Notes on the origins, occurrence, and potential uses as a primary energy resource of uranium

The question of the origins of uranium with its 2 radioisotopes, U-235 and U-238, leads back to the origins of chemical elements in general, which must be discussed in connection with the development of the Universe. A rough classification into 3 phases may be helpful in this attempt. * In the early phase of the Universe, the generation of protons and neutrons was followed mainly by the production of helium nuclei, i.e. light elements. Astrophysicists refer to this nuclear fusion also as primordial nucleosynthesis. * Medium-heavy elements up to the range of iron (Fe) were generated in nuclear fusion processes in the stars. * The heavy elements above iron were created in neutron capture processes occurring in stars rich in mass, and in supernova explosions. These processes are sketched with a view to the generation of uranium within the standard model of cosmology. In addition, occurrences of uranium on Earth and uranium deposits as potential long-term sources of nuclear fuel are described in a summary overview. Approx. 4.7 million tons of recoverable natural uranium reserves and another 10 million tons of prognosticated reserves constitute sufficient long-range uranium resources. (orig.)