Hyperion Power Generation is claiming that it can mass produce a 25 megawatt reactor in the volume of a refrigerator, 1.5m in diameter, and 2.5 m high.

As you can see from the picture, this is just the reactor, and the full installation is a lot larger than a refrigerator, but if you are dumping your heat into an infinite 20°C liquid, the ocean, and you eliminate the super-heating setup, since space is at more of a premium than efficiency, and I can see putting in something north of 15MW in a with a 10 foot stretch.

Hyperion is hawking their technology for military applications as well, albeit for remote bases, not warships.

I would note that their design, which uses convection cooling with a lead-bismuth coolant (the heat carrying capacity of the molten metal explains the small size) sound to me like it would be rather quiet too.

By way of comparison, a stretched Kilo would displace about 4,500 tons submerged, as compared to a Seawolf, which displaces around 9,100 tons and has a s power plant that puts out something north of 45MW, and the Kilo’s Wiki page has it exceeding 20 kts with less than 5MW on batteries.

It would probably keep the aircraft carrier battle group a few hundred miles further off a country’s shoreline during a time of heightened tensions.

That is assuming, of course, that their numbers are not too good to be true.