rt can you point to some scientific details on that? Your post is the first I have heard of it being more than a hydrogen explosion blowing the roof off, or of fuel rods being ejected (presumably from the storage ponds, not the reactors, as they remained essentially intact)
As in my original post go here:
http://vimeo.com/22865967 the video explains the evidence but in a nutshell the unit 3 explosion was too energetic to have been solely a hydrogen explosion. I did think it went with a bang....compared to unit 1. The presenter of the video goes into the detail of why he thinks it was a "prompt nuclear reaction" in the fuel rod storage area.