SuperPhénix was cool on paper but I'm actually surprised that they built it and after that it took so long to stop it. It used sodium, a lot of it, which explodes violently in contact of water.
That's an issue for most people. The political pressure was huge to stop the project. The CEA wasn't even that good at manipulating sodium, they got two known major incidents in Cadarache. One quite spectacular with a huge cloud of fire.
I think nuclear power is great to research and the risk is sometimes worth it, but SuperPhénix was too risky.
The issues with sodium are manageable, as seen in other sodium-cooled reactors like the Russian BN-XXX or the US EBR-II. Sodium has other good properties which make up for the downsides, which is why most fast reactor designs have chosen sodium has the coolant.
That's an issue for most people. The political pressure was huge to stop the project. The CEA wasn't even that good at manipulating sodium, they got two known major incidents in Cadarache. One quite spectacular with a huge cloud of fire.
I think nuclear power is great to research and the risk is sometimes worth it, but SuperPhénix was too risky.