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>> A mushroom cloud in a 1950s blast
ATOM AND HYDRO BOMBS.
* An atom bomb is a fission bomb.
* It contains a sphere of plutonium-239 about the size of a grapefruit.
* Chain reactions start in this sphere whenever a stray neutron enters a plutonium nucleus, but they rapidly fizzle out; too few of the neutrons find other plutonium nuclei.
* The sphere is surrounded by shaped explosive charges.
* The sphere is suddenly compressed into a much smaller volume when these explode.
* The nuclei are now closer together and the chain reaction goes ahead.
*A neutron source ensures there is a neutron there to start the reaction.
* There is a terrific burst of heat energy. This is equivalent to about 20,000 tonnes of TNT.
* Many of the radioactive atoms produced are carried up into the stratosphere.
* Eventually they reach the ground, all over the world, as fallout.
* Two heavy hydrogen nuclei can fuse together to produce a helium nucleus.
* This reaction can be triggered by a fission bomb.
* The trigger is surrounded by a jacket containing heavy hydrogen (deuterium).
* The resulting bang is equivalent to at least a million tonnes of TNT - the biggest was a hundred times more
powerful.
* Fission energy is released in a controlled way in a reactor.
* Nobody has yet managed to generate power by controlled fusion.
* The Sun and other stars, however, get their energy from nuclear fusion.
(SOURCE www.sciencenet.org.uk/database/Physics/Atomic/p00418b.html)
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