There always seem to be so many assumptions in these safety claims. I'm not really for or against fission power but I don't like to feel like I'm being conned by sales literature masquerading as science. Questions that seem unanswered by NuScale revolve around their subterranean cooling pool. The ultimate safety claims require this thing to be full of water, so the obvious question is: what if it springs a leak? What if the pool drains around the containment structure in such a way that the hydrostatic pressure of its own lost coolant forces it out of the ground, like an empty swimming pool in a flood? Speaking of which, what about floods? Also their safety claims rely on vacuums and anoxic environments, but this is Earth so what happens during oxygen intrusion?

Fission people spent the entire 1990s hyping pebble bed reactors but ultimately they had these problems. The safety of a PBR lies in having an inert atmosphere. During an air or water intrusion event the whole this will burn, explode, and melt. Again, Earth is absolutely filthy with oxygen so this is a legitimate concern.