Iridium-192

Iridium-192 (symbol ¹⁹²Ir) is a radioactive isotope of iridium, with a half-life of 73.82 days. It decays by emitting beta (β) particles and gamma (γ) radiation. 95.24% of ¹⁹²Ir decays occur via β^- emission, leading to ¹⁹²Pt; the remaining 4.76% occur via electron capture to ¹⁹²Os; both modes involve gamma emission. 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 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 gamma rays produced in its beta-minus decay, ranging from 296.0 to 612.5 keV, and two produced in its electron capture decay at 205.8 and 484.6 keV.^[6] It is commonly used as a gamma ray source in industrial radiography to locate flaws in metal components.^[7] 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.^[8]

Iridium-192

General
Symbol	192Ir
Names	Iridium-192
Protons (Z)	77
Neutrons (N)	115
Nuclide data
Natural abundance	synthetic
Half-life (t1/2)	73.82 days[1]
Isotope mass	191.962605[2] Da
Spin	4+
Parent isotopes	192mOs (β−)
Decay products	192Pt 192Os
Decay modes
Decay mode	Decay energy (MeV)
Isotopes of iridium Complete table of nuclides

The metastable isomer ^192m2Ir is iridium's most stable isomer. It decays solely by isomeric transition (to this ground state) with a half-life of 241 years,^[1] which is somewhat unusual for its long half-life and that said half-life greatly exceeds that of the ground state.

See also

• Isotopes of iridium