How many kilograms of Uranium-238 did the bombs dropped on Hiroshima and Nagasaki each contain?

Answer 1

None. The first atomic bomb was made with enriched uranium. Note: There is a "slight technicality" with this one. Here's the deal. Any time that a small quantity (or a slightly larger quantity) of uranium is found, either in nature or in the physics lab, there will be a tiny bit of plutonium in the sample. Only the tiniest bit, but it will be there. Uranium's isotopes are all unstable, and they will decay by spontaneous fission or alpha emission. Within that decay environment, a few atoms of uranium are transformed into atoms of plutonium. As stated, it's a "technicality" as such, but it's a fact.

Answer 2

The fissile isotopes used in the first bombs are the same as used in current bombs: Uranium-235 and/or Plutonium-239. Plutonium is most common, as can be seen from the following list of the first 5 bomb detonations:

1. Trinity proof test, Plutonium-239
2. Little Boy, Uranium-235, first combat use, Hiroshima
3. Fat Man, Plutonium-239, second & last combat use, Nagasaki
4. Crossroads Able effects test, Plutonium-239
5. Crossroads Baker effects test, Plutonium-239

Answer 3

The Hiroshima bomb (little boy) contained only highly enriched uranium (approx. 64 kg).
The Nagasaki bomb (Fat man) contained depleted uranium only as a damper. The explosive was plutonium.

Answer 4

The first atomic bomb has 64 kg enriched uranium.

For more details see: http://en.wikipedia.org/wiki/Little_boy.

Answer 5

The two dropped in WW2 weighed 4.5 tons and 5 tons.

Since then bombs have been built as light as about 50 pounds to as much as about 500 tons.

Answer 6

Approximately none. The first bomb, "Gadget," was the one set off in the Trinity test. The second bomb, "Little Boy," was the Hiroshima bomb. It used uranium, not plutonium.