"Radioactive waste will stay dangerous for hundreds of thousands of years" There's one statement which's always used by people opposed to nuclear power - that the waste will stay dangerous for thousands, ten thousands and even hundred thousands of years. But I'm wondering - is this accurate? After following the Fukushima accident for over one and a half years, I came to the conclusion that stuff like Cesium, Iodine, Strontium, etc. is the most dangerous, but all those isotopes have half times of "not more" than several decades. Meaning that they'll be mostly gone after several hundred years. Of course there's other stuff like Plutonium which's halftime is close to 25000 years, but it's a heavy metal and while it's also very poisonous, it won't be nearly as volatile as Cesium. So... what hazard would a spent fuel cask pose after 1000, 10000 and 100000 years?