Investigating the neutron-induced subsurface production of environmental isotopes ³⁷Ar, ³⁹Ar, ³H and ³⁶Cl with neutron irradiation of aquifer material.

In continuation of the efforts of Y. Feige and coworkers and J.N. Andrews and coworkers to study the in situ production of environmental isotopes, new experimental results obtained by irradiation of natural rock samples with moderated neutrons are reported. Changes of the Ar and Cl isotope ratios offer an experimentally based correction for in situ 39Ar, 37Ar, 3H and 36Cl isotope production. By comparing the 39Ar, 37Ar and 36Cl isotope production rates and depending on the neutron energy distribution achieved, the mean reaction cross-section for the production of 37Ar from 40Ca is estimated to range from 10 to 19 mbarn