Big Bang nucleosynthesis amounts of the hydrogen isotope deuterium (H or D), the helium isotope helium-3 (He), and a very small amount of the lithium isotope lithium-7 (Li). In addition to these stable nuclei, two unstable or radioactive isotopes were also produced: the heavy hydrogen isotope tritium (H or T); and the beryllium isotope beryllium-7 (Be); but these unstable isotopes later decayed into He and Li, as above. Essentially all of the elements that are heavier than lithium were created much later, by stellar nucleosynthesis in evolving and exploding stars. There are several important characteristics of Big Bang nucleosynthesis (BBN): The key parameter
Radioactive waste these wastes must be shielded for centuries and isolated from the living environment for millennia. Since radioactive decay follows the half-life rule, the rate of decay is inversely proportional to the duration of decay. In other words, the radiation from a long-lived isotope like iodine-129 will be much less intense than that of a short-lived isotope like iodine-131. The two tables show some of the major radioisotopes, their half-lives, and their radiation yield as a proportion of the yield of fission of uranium-235. The energy and the type of the ionizing radiation emitted by a radioactive substance are also important