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 ABSTRACT

Background: There are relatively rich uranium mines in regions of Saghand and Bafgh in Yazd province. This survey was carried out to provide a map of ambient gamma radiation of Yazd province and the probable effects of the existence of these mines on background radiation dose rates.

Materials and Methods: The measurements of the outdoor and indoor–environmental exposures (including cosmic and terrestrial components) were accomplished by a portable Geiger Muller detector in the five areas in each of eight big cities of Yazd province.

Results: The average exposure rates of indoor and outdoor ambient of Yazd province were 13.9 ±0.7 µRh^-1 and 11.6 ±0.8 µRh^-1 respectively. The average dose rates in air, resulting from gamma background radiation of indoor and outdoor were 122±6.8 nSvh^-1 and 101.4 ±7.4 nSvh^-1 respectively. The annual average of equivalent dose in air was found to be 1.03 ± 0.05 mSv, and the annual average of effective dose was 0.72 mSv.

Conclusion: The results of this study in comparison with the same measurements in some other cities in Iran such as Isfahan and Tabriz, proves that the existence of uranium mines doesn’t affect gamma background radiation of Yazd province.

 

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Background: The exposure of human being to ionize radiation from natural sources is a continuing, inescapable feature of life on earth. Direct measurement of absorbed dose rates in air has been carried out in many countries of the world during the last few decades. Such investigations can be useful for assessment of public dose rates, the performance of epidemiological studies, and keeping reference-data records to ascertain possible changes in the environmental radioactivity duo to nuclear, industrial, and other human activities. Materials and Methods: The measurements of the outdoor and indoor- environmental exposures including cosmic and terrestrial components were accomplished by a portable Geiger Muller detector (RDS -110). The measurements were made during daylight from September to October 2009, in five areas within nine big cities of Lorestan province. In each area, one building was randomly selected for indoor and outdoor measurements. Measurements were made for each region and an average value was used to calculate the exposure rate from gamma background radiation. Results: The results showed the Maximum and minimum outdoor dose rates as 166±44 and 65±8 nSvh^-1 in Borujerd and Pol-e- dokhtar, respectively. The average of outdoor dose rates was determined 113±26 nSvh^-1. Also the maximum and minimum values of indoor dose were 157±52 and 74±14 nSvh^-1 in Borujerd and Pol-e-dokhtar, respectively. The average indoor dose rates were determined as 119±27 nSvh^-1. Conclusion: The average annual effective dose for gamma background radiation in Lorestan province has been 0.72 mSv, with the range of 0.3– 0.6 mSv which was more than the global value (0.48 mSv). A poor correlation coefficient between was observed altitude and absorbed dose rates. Iran. J. Radiat. Res., 2011 9(2): 89-93