There is also the detail of where on the ship you're going to install all that plant - neither option is exactly compact. The size of the steam plant tends to get overlooked because current systems share steam plant with the propulsion system, but people seem to think the electrical system is small. It isn't, of course, because it needs something to store and deliver the energy. The most effective solution appears to be large flywheel-alternators which are spun up (slowly) with motors from the electrical system and then essentially shorted out by the cat which draws the energy out in a few seconds. These flywheel alternators are huge, highly stressed and have massive gyroscopic moments which need to be accommodated in the mounting structure. They're not the sort of thing which can be tucked behind the shower in the chief engineer's cabin.
PDR