What makes radioactivity from a nuclear bomb so deadly? What consists
inside of nuclear bomb to make it so powerful?
Nuclear bombs are powerful for the same reason nuclear reactors
are able to produce lots of energy out of a small amount of fuel -
the nuclear reactions involved just do give out a lot of energy,
much more per unit weight than chemical explosives. The reason
is the very small mass differences between the two sides of a
nuclear reaction get multiplied by the speed of light squared
(remember E = mc^2) which is a huge number, and so there is a lot
of energy involved.
There is lots more to it of course - in order to get the reaction
going you have to produce neutrons. If you control the neutron
production you can get a nice stable reaction going, as in a nuclear
power station. If you do not control it, you get a "chain reaction":
which explodes. And that is just for fission reactions - there is
also a fusion process that has only been successfully implemented
in bombs, because it is such a hard problem to make a reactor
that controls fusion reactions. But the energy comes from the
same kind of process (in fission it is heavy nuclei splitting apart,
in fusion it is light nuclei joining together).
Why is radioactivity from a bomb so deadly? Well, it is because of
that uncontrolled "chain reaction" that is spewing neutrons in
all directions, and those extra neutrons cause all sorts of trouble.
At least, that is the immediate effect. The nuclear reactions also
result in the release of all kinds of harmful radioactive byproducts
that last for many years. So in general it is pretty nasty stuff.
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Update: June 2012