[jeffbee]

I don't know if they are safe or not but one thing that disturbs me about neo-fission propaganda is how they so nonchalantly dismiss what seem to me to be threats worth discussing. For example, MSR fans will say that they operate at standard pressure, and therefore can't rupture. Also, gaseous fission products are removed continuously. OK but what about the gaseous fission products if the removal system ceases to function? Then what about the pressure? Same question about water. MSRs are safer because they contain no water, which can't flash to steam and explode. OK, but what about water intrusion on the surprisingly wet planet Earth? What if the reactor is flooded? Would a flooded reactor stop the passive safety plug from melting?

I always had the same suspicions about the pebble bed reactor boosters. That was a design that was always sold as being inherently safe and self-moderating, with the huge, huge asterisk that if any oxygen or water ever gets anywhere near the fuel the whole thing will explode and then catch on fire, which seems like a pretty severe drawback. Any time you see a claim that a reactor vessel "does not contain" either water or oxygen, just mentally translate that to "is not designed to contain" or "does not initially contain" before reading further.