Back نظير اليود 131 Arabic Iod-131 German Ιώδιο-131 Greek Yodo-131 Spanish ید-۱۳۱ Persian Radiojodi Finnish Iode 131 French Iodio-131 Italian ヨウ素131 Japanese 아이오딘-131 Korean

Iodine-131

Iodine-131, 131I
General
Symbol131I
Namesiodine-131, 131I, I-131,
radioiodine
Protons (Z)53
Neutrons (N)78
Nuclide data
Half-life (t1/2)8.0197 days
Isotope mass130.9061246(12) Da
Excess energy971 keV
Isotopes of iodine
Complete table of nuclides

Iodine-131 (131I, I-131) is an important radioisotope of iodine discovered by Glenn Seaborg and John Livingood in 1938 at the University of California, Berkeley.[1] It has a radioactive decay half-life of about eight days. It is associated with nuclear energy, medical diagnostic and treatment procedures, and natural gas production. It also plays a major role as a radioactive isotope present in nuclear fission products, and was a significant contributor to the health hazards from open-air atomic bomb testing in the 1950s, and from the Chernobyl disaster, as well as being a large fraction of the contamination hazard in the first weeks in the Fukushima nuclear crisis. This is because 131I is a major fission product of uranium and plutonium, comprising nearly 3% of the total products of fission (by weight). See fission product yield for a comparison with other radioactive fission products. 131I is also a major fission product of uranium-233, produced from thorium.

Due to its mode of beta decay, iodine-131 causes mutation and death in cells that it penetrates, and other cells up to several millimeters away. For this reason, high doses of the isotope are sometimes less dangerous than low doses, since they tend to kill thyroid tissues that would otherwise become cancerous as a result of the radiation. For example, children treated with moderate dose of 131I for thyroid adenomas had a detectable increase in thyroid cancer, but children treated with a much higher dose did not.[2] Likewise, most studies of very-high-dose 131I for treatment of Graves' disease have failed to find any increase in thyroid cancer, even though there is linear increase in thyroid cancer risk with 131I absorption at moderate doses.[3] Thus, iodine-131 is increasingly less employed in small doses in medical use (especially in children), but increasingly is used only in large and maximal treatment doses, as a way of killing targeted tissues. This is known as "therapeutic use".

Iodine-131 can be "seen" by nuclear medicine imaging techniques (e.g., gamma cameras) whenever it is given for therapeutic use, since about 10% of its energy and radiation dose is via gamma radiation. However, since the other 90% of radiation (beta radiation) causes tissue damage without contributing to any ability to see or "image" the isotope, other less-damaging radioisotopes of iodine such as iodine-123 (see isotopes of iodine) are preferred in situations when only nuclear imaging is required. The isotope 131I is still occasionally used for purely diagnostic (i.e., imaging) work, due to its low expense compared to other iodine radioisotopes. Very small medical imaging doses of 131I have not shown any increase in thyroid cancer. The low-cost availability of 131I, in turn, is due to the relative ease of creating 131I by neutron bombardment of natural tellurium in a nuclear reactor, then separating 131I out by various simple methods (i.e., heating to drive off the volatile iodine). By contrast, other iodine radioisotopes are usually created by far more expensive techniques, starting with cyclotron radiation of capsules of pressurized xenon gas.[4]

Iodine-131 is also one of the most commonly used gamma-emitting radioactive industrial tracer. Radioactive tracer isotopes are injected with hydraulic fracturing fluid to determine the injection profile and location of fractures created by hydraulic fracturing.[5]

Much smaller incidental doses of iodine-131 than those used in medical therapeutic procedures, are supposed by some studies to be the major cause of increased thyroid cancers after accidental nuclear contamination. These studies suppose that cancers happen from residual tissue radiation damage caused by the 131I, and should appear mostly years after exposure, long after the 131I has decayed.[6][7] Other studies did not find a correlation.[8][9]

  1. ^ "UW-L Brachy Course". wikifoundry. April 2008. Retrieved 11 April 2014.
  2. ^ Dobyns, B. M.; Sheline, G. E.; Workman, J. B.; Tompkins, E. A.; McConahey, W. M.; Becker, D. V. (June 1974). "Malignant and benign neoplasms of the thyroid in patients treated for hyperthyroidism: a report of the cooperative thyrotoxicosis therapy follow-up study". The Journal of Clinical Endocrinology and Metabolism. 38 (6): 976–998. doi:10.1210/jcem-38-6-976. ISSN 0021-972X. PMID 4134013.
  3. ^ Rivkees, Scott A.; Sklar, Charles; Freemark, Michael (1998). "The Management of Graves' Disease in Children, with Special Emphasis on Radioiodine Treatment". Journal of Clinical Endocrinology & Metabolism. 83 (11): 3767–76. doi:10.1210/jcem.83.11.5239. PMID 9814445.
  4. ^ Rayyes, Al; Hamid, Abdul (2002). "Technical meeting of project counterparts on cyclotron production of I-123" (pdf). International Nuclear Information System. IAEA.
  5. ^ Reis, John C. (1976). Environmental Control in Petroleum Engineering. Gulf Professional Publishers.
  6. ^ Simon, Steven L.; Bouville, André; Land, Charles E. (January–February 2006). "Fallout from Nuclear Weapons Tests and Cancer Risks". American Scientist. 94: 48–57. doi:10.1511/2006.1.48. In 1997, NCI conducted a detailed evaluation of dose to the thyroid glands of U.S. residents from I-131 in fallout from tests in Nevada. (...) we evaluated the risks of thyroid cancer from that exposure and estimated that about 49,000 fallout-related cases might occur in the United States, almost all of them among persons who were under age 20 at some time during the period 1951–57, with 95-percent uncertainty limits of 11,300 and 212,000.
  7. ^ "National Cancer Institute calculator for thyroid cancer risk as a result of I-131 intake after nuclear testing before 1971 in Nevada". Ntsi131.nci.nih.gov. Archived from the original on 23 July 2012. Retrieved 17 June 2012.
  8. ^ Guiraud-Vitaux, F.; Elbast, M.; Colas-Linhart, N.; Hindie, E. (February 2008). "Thyroid cancer after Chernobyl: is iodine 131 the only culprit ? Impact on clinical practice". Bulletin du Cancer. 95 (2): 191–5. doi:10.1684/bdc.2008.0574 (inactive 31 January 2024). PMID 18304904.{{cite journal}}: CS1 maint: DOI inactive as of January 2024 (link)
  9. ^ Centre for Disease Control (2002). The Hanford Thyroid Disease Study (PDF). Retrieved 17 June 2012. no associations between Hanford's iodine-131 releases and thyroid disease were observed. [The findings] show that if there is an increased risk of thyroid disease from exposure to Hanford's iodine-131, it is probably too small to observe using the best epidemiologic methods available Executive summary

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