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Tritium Breeding. Deuterium-Tritium fusion is the most promising of the hydrogen fusion reactions, but no tritium occurs in nature since it has a 10 year half-life.
As Deuterium and Tritium are both merely isotopes of Hydrogen and not elements in their own right, they both have an atomic number of 1, just like Hydrogen (Hydrogen-1).
DEUTERIUM-1 neutron TRITIUM-2 neutrons. Z A; What is the relationship between hydrogen, deuterium and tritium?