Terrestrial gamma dose rates along one of the coastal highways in Sri Lanka

This study reports a van borne radiometric survey carried out along the A2 route to assess the annual radiation dose received by a commuter from Galle to Colombo using in-situ gamma spectrometry and a hand held environmental GM survey meter. A vehicle borne gamma spectrometric survey normally provides preliminary coverage of the radioelements in the top most part of the earth’s crust. The ground concentrations of K, Th and U were also obtained along the route. The daily equivalent dose calculated was 0.50 µSv in this route. The highest dose rates were measured from Kosgoda to Ambalangoda where activity concentrations of Th was around 0.30 Bq g-1. Activity concentration of U was the least and was not detected in many places along the route. Southern Province has an average outdoors-equivalent dose of 1.54 mSv y-1. The calculated dose along the A2 route was 0.12 mSv for a commuter for 240 working days and gives the upper limit. This dose is about 10 % of the average measured value for the Southern Province and is no more than a statistical variation of the natural background radiation. 1