Radionuclide Basics: Tritium
Tritium (abbreviated as 3H) is a hydrogen atom that has two neutrons in the nucleus and one proton. Tritium is produced naturally in the upper atmosphere when cosmic rays strike nitrogen molecules in the air. Tritium is also produced during nuclear weapons explosions, and as a byproduct in nuclear reactors. Although tritium can be a gas, its most common form is in water because radioactive tritium reacts with oxygen to form water.
Tritium behaves like other forms of hydrogen in the environment. Just as non-radioactive hydrogen reacts with oxygen to create water (H2O), tritium also reacts with oxygen to form “tritiated water” (HTO). As a liquid, tritium moves easily through the environment just like water. Tritium occurs naturally in the environment in very low concentrations.