I had read somewhere that if it got bad enough there that they would evacuate Tokyo. I don’t know if this is “bad enough” though.
With respect to Tokyo and most of Japan, there is a mysterious black soot or dirt appearing in cities near Fukushima and Tokyo. We suspect right now its origin is from the steam fissures around the Fukushima plant. You only occasionally see the steam when its concentration is thick enough. Normally it is too thin to be seen. It contains very fine particles from the soil, Fukushima material disintegrating and corium. It is traveling and depositing all over Japan and soon the West coast US. Its is highly radioactive with numerous hot particles. Japaneses citizens are breathing that into their lungs, right now. Basically they have created an extra fine corium debri field all over Japan. And this is just the beginning of the crisis.
Please note - The above is all IMHO. So take all this with a grain of salt or a tincture of iodide.