There is as yet no proven safe method for permanently disposing of high level radioactive waste. Although plutonium is an indirect byproduct of the fission process, it is not a fission product. Click on this image to view an animation. Additional neutron captures yield other transuranic elements, such as neptunium, americium, curium and californium. Most of them, including plutonium, will continue to give off alpha radiation for centuries or even millenia.
Plutonium is one of the most toxic man-made substances there is.
A few milligrams of plutonium dust inhaled into the lungs, though invisible to the naked eye, will cause death in a short time due to massive fibrosis of the lungs. Plutonium, like uranium, can undergo nuclear fission. This substance can therefore be used as a nuclear explosive or as fuel for a nuclear reactor. As noted earlier, the Nagasaki bomb utilized plutonium. For technical reasons, it is easier to use plutonium instead of uranium as a nuclear explosive.