What is the feul for nuclear power plants and where does it come from?

Answer 1

Either yellow uranium oxide (yellowcake) or metallic uranium in most reactors. In moderated thermal neutron reactors the uranium is usually enriched to 3% to 5% uranium-235 isotope, in unmoderated fast neutron reactors the uranium is enriched to 20% to 95% uranium-235 isotope.

This uranium comes from mines (similar to coal or iron ore mines). What is mined is usually black uranium oxide ore. This ore is processed to make unenriched yellowcake (0.7% uranium-235) and shipped to the enrichment plant. Most enrichment plants process the yellowcake to make uranium hexafloride then run that through their system, producing both enriched uranium (product) and depleted uranium (waste). The enriched uranium hexafloride is then processed back to yellowcake and shipped to a finishing plant that uses it to make the required fuel assemblies.