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
Tritium 65 nuclear sites in the US. In one case, leaking water contained of tritium per litre, which is 375 times the EPA limit for drinking water. The US Nuclear Regulatory Commission states that in normal operation in 2003, 56 pressurized water reactors released of tritium (maximum: 2,080 Ci; minimum: 0.1 Ci; average: 725 Ci) and 24 boiling water reactors released (maximum: 174 Ci; minimum: 0 Ci; average: 27.7 Ci), in liquid effluents. According to the U.S. Environmental Protection Agency, self-illuminating exit signs improperly disposed in municipal landfills have been recently found out to contaminate waterways. The legal limits for tritium