Neptunium - Tales from the Periodic Table

The 93rd element in the periodic table, Neptunium, due to its relatively short half live is rare in its natural form on the Earth's surface, but much more common in nuclear waste from reactors. Its main use is in the production of Plutonium 238, used in spacecraft thermoelectric generators. Unlike other radioactive elements, you probably have some Neptunium in your house. Most smoke detectors today use a tiny bit of alpha-emitting Americium which decays into Neptunium.