Dangerous for hundreds of thousands of years is pure fearmongering. There are loads of chemicals, metals and other nasty stuff that are dangerous forever and also need to be stored somewhere safely, indefinitely.

I personally live close to a commercial Asbestos dump (an old mine) and absolutely nobody cares about it. It's so unimportant it doesn't even have a Wikipedia article.

Yet the second radioactive waste is concerned (even if it's just old rubble) everybody seems to lose their minds and refuses to even think rational.