There should be pretty strict regulation for fission reactor development, simply because radioactive materials in runaway reactions can have totally uncontrollable, millennia-spanning consequences. Very few other technologies have this potential - even a regular chemical explosion poses little risk to future generations in a large radius. Certain materials (plutonium, for instance) can reach criticality very quickly and in tiny quantities, and plutonium is a byproduct of fission. (I’m not a nuclear physicist, so my understanding of the real potential here might be wrong, because I have no sense of the quantities that might be experienced).

This isn’t a defense of the current regulatory process. The time frames, in particular, sound pretty egregious (4 years to approve a prototype, and 2m pages of documentation feels like a lot, too, but again I don’t know how these things are designed). But I would be extremely uncomfortable with lax regulatory oversight, given that nuclear accidents have permanent, irreversible impacts on society and geography.

Now, small-scale reactors may be a different beast entirely. If the quantity of materials is pretty much guaranteed not to have potential to cause problems for anyone but the operators for a short period of time…. Then there certainly seems to be a case for a shorter regulatory cycle. But I would be shocked if scale isn’t already taken into account for the current regulatory burden.