Some key insights from the article:
Basically, what they did was to look at how much batteries would be needed in a given area to provide constant power supply at least 97% of the time, and the calculate the costs of that solar+battery setup compared to coal and nuclear.
This is still more polluting to mine than going nuclear, even accounting for nuclear waste.
Do you have a source for that claim? Genuine question.
My intuition is that the types of impact are widely different, so hard to reduce to a single number that can be compared.