Uranium is $128.30/kg
After enrichment, conversion and fabrication that’s $3400/kg for 4.95% fuel.
At 36-45MWd/kg and a net thermal efficiency of 25% or $12.5/MWh up front.
With a 90 month lead time (72 month fuel cycle and 18 months inventory) at 3% this is $16.2/MWh
It’s not a small fraction it’s less but it’s not a small fraction.
Overcast days typically generate about 40% of what they would generate on a sunny day. Remember temperature isn’t relevant, in fact they don’t actually like being too hot, so weirdly solar panels might actually not work very well in the Sahara desert.
So unless you regularly have to deal with San Francisco style fog, and basically only San Francisco has fog like that because it’s quite a weird microclimate, you’ll be alright with solar pretty much anywhere in the world that isn’t inside the Arctic circle.