Which presumably drives a turbine to make electric which can run motors, charge batteries, run scrubbers, run heaters, etc., presumably.

They're not direct driving the screw with steam power from the reactor heat-exchange, surely.

It's hard to find anything like a schematic of a Nimitz-class carrier for obvious reasons, but as far as I can tell yes, it's all directly steam powered. The reactor boils (sea)water, which is used to power 4 steam turbines[1][2][3], those turbines drive the propellers.

You've probably seen aircraft carrier decks covered in smoke. This is because the Nimitz's catapult system is directly steam powered, service steam is widely used on the class. I can't find a citation for this now (this is from memory) but I saw some documentary on it once where it was mentioned in passing that even the washing machines on the ship were steam powered. There's service steam everywhere on the Nimitz.

Having steam power everywhere introduces a lot of complexities, which is why the Navy's moving away from it with their new carrier class[4]. The Gerald R. Ford-class does away with service steam in favor of more powerful electric generators. There'll be no service steam, just steam to drive the electric turbines.

1. http://www.nimitz.navy.mil/FACTS.html

2. https://en.wikipedia.org/wiki/Nimitz-class_aircraft_carrier#...

3. https://www.marinelink.com/news/dresserrand-propulsion302604

4. https://en.wikipedia.org/wiki/Gerald_R._Ford-class_aircraft_...

I love the way they did the electromagnetic catapult.

https://en.wikipedia.org/wiki/Electromagnetic_Aircraft_Launc...

Basically they spin up flywheels that then dump their kinetic energy back into electric power as the catapult is released.

And it allows them to finely adjust the speed of the catapult depending on the kind of aircraft they are launching.

some nuclear submarines are not steam powered directly, they use electric engines.

Very few, if https://en.wikipedia.org/wiki/Integrated_electric_propulsion... and https://en.wikipedia.org/wiki/Columbia-class_submarine#Elect... are to be believed. The latter claims that as of 2013 there is exactly one nuclear submarine class (https://en.wikipedia.org/wiki/Triomphant-class_submarine to be exact) that uses electric engines.

> They're not direct driving the screw with steam power from the reactor heat-exchange, surely.

Yes, they are, for the simple reason that it's more efficient. This is beginning to give way to a series electrical design, but that's for reasons of increased stealth and other concerns, at the cost of overall thermodynamic efficiency.

On all existing nuclear carriers steam is used for the catapults (and this is much more demanding than many people are aware of). The Ford class is developing electromagnetic catapults, which are also proving to be demanding to perfect.