There's one in Finland:

https://en.m.wikipedia.org/wiki/Onkalo_spent_nuclear_fuel_re...

They have thought thousands of years ahead and set up many different types of warning signs and symbols in case a future civilization discovers it.

I think the difference is that the one in Finland can still be entered like a normal tunnel. The deep borehole is literally just a vertical shaft that goes 5-6km down, you put the waste on the bottom and fill it back up. No geological process is bringing the waste back up in any conceivable timescale, and even if the entire civilization collapsed no primitive society can dig to 5km depth, so there's no need for much long lasting signage, no one is going to stumble upon it by accident.

No, they put zero warnings. Warnings only make it more likely that someone decides to start digging.

The idea that civilisation collapses and then recovers to the specific extent, where it is advanced enough to have coal-mines or similar, but not to know about radiation. Then it must find this particular repository and start digging, and die. Thousands of years must pass but they must dig up this sight withing a particular 100-year period of their development.

This is such a stupidly contrives scenario that you might as well plan for an alien incasion or zombie apocalypse. Lime prerequisite for that theory is civilisation collapsing, our investment in making sirebcovilisation does not xollapse is zero. You deal with it by making sure civilisation does not collapse.

Then they will know about radiation.

> They have thought thousands of years ahead

That level of stupid theatrics really annoys me. If society has regressed then it will be a godsend to rediscover nuclear power. If society has advanced this is like the Romans trying to anticipate modern problems.

And than there is Asse: https://en.wikipedia.org/wiki/Asse_II_mine

You just don't know.

The time frame is too long. It's too long for natural causes and far too long for human civilisation. The earlier we stop producing this crap, the better.

Sure, but that's why I suggested deep borehole storage - there is no known geological process that can bring up material stored at 5km+ depth into the surface on any sort of human timescale. A mine, even at 700m depth, is just too shallow for long term storage.

But there are many human processes which can.

....and? If you wanted highly dangerous materials to use for some evil purposes it's 1000x easier to just manufacture some poison rather than dig 5km deep. I'd argue that making radioactive isotopes in an accelerator is still easier than digging. Not sure what your concern is here.

> It's not coming back no matter what

If you can drill down to put it in, can't you also drill down (or use the same hole) to get it out?

Well, yes, technically. I meant more that the waste won't come back on its own, through tectonic movements, earthquakes, meteor strikes or pretty much any other natural process known to man. You could drill down to retrieve it, but then it's a very specific thing serving one specific purpose. It's not like mine repositories, where they are at a much shallower depth and could be entered "easily" from the surface.