South Korea builds nuclear power plants in five years.

Not any more they don't. Those were older reactor designs which nobody wants now. And the 5 years was first-pour to switch on. Add a few years for planning, permitting and actually supplying to the grid.

Newly approved Korean plans are aiming for 2038. Best of luck to them. I'm sceptical they'll make it.

https://www.world-nuclear-news.org/articles/plans-for-two-ne...

Edit to add:

They used to be pretty fast but like everyone else seem to be slowing down significantly.

https://world-nuclear.org/information-library/country-profil...