Beyond the political outrage, what's interesting is that France is one of the only countries that makes nuclear safety legislation retroactive. This means that

Beyond the political outrage, what's interesting is that France is one of the only countries that makes nuclear safety legislation retroactive. This means that when new measures are decided, all existing reactors need to be upgraded before they can operate. This is not the case in the US for example. A few years ago during maintenance ops they discovered stress beyond tolerance on heavy steel pieces in some reactors that led to a change in regulation requiring new ways to measure carbon content in those pieces. From what I gathered basically the rule mentioned where measurements would be made to determine carbon content, and of course manufacturers didn't measure anywhere else themselves. Now the problem is that some of these are >100 tons parts in irradiated zones, it's not as easy as just going in with a carbon meter and taking readings. These have been built decades ago, some in other countries, so the know-how is somewhat lost. Plus they're under heavy industrial secret protection. From what I gather, EDF is now coming up with simulations based on their understanding of the manufacturing process to prove they're up to code and restart the plants.