The first commercial reactor designs are probably 50 years away and another 50 years before costs come down to be reasonable / we can build enough to start replacing existing fission and coal. This is from the CEO of General Fusion a leader in the space. I think if even the fusion people are saying “build fission today to solve global warming” then that tells you something about the time scale this is happening on.

I suspect the regulatory environment is from regulatory capture by the fossil fuel industry. Otherwise why would Gen IV reactors, which can’t meltdown, be suffering many regulatory delays? What kind of nuclear proliferation concerns exist for reactors built and deployed within the US?