environmental gamma radiation dose rate in the open space of Bojnourd City

The human living environment has some extent of ionizing radiation that depends on the latitude and altitude of the region. Identifying the amount of this radiation can determine the suitable healthy living environment. In this study, for the first time, the outdoor radiation dose rate in the city of Bojnurd (North Khorasan Province, center latitude and longitude 27.37 and 2.57 degrees and elevation 1070 m above sea level), has been measured by survey meter. In order to determine the amount of outdoor gamma radiation dose rate, in Bojnurd, a survey meter was used. Measurements for 30 points and four seasons of the year were done. Detector was placed on tripods and at a height of 1 m from the surface of the earth and each time, the dose rate was read at the desired location for 50 minutes. Absorbed dose rate in different parts of the city and for the seasons of spring 133.5 nGy/h, summer 140.0 nGy/h, autumn 135.2 nGy/h and winter 126.3 nGy/h were measured. According to these values, the annual average absorbed dose rate 133.7 nGy/h, and the outdoor annual effective dose absorbed by the residents of the city was estimated to be an average of 0.16 mSv. The annual effective dose caused by natural gamma for residents of Bojnurd is more than the double of world average value (0.07 mSv, UNSCEAR-2000).