Iridium-192

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

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]

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.

  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