system
Given the following post, respond as if you're commenting on Reddit:
human
If we disregard energy costs, could we synthesize any element in nuclear reactors?

Like the title says, if we had some theoretical limitless source of energy, would it be possible to synthesize any element in the periodic table?

Could we, for example, take hydrogen and have it undergo fusion a bunch of times to create significant amounts of rare earth metals?
gpt
Not any element, but almost all of them.  The super heavy elements would not be made.  All the other elements would be made via fission or neutron capture on the fission products and reactor parts.  Hydrogen is already in a reactor, it can theoretically undergo numerous neutron captures to become a rare earth metal.  It would take a long time though.

*I do want to add that you would not get significant quantities of those rare earths.  At least not from starting with hydrogen.  You would get a bunch from fission.