الفهرس 
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Abstract
Radon (222Rn) significantly contributes to the natural radioactivity of the Earth’s crust. It is a noble gas and has a relatively long physical half-life, leading to a great mobility to reach considerable distances in different geological environments. Radon exists everywhere with different concentrations in rock, soil, deep water, subsurface, atmosphere and indoor air. According to the level of radon and the duration of its exposure, radon is considered to be one of the toxic substances that may induce health hazards; coming from its radioactive decay products trapped in lungs which depositing α- particle energy in tissue.
Many archeological sites in Egypt are worldwide unique, such as ancient tombs and pyramids, because they document fundamental developments in human civilization that took place several thousands of years ago. For this reason; these sites are visited by numerous visitors every year.
In this dissertation, radon concentrations in some important tombs that are located in two different archeological regions were studied. The first region is the Valley of the Kings in Luxor (650 km south of Cairo) while the second region is Saqqara (28 km southwest Cairo).
For the accurate assessment of inhalation doses due to radon and its progeny inside the studied ancient Egyptian tombs, seasonal radon- concentrations have been measured and the corresponding effective dose rates were calculated. These measurements were done by using both a new electronic device that allows the measurement of real-time-resolved radon concentrations and also a portable radon monitor RTM 1688-2, SARAD. It is shown that workers receive higher annual effective doses, ranging from 19.7 to 88.8 mSv/y, while lower annual effective doses ranging from about 2.1 to 9.3 mSv/y, are received by guides. These dose ranges exceed the annual dose limits recommended by the International Commission on Radiological Protection. In contrast, dose levels much below these limits ranging from 0.01 to 0.02 mSv were obtained for visitors in all tombs, for one visit. The obtained results are somewhat different but still consistent with those previously obtained by means of a passive technique integrating radon concentrations over several months. This indicates that the electronic devices used in the present work have the advantage of evaluating radon concentrations in real time.
The mean specific activities of 226Ra, 232Th and 40K in the samples collected from the interior walls of studied Saqqara tombs were determined using a hyper-pure Ge detector and found to have an average values of 16, 8.5, 45 Bq/kg, respectively. To avoid the health hazards associated with the exposure to radon during the long period of work inside these tombs, proposed solutions are introduced.
The hazards from radon inhalation (internal exposure) exceed that from radioactive γ-emitters (external exposure) by a factor ranging from few hundreds to more than a thousand. There is no correlation between internal and external exposure, because internal exposure depends on the ventilation rate, aerosols concentration and the dimensions of the tomb under study The main parameters which manifest the percentage of radon daughters’ concentration in air which is responsible for the radon inhalation hazards, is the ventilation rate which is a direct function of the equilibrium factor that is used in the calculation of the effective dose. The measurement of ventilation rates depends mainly on the measurement intervals that is continuously variant, which introduce high uncertainty for calculating the annual effective doses for different individuals.
For these reasons, an analytical model has been developed in this thesis, to calculate the radon concentration inside the investigated ancient Egyptian tombs under different physical conditions. With this internal and external effective doses due to inhalation of radon and exposure to natural radiation for different individual’s residence time inside the tombs can be calculated.
This model can also suggest a solution to minimize the radon concentration by allowing the user to establish windbreaks at the tomb’s entrance which will enhance the natural ventilation rate. Reduction in radon concentration by the suggested solution will be enough to minimize the radon exposure doses for guides while, workers still need to minimize their working hours to acquire not more than the permissible dose. Good agreement within 94% was obtained between the steady-state radon concentrations calculated with the analytical model developed in the present thesis, and the measured radon concentrations was obtained.
Trials have been done to measure thoron concentrations inside the studied tombs using a portable RTM 1688-2, SARAD device. The obtained results in general were low, and most of the time the thoron concentrations present were below the detection limit of the instrument.