放射性微尘 (Fallout)
Nuclear meltdown. Sounds real scary, don't it? Hear the word nuclear and you're liable to think of atomic bombs, gigantic, mutated ants, or George W. Bush and his hilarious pronunciation of it. Hear the word melt and you're liable to be grossed out while imaging the Wicked Witch of the West disappearing into her robes, or the scary as fuck insane cartoon from Who Framed Roger Rabbit that got killed by the dip. However, while a nuclear meltdown can be quite a motherfucker to take care of (Chernobyl), it can also be relatively harmless (Lucens, Three Mile Island) and only require an expensive years long clean up and closure of the plant.
A meltdown is what occurs when the fuel rods in the nuclear reactor overheat and melt. Typically this happens when there isn't enough coolant in the core to suck away the heat produced by the rods. What happened was after the earthquake the power at the plant went offline and the backup generators failed to work. Then the tsunami kind of fucked everything else up. With the coolant levels low, the fuel rods were exposed to the air and started overheating. Basically a partial meltdown is occurring and people in a 12 mile radius have been told to get the fuck away while people slightly further outside that radius have been told to stay indoors.
A partial meltdown is bad, but not Chernobyl bad. More like Three Mile Island bad. Three Mile Island, the most recent nuclear accident before Chernobyl, was a plant in Pennsylvania where a partial nuclear meltdown occurred and there was no damage to the surrounding area or people in it. The island itself has been closed off of course, but otherwise things are all good. Should the people at the Fukushima Daiichi plant be able to stave off further melting of the fuel rods, then things should similarly be all good in Japan. Should they melt further or, worse, progress into full on meltdown mode, then yeah, that'd be something to worry about.
Me? Personally I'm not in freak the fuck out mode yet. Apparently I'm not alone. Even people in the affected areas haven't broken out into a panic. Okinawa is about 1850km (1200 mi) from the plant so I'm not sure how affected we are by what's going on up north. Hopefully the government will be more forthcoming with all the details so we can know when to evacuate Japan or not.