Similar to sodium cooled reactors, there are also lead or lead-bismuth cooled reactors, which have had one real life deployment ( onboard the Soviet Alfa class submarines), with its own advantages and disadvantages, and there are proposals to develop new versions.
There's so much interesting nuclear-related tech and concepts we haven't fully explored because of nuclear FUD ( much of which would be solved by the new tech).
Thanks, I had no idea lead-bismuth reactors existed. It seems the large number of unstable lead isotopes and their long decay chain would assure a long cooldown requirement before any maintenance could be done in the reactor compartment/primary coolant system. Not only that, but this stuff would present a huge disposal problem. https://en.wikipedia.org/wiki/Isotopes_of_lead
There's so much interesting nuclear-related tech and concepts we haven't fully explored because of nuclear FUD ( much of which would be solved by the new tech).