A white metallic transuranic element of the actinide series, having isotopes with mass numbers from 237 to 246. It exists in many forms such as rags, paper, plastic, glassware, filters, soil and building rubble. It is ''pyrophoric,'' which means that, in some forms, it can burn when exposed to oxygen. It is also toxic, and fissile. Plutonium 239, which comprises most of Rocky Flats', has a half-life of 24,100 years.
Plutonium is used almost exclusively for nuclear fuels and nuclear weapons.
Colorado Dept. of Public Health and Environment and the Defense Nuclear Facilities Safety Board. A heavy silvery-white metallic element, radioactive, easily oxidized, and having 14 known isotopes of which U238 is the most abundant in nature. It is used in research, medicine, nuclear fuels and atomic weapons.