Assessment of Background Radiation and Associated Dose Rates in Soil Samples from Norochcholai in the North Western Coast of Sri Lanka

This study assesses radiation levels in soil, water and air in the Norochcholai, an area in Sri Lanka closest to the Kundankulam nuclear power plant, India which is situated in the North Western coast. This is important for monitoring radiation hazards and will be useful in case of a nuclear accident. Superficial soil and water samples from 23 locations were analyzed by Gamma spectrometry using HPGe detector. The activity concentrations of Th232, K40, Ra226 and Pb210 in the soil were 56.0 Bq·kg-1, 96.0 Bq·kg-1, 24.0 Bq·kg-1 and 27.0 Bq·kg-1 respectively. Dose rate at 1 m height was recorded using a survey meter (Automess 6150AD). Median dose rate was 0.098 μSv·h-1. The median gamma ray absorbed dose rate was 51.2 nGy·h-1, which is lower than the global average of 57 nGy·h-1. Radium equivalent activity (Raeq) ranged from 30.3 Bq/Kg - 458.3 Bq/Kg and only one sample recorded the Raeq > 370 Bq/Kg as safe to be used in building materials. External hazardous indices of all the samples were below 1 and the mean annual effective dose was within the safe limit of 1 mSv/y. The health risk of exposure to terrestrial radiation from the soil in the area is minimal. These data could be used as baseline for radiation assessment.