So, add a dash of iron to the nuclear waste and it's sealed forever. I never thought of that, but the iron rusting takes out all the free oxygen, and puts out hydrogen, which clogs all the pores. However, none of the 'recipes' for Canadian high-level waste had good old rusty iron. That stuff is reserved for Obama Barrels on rivers, where iron is not so good.
As I've said before, the only good geological repository is one that is stable, and only has diffusion to worry about. Put in some iron, and you're good for another 10.000 years. The practical end of 'worry' is at the natural uranium ore level (or coal ash!), not every last Plutonium atom at a few million years. If the politics can be left out, then this is a simple problem.
But, we're not going to have this nice solution! Oh, no, we're going to have something horrible, on top of the biggest fault in North America, in fractured rock with fluid flow. Sure, you can say the fluid down there is 10,000 years old, but start pumping for an excavation! I shudder to think...