Again, simple ignorance. The reason it lasts so long is that we aren't allowed to reprocess it for rather illogical reasons. Also, most of the "waste" from the reactor are either rare earths or silver (which is stable from the moment it is created) or valuable and useful gases. It can also be reprocessed and the nuclear fuel can be put into another reactor. We don't do this because of the absurdly small chance someone could get some Pu-239 (which would still require very advanced and noticeable processing). Basically things that only happen in James Bond movies and because some politician without any scientific knowledge can imagine it, it gets banned.