Environmental radioactivity evaluation in the coastal stretch of Bay of Bengal from Pondycherry to Velanganni (South East coast of India)

Since the Madras Atomic Power Station, Kalpakkam and Kudankulam Nuclear Power Plant, Kudankulam are sited in Bay of Bengal coast, radiological study of this coastal environment is imperative to assess the impact of operation of nuclear power plant, if any, on the radioactivity profile of the coast. In the present study the environmental radioactivity was evaluated by measuring activity concentrations of primordial radionuclides namely 238U, 232Th and 40K in the beach sand samples using high purity germanium gamma ray spectrometry. 10 sampling stations were fixed along a 290 km coastal stretch of Bay of Bengal from Pondycherry to Velanganni. The activity concentration of 238U is always much less than that of 232Th and 40K and it ranged from 9 Bq/kg (Pondicherry coast) to 93 Bq/kg (Karaikal coast). However, 232Th concentration fluctuated from 12 Bq/kg (Pichavaram Mangrove) to 1075 Bq/kg (Karaikal coast). The activity concentration of 40K varied within a narrow range from 162 Bq/kg to 474 Bq/kg. The distribution of primordial radioactivity was non-uniform along the entire stretch of Bay of Bengal. The elevated levels of 232Th were recorded in Karaikal coast (S7) (1075 Bq/kg), Tirumullaivasal coast (S4) (215 Bq/kg), and Nagapattinam coast (S9) (146 Bq/kg) and attributed to the presence of thorium-rich monazite as beach placer in coastal sands. The total absorbed gamma dose contributed by the activity of 238U, 232Th, and 40K varied between 29 nGy/h and 308 nGy/h with a GM value of 64.4 nGy/h. Similarly, the annual effective dose recorded for Bay of Bengal ranged from 0.04 mSv/year to 0.38 mSv/year, indicating that the Bay of Bengal, in general, falls under Normal Background Radiation Area. (author)