I remember my trip into Elliot Lake more than 20 years ago. I was at the height of my career, we had a thriving Geotechnical Department, and we were looking for more nuclear plants, and even had a big project on an underground nuclear plant. Ah, those were the days!
So you had to fly in on this tiny 13 seater airplane. I was jammed right behind the pilot. They only have a single runway, and there was a cross-wind. Wow!
The rock there is very tight and under very high horizontal stress. We were looking at a uranium mine which had experienced some large rockbursts. We climbed through the mine looking at the devastation. That's where I got a real appreciation for the power of stressed rock, and it led me to more earthquake studies.
We must realize that there is no difference between 'intermediate' waste and the used fuel, which is called 'high level' waste. Really, in Canada, we don't have high level waste, which I would classify as pure liquid Plutonium, extracted. That's high-level waste! The only thing about the fuel is that it can still produce a lot of heat. Thus we have a problem in that extra heat will stress the rock.
Even if we go to my favourite site in Wesleyville, we have the problem of highly stressed rock and heat. This is a rock mechanics question at its best! I believe it is easily done.