The density of space? I don't follow. 1kg of uranium produces about 10^7 times more energy than 1kg of lithium batteries.
Uranium is denser than batteries too, so 1kg of uranium takes up less volume than 1kg of batteries. Is that what you meant?
Edit: sorry I was being slow. Yes, since uranium is 10 million times more energy dense than batteries, the infrastructure will be smaller than that of batteries for the same amount of energy.