Plutonium<span> is </span>made<span> from U-238. Pu-239 is normally </span>created<span> in nuclear reactors by transmutation of individual atoms of one of the isotopes of uranium present in the fuel rods. Occasionally, when an atom of U-238 is exposed to neutron radiation, its nucleus will capture a neutron, changing it to U-239.</span>
12, if the decimal is over five, round up. If it's not, round down. Not sure what you mean by significant figures.
Temperature of somewhere.
