Also potentially safer failure mode: in a run-away vent, it heats up, melts through a plug in the reactor base and drains out into a settling pan, which stops the reaction dead.

The worst thing about modern nuclear power is we won't shut the old reactors the hell down, so when you get a Fukushima it's because at every junction proposals to replace it were held up, but no one would brook just shutting it down either.