or severe nuclear reactor accidents like the Chernobyl disaster).
This is not good stuff to have floating around, obviously, but the amount you ingest matters a lot.
Updated by blue aardvark at Thu Mar 31, 2011 at 11:03 AM MST
Ground water 15 meters below one reactor has radioactivity 10,000 times government standard.