A
submarine which is powered by a
nuclear reactor. The
United States Navy runs many of these out of
naval bases
such as that at
Pearl Harbor.
Nuclear power is good
for submarines because it lets them operate for a long time
without surfacing to refuel. A nuclear submarine does not
necessarily carry nuclear weapons.
Some early nuclear submarines had a problem with their reactor cooling systems
which caused their sterns to glow blue with Cerenkov radiation.