Fission Products (by Element) - Iodine-127, 129, 131

Iodine-127, 129, 131

131I, with a half-life of 8 days, is a hazard from nuclear fallout because iodine concentrates in the thyroid gland. See also Radiation effects from Fukushima Daiichi nuclear disaster#Iodine-131 and Downwinders#Nevada.

In common with 89Sr, 131I is used for the treatment of cancer. A small dose of 131I can be used in a thyroid function test while a large dose can be used to destroy the thyroid cancer. This treatment will also normally seek out and destroy any secondary tumor which arose from a thyroid cancer. Much of the energy from the beta emission from the 131I will be absorbed in the thyroid, while the gamma rays are likely to be able to escape from the thyroid to irradiate other parts of the body.

Lots of 131I was released during an experiment named the Green Run in which fuel which had only been allowed to cool for a short time after irradiation was reprocessed in a plant which had no iodine scrubber in operation.

129I, with a half-life almost a billion times as long, is a long-lived fission product.

127I is stable, the only one of the isotopes of iodine that is nonradioactive. It makes up only about 1/6 of the iodine in spent fuel, with I-129 about 5/6.