Well, it now turns out that many of my worst fears about Fukushima have been confirmed with the news that TEPCO has finally admitted that Reactor #1 has experienced a meltdown event that may have breached the primary containment vessel. Further, truly alarming levels of radiation are now being reported in and around Tokyo.
The prospects for containing the situation at Reactor #1 are now much dimmer than previously admitted. A melted core is far more difficult to cool because the geometry of the slag heap at the bottom is not nearly as favorable as long thin tubes around which water can be relatively easily circulated.
Worse, if the slag has either melted through the primary containment vessel or somehow leaked out through a fitting that has failed, then the ability to circulate water is even more compromised.