Iridium-192 (symbol 192Ir) is a radioactive isotope of iridium, with a half-life of 73.827 days.[1] It decays by emitting beta (β) particles and gamma (γ) radiation. About 96% of 192Ir decays occur via emission of β and γ radiation, leading to 192Pt. Some of the β particles are captured by other 192Ir nuclei, which are then converted to 192Os. Electron capture is responsible for the remaining 4% of 192Ir decays.[2] Iridium-192 is normally produced by neutron activation of natural-abundance iridium metal.[3] Iridium-192 is a very strong gamma ray emitter, with a gamma dose-constant of approximately 1.54 μSv·h−1·MBq−1 at 30 cm, and a specific activity of 341 TBq·g−1 (9.22 kCi·g−1).[4][5] There are seven principal energy packets produced during its disintegration process ranging from just over 0.2 to about 0.6 MeV. It is commonly used as a gamma ray source in industrial radiography to locate flaws in metal components.[6] It is also used in radiotherapy as a radiation source, in particular in brachytherapy. Iridium-192 has accounted for the majority of cases tracked by the U.S. Nuclear Regulatory Commission in which radioactive materials have gone missing in quantities large enough to make a dirty bomb.[7]

Iridium-192, 192Ir
General
Symbol192Ir
NamesIridium-192, 192Ir, Ir-192
Protons (Z)77
Neutrons (N)115
Nuclide data
Natural abundancesynthetic
Half-life (t1/2)73.827 days
Isotope mass191.9626050(18) Da
Spin4+
Parent isotopes192mOs (β)
Decay products192Pt
192Os
Decay modes
Decay modeDecay energy (MeV)
Isotopes of iridium
Complete table of nuclides

The metastable isomer 192m2Ir is iridium's most stable isomer. It decays by isomeric transition with a half-life of 241 years,[8] which makes it unusual, both for its long half-life for an isomer, and that said half-life greatly exceeds that of the ground state of the same isotope.

See also

edit

References

edit
  1. ^ "Radioisotope Brief: Iridium-192 (Ir-192)". Retrieved 20 March 2012.
  2. ^ Braggerly, L. L. (1956). The radioactive decay of Iridium-192 (PDF) (Ph.D. thesis). Pasadena, Calif.: California Institute of Technology. pp. 1, 2, 7. doi:10.7907/26VA-RB25.
  3. ^ "Isotope Supplier: Stable Isotopes and Radioisotopes from ISOFLEX - Iridium-192". www.isoflex.com. Retrieved 2017-10-11.
  4. ^ Delacroix, D; Guerre, J P; Leblanc, P; Hickman, C (2002). "Radionuclide and Radiation Protection Data Handbook" (PDF). Radiation Protection Dosimetry. 98 (1) (2nd ed.). Ashford, Kent: Nuclear Technology Publishing: 9–168. doi:10.1093/OXFORDJOURNALS.RPD.A006705. ISBN 1870965876. PMID 11916063. S2CID 123447679. Archived from the original (PDF) on 2019-08-22.
  5. ^ Unger, L M; Trubey, D K (May 1982). Specific Gamma-Ray Dose Constants for Nuclides Important to Dosimetry and Radiological Assessment (PDF) (Report). Oak Ridge National Laboratory. Archived from the original (PDF) on 22 March 2018.
  6. ^ Charles Hellier (2003). Handbook of Nondestructive Evaluation. McGraw-Hill. p. 6.20. ISBN 978-0-07-028121-9.
  7. ^ Steve Coll (March 12, 2007). "The Unthinkable". The New Yorker. Retrieved 2007-03-09.
  8. ^ Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001