Measurements of the emanation of 37Ar and 39Ar from irradiated rocks and powders

The emanation of radionuclides has been highlighted as a known source of uncertainty in the estimation of radionuclide source signatures from underground nuclear tests and other nuclear activities, particularly in the case of activation products. A system was developed at Pacific Northwest National Laboratory to quantify the emanation of argon from two powders and five rock types ranging in particle size from powder to small rocks. Samples were neutron irradiated and the percent emanation of 37Ar was measured to range between 0.3 and 25%. Measurements were also made of the 39Ar emanation for four of these materials and was found to be consistently lower than that of 37Ar.