Of that 64 kg (of U-235), only about 1 kg actually underwent fission. The other 63 kg of uranium were vaporized and sent spewing into the atmosphere over
This Atomic Bomb was less than 3000 times as powerful as the Hydrogen Tsar Bomba of Russia in 1961:
Thirty one Little Boy assemblies were built by 1947. Nagasaki's Fat Man was named after Sydney Greenstreet (left) from the movie, Maltese Falcon, while Little Boy (right below, Elisha Cook) also came from that film.
I have long wondered how Nagasaki and Hiroshima can be safe when Plutonium and Uranium have half lives of hundreds of thousands to a million years. Hiroshima, for example, has to account for 141 pounds of highly radioactive U-235, which has a half life of 704 million years.
Here is the answer, from my Huffington Post article (which was a consensus summary of a dozen colleagues in physics and engineering) of April 13, 2011:
Why worry about Fukushima when Hiroshima and Nagasaki are safe?
For an Atomic-Bomb, the Uranium and Plutonium half-lives are so long that there is almost no radioactivity to affect humans. For Chernobyl and Fukushima, the dangerous radioactive elements are not Uranium nor Plutonium, but Cesium-137, which has a half-life of 30 years, Iodine-131 of only 8 days and Strontium-90 with 28 years. Both Fukushima and Chernobyl will be barren for hundreds of years. Nagasaki and Hiroshima are today thriving cities.
So is nuclear warfare safe and nuclear power plants dangerous? The former is certifiably terrible, and the latter, potentially worse. Anyway, I visited the Hiroshima Peace Park today:
The day before Thanksgiving, the Dow Jones Industrial Average broke its all-time high for the 30th time this year, up 13 to 17,828.