Isotope persisted down to the present because their rate of decay is so slow (e.g. uranium-238 and potassium-40). Post-primordial isotopes were created by cosmic ray bombardment as cosmogenic nuclides (e.g., tritium, carbon-14), or by the decay of a radioactive primordial isotope to a radioactive radiogenic nuclide daughter (e.g. uranium to radium). A few isotopes are naturally synthesized as nucleogenic nuclides, by some other natural nuclear reaction, such as when neutrons from natural nuclear fission are absorbed by another atom. As discussed above, only 80 elements have any stable isotopes, and 26 of these have only one stable isotope. Thus, about two-thirds
Isotope separation first isotope separator was developed at the Copenhagen Cyclotron by Bohr and coworkers using the principle of electromagnetic separation. Today, there are many laboratories around the world that supply beams of radioactive ions for use. Arguably the principal Isotope Separator On Line (ISOL) is ISOLDE at CERN, which is a joint European facility spread across the Franco-Swiss border near the city of Geneva. This laboratory uses mainly proton spallation of uranium carbide targets to produce a wide range of radioactive fission fragments that are not found naturally on earth. During spallation (bombardment with high energy protons), a uranium carbide target