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What Are Nuclear Weapons And How Do They Work?
     Nuclear weapons are some of the most destructive technology that has ever been invented. As we saw in World War II, nuclear weapons have the power of mass destruction. Whole cities can be eliminated with a single bomb. The results of nuclear weapons have become a major issue in our world. The effects of nuclear weapons have raised numerous questions. Should countries be allowed to build nuclear weapons? How will this new technology be controlled in the future? Nuclear weapons could be disastrous to not only humans but the entire earth.

Why do Nuclear Weapons Explode?

     Nuclear bombs involve the strong and weak forces that hold the nucleus of an atom together, especially atoms with unstable nuclei. There are two basic ways that nuclear energy can be released from an atom. Energy can be released through fission or fusion. Fission is the slitting apart of an atom. With fission the nucleus of an atom is split into two small pieces with a neutron. Isotopes of uranium (uranium-235, uranium-238) or plutonium-239 are involved in this process.

     Fusion is the opposite of fission. It is the combination of two atoms into one large atom. Fusion brings together hydrogen or hydrogen isotopes (deuterium, tritium), together to form a larger atom (helium or helium isotopes).

     Both fission and fusion give off large amounts of energy and heat. The splitting of an atom or the combination of atoms gives off an enormous amount of energy because it changes the stability of the particles within the atom – the protons, neutrons, and electrons. This is why nuclear bombs can explode in such a powerful manner. Nuclear technology gets its power from fusion and fission. It is hard to imagine how so much energy can come out of a process that deals with something as small as an atom.

Types Of Nuclear Bombs and How They Work

     Nuclear bombs can be categorized in fission and fusion bombs. Even within these categories there are different methods for the bombs to explode. With fission bombs, there are gun-triggering devices that help set off the bomb. The triggering device is needed along with a way to allow the majority of the fuel to fuse before an explosion. Some fission bombs are implosion triggered. Fusion bombs are different from fission bombs. They are more powerful than fission bombs and work in a different manner.

Fission Bombs
     Fission bombs are also known as A-bombs or Atomic bombs. A fission bomb uses an element like uranium-235 to create a nuclear explosion. Uranium-235 has an extra property that makes it useful for both nuclear-power production and nuclear-bomb production - U-235 is one of the few materials that can undergo induced fission. If a free neutron runs into a U-235 nucleus, the nucleus will absorb the neutron without hesitation, become unstable and split immediately. As soon as the nucleus captures the neutron, it splits into two lighter atoms and throws off two or three new. The two new atoms then emit gamma radiation as they settle into their new states. An atom of U-235 cab capture a neutron at a very high probability. In a bomb, more than one neutron ejected from each fission causes another fission to occur. An incredible amount of energy is released, in the form of heat and gamma radiation, when an atom splits. The energy released by a single fission is due to the fact that the fission products and the neutrons, together, weigh less than the original U-235 atom. In a fission bomb, the fuel must be kept separate to prevent a premature explosion. They are kept separate in what are called subcritical masses. To bring the subcritical masses two forms of technology are used - a gun-trigger device and an implosion device.

     A gun-trigger device shoots one mass into another causing the explosion. Inside the sphere of the fission bomb a small bullet of U-235 is dropped through a barrel onto a separate sphere of U-235. When these two collide the bomb explodes. Little Boy is an example of a gun-triggered bomb.

     The other technology for a fission bomb is one that implodes. Inside the sphere of the bomb in this technology, explosives are fired causing a shock wave which brings together plutonium pieces. The plutonium pieces strike a beryllium/polonium core in the center of the bomb which induces fission causing the bomb to explode. Fat man is an example of a implosion nuclear bomb.

Fusion Bombs

     Fusion Bombs are called H-bombs, hydrogen bombs, or thermonuclear bombs. They are generally more powerful than fission bombs. Deuterium and tritium are the fuel for fusion bombs. Fusion bombs work in two stages. In the first stage, the primary reaction is a regular fission chain reaction. This part heats up the interior of the bomb so that fusion can occur. It consists of a relatively small quantity of conventional explosives whose detonation brings together enough fissionable uranium to create a fission chain reaction, which then produces another explosion and a very high temperature. When the temperature reaches 10,000,000 K fusion reactions take place. The neutrons given off in the first part start the second stage. The lithium deteuride, under intense heat, splits apart into lithium and deuterium ions. The neutrons from the first stage react with the lithium ions. Fusion bombs designed to release neutrons rather than causing further fission reactions are called neutron bombs. Neutrons kill people, leaving the hardware and buildings intact. The first thermonuclear bomb called Ivy Mike.

Written by Gus Federle

Bibliography:

The MILNET project. http://www.milnet.com/milnet/index.html
The History of the Atomic Bomb. http://inventors.about.com/library/weekly/aa050300a.htm
Nuclear Fission, Nuclear Fusion: Technologies for the new millennium forge ahead. http://www.fast-times.com/edge/nuclear.html