IEER
Brief Fact Sheet on Iodine-131
and Nevada Test Site Fallout
- Origin: Fission product, created in nuclear reactors and nuclear weapon explosions
Half-life: 8 days
- Organ most affected: thyroid
- Main pathway: milk
- Other pathways: vegetables, fruits, inhalation, and external irradiation
- Direct physical effects: radioactive iodine damages or destroys thyroid cells.
- Health effects: Increased risk of all thyroid tumors, notably in children. Likely increase of thyroid cancer risk in children exposed before the age of 15 years. Females appear to be more at risk than males. Children under five are the highest risk group.
- Rad: a measure of radiation dose. One rad equals 100 ergs of radiation energy deposited in one gram of tissue.
- Release per kiloton of fission explosive power: 125,000 curies
- National Cancer Institute estimate of releases from the Nevada Tests: 130 million curies
- Official iodine-131 release estimate from Chernobyl: 7.3 million curies -- decay-corrected to ten days after the start of the accident.
- Iodine-131 inventory in the Chernobyl reactor on April 26, 1986, the day the accident started: approximately 83 million curies. Official Soviet estimate of fraction released = 20 percent. Release occurred over the ten day period of the fire from April 26 to May 6, 1986.
- Rough estimate of actual releases from Chernobyl over the course of the ten-day fire: 10 to 15 million curies, assuming a release fraction of 20 percent. Calculations by IEER, based on NUREG-1250, U.S. Nuclear Regulatory Commission, 1987.
- National Cancer Institute estimate of cumulative average thyroid dose per person to the US population of the 1950s: 2 rad (or 0.02 gray)
- National Cancer Institute estimate of exposure to children aged 3 months to five years in high fallout areas: 50 to 160 rad.
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Institute for Energy and Environmental Research
Comments to Outreach Coordinator: ieer@ieer.org
Takoma Park, Maryland, USA
October, 1997