摘要
Tritium is a cosmogenic radioactive isotope of hydrogen. It originates from interactions between cosmic rays and the constituents of the upper atmosphere. The dominant nuclear reactions are such as 14N（n, 3H）12C and 16O（p, 3H）14O, etc. By β--decay, 3H. whose half-life is 12.26 years. may change into 3He. a stable isotope
