I disagree. building big infrastructure projects always scales well. As stated by the project managers at Hinkley Point C (the most expensive nuclear reactor ever) they estimate that build times and cost will be significantly reduced for the second reactor due to the knowledge and expertise baked into the workforce. Frances nuclear revolution during the 1972 oil crisis also shows the same thing with construction cost getting lower the more reactors built.
There are other reactor designs that do not use uranium that have been tested and hypothesized.
Unless you are the US Navy. It probably helps that they churn out dozens of the same few cookie-cutter designs without needing permission from NIMBYs.
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.
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.
This is absolutely a terrible idea about how to deal with a meltdown.