We had a fast breeder reactor here in France before, creating energy from nuclear waste. Oil/"green" lobbies made it to close: http://en.wikipedia.org/wiki/Superph%C3%A9nix EDIT: And also terrorists and molten sodium.
IANAS but it appears that Superphenix used liquid sodium as a coolant, whereby Transatomic is proposing a molten salt (not sodium) fuel.
Yup, liquid sodium was scaring the hell out of the workers on the site, and rightfully.