France standardized all of their reactors. You could swap components in and out of any number of their nuclear reactors.

https://www.iaea.org/newscenter/news/frances-efficiency-in-t...

That's not how most other countries handled their nuclear power architecture and I think it's one of the main reasons why France has had major success with no issues. There's nothing flashy about how their nuclear reactors operate but they're very easy to staff and maintain long-term.