I don't know where you get that information from, but I have been there and can say with absolute certainty that your 80% figure is completely bogus.
The Japanese government has recognized about 650,000 people as hibakusha. As of March 31, 2016, 174,080 are still alive, mostly in Japan. The government of Japan recognizes about 1% of these as having illnesses caused by radiation. (Wikipedia)
Show me the numbers
Those are people that were not at the blast site (i.e. epicenter), but were within the radiation zones.
And this actually disproves your assertion, due to them being affected by the RADIATION from the bomb.
Before the US govt exploded the first atomic bomb they did an experiment where they poured molten radioactive materials into the center of a large pile of TNT.
The US govt had a plan to fake nuclear bombs if they didn't work. Just the threat of them being real was enough to rule the entire world it was decided.
(post is archived)