Deuterium-depleted water (DDW) is water that has a lower concentration of deuterium than occurs naturally at sea level on Earth.
DDW is sometimes known as “light water,” although “light water” has long been referred to as ordinary water, specifically in nuclear reactors.
Deuterium-depleted water has a lower concentration of deuterium (2H) than occurs in nature at sea level.
Deuterium is a naturally-occurring, stable (non-radioactive) isotope of hydrogen with a nucleus consisting of one proton and one neutron.
The nucleus of ordinary hydrogen (protium) consists of one proton only and no neutron. Deuterium atoms have about twice the atomic mass of normal hydrogen atoms as a result. Heavy water consists of water molecules with two deuterium atoms instead of the two normal hydrogen atoms.
The hydrogen in normal water consists of about 99.98% (by weight) of normal hydrogen (1H).
Heavy Water production involves isolating and removing deuterium-containing isotopologues within natural water.
The by-product of this process is deuterium-depleted water.
Due to the heterogeneity of hydrological conditions, the isotopic composition of natural water varies around the Earth. Distance from the ocean and the equator and the height above sea level positively correlate with water deuterium depletion.
In Vienna Standard Mean Ocean Water (VSMOW) which defines the isotopic composition of the ocean water, deuterium occurs at a concentration of 155.76 ppm. For the SLAP (Standard Light Antarctic Precipitation) standard that determines the isotopic composition of natural water from the Antarctic, the concentration of deuterium is 89.02 ppm.
Snow water, especially from glacier meltwater, is significantly lighter than ocean water. The weight quantities of isotopologues in natural water are calculated based on the data collected using molecular spectroscopy.