Quote Originally Posted by 2F/2F View Post
I am just surprised that backup generators were located low enough that they could get flooded.
Agree. It was clearly the greatest single design mistake. However, as it seems now, even after getting power back, the cooling systems are damaged too, probably in the tsunami, so maybe it wouldn't have helped even if the generators were on the upper grounds.

I also cannot believe that there was not a powerless emergency cooling system that works by convection.
There was but it failed. It worked for some time before failing, but it is still a bit unclear to me whether it failed because the 8-hour battery power ran out or was it going to fail anyway.

As said, this is clearly the most complex nuclear accident ever.