Plastic nuclear track detection methods for estimation of thorium to uranium ratio in thick natural materials

Two methods have been presented to estimate thorium to uranium ratios in thick samples, assuming that the thorium and uranium are in secular equilibrium. The registration sensitivities of CR-39 and LR-115 solid state nuclear track detectors exposed in close contact with the sample, have been calculated. The registration sensitivity of a CR-39 plastic nuclear track detector for non-contact alpha-autoradiography at different absorber thicknesses has also been calculated. The registration sensitivity is expressed in α-tracks cm-2 per 30 days exposure for one ppm parent nuclide concentration in the sample