How small could a nuclear-powered surface vessel be?

What minimum beam and draught would a vessel need to carry a small modular reactor?

There is no single minimum dimension: reactor barges and cruiser-sized installations show different possibilities, but cost discourages small combatants unless reactors become much cheaper.

There is no universal minimum beam or draught because the reactor installation can be designed around the vessel. A shallow-draught barge carrying its plant above the hull presents a different arrangement from a warship with the plant inside it. The Virginia-class nuclear cruisers provide an example of a ship about 180 metres long and 19 metres in beam, narrower than a Type 45. A vessel of about 7,000 tons is accepted as theoretically possible, although reactor costs make such a choice unattractive without a substantial price reduction. Small modular reactors could change the economics if widespread production brought costs down. A final qualification stretches 'nuclear-powered' to include a very small passive sensor vessel using a radioisotope thermoelectric generator, an RTG, instead of the reactor arrangement originally discussed.