Measurement of radioactivity and radon exhalation rate in different kinds of marbles and granites

Geological materials usually contaminated with naturally occurring radioact ive materials (NORM) have become a focus of great attention. These NORM und er certain conditions can reach hazardous contamination levels. Some contam ination levels may be sufficiently severe that precautions must be taken. The present study deals with 60 geological samples (marble and granite) fro m both Egyptian and foreign locations. The studied samples were analyzed an d the concentrations in Bq/kg dry weight of radioisotopes were determined b y gamma-ray spectrometry using hyper-pure germanium (HPGe) detector in Bq/k g dry weight. The absorbed dose rate due to the natural radioactivity in th e samples under investigation ranged from 2.45 +/- 0.07 to 64,44 +/- 1.93 n Gy/h for marble and from 41.55 +/- 1.25 to 111.94 +/- 3.36 nGy/h for granit e. The radium equivalent activity varied from 5.46 +/- 0.16 to 150.52 +/- 4 .52 Bq/kg for marble samples and from 229.52 +/- 6.89 to 92.16 +/- 2.76 Bq/ kg for granite. The representative external hazard index values for the cor responding samples are also estimated and given. The radon exhalation rates for marble and granite samples were also calcula ted by using solid state nuclear track detector (CR-39). The value of radiu m exhalation rate varied from 8.0 +/- 2.39 to 30.20 +/- 5.06Bq/m(2)/d for m arble and 6.89 +/- 1.72 to 25.79 +/- 4.38 Bq/m(2)/d for granite and the eff ective radium content was found to vary from 1,700 +/-0.51 to 6.42 +/-1.08 Bq/kg for marble and 1.29 +/-0.32 to 5.63 +/-0.96 Bq/kg for granite. The va lues of the radon exhalation rate and effective radium content are found to correspond with the values of uranium concentration measured by the HPGe d etector in the corresponding sample. (C) 2001 Elsevier Science Ltd. All rig hts reserved.