The Australian ABC reports that TEPCO have announced that the nrs 2 and 3 reactors were subject to meltdown shortly after the earthquake and tsunami.
Actually, this information is not new, because it has been known for quite a while that there was a partial meltdown in both reactors nr 2 and 3. One of those reactors was the one where it was first known that the rods had been exposed for a period of time. It seems that there has been some confusion over the timing of each of the events, when it comes to the information as it was first released. We only heard recently about the actual damage to the nr. 1 reactor, where there had also been a meltdown shortly after the major earthquake and tsunami.
If the tsunami had been smaller in size the generators would not have been knocked out. This is the really critical information in understanding what took place. The way in which the operation was set up, the diesel powered generators kicked in as soon as the reactors began shut-down as a result of the earthquake. The role of the generators was to provide the means by which the water flowed to allow the rods to cool. However, the generators were knocked out by the tsunami. This left battery operated generators that had a life of about 8 hours and those soon failed. It is this generator failure that has led to most of the subsequent damage and the sequence of events that have come after the main events.
If the generators had not failed, then there would not have been the meltdown, or the explosions caused by hydrogen build-up.