The nucleus of tritium sometimes called a triton contains one proton and two neutrons , whereas the nucleus of the common isotope hydrogen-1 protium contains just one proton, and that of hydrogen-2 deuterium contains one proton and one neutron. Naturally occurring tritium is extremely rare on Earth. The atmosphere has only trace amounts, formed by the interaction of its gases with cosmic rays. It can be produced by irradiating lithium metal or lithium-bearing ceramic pebbles in a nuclear reactor. Tritium is used as a radioactive tracer , in radioluminescent light sources for watches and instruments, and, along with deuterium , as a fuel for nuclear fusion reactions with applications in energy generation and weapons. Tritium was first detected in by Ernest Rutherford , Mark Oliphant , and Paul Harteck after bombarding deuterium with deuterons.
The Reston Groundwater Dating Laboratory
USGS Groundwater Dating Lab
Helium-3 3 He , tralphium ,   see also helion is a light, non- radioactive isotope of helium with two protons and one neutron common helium having two protons and two neutrons. Other than protium ordinary hydrogen , helium-3 is the only stable isotope of any element with more protons than neutrons. Helium-3 was discovered in Helium-3 occurs as a primordial nuclide , escaping from the Earth 's crust into the atmosphere and into outer space over millions of years. Helium-3 is also thought to be a natural nucleogenic and cosmogenic nuclide , one produced when lithium is bombarded by natural neutrons, which can be released by spontaneous fission and by nuclear reactions with cosmic rays. Some of the helium-3 found in the terrestrial atmosphere is also a relic of atmospheric and underwater nuclear weapons testing.
Tracing and Dating Young Ground Water
This document is also available in pdf format: Information about the age of ground water can be used to define recharge rates, refine hydrologic models of ground-water systems, predict contamination potential, and estimate the time needed to flush contaminants from ground-water systems. CFCs also can be used to trace seepage from rivers into ground-water systems, provide diagnostic tools for detection and early warning of leakage from landfills and septic tanks, and to assess susceptibility of water-supply wells to contamination from near-surface sources. During the past 50 years, human activities have released an array of chemical and isotopic substances to the atmosphere.
Tritium 3 H, half-life of Tritium input to ground water has occurred in a series of spikes following periods of atmospheric testing of nuclear devices that began in and reached a maximum in Concentrations of 3 H in precipitation have decreased since the mids bomb peak, except for some small increases from French and Chinese tests in the late s.