It is an excellent tracer for determining timescales for the mixing and flow of waters because it is considered to be relatively conservative geochemically, and is ideally suited for studying processes that occur on a timescale of less than 100 yr.
Tritium ( 3H) is a radiogenic and radioactive isotope of hydrogen with a half-life of 12.4 yr. Doctor, in Treatise on Geochemistry, 2003 5.11.2.2. The natural activities in precipitation vary from about 25 TU at high latitudes to about 4 TU in the equatorial zone ( Geyh and Schleicher, 1990).Ĭ. Tritium activities are commonly described in terms of tritium units (TU), where 1 TU = 1 atom of tritium per 10 18 atoms of hydrogen or 1 TU = 7.19 DPML −1 of water = 0.118 Bq L −1 of water. Regulated monitoring of specific sites and hydrological studies are the principal applications of environmental tritium analysis, and, of course, as the “background” levels decrease, there is a corresponding requirement for the measurement of lower and lower activities. Generally, nuclear fuel cycle operations are of concern to the immediate locale only, with relatively minor contributions to more general environmental tritium levels. Since the partial atmospheric nuclear test ban treaty in 1963, the worldwide levels of tritium in the environment have been decreasing at a rate approximately equal to its half-life (Okada and Momoshima, 1993). Present-day tritium has three major sources of origin: (1) natural production in the upper atmosphere through cosmic ray-induced spallations of nuclides and particle capture reactions of nitrogen and oxygen ( Geyh and Schleicher, 1990), (2) residual activities from atmospheric nuclear weapons testing ( Libby, 1963), and (3) on-going nuclear fuel cycle operations. Tritium is a pure, low-energy beta emitter ( E max = 18.6 keV) with a half-life of 12.43 years. BRIAN CARTER, in Handbook of Radioactivity Analysis (Second Edition), 2003 1.
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