I suspect a big part of the reason why submarine reactors are able to be so small is because they sit on a planet-covering heatsink. Terrestrial plants accompl

I suspect a big part of the reason why submarine reactors are able to be so small is because they sit on a planet-covering heatsink. Terrestrial plants accomplish the same with artificial lakes and large cooling towers; the actual "nuclear" parts are already pretty small in comparison. But yes, assuming the cooling systems could be similarly mass-produced, it would make sense to mass-produce small-scale nuclear plants as well.