Page 38 - Curriculum Visions Dynamic Book

Nuclear weapons
Everyone knows that the most powerful weapons in the world are nuclear weapons. The first nuclear bomb was the atomic bomb.
Fission bombs
The atomic bomb releases its energy through an uncontrolled chain reaction of the same kind that is used in nuclear power stations. That is, the atomic bomb is a device for splitting atoms (see page 28).
The atomic bomb was developed in the United States
during World War II. The development of the bomb was called the Manhattan Project, and it used many of the world’s
top scientists. It was begun because it was feared that the scientists in Hitler’s Germany were making such a bomb, and it was essential that the allies have a weapon to counter it.
During this time an enormous amount was learned about how atoms work; and this, in the long run, was to prove very useful for making nuclear reactors for peaceful purposes. For the bombs scientists enriched the uranium to about 90% (it is a mere 3% in power stations.).
The bomb was made of two parts, each containing a piece of uranium too small to produce nuclear fission on its own. When the bomb fell on Hiroshima, Japan, on August 6, 1945, a high explosive charge forced these two pieces of uranium together very rapidly and held them in place for the microseconds needed for the uncontrolled chain reaction to occur.
Plutonium can also be used to split the atom. This was the material used for the bomb dropped on Nagasaki on August 9, 1945.
Fusion bombs
The fusion reaction is far more powerful than the fission reaction, but it is also harder to create. The hydrogen bomb, H-bomb, or thermonuclear device, was the first nuclear bomb to use fusion. An H-bomb is about a thousand times more powerful than an atom bomb (A-bomb) for the same mass
of materials.
The problem with a fusion reaction is that it will only work
with extraordinarily high temperatures. This is provided by exploding an A-bomb next to the materials that will be involved in fusion. Thus the A-bomb becomes the trigger for the fusion bomb. Today all large nuclear devices use fusion as the means of producing an explosion.
Various isotopes of hydrogen, including deuterium (which can be obtained from “heavy water”, D2O) and tritium, are now used for the H-bomb.
A 20 megaton bomb can probably destroy everything within a 16 km radius of where it falls. This devastating effect is too ghastly to contemplate, which is why most major nuclear countries continue to make efforts to reduce their stockpiles of such weapons, and why they try to stop other countries from making such weapons.
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