Definition of Deuterium

Deuterium is a stable, naturally-occurring isotope of hydrogen with an atomic mass of two (one proton and one neutron). There is approximately 1 part of deuterium to 5000 parts of normal hydrogen found in nature. Deuterium is sometimes called heavy hydrogen. When combined with oxygen, the oxide form is referred to as heavy water and is used to moderate fission reactions in certain nuclear reactors.

ITER Test Blanket