What on earth are you talking about? You realize you are full of alpha emitters?
> As stated above your 600 year timescale is off by close to three orders of magnitude
Nope, see this chart: https://whatisnuclear.com/img/ingestion-radiotoxicity-nuclea...
> you appear to be pretending groundwater either doesn't exist or can't move
That's why you bury it in rock where it doesn't move and we know it doesn't. Like the Permian Basin or where the Oklo natural reactors occurred in Gabon.
Oh yes, did you know nature formed fission reactors billions of years before we did ever existed? This always pisses off the hippies when I tell them. And guess what? The fission products from this natural process moved mere centimeters over 2 billion years.
This is a solved problem. It's just that some people desperately want it not to be.