Exposure rates due to naturally occurring radioelements over parts of Singhbhum District, Bihar

Airborne gamma ray spectrometric survey data from parts of Singhbhum Shear Zone (covering 16000 sq km.) have been used to calculate the average ground level exposure rates from naturally occurring radioelements potassium, uranium and thorium. The exposure rates vary in the range 0.4 to 46.0 μR/hr. In addition to the above exposure rates, there will be a component due to cosmic background which will be constant throughout the area (3,767 μR/h) and has been taken into account while computing the total dose. The highest levels of exposure to radioactivity were found in Jaduguda and Chhotanagpur region and were generally related to granitic rocks. The lowest levels are associated with Dalma lava. These exposure rates are found to be well below the maximum permissible rates as approved by the International Commission on Radiological Protection. (author). 14 refs., 4 tabs., 3 figs