France built hardly any.
And that's the complete answer: we know how to build nuclear reactors quickly and cheaply.
Building only very few of different novel designs while slowly (or quickly) losing the industrial base to do so, for example by making it illegal to build more (or at all) is exactly how you don't do it.
Currently they can’t even agree on how to fund the absolutely insanely bonkers subsidies.
Now targeting investment decision in H2 2026… And the French government just fell because they are underwater in debt and have a spending problem which they can’t agree on how to fix.
A massive handout to the dead end nuclear industry sounds like the perfect solution!
But nuclear is fast to build, if we ignore all modern western examples!
As per recent French nuclear construction they are on a path of replacing it with renewables because it is horrifically expensive and they are unable to finance new construction.