20 year to build a nuke plant? You'll want to learn about the "plan Messmer". Or 6 years to build 13 900 MW reactors. When they only had experience with UNGG tech and wanted to use PWR.

I think in the end, 55 reactors were build in 12 years, replacing all coal and gas plants except for 2.

I mean, 50 000 MW in 12 years, basically. For today equivalent of 50 billions USD.