You might be surprised how much nuclear waste is out there. A bunch of estimates on this thread put it in the "millions of cubic feet" range, which is considerably more than what could fit in a single underground site:
Note also that this is mostly just considering high level waste (like, the actual spend fuel rods and reactor parts), and not all low- and intermediate-level waste, of which there is a lot more:
If I follow your link, I read this: Over the past four decades, the entire industry has produced about 62,500 metric tons of used nuclear fuel. That's the high-level waste.
The rest of the comment goes on to explain that including all low- and intermediate-level waste, plus legacy waste from military activities, then it may reach the millions of cubic feet you're citing.
Low-level waste is not much more dangerous than the extra natural radiation you receive from a plane trip, so the real danger is high-level waste. And that can fit in a fraction of the space required for a single solar park.
UK estimates that the amount of nuclear wast we'll have (both high and low-level) will be smaller than the volume of one of the UK's national sports stadiums
https://www.quora.com/What-is-the-total-mass-and-volume-of-a...
Note also that this is mostly just considering high level waste (like, the actual spend fuel rods and reactor parts), and not all low- and intermediate-level waste, of which there is a lot more:
https://en.wikipedia.org/wiki/Radioactive_waste#Classificati...