Nuclear Weapons


Chemistry CP


4/7/02


A nuclear weapon is any type of weapon that explodes because of the transformation of matter in atoms into energy. There are two types of nuclear weapons, fission weapons, which are known as atomic weapons and thermonuclear weapons, which are commonly called hydrogen or fusion weapons.


In fission weapons, matter is changed into energy when uranium isotopes U-235, U-238, or the plutonium isotope Pu-239 are split. Once the nucleus splits, the little matter is made into a large amount of energy. Additional neutrons are released which spilt other nuclei. A self-sustaining uncontrolled chain reaction will form in which each split nucleus provides the means of splitting other nuclei. The self-sustaining reaction needs a minimum mass of fissionable material, this mass is known as critical mass. The mass too small to support a self-sustaining reaction is called a subcritical mass. The abundance of fissionable material is called a supercritical mass.


There are two designs of fission weapons, the gun-type method, and the implosion method. In the gun type method, two subcritical pieces of material are placed in a barrel type compartment. One is placed at the front end, the other at the far end with a conventional explosive packed behind it. When the weaponís fuse is lit, the conventional explosive propels the second subcritical mass at a very high speed into the first. This makes it so the mass can become supercritical, causing the rapid, self-sustaining chain reaction. This was the type of bomb that the US used at Hiroshima, it is equal to 13,000 tons of TNT.


In the implosion type method, a subcritical mass is made to explode by compressing it to a smaller volume. The ball-shaped sub-critical mass is put at the center of the weapon. This is surrounded by conventional explosives that go off all at the same time when the fuse is lit. This compresses the mass into a supercritical mass, and the explosion occurs. This was dropped at Nagasaki by the US during WWII.


In thermonuclear weapons, or fusion weapons, the nuclei fused are of the hydrogen isotope deuterium (H-2), and tritium (H-3). This can only occur if the temperature is equal or greater than that of the sun. In order to achieve these temperatures, is to first create a fission reaction. Once the fission device explodes, this will bombard the compound inside, Lithium 6 deuteride, which is composed of deuterium and lithium 6, an isotope of lithium. Once the neutrons that are released by the fission reaction strike it, the lithium 6 forms helium and tritium. Then pairs of tritium nuclei and deuterium nuclei and form to fuse helium nuclei. The matter of tritium and deuterium is converted into energy. These bombs are 40 times as powerful as the Hiroshima bomb. The explosive power of a thermonuclear weapon can be increased by surrounding the lithium 6 deuteride with a blanket of the uranium isotope U-238. The U-238 undergoes fissioning in the course of the hydrogen explosion.


The weapon's explosion produces four basic effects: (1) a blast wave, (2) thermal radiation, (3) initial nuclear radiation, and (4) residual nuclear radiation. The blast wave is the formation of a fireball, which consists of a cloud of dust and of extremely hot gases under very high pressure. The thermal radiation is the ultraviolet, visible, and infrared radiation given off by the fireball. This causes flash burns. The initial nuclear radiation is the gamma rays given are given off within the first minute of the explosion. The residual nuclear radiation given one minute after the explosion. It is made up of neutrons which strike particles of earth, that make up the mushroom cloud. These particles become radio active, and when they fall back to the ground, they are known as fall-out.