Transcript Nuclear Bombs - nhscrazy4chem

Nuclear Bombs
The First Nuclear Bombs
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There are two main types of bombs which
release energy from the nuclei of atoms.
The simplest kind is an atomic bomb. Like
a nuclear power plant, it releases great
quantities of energy through a process
called nuclear fission, or 'splitting', of a
large unstable (radioactive) element like
uranium or plutonium.
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The energy source is a
mass of radioactive
material such as uranium
or plutonium. This
material is very unstable;
every atom's nucleus is
ready to fall apart
('decay') at the slightest
nudge, releasing
unneeded energy and
extra neutrons. In the
diagram, the plutonium
(B) is given that nudge by
the outer casing of TNT
(A), which explodes all
around it.
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The plutonium is unstable, or radioactive. Its
atoms are constantly 'falling apart', breaking
up into smaller elements that are more stable.
Every time one nucleus does this, it releases
the extra energy it no longer needs to hold it
together, as well as a few left-over neutrons.
This energy, and the escaping neutrons, is
what we describe as the radiation being
emitted from the radioactive plutonium. This
energy and flow of escaping neutrons can
damage human cells, so radioactivity is
dangerous.
Enough atoms in the chunk of plutonium are
breaking down at any one time to make the
chunk of plutonium warm up, but not enough
to be considered an explosion.
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What happens in the bomb, however,
changes that! The force of the TNT explosion
causes the plutonium to be squashed, or
compressed in size, and become very dense.
This is called its 'critical mass'; the plutonium
is now so densely packed together that the
neutrons escaping from the decaying nuclei
of plutonium cannot escape from the
plutonium without bumping into another
plutonium atom!
When they hit another atom, they cause that
nucleus to break down too, whether it was ready
to or not. That second nucleus releases more
energy, and more neutrons, which in turn go on
to hit and break up further nuclei. The decaying
nuclei cause more decaying nuclei, and so on, in
a rapidly escalating chain reaction ... and all
because the plutonium has been squeezed into
such a dense state (by the TNT) that the
escaping neutrons that normally would fly out
of the material now can't, without hitting other
nuclei!
Within a very tiny fraction of a second, all
the nuclei in the chunk of plutonium have
been hit by escaping neutrons, and have
broken down. The extra energy in
trillions of atomic nuclei is all released at
once! This energy is considerable; the
atomic bomb dropped on Hiroshima in
WWII was an example of this process.
Initial Explosive Conditions
Maximum temperature at burst point:
several million degrees centigrade. A
fireball of 15-meters radius formed in
0.1 millisecond, with a temperature of
300,000 degrees centigrade, and
expanded to its huge maximum size in
one second. The top of the atomic cloud
reached an altitude of 17,000 meters.
Black Rain
Radioactive debris was
deposited by "black rain" that
fell heavily for over an hour
over a wide area.
Damaging Effects of the Atomic
Bomb
Intense thermal heat emitted by the
fireball caused severe burns and loss of
eyesight. Thermal burns of bare skin
occurred as far as 3.5 kilometers from
ground zero (directly below the burst
point). Most people exposed to thermal
rays within 1-kilometer radius of ground
zero died. Tile and glass melted; all
combustible materials were consumed.
Blast
An atomic explosion causes an enormous
shock wave followed instantaneously by a
rapid expansion of air called the blast; these
represent roughly half the explosion's
released energy. Maximum wind velocity:
440 meters per second. Wooden houses
within 2.3 kilometers of ground zero
collapsed. Concrete buildings near ground
zero (thus hit by the blast from above) had
ceilings crushed and windows and doors
blown off.
Bodily Injuries
Acute symptoms. Symptoms appearing in the
first four months were called acute. Besides
burns and wounds, they included: general
malaise, fatigue, headaches, loss of appetite,
nausea, vomiting, diarrhea, fever,
abnormally low white blood cell count,
bloody discharge, anemia, loss of hair.
Aftereffects. Prolonged injuries were associated
with aftereffects. The most serious in this
category were: keloids (massive scar tissue
on burned areas), cataracts, leukemia and
other cancers.
Radiation
People exposure within 500 meters
of ground zero was fatal. People
exposed at distances of 3 to 5
kilometers later showed symptoms
of aftereffects, including radiationinduced cancers.