Natural environmental radioactivity in the Northern State of Sudan

This work is concerned with the study of the natural radioactivity in soil and food samples collected from the Northen State and other regions in the Sudan. The present research aimed to study the concentration of natural radionuclides ''2''2''6Ra, ''2''3''2Th and ''4''0K, to determine the value of absorbed dose rate and annual effective dose and estimate the exposure of population to the external and internal radiation. In this work, hundred (100) soil and food samples were collected from different locations in Northen State. Their activity concentrations were measured at Egypt Atomic Energy Authority, Nuclear Research Centre, using the high purity germanium (HPGe) detector gamma spectrometer with efficiency of 70%. The activity concentrations of ''2''2''6R, ''2''3''2Th, and ''4''0K radionuclides of eleven (11) soil samples collected from Khartoum State and Nyala City were also measured and compared. With the data obtained, the mean values and standard deviations of the radionuclide activities for Northen State, Khartoum and Nyala were calculated. From the activity concentrations of ''2''2''6Ra, ''2''3''2Th, and ''4''0K radionuclides, the quantities for estimating the external exposure to the population of Northen State, Khartoum and Nyala, such as the external absorbed dose rate in air and annual effective dose were calculated. The radium equivalent activity, the external and internal hazard indices were applied for estimating the radiation hazards of soil used as building material. The mean activity concentration of ''2''2''6Ra, ''2''3''2Th and ''4''0K in soil samples of Northen State were found to be 43.6±3.1Bq/kg,17.4±2.1Bq/kg and 398.9±16.4Bq/kg, respectively. For soil samples of Khartoum and Nyala these values were 31.0±10.8, 12.1±2.4 and 333.9±77.7Bq/kg and 44.0±19.0, 27.5±3.6 and 925.0±244.4Bq/kg, respectively. The obtained results were compared with other data from Sudan and other countries and were found to be lower than corresponding global values reported in United Nation Scientific Committee on the effects of atomic radiation (UNSCEAR) for normal background areas. Subsequently assessed radiological effects show that the mean value of outdoor gamma absorbed dose rate in air at 1meter above ground were 47.3 ±2.0nGy/h, 35.7 ±9.0nGy/h and 75.8 ±21.0nGy/h for Northern State, Khartoum State and Nyala, respectively. These values lie within the worldwide range for normal radiation background areas, except the value obtained for Nyala. The mean value of the annual effective radiation dose for persons living in Northern State, Khartoum and Nyala were found to be below the limit of 1.0mSv/y recommended by the International Commission on Radiological Protection, for the general public. The mean values of external and internal hazard indices for persons living in Northen State, Khartoum and Nyala were found to be lower than unity, which is the value specified by the European Commission on Radiation Protection for safe soils, which can be used as construction materials without posing significant radiological threat to the population. The mean value of radium equivalent activity of Northen State, Khartoum and Nyala soils were found to be 99.6±4.4Bq/kg, 74.2±18.7Bq/kg and 154.7±42.4Bq/kg, respectively which is well below the threshold value of 370Bq/kg. The mean values of activity concentrations of ''2''2''6Ra, ''2''3''2Th and ''4''0K in vegetables, cereals and fruits samples were found to be 40±11, 10±2 and 1308±213Bq/kg, respectively. It was found that these values lie within the worldwide range for radioactivity in food.(Author)