ABSTRACT
The existence of an isolated, purely monoatomic and mono nuclidic radioactive species such as 239PU is only conceptual. In reality, after the very first decay, the radioactive species are mixed with the stable or radioactive (isotopic or nonisotopic) daughter nuclide, in this case, 235U. The relative proportion of daughters increases steadily with time and eventually the original population of radionuclides is replaced by an assembly of stable atoms. In a very remote but calculable future, all uranium present on earth will be replaced by the same number of stable lead atoms and the intermediate radioelements will be extinguished. The same will apply after a still longer period for thorium. All stable nuclides in the universe are the end products of the decay of radionuclides produced during the nUcleogenesis of the elements.
