Question

What isotopes are used in nuclear power?

Answer 1

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 `99.3%` of natural uranium, is not fissionable by slow neutrons. So U-238 has a small probability for spontaneous fission and also a small probability of fission when bombarded with fast neutrons, but it is not useful as a nuclear fuel source.

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.