Speculate a loss-of-cooling accident (LOCA) caused disassociation of cooling H2O into H2 and O2. Operators attempted limited venting of H2 to local environment, but air/H2 mixture accidentally ignited. Hydrogen explosion is a very powerful event which could breach both the primary and secondary containments.
While this does not mean the core has melted, it does mean we could be looking at a hefty release of contamination.
Again, speculation on my part.
Jonah,
I think you nailed it. A high order hydrogen explosion has completely gutted on the reactor buildings.
Remember folks how that was the big fear during Three Mile Island?
Well, it happened.
Not a good sign that the PM didn’t even mention this during his latest presser.
It is hard for the Japanese to admit that the situation is out of control. Especially a nuclear situation.