Properties of water water isotopes. Naturally occurring water is almost completely composed of the neutron-less hydrogen isotope protium. Only 155 ppm include deuterium ( or D), a hydrogen isotope with one neutron, and fewer than 20 parts per quintillion include tritium ( or T), which has two neutrons. Oxygen also has three stable isotopes, with present in 99.76%, in 0.04%, and in 0.2% of water molecules. Deuterium oxide, , is also known as heavy water because of its higher density. It is used in nuclear reactors as a neutron moderator. Tritium is radioactive, decaying with a half-life of 4500 days; exists in nature
On-Line Isotope Mass Separator or to the REX accelerator for acceleration to higher energies. The facility is operated by the ISOLDE Collaboration comprising CERN and 9 European countries. One of the major experiments in ISOLDE is the Miniball-setup. An upgrade of the post-acceleration system is currently on-going, ready to produce energetic Radioactive-Ion Beams (RIBs) of up to 10 MeV per nucleon in 2018. On-Line Isotope Mass Separator The On-Line Isotope Mass Separator, also known as the ISOLDE Radioactive Ion Beam Facility, is a facility located at CERN on the PS Booster. It started operating in 1967 and was rebuilt twice with major upgrades in