What happens if some geologist of the future unknowingly takes a core sample in just the wrong place, to name just one of many not entirely unlikely scenarios.

They'll get sick and die. Unfortunate. Others will take note, and declare the place dangerous. If they don't, then they're stupid and I just can't bring myself to caring about it.

I don't think it's necessary to make huge precautions about warnings and such, just leave a sample in a hallway before the main storage, entities entering the facility should be able to take note of the fact that there is danger ahead and proceed with caution, regardless of their technological level.

For goodness sake, my local council doesn't even know where all its buried services are located under the roads and pavements. Do we really think we can preserve data and ensure political stability for 10000 years?

Of course not, you tit.

This has to be the biggest argument against nuclear power.

Yes it, in fact, is, but it's WAY too late in the game to ponder it, the waste is there and something has to be done about it. And any new amounts of waste will not make much difference, so continuing to use nuclear power is just as ecologically sound as it ever was.

Forget the operational safety aspects.

The what?