Monju was a poorly designed machine which was particularly badly run. I recently found a book they wrote about it and when I looked at the plans I thought "I can't believe they built that in an earthquake zone". I don't know if anyone is ever going to build another loop-type LMFBR as many of the problems you can have with a loop-type can't happen in pool-type reactors.

What was most shocking about the fire at Monju wasn't that it happened but that they tried to cover it up. Neither that nor the incident where they dropped the refueling machine into the reactor vessel were dangerous to people off site but the latter sure convinced everyone they didn't know what they were doing.

Contrast that to Superphenix where the fuel transfer drum failed and they struggled with a steam turbine system that was procured under corrupt contracts but overall had a good operational record. Or the three pre-1970s cases where there was significant fuel damage in the US but they found that a core melt in a LFMBR isn't as bad as it sounds because the iodine (most dangerous radioactive element in the fission products) reacts with the sodium and the NaI dissolves in the sodium so it doesn't go anywhere. Or EBR-II and the FFTF which performed flawlessly, or the highly successful fast reactors in Russia.