[ZenGum]

The reactors are designed so that in the event of earthquake or similar, boron control rods automatically drop in to the core and absorb excess neutrons, ending the nuclear reaction. The problem now is remaining heat, which the cooling system is *supposed* to deal with.
It isn't going to go Chernobyl, but it might be a bit of a Three Mile Island. Still not pretty.

I have several friends in Japan, mostly in Nagoya and one in Tokyo, but they have all touched base.