Nuclear / Particle Physics

Effects of the Atomic Bombs on Hiroshima and Nagasaki

Ever since the dawn of time man has found new ways of killing each other. The
most destructive way of killing people known to man would have to be the atomic bomb.
The reason why the atomic bomb is so destructive is that when it is detonated, it has
more than one effect. The effects of the atomic bomb are so great that Nikita
Khrushchev said that the survivors would envy the dead (International Physicians for the
Prevention of Nuclear War, 1982). These devastating physical effects come from the
atomic bomb’s blast, the atomic bomb’s thermal radiation, and the atomic bomb’s
nuclear radiation.
An atomic bomb is any weapon that gets its destructive power from an atom.
This power comes when the matter inside of the atoms is transformed into energy. The
process by which this is done is known as fission. The only two atoms suitable for
fissioning are the uranium isotope U-235 and the plutonium isotope Pu-239 (Outlaw
Labs). Fission occurs when a neutron, a subatomic particle with no electrical charge,
strikes the nucleus of one of these isotopes and causes it to split apart. When the nucleus
is split, a large amount of energy is produced, and more free neutrons are also released.
These neutrons then in turn strike other atoms, which causes more energy to be released.
If this process is repeated, a self-sustaining chain reaction will occur, and it is this chain
reaction that causes the atomic bomb to have its destructive power (World Book, 1990).
This chain reaction can be attained in two different ways.
The first type of atomic bomb ever used was a gun-type. In this type two
subcritical pieces of U-235 are placed in a device similar to the barrel of an artillery
shell. One piece is placed at one end of the barrel and will remain there at rest. The
other subcritical mass is placed at the other end of the barrel. A conventional explosive
is packed behind the second subcritical mass. When the fuse is triggered, a conventional
explosion causes the second subcritical mass to be propelled at a high velocity into the
first subcritical mass. The resulting combination causes the two subcritical masses to
become a supercritical mass. When this supercritical mass is obtained, a rapid
self-sustained chain reaction is caused (World Book, 1990). This type of atomic bomb
was used on Hiroshima, and given the nickname “Little Boy” after Franklin D. Roosevelt
(Outlaw Labs).
The second type of atomic bomb is an implosion bomb. In this type a subcritical
mass, which is in the shape of a ball, is placed in the center of the weapon. This
subcritical mass is surrounded in a spherical arrangement of conventional explosives.
When the fuse is triggered all of the conventional explosives explode at the same time.
This causes the subcritical mass to be compressed into a smaller volume, thus creating a
supercritical mass to be formed. After this supercritical mass is obtained, a self-sustained
chain reaction takes place and causes the atomic explosion (World Book, 1990). This
type of stomic bomb was used on Nagasaki, and given the nickname “Fat Man” after
Winston Churchill (Outlaw Labs).
The blast from an atomic bomb’s explosion will last for only one-half to one
second, but in this amount of time a great deal of damage is done (Physicians and
Scientists on Nuclear War, 1981). A fireball is created by the blast, which consists
mainly of dust and gasses. The dust produced in this fireball has no substantial effect on
humans or their environment. However, as the gasses expand a blast wave is produced.
As this blast wave moves, it creates static overpressure. This static overpressure then in
turn creates dynamic pressure. The static overpressure has the power to crush buildings.
The dynamic pressure creates winds, which have the power to blow down trees
(International Physicians for the Prevention of Nuclear War, 1982). The blast pressure
and fireball together only last for approximately eleven seconds, but because it contaitns
fifty percent of the atomic bomb’s latent energy a great deal of destruction occures (The
Committee for the Compilation of Materials on Damage Caused by the Atomic Bombs in
Hiroshima and Nagasaki, 1981).
In Hiroshima the blast from the atomic bomb was measured to be about four and
a half to six and seven tenths tons of pressure per square mere, while in Nagasaki the
blast was measured to be about six to eight tons of pressure per square meter
(International Physicians for