Plutonium is a by-product of the
fission process in nuclear reactors, due to neutron capture by uranium-238 in particular. When operating, a typical
nuclear reactor contains within its
uranium fuel load about 325
kilograms of plutonium, with plutonium-239 being the most common isotope. In a power reactor, much of the energy from the fission process is due to the plutonium, complementing that from the uranium-235.
The main isotopes of plutonium are:
- Pu-238, (half-life 88 years)
- Pu-239, fissile (half-life 24 000 yrs)
- Pu-240, fertile (half-life 6 500 yrs)
- Pu-241, fissile (half-life 14 years)
- Pu-242, (half-life 37 600 yrs)