Iodine-125 is preferred for this purpose, due to better radiation penetration and shorter half-life (13 hours). I-125 is useful for Glomerular filtration rate (GFR) testing in the diagnosis or monitoring of patients with kidney disease. I-125 is used in Iodine-125 is used "therapeutically" in brachytherapy treatments of tumors. For radiotherapy ablation of tissues that absorb iodine (such as the thyroid), or that absorb an iodine-containing radiopharmaceutical, the beta-emitter iodine-131 is the preferred isotope. I is created by the electron capture decay of Xe, which is a synthetic isotope of xenon, itself created by neutron capture of the slightly radioactive Xe, which
Isotopes of iodine iodine-135 can temporarily preclude a shut-down reactor from restarting. This is known as xenon-poisoning or "falling into an iodine pit". Iodine fission-produced isotopes not discussed above (iodine-128, iodine-130, iodine-132, and iodine-133) have a half lives of a couple of hours or minutes, rendering them almost useless in other applicable areas. Those mentioned are neutron-rich and so go through beta decay to their xenon counterparts. Iodine-128 (25 min half-life) can decay to either tellurium-128 by electron capture, or to xenon-128 by beta decay. It has a specific radioactivity of 2.177 x 10 TBq/g. Colloquially, radioactive materials can be described as "hot,"