Process by which the relative frequency of an Atoms of the same atomic number (i.e. the same chemical elem... in an Chemical base material which cannot be chemically converted ... is increased. Example: Process by which the share of a certain isotpe in an element... of Natural radioactive element with the atomic number 92. The n... at the uranium-235 Atoms of the same atomic number (i.e. the same chemical elem...; See ‘Enriched uranium’.