It's not that trivial. It's hard to find places that are geologically stable over very long timeframes.
However, anti-nuclear activists deliberately focus too much on the problem of storing it indefinitely in the near term.
If we plan storage for tens of thousands of years, waiting out a few hundred years for economic and technological development is in order. The waste of tomorrow might be the fuel of the future.
The waste needs to be stable over the span of ~10,000 years. This is very short in terms of geological time frames. Yucca mountain isn't going to be pulled apart by continental drift any time in the next several million years.
> The waste needs to be stable over the span of ~10,000 years.
How did you arrive at that number? The waste is harmful for hundreds of thousands or even millions of years.
Like I said, I think the "indefinite storage" question is a red herring posed by anti-nuclear activism.
Perhaps a better question would be: How much we should be concerned about the inhabitants of this planet in 10,000 years when supposedly there's a mass extinction coming up in the next 100 years due to the energy needs of today and yesterday.
The waste itself is harmful, for eternity, simply by virtue of the fact that it is uranium. It's a toxic heavy metal, like lead, regardless of any radioactivity. The duration of the serious concern due to radiation is gone in roughly 10,000 years but if course the original enrichment and subsequent use of the fuel can have large impacts on this figure.
The reality is, nuclear waste should mostly be treated similarly to the toxic waste that is generates by other sectors of heavy industry.
However, anti-nuclear activists deliberately focus too much on the problem of storing it indefinitely in the near term.
If we plan storage for tens of thousands of years, waiting out a few hundred years for economic and technological development is in order. The waste of tomorrow might be the fuel of the future.