Risk assessment to natural radiation exposure from soil samples in the Jasmine rice cultivated area, Roi Et province, Thailand

Roi Et is one of the provinces with rice farming and exported to many countries around the world. In order to assess the radiation risk index from Jasmine rice cultivated soils, 175 samples in Roi Et province were measured using the gamma ray spectrometry technique for estimating the natural radioactivity levels. The specific activity of ²²⁶Ra, ²³²Th and ⁴⁰K was found from 7.14 to 29.02 Bq/kg, 7.24 to 33.40 Bq/kg and 18.17 to 129.65 Bq/kg with a mean value of 16.92 ± 1.16 Bq/kg, 16.99 ± 2.24 Bq/kg and 46.95 ± 6.79 Bq/kg, respectively. However, the values of radium equivalent activity (Ra_eq), the external hazard index (H_ex), the gamma-absorbed dose rate (D) and the annual effective dose equivalent (AEDE_out) were also calculated to evaluate radiological hazards. The average values of Ra_eq, H_ex, D and AEDE_out were found to be 44.83 Bq/kg, 0.12, 20.03 nGy/h and 0.02 mSv/y, respectively. From the results can demonstrate that the natural radioactivity from soil are not affect to population in the area, which the natural radioactivity levels and the radiation risk values of Roi Et soil samples are lower than the UNSCEAR values. (paper)