| Iridium-192 | |
| Mass Number: | 192 |
| Symbol: | Ir |
| Num Neutrons: | 115 |
| Num Protons: | 77 |
| Abundance: | synthetic |
| Halflife: | 73.827 days |
| Decay Product: | Platinum-192 |
| Decay Mass: | 192 |
| Decay Symbol: | Pt |
| Decay Product2: | Osmium-192 |
| Decay Mass2: | 192 |
| Decay Symbol2: | Os |
| Parent: | Osmium-192 |
| Parent Mass: | 192m |
| Parent Symbol: | Os |
| Parent Decay: | β- |
| Mass: | 191.9626050(18) |
| Spin: | 4+ |
| Decay Mode1: | β- |
| Decay Mode2: | ε |
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, 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.