Nuclear Bombs

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Nuclear Bombs
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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!

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• 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!

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• 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.

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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.

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Black Rain

• Radioactive debris was deposited by "black rain"
  that fell heavily for over an hour over a wide
  area.

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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.

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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.

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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.

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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 radiation-induced cancers.