@ChrisMayLA6 The other one I can think of is "Core Disruptive Accident" but it's mainly theoretical and even the physicist who dreamt it up (Hans Bethe) later said it was likely nonsense. The idea was that a fast reactor core would melt and the lower 2/3 or so would slump into the lower head of the reactor vessel and go subcritical (i.e. shut down) until the remaining upper 1/3 of the core suddenly gave way, dropped on to the rest of the core debris causing the whole thing to go prompt-critical with a stupidly huge burst of energy until the thing blew itself apart. This isn't an issue with water-cooled power plants, only with fast reactors that don't use a moderator to slow neutrons down - those can't go critical without a lot of water or carbon mixed in with the fuel. The CDA is a nice science fiction scenario but it's so far beyond low probability as to be a fantasy.