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ASSESSMENT OF RADIOACTIVITY AND ESTIMATION OF EFFECTIVE RADIATION DOSE RECEIVED BY VILLAGERS RESIDING AT NATURAL HIGH BACKGROUND AREAS OF COASTAL REGIONS OF TAMIL NADU

Esaiselvan Kanthasamy, Allen Gnana Raj

Radiation exposure and effective dose received by villagers residing at twenty villages belonging to Natural High Background Radiation Areas of coastal regions of Tamil Nadu were studied; five houses in each village were selected. The NHBRA villages were of similar construction pattern (brick wall-tiled roof, cement flooring). Measurements of radon (220Ra), thoron (222Ra) and their progeny, produced by the decay of naturally occurring radiosotopes uranium and thorium in dwellings is the largest contributor to the average internal effective dose received by human beings. Internal doses due to radon/ thron and their progeny were estimated using, Solid State Nuclear Track Dectors (SSNTD), LR-115, as the detector. External doses were estimated by gamma measurement using scintillometer and Thermo Luminescent Dosimeter (TLD); TLDs were exposed for one year, on a quarterly basis, inside the house at a height of 3 meters and about 1 meter away from the walls. The SSNTD cups were exposed adjacent to the TLDS, and the exposure as for a period of three months each. Inhalation dose due to Th and Th (B) in mWL were estimated by collecting air samples from each house, for one hour each, during the replacement time of TLD and SSNTD Cups. For inhalation dose estimation the occupancy factor was assumed to be 0.8. The soil samples were also collected from each sampling point. Effective radiation dose received by the villagers residing at Natural High background Radiation area is ranging from 4.47 to 8.38 mSvy-1.