alt Hacker NewsEven at military contracting prices, estimates put them at $100-200M each IIRC. That's not terrible.
The highly enriched fuel is used because it simplifies the design and maintenance. It eliminates all the machinery you'd need to support things like operational refueling of the reactor. Old designs still needed to be rebuilt every 25 years but the new ones are sealed systems that are never supposed to be cracked open over their design life.
I think the main reason we don't use HEU in civilian reactors is non-proliferation concerns, valid or not. Ideally you'd want maximally simple, sealed reactors for the same reason the US Navy does.
I'm not finding much support costs being that low... best collection of info I have seen is here:
https://www.construction-physics.com/p/why-are-nuclear-power...
At 1.5-1.7x the cost of diesel ship, and the "well-managed" Virginia class costing $3.6B, we are at over $1B for 60MW of power, 200MW thermal, which is far worse than larger civilian reactors per watt.
The reason we use nuclear submarines and aircraft carriers are their far superior operational characteristics when compared to hydrocarbon fuels. That benefit is massive and well worth it. For terrestrial grid electricity those benefits don't really exist.