What is the difference between natural and induced transmutation?

Answer 1

Nuclear transmutation is the conversion of one chemical element or isotope into another. In other words, atoms of one element can be changed into atoms of other element by 'transmutation'. This occurs either through nuclear reactions (in which an outside particle reacts with a nucleus), or through radioactive decay (where no outside particle is needed).

Source:wikip

Answer 2

Natural transmutation occurs in natural radioactivity where alpha or beta particles are emitted. There are some long chains of radioactivity in the heavy element range, which occur naturally, for example including radium, and these have been proceeding ever since Big Bang, so that proportions of elements have changed over geologic time. U235 used to be more abundant for example.

Induced radioactivity as occurs in fission products in spent nuclear fuel adds a large number of radioactive isotopes that don't ocur in nature, but the process is in essence no different to what occurs naturally in radioactive decay.

Transmutation can also be produced by irradiating substances in nuclear reactors where the neutron flux causes neutron capture in materials which have a capture cross section. Some capture thermal (slow) neutrons whilst others capture fast neutrons. Uranium 238 for instance captures fast neutrons to become plutonium 239, and hence breeds fissionable fuel. It has been proposed to eliminate some fission products in spent fuel by irradiation, to turn them into harmless isotopes of other elements, and this may eventually turn out to be an acceptable way of dealing with nuclear waste, though it won't work with all the range of fission products because some don't capture neutrons effectively.