Distribution of the fission products of plutonium
The distribution of the number of nucleons of the fission products of a minor actinide is similar to that of a fissile heavy nucleus such as uranium-235 or plutonium-239. Almost all the fragments from fission, which start off highly radioactive, become stable again after a few years. Some of the fission products shown in the figure persist: strontium-90 and caesium-137 with a half-life of around 30 years; and technetium-99, iodine-129 and caesium-135, with half-lives in excess of hundreds of thousands of years.