الفهرس 
Basics of Nuclear DecaysOnly 14 pages are availabe for public view
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Abstract
Phosphate rock used for the production of phosphorous based fertilizers, acids, detergents and many products. Phosphate rock is a source of heavy metal pollution of air, soil, water and food chain. Radiological impact of phosphate rocks mining and manufacture could be significant due to elevated radioactivity contents of the natural occurring radioactive materials (NORM), such as 238U and 232Th series and 40K, contribute to enhanced levels of natural radionuclides in the environment. The main aim of this study is to evaluate the levels of natural radioactivity and to determine heavy metals and toxic elements in the collected samples using different techniques.
Sixteen samples of phosphate rocks and it’s by products were collected from different regions in Egypt (Abu-Tartor, Wadi Qena, El sebaeya and Kafr El-Zayat).
Radionuclide concentrations of 226Ra, 232Th, and 40K were measured using a high- purity germanium (HPGe) detector and its electronic circuit in 16 samples from raw phosphate and its product. The obtained results show remarkable wide variation in the radioactivity contents of the different phosphate samples. The range of specific activities for 235U, 226Ra, 238U, 232Th and 40K in (Bq/Kg) are (10.92 and 86.23), (302.88 and 1496.31), (283.54 and 2032.50), (11.49 and 200.81) and (572.77 and 979.72) respectively.
Based on the measured activities, the radiological health hazard parameters are assessed. The radium equivalent activities (Raeq) vary between (421.97 and 1852.09) Bq/Kg, this is higher than the world’s average value (370 Bq/Kg). The values of the external hazard index (Hex) vary between (1.25 and 5.01), and the internal hazard index (Hin) vary between (2.27 and 9.05), the values of theses indices are higher than the permissible level which is unity (UNSCEAR, 2008). The values of gamma radiation level index Iγ vary between (1.61 and 6.29).
The values of outdoor absorbed dose rate D(out) vary between (207.62 and 809.84) nGy/h, and indoor absorbed dose rate D(in) vary between (429.90 and 1669.68) nGy/h, these values are higher than the world average mean value 58 nGy/h for all samples. The values of outdoor effective dose Eeff(out) for samples vary between (0.25 and 0.99) mSv/y, this is less than the permissible limit 1 mSv/y. Similarly, the values of indoor effective dose rate Eeff(in) vary between (2.11 and 8.19) mSv/y, these values are higher than the recommended value 0.41 mSv/y for all studied samples (UNSCEAR, 2008).
The emanation coefficient (F) and the 222Rn mass exhalation rate (ERn) of all samples vary between (0.02 and 0.29) and between (0.008 and 0.82) respectively. Inhalation of dusts containing naturally occurring radionuclides may be a significant exposure pathway in some factories. This may indicate that workers receive the highest doses due to the inhalation of dust containing radon.
IV
The excess lifetime cancer risk (ELCR) has been calculated. ELCR(out) for outdoor exposure vary between ( 0.83x10-3 and 3.27x10-3) and the values of indoor exposure ELCR(in) vary between (6.96x10-3 and 27.03x10-3), while the total ELCR(total) vary between (7.79x10-3 and 20.43x10-3), this value is higher 9.34 times than the worldwide average limit (Qureshi et al., 2014). Total excess lifetime cancer risk (ELCR) was found to be high in all samples of phosphate and its by-products, which related to high radioactivity, representing radiological risk for the health of the population.
The samples were elementally analyzed by using XRF to determine the concentration of major elements, trace elements and minor elements. The results showed that variable contents of heavy metals, some of which are significantly higher than natural concentrations in soil, which suggests that they need to the continuously monitoring of soils heavy metals compositions, particularly in case of long-term fertilization.
Therefore phosphate rock and its by-products samples pose significant radiation hazards and are not safe for use, and need some careful regulations to reduce the hazardous radiation released into surroundings.