الفهرس 
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Abstract
Natural radioactivity is wide spread in the earth’s environment,
it exists in soil, plants, water and air. Environmental natural gamma radiation is formed from terrestrial and cosmic source. In the present study, seventeen samples of Egyptian clay were analysed using gamma-ray spectrometry based on coaxial HpGe detector shielded by cylinders of lead, copper and cadmium. The analysis of data is completed by computerized multichannel analyzer with high level software programs to determine the activity concentrations of 238U, 226Ra , 232Th and 40K. Ten of these samples were analysed using flame atomic absorption spectrometer (FAAS) to determine the concentrations of heavy metals (Cu, Cd, Fe, Mg, Mn, Ni and Zn). Clay, consisting fine grained materials, is an interesting materials and can be used in a variety of different fields. The knowledge of the radioactivity levels and heavy metals concentrations in these commonly used materials was of great importance in the assessment of possible radiological risks to human health. The purpose of this study was to determine the natural radioactivity due to 238U,232Th and 40K and heavy metals concentration (Cu, Cd, Fe, Mg, Mn, Ni and Zn) in some Egyptian clay samples using gamma ray spectroscopy and flame atomic absorption spectrometer respectively. The activity concentration of 226Ra, 238U,232Th and 40K of all clay samples ranged from (8.44 to 203.09) , (5.93 to 85.26),( 2.88 to 99.98) and (8.72 to 428.92) Bq/kg respectively. It was found that the concentration of heavy metals lies between 0.1 ppm for Mn to 68.8 ppm for Fe in clay samples. Radium equivalent activities and various hazard indices were also calculated to assess the radiation hazard. The radium equivalent activities Raeq ranged from (32.78 to 354.49) Bq/kg was lower than the permissible limit 370 Bq/kg. The calculated values of external hazard index Hex ranged from (0.088 to 0.95) and the representative level index I ranged from (0.24 to 2.43). The absorbed gamma dose rate (DR ) nGy/h was determined. The results show that the values of the absorbed dose rate were slightly high in: Sample (1) Aswanly clay where it helps in treatment. Sample (4) Kaolin was used in the component of ceramic; it was used with small quantity which had no significant hazard on this production .Sample (6) Grog clay was used as high temperature isolation in fire furnace which didn’t effect on the human health. Samples (8, 10, 11, 14, and 15) were used in cooking, hazard effects were found on the human health then care must be taken. Sample (16) red brick used in building materials, sample (17) was used for decoration they have indirect effect on the human body. In case of Hin we showed that samples (6,8) have values more than 1 we recommended to make good ventilation in case of storing these products to avoid the accumulation of radon gas which have a harmful effect on human health. from these results we recommended using other material for cooking instead of clay. It was found that the concentration of heavy metals lies between 0.1 ppm for Mn to 68.8 ppm for Fe in clay samples. Also the sensitivity of the determined heavy metals was calculated and it was found to be 0.0062 ppm for Mg to 0.133 ppm for Fe. The results show that the concentration of U, Th and K for most samples are within the values accepted as normal and all heavy metals have low concentration except The concentration of Fe is high in all samples due to Fe is from the constituent of the earth crust. Therefore Egyptian clay samples can be used for some kinds of fabricated goods such as red brick for building materials, vase for decoration and ceramic industry. Egyptian clays have an important economic effect due to their low cost.