They were old, some came online in the 60s. Check the situation in France right now -- half of their aging fleet is offline because they basically can't get them to work. The NY Times had an article on it recently.
Last 10 gigawatts of shut down reactors were all finished in 80's and probably had half of their design age left, all the really old were shut down already in nineties.
But the industry has tumbled into an unprecedented power crisis as EDF confronts troubles ranging from the mysterious emergence of stress corrosion inside nuclear plants to a hotter climate that is making it harder to cool the aging reactors.
The outages at EDF, Europe’s biggest electricity exporter, have sent France’s nuclear power output tumbling to its lowest level in nearly 30 years, pushing French electric bills to record highs just as the war in Ukraine is stoking broader inflation.
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The article also mentioned EDF might need to be nationalized since it's in so much debt, and in fact this was announced a few days ago.
No, you can't maintain them forever. The EDF is mismanaged, in Germany we never had this kind of problems with nuclear plants. South Korea also has an excellent track record with building new plants.
This is repeated over and over again, but you have to shut them down ( or heavily sanitize ), because stuff under radiation fire just ages even more quickly than (simplified) normal ""rusting"".. just look at the increased maintenances that risk in France they get blackouts even they compensate via imports?
Just few days ago there was a documetary in ARD, a neutral one, about building back plants to green lawn, the cost and the almost century long effort to build them back that is ridiculous (multiple billions) , that is usually never priced in.
And then also that even if we accept all those downsides, the unsolved waste problem, (yeah a lot of people will give me armchair proposals or the new non-existing reactors that would just eat everything and leave nothing behind... not), that it is not cost competitive, the risk (yes, you tell me Russians are stupid, Fukushima was an exception, 3mile and other incidents were perfectly avoided, but please consider also war and terror), there just wouldn't be enough fuel for the whole word to go all-in (yeahyeh we just scrub it from the sea.. in theory, as much as we could just get all the drinking water from the sea or scrub all the CO2 from the atmosphere with current tech..).
But even if you ignore that again and believe it will be fine, even then if the world would now decide to go all in, the time it takes to build means it wouldn't even make a dent in 15 years - WHICH IS TOO LATE.
We could have avoided a lot if the world went all in renewables the 20-30 years back where we already knew what was coming.. and this is the most surprising thing to me. We could do so much suddenly in regard to Pandemic and now the war.. but in relation to the climate catastrophe they are minor annoyances, still we don't start acting but deter us constantly from the right thing by dreaming of the assumed easy nuclear solution out. Humans!!!
I derailed, sorry. But it will be bad, and nuclear just wont help even a bit.