Nuclear Fission Explosions
Hiroshima (14 kt: 06 Aug 1945) and Nagasaki (22 kt: 09 Aug 1945)
Fission weapons
(popularly called "atom
bombs") produce an explosive release of energy
by bringing together a "critical mass" of
radioactive uranium or plutonium sufficient
to produce a "chain reaction." The "Little Boy" bomb dropped
on Hiroshima was a gun-assembly of a critical mass of uranium.
The "Fat Man" bomb
dropped on Nagasaki three days later was a plutonium
implosion weapon, based on the "Trinity"
device tested at Alamogordo, New Mexico, in July 1945. Energy
yields were originally measured as the equivalent explosion of
thousands of tons of trinitotoluene (TNT) (kilotons or kt).
In SI units, 1 kt =
4.184 x 1012 J = 4.184
TJoules. The estimated yield of the "Little Boy"
explosion was 14 kt = 59 TJ of energy,
accompanied by the release of 8×1012
PBq = 8 YottaBq of ionizing
radiation. [The explosive yield of the Trinity test
was 25 kt = 105 TJ].
"Atomic energy" misrepresents the nature of fission reactions. The phrase came into use because the word 'nuclear' was avoided during the Manhattan Project due to security concerns. Typical chemical processes, including conventional explosives, generate 'atomic energy' in the course of a reaction. Robert Oppenheimer, Director of the Manhattan Project, was once asked before a Congressional committee if research isotopes could be used to produce 'atomic energy'. His response was that they could, and so could a bottle of beer.
"Atomic energy" misrepresents the nature of fission reactions. The phrase came into use because the word 'nuclear' was avoided during the Manhattan Project due to security concerns. Typical chemical processes, including conventional explosives, generate 'atomic energy' in the course of a reaction. Robert Oppenheimer, Director of the Manhattan Project, was once asked before a Congressional committee if research isotopes could be used to produce 'atomic energy'. His response was that they could, and so could a bottle of beer.