Topic summary
Americium-241
Americium-241 (Am, Am-241) is an isotope of americium. Like all isotopes of americium, it is radioactive, with a half-life of 432.6 years. Am is the most common isotope of americium as well as the most prevalent americium isotope in radioactive waste. It is used in ionization-type smoke detectors and is a potential fuel for long-lifetime radioisotope thermoelectric generators (RTGs). Its common parent nuclides are Pu (by beta decay), Cm (by electron capture), and Bk (by alpha decay). Am is fissile, with the critical mass of a bare sphere of 57.6–75.6 kilograms (127.0–166.7 lb) (diameter of 19–21 centimetres (7.5–8.3 in)). Americium-241 has a specific activity of 3.43 Ci/g (126.91 GBq/g). It is commonly found in the form of americium-241 dioxide (AmO2). The presence of Am in plutonium is determined by the original concentration of plutonium-241 (which decays to it) and its age. Older samples of plutonium containing Pu build up Am and may require chemical removable of americium-241 (e.g., during reworking of plutonium's pits).