I grew up an hour from a lake you couldn’t swim in because the cooling equipment for the plant caused microbes to grow that cause encephalitis. Those regulations are written in blood and you’re fantasizing about an unattended reactor as the next generation? No. Dream on.

I’m not saying it’ll never happen. I’m saying the work hasn’t been done and this is more snake oil.

And then there’s the physics and logistics the other responder mentioned. For conventional reactors, that much concrete of a very specific and difficult quality to achieve in that many layers is expensive. The last one I heard about being built they had to jackhammer off many feet of the base because they missed spec, and lay it all over again. And the carbon footprint of that much concrete is not tiny. The embodied cost of a built plant is huge, and repairs are constant. They aren’t free, even if you ignore heat pollution, and we are running out of runway for that conceit.

FAA regulations are written in blood, too - and yet our private aircraft technology is ancient (and likely less safe than modern tech could facilitate) because those same regulations make the cost to innovate astronomical. I would not make the mistake of believing that regulations do more than freeze our tech in a relatively safe local minima.

You're describing the engineering problems of rarely-produced machinery, and seem to imagine that we can't figure out how to do that better, and cheaply, at scale? The potential market for a shipping-container-sized MW-scale power supply is likely huge.