Comment by esarbe

France's reactors became successively more expensive as the need for more layered safety features was exposed. The first generation (CP0, CP1, CP2) was quite inexpensive, the P4 and P'4 designs were already more expensive and the N4 was yet more expensive.

At this point I think if you want inexpensive nuclear, you just have to accept some risk. Going from 99.9% safety to 99.99% adds just too much complexity to remain economically viable.