The problem (as I understand it; I'm an engineer but not a NucE) is that the reactor core is so hot that even if you shut it down immediately in the earthquake, which these were designed to do and in fact did, it takes 24 to 48 hours to bring the core down to a temperature where it won't melt down if not cooled.
Apparently the loss of the backup/emergency diesel generators to the tsunami left them with only 8 hours of battery-powered cooling. Not enough.
(I got to tour an aircraft carrier a few years ago, and was a bit surprised that it took something like 48 hours or so --number forgotten-- to get the reactor up to operating temp. Not a case of inserting the key, turning the ignition switch, and roaring off.)
>Apparently the loss of the backup/emergency diesel generators to the tsunami left them with only 8 hours of battery-powered cooling. Not enough.
Maybe I’m oversimplifying things but why not deliver a bunch of portable generators to pump the cooling water?