La Hague used to dump small quantities of radioactive liquid (mainly water used to clean barrels that contained weakly radioactiv waste) in Nort Sea. When I left (in 1999), the project to completely stop this dump was well advanced. The idea was to vaporized the water and collect the remains in a barrel.

You are right that we have a lot of plutonium that we can not use. The intent of superphenix was to use this plutonium. It failed.