measuring γ–ray dose of terrestrial samples using β-γ spectrometry

background: the existence of some radionuclides in soil and some building materials produce a β-γ radiation field, which in some regions the exposure of these radionuclides to human is high. materials and methods: the air-absorbed dose, indoor and outdoor annual effective dose of soil and some building material samples (ceramic, granite, gypsum, etc.). the samples were collected from 35 different regions in the northwest of iran were calculated. specific activity of natural radionuclides 226ra, 232th and 40k were measured by using a β-γ spectrometer consisted of nai(tl) and organic scintillators. the analysis of measured spectra was based on maximum likelihood estimation. the calculated data were compared with world's mean values. results: it is found that the specific activity of 40k ranges from 573.8 to 1392 bqkg-1, for 232th ranges from 6 to 54.6 bqkg-1 and for 226ra ranges from and 5.1 to 36.2 bqkg-1. in some regions, the concentrations of natural radionuclides (40k, 232th, 226ra) were higher than standard level. conclusion: experimental results related to specific activity, indoor and outdoor annual effective doses of 226ra, 232th and 40k revealed that radionuclide concentration in soil and some building material samples of some regions of northwest of iran are of some radiological importance. iran. j. radiat. res., 2011 8(4): 237-242