LAUSR

In this paper an original Monte Carlo code for calculating the mean critical angle of etching of the CR-39 and LR-115 type II solid state nuclear track detectors SSNTD have been developed in order to determine the levels of uranium and thorium contents in a variety of natural material samples. We have also measured these concentrations via others techniques. Results obtained by the current method are more precise than those obtained by detection efficiency and isotope dilution mass spectrometry methods. The dependence of the SSNTDs means critical angles on the initial alpha particle energy and the density of the material have been investigated. A series of equations were used to calculate the mean critical angle of SSNTDs detectors and to estimate the concentrations of uranium and thorium inside studied materials.