Decay chain equilibrium is achieved, each successive daughter isotope is present in direct proportion to its half-life; but since its activity is inversely proportional to its half-life, each nuclide in the decay chain finally contributes as many individual transformations as the head of the chain, though not the same energy. For example, uranium-238 is weakly radioactive, but pitchblende, a uranium ore, is 13 times more radioactive than the pure uranium metal because of the radium and other daughter isotopes it contains. Not only are unstable radium isotopes significant radioactivity emitters, but as the next stage in the decay chain they also generate
Fission products (by element) Fission products (by element) On this page, a discussion of each of the main elements in the fission product mixture from the nuclear fission of an actinide such as uranium or plutonium is set out by element. Se-79, half-life of 327k years, is one of the long-lived fission products. Krypton-85, half-life 10.76 years, is formed by the fission process with a fission yield of about 0.3%. Only 20% of the fission products of mass 85 become Kr itself; the rest passes through a short-lived nuclear isomer and then to stable Rb. If irradiated reactor fuel is reprocessed, this radioactive krypton