... If those people in Tokyo are not threatened today, they may be threatened tomorrow if the wind blows the right way...
Nobody knows what will happen tomorrow
- problem at Fukushima is there's such contradictory information about what's happening there today
. At least some things are known to be impossible, such as a Chernobyl-type explosion; but radiation can unfortunately get much worse.
And the wind has already shifted toward Tokyo. There's no way to evacuate 36 million people so they have to stay put; but there are efforts to mitigate the effects of additional radiation - IFF (if and only if) it does get to that - by distributing potassium iodide to populations, telling them to stay indoors, and at least moving the most vulnerable (pregnant women, small children etc) out of town.
So, the key is: will things at Daiichi get worse? All I can give you is probabilities: if pressures / temperatures can be brought down and kept down (see my note to Farmerman) for the next several days then the answer is NO. That's the maximum probability
After that's done they can clean up any loose radioactive pellets before they seep into the groundwater, clean up with robots the whole plant, and then cover the damn thing up with boron-loaded concrete. What radiation has already leaked into the atmosphere will stay out there.
But then there's a small residual probability, which is what you're asking: might things not work out? They might. But that probabilityevaluated at this time
is too small to justify panic anywhere outside Fukushima prefecture in Japan and certainly too small to justify a run on potassium iodide in the West Coast. If someone out there has perfect information on the exact status of Daiichi, he can come up with a better quantification of probabilities than "very large" v. "very small". I don't have that information. If you want the gory details of what that very small probability involves, I can do that...