Uranium and thorium content determination in solids using thermal neutron and double gamma irradiation methods

Abstract Two different methods for simultaneous determination of the uranium (U) and thorium (Th) content in diverse solid construction materials, soil samples and natural minerals were applied. The first method consists in the double irradiation of diverse powdered solid, packed in Mylar envelops used as fission fragment track detectors, with 23 MeV gamma rays and then after remounting, with thermal neutron at the JINR microtron MT- 25. The second method consists in the double irradiation of the same specimens mounted as layers, also in contact with Mylar, with high fluence (up to 10 19 cm −2 ) of 23 and 15 MeV gamma rays. In both cases well-calibrated U nat etalon layers were used to check gamma ray and thermal neutron fluence. The data obtained display the reliable correspondence of both methods in the interval of 10 −6 – 10 −8 g / g of U and Th content in diverse solid samples.