الفهرس 
Chapter one: IntroductionOnly 14 pages are availabe for public view
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Abstract
The natural radioactivity of volcanic samples at six regions in Yemen has been studied. The radio activities of 50 samples have been measured with high resolution HPGe detector. The average activity concentrations of 238U, 232Th and 40K were found to be 24.25±1.74 Bq kg-1, 18.19±1.45 Bq kg-1and 378.31±20.52 Bq kg-1, respectively. While, the natural radioactivity of 42 rock samples at five regions in Yemen has been studied. The average activity concentrations of 238U, 232Th and 40K were found to be 20.23±1.57 Bq kg-1, 16.04±1.24 Bq kg-1and 386.39±30.93 Bq kg-1, respectively. The radiological hazard parameters such as radium equivalent activity (Raeq), absorbed gamma dose rates (DR), annual external effective dose rate, annual effective dose equivalent (AEDE), external hazard index (Hex) ,internal hazard index (Hin) and the gamma activity concentration index associated with the radionuclides were calculated and compared with internationally approved values of the volcanic and rock samples.
Radon exhalation rates and mass exhalation rates were measured by using “sealed can technique” using CR-39 nuclear track detectors. The mean radon exhalation rate is found to be 1771.64±133.41mBq m-2h-1, whereas the mean mass exhalation rate is found to be 23.47±1.81 mBq kg-1 h-1 for volcanic samples. In rock samples the mean radon exhalation rates is found to be 1349.41±114.99 mBq m-2h-1, whereas the mean mass exhalation rates is found to be 21.77±2.90 mBq kg-1 h-1.