Natural tritium

Abstract

The subject of natural tritium is reviewed from the inception of the search for this isotope in 1932 until the present. Three sources of natural tritium are considered: production in the atmosphere by galactic cosmic rays, production in the atmosphere by solar flare accelerated particles, and accretion from the sun. A recalculation of the cosmic‐ray production rate utilizing experimental data for the last solar cycle yields a worldwide average of 0.20 ± .09 triton/cm² sec during solar minimum and 0.16 ± .09 triton/cm² sec during solar maximum. Production of tritium by interaction of solar flare accelerated particles with the atmosphere is found to be less than 3% of the production by galactic cosmic rays. Calculations of the tritium decay rate from material balance, utilizing measured tritium concentrations of rain and ocean water corrected for synthetic tritium, are consistent within the limits of error with the production rate by galactic cosmic rays. The best estimate of the pre‐bomb inventory corresponds to a decay rate of 0.5 ± .3 triton/cm² sec as compared with the estimated production rate of 0.19 ± .09 triton/cm² sec. In view of the large errors it is not possible to determine whether appreciable amounts of tritium are accreted from the sun.

Interstellar-Terrestrial Relations: Variable Cosmic Environments, The Dynamic Heliosphere, and Their Imprints on Terrestrial Archives and Climate

“…The first extensive and pioneering work in this field by Lal and Peters (1967) was based on data from direct observations limited to a few years. Subsequently there have been a number of model calculations devoted to particle and cosmogenic nuclide production in the atmosphere (Hess et al, 1961;Newkirk, 1963;Lingenfelter, 1963;Oeschger et al, 1969;Light et al, 1973;O'Brien, 1979;Blinov, 1988;Masarik and Reedy, 1995), see also the previous section.…”

“…While most authors consider only the interaction of solar energetic protons with the atmosphere, Schroeter To quantify the effect of cosmic rays on the Earth's environment it is important to know precisely the flux of cosmic ray shower particles in function of position, atmospheric depth, and time. For this purpose complex codes that simulate the transport of cosmic rays through the Earth's atmosphere have been developed by several groups and validated with experimental data (O'Brien, 1979;Velinov et al, 2001;Zuccon, 2002;Clem et al, 2003;Webber and Higbie, 2003;Lei et al, 2004;Desorgher et al, 2005;Schröter et al, 2005). One of this code is the Monte Carlo ATMOCOSMICS 2 code, based on Geant4 (Geant4 Collaboration et al, 2003), that allows to simulate the hadronic and electromagnetic interaction of energetic particles (<1 TeV) with the Earth's atmosphere (Desorgher et al, , 2005.…”

“…Otherwise they were estimated from similar reactions on other isotopes. For the tritium production the cross sections of Nir et al (1966) were applied.…”

3He mass spectrometry for very low-level measurement of organic tritium in environmental samples

“…Natural production 75 1370 Craig and Lal (1961), Nir et al (1966) Krejci and Zeller (1979), Combs and Doda (1979) and Okada and Momoshima (1993) a 1995-1997 Average. b Cumulated releases of atmospheric tests.…”

Analysis of vadose zone tritium transport from an underground storage tank release using numerical modeling and geostatistics

“…3H production by natural processes was discovered by Libby (1946) and has been reviewed by Nir et al (1966). 3H is a normal constituent of the atmosphere and biosphere, produced by the fission of radioactive elements in the cart h's crust, as well as by cosmic ray irradiation of stable nitrogen in the atmosphere (NCRP Report, 1979).…”