| Summary: | Southern Tamil Nadu has placer deposits, which is rich in minerals like zircon, garnet, monazite and rutile containing with radionuclides of U, Th and their decayed products. The present study is to identify the high background radiation areas in the regions of South west–east coast of Tamil Nadu. The ground radiometric survey was conducted in different seasons using portable radiation survey meter and global positioning system. Total of 137 observation spots were marked from 5 blocks for repeat measurements. Then calculated for the outdoor effective external terrestrial dose to the public residing in these blocks. The survey found average absorbed dose rate of block in this order 3>2> 4>1>5 (1394, 641, 247, 225, 167 nGy/h, respectively). From the data, a spatial mapping was performed for seasonal variation and interpolated for the unknown areas of dose rate. The outdoor effective dose to the public was found to be 1.66> 0.79>0.31>0.27>0.20 mSv/y with respective blocks. Conclusion: The dose to public was found to be lower, when compared with other high background radiation areas in the world. Therefore, there is no significant radiological risks to the public from natural radiation exposure.
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