Americium-241 (241Am, Am-241) is an isotope of americium. Like all isotopes of americium, it is radioactive, with a half-life of 432.2 years. 241Am is the most common isotope of americium as well as the most prevalent isotope of americium in nuclear waste. It is commonly found in ionization type smoke detectors and is a potential fuel for long-lifetime radioisotope thermoelectric generators (RTGs). Its common parent nuclides are β− from 241Pu, EC from 241Cm, and α from 245Bk. 241Am is fissile and the critical mass of a bare sphere is 57.6–75.6 kilograms and a sphere diameter of 19–21 centimeters. Americium-241 has a specific activity of 3.43 Ci/g (curies per gram or 126.8 gigabecquerels (GBq) per gram). It is commonly found in the form of americium-241 dioxide (241AmO2). This isotope also