Radioactive Japan Then And Now

This is not an exact comparison but will give you some idea of the order of magnitudes involved: The Hiroshima bomb contained about 64 kg of Uranium. The Nagasaki bomb had about 6.2 kg of Plutonium plus maybe tens to hundreds of kg of Uranium.

The Fukushima reactors and spent fuel rods amount to a total of 1,814 tons of Uranium. Say we go with just plant number three which has likely suffered a melt down. That would be 88 tons of Uranium. Roughly 1,000X as much Uranium as the Hiroshima bomb.

Now this is not a direct comparison of the two events. It is not a technical analysis. It is just to give you a very rough idea of the amounts of radiation involved. Will the dispersion be as good as it was from a bomb? No. And that is good and bad. There will be hot spots. Maybe if we are lucky a lot of the radioactives will remain on site.

Anyway you look at it the contamination will be much worse than that from a single primitive bomb.