um, nuclear power inside a power plant and nuclear power inside a bomb are completely different.
a bomb works on making uranium go above critical mass. that means compressing it.
one way to compress it was to slam it together. Little Boy was an example of this. it was a piece of Uranium at 1 end of a cannon barrel, and another piece of uranium, shot from the other end of the barrel at the first piece of uranium.
Later, (by a few days) we developed a better method, a sphere implosion technique. you surround a sphere of uranium with plastique, and detonate that, compressing the inner uranium. that's the other way to reach supercritical mass.
when that happens, it becomes extremely unstable, and releases a huge amount of energy in a split second, blowing apart the casing, and sending out a shockwave, along with some radiation, destroying stuff in it's path.
that's the simple version of a very complex process.
Oh, and in the event of a nuclear blast, hope your bomb shelter is directly underneath the blast, and shielded from radiation, cause that way the buildings overhead wont come down and wreck your shelter.
Oh, and the making of the Atomic Bomb by Richard Rhodes is a very good book. I also Reccommend Dark Sun, the making of the Hydrogen Bomb. They are really very historically informative.