Sodium has two radioactive cosmogenic isotopes (22Na, with a half-life of 2.6019(6) years; and 24Na, with a half-life of 14.9560(15) h). With the exception of those two isotopes, all other isotopes have half-lives under a minute, most under a second. The shortest-lived is 18Na, with a half-life of 1.3(4)×10-21 seconds.
Sodium-22 is a radioactive isotope of sodium, undergoing positron emission to 22Ne with a half-life of 2.6019(6) years. 22Na is being investigated as an efficient generator of “cold positrons” (antimatter) to produce muons for catalyzing fusion of deuterium. It is also commonly used as a positron source in positron annihilation spectroscopy.
22Na is a positron-emitting isotope with a remarkably long half-life. It is used to create test-objects and point-sources for positron emission tomography.
5 minute measurement with a High Purity Germanium (HPGe) radiation detector.