A few of my questions about the Fukushima I cooling crisis at Unit 1 and possibly Unit 3:
What's the cloud visible in videos? It looks like concrete dust to me.
How much of the crisis was really due to lack of emergency generation capacity, and how much to difficulty of getting access to controls and instrumentation?
How did radioactivity get into the control room?
Is the primary containment intact?
What's the status of the spent fuel in the pool next to the drywell? Once the secondary containment shell blew out, it would appear that a fair amount of structural steel and concrete fell in there.
I'll be adding some links, but in the meantime here's a good one from David Lochbaum on the workings and layout of the troubled reactor.