context: Plutonium's most famous application is Nuclear Weapons, an example of which is Fat Man dropped into Nagasaki during World War II. Only the fissionable 239Pu isotope is suitable for nuclear use and must have an isotopic purity or / or concentration of more than 90%. Plutonium can also be used as a nuclear fuel, whereby the fissionable and chain reactive nuclide is also 239Pu.
question: What is plutonium used for?
answers.text: Nuclear Weapons