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Reply #89: NRC Data Sheet on the Tooth Fairy Project [View All]

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SidDithers Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Dec-03-09 08:58 PM
Response to Reply #80
89. NRC Data Sheet on the Tooth Fairy Project
Edited on Thu Dec-03-09 09:12 PM by SidDithers
http://www.nrc.gov/reading-rm/doc-collections/fact-shee...

Strontium-90 Sources

Strontium is a silvery-white alkaline earth metal that exists in several stable and unstable or radioactive isotopes (Sr-89 and Sr-90). Strontium-90 is a radioactive isotope that is produced in nuclear fission--splitting of an atoms center that releases energy-- and has a half-life (decay of half its radioactivity) of about 28 years. In the United States, the primary pathway for Sr-90 to enter the body is through ingestion of contaminated foods and cows milk.

Strontium-90 does not occur naturally. It comes from three sources:

1) fallout from above-ground explosions of nuclear weapons testing worldwide from 1963 to 1980;
2) radioactive releases from the 1986 Chernobyl nuclear power plant accident in the Ukraine; and
3) radioactive releases from nuclear power plants into the environment.

By far, the largest source of Sr-90 in the environment (~99%) is from weapons testing fallout. Approximately 16.8 million curies of strontium-90 were produced and globally dispersed in atmospheric nuclear weapons testing until 1980 (UNSCEAR 2001)2. With a 28 year half-life, Sr-90 still remains in the environment at nominal levels. Numerous measurements were made during weapons testing which found that the worldwide average radiation dose from ingesting Sr-90 (1945 to present) is 9.7 millirem (about equal to radiation doses from a transpolar flight), and the dose from inhaling strontium-90 (1945 to 1985) is 0.92 millirem (about equal to the dose from an arm or leg x-ray). These doses are well below those doses known to cause any effects on health (NCRP 1991)3. The doses from Sr-90 in the environment are about 0.3% of the average annual dose a person in the United States receives from natural background radiation (~300 millirem).

As a result of the Chernobyl accident, approximately 216,000 curies of Sr-90 were released into the atmosphere. An increase in the incidence of childhood thyroid cancer in the area directly affected by the accident has been attributable to radioiodine ingestion. No other increase in overall cancer incidence or mortality has been observed that can be attributed to radiation from the accident (UNSCEAR 2000)4.

The total annual release of strontium-90 into the atmosphere from all 103 commercial nuclear power plants operating in the United States is typically 1/1000th of a curie. (NUREG/CR-2907, Vol. 12)5. At an individual nuclear power plant, the amount of Sr-90 is so low that it is usually at or below the minimum detectable activity of sensitive detection equipment. Radiation doses from Sr-90 to individuals living within 30 miles of a nuclear power plant would be a tiny fraction of less than one millirem. As indicated above, nuclear power plant emissions of Sr-90 are inconsequential compared with other man-made sources and, thus, it is reasonable to conclude that the vast majority of Sr-90 that can be detected in, for example, baby teeth would be attributable to fallout from nuclear weapons testing or, possibly, the Chernobyl accident.


References at the bottom of the linked site.

Sid
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