What isotopes are used in nuclear power?
Uranium-235, Plutonium-239, Thorium-232 and Uranium-233 are used or could be used in nuclear power.
While uranium-235 is the naturally occurring fissionable isotope, there are other isotopes which can be induced to fission by neutron bombardment.
Plutonium-239 is also fissionable by bombardment with slow neutrons. Plutonium-239 can be produced by "breeding" it from uranium-238.
Uranium-238, which makes up
Thorium-232 is fissionable, so could conceivably be used as a nuclear fuel. The only other isotope which is known to undergo fission upon slow-neutron bombardment is uranium-233.