Uses of heavy water

Heavy water has three principal uses, all exploiting properties distinct from ordinary water:

1. Moderator in nuclear reactors -- heavy water is widely used to slow down (moderate) the fast neutrons released in nuclear fission, bringing them down to the thermal energies needed to sustain the chain reaction.
2. Tracer -- heavy water (or D₂O-derived deuterium labelling) is commonly used to trace and study organic reaction mechanisms and the mechanisms of metabolic reactions in living systems. …