Of course, all the ratios are wrong is you scale everything and you might not get to criticality. So it is a completely different design with different manufacturing techniques for many parts. It is like a model of an airplane also wouldn't fly without adjustments to many parts which of course changes various ratios.
I'm aware of that, but to get to normal sized reactors they first built smaller prototypes that had outputs that were much closer to the modular reactors that are now being investigated. So they're not really theoretical.
I would have thought that SMR design would be more inspired by nuclear submarines and such which are already small, not necessarily large power stations, but admittedly I don't know anything in this area.
Nuclear subs are a lot more exotic, you need to go from 0-60 in a few seconds, so they make fuel plates instead of rods so it really bumps up the neutron population quickly.
There’s no need to adjust criticality that rapidly at a generating station.
Also, they tend to use much higher enrichment ratios on the fuel from what I have read. I guess that is all for the fast power output regulation as you write. Stunning technology and a security nightmare, just imagine a nuclear sub bumping into a click in territorial waters of a not-so-friendly nation and making the area uninhabitable.
How are they different from the reactors in US Navy submarines?