Radioactivity of sand in the coastal strip from Beruwala to Dondra, Sri Lanka

Abstract

All living beings on earth are continuously exposed to radiation from primordial radio nuclides 232Th, 238U and 40K present in soils and sands. Due to their long half lives these radionuclide remain in soils and sands for long periods of time contributing to the natural background radiation. This study was carried out as a part of the island wide survey to measure the radioactivity levels in beaches around the country. The stretch covered in this study was from Beruwala to Dondra. A sand sample at each 1 km interval from Beruwala to Dondra was collected and activity concentrations of 232Th, 238U and 40K were measured using gamma ray spectrometry. Based on the activity concentrations, the annual effective dose rates were calculated. At each sampling location the radiation dose rate at 1 m above ground was also measured using a portable survey meter. The activity concentrations of sand ranged from 6 - 17058 Bq/kg for 232Th, 3 - 3584 Bq/kg for 238U and 3 - 1063 Bq/kg for 40K. Measured gamma dose rates of the sampling locations varied from < 0.01 to 8.61 uSv/h. Annual effective gamma dose rates calculated ranged from 0.01 to 75.38 mSv/yr. The maximum activity concentration of all three radionuclide and the dose rate were measured at Dondra.