Prida Nuanjing, Thawat Chittrakarn, and Tripob Bhongsuwan

pp. 1183 - 1198

Abstract

This research work aims to study the specific activity of natural radioactivity in soil, rock, construction sand and shallow well water samples in the area of Nakhon Si Thammarat Province. Totally 161 samples were collected and analysed using gamma-ray spectrometry technique. The specific activities of Ra-226, Th-232 and K-40 in soil samples ranged from 8 to 203 (mean 96±18) Bq/kg, 12 to 236 (mean 88±23) Bq/kg and 21 to 1191 (mean 524±127) Bq/kg, in rock samples ranged from 11 to 113 (mean 46±14) Bq/kg, 3 to 113
(mean 47±16) Bq/kg and 18 to 1305 (mean 472±187) Bq/kg, in sand samples ranged from 3 to 91 (mean 42±5) Bq/kg, 14 to 91 (mean 50±5) Bq/kg and 102 to 966 (mean 509±57) Bq/kg, respectively. The radium equivalent
activity of soil samples in 2 districts was found to be higher than 370 Bq/kg. The radiation hazard indices calculated for assessment of the radiation hazards arising due to the use of these rock and sand samples in the construction of dwellings were within the safety limits recommended by UNSCEAR. The mean estimated outdoor dose rates in soil and rock samples were 119±23 and 70±21 nGy/h, respectively. The mean estimated indoor dose rate in sand samples was 134±9 nGy/h. The specific activities of Ra-226 in well water samples ranged from 2 to 179 (Mean 17±7) mBq/l. Only one water sample from Muang District had the Ra-226 specific activity of 179 mBq/l, which was higher than the maximum contaminant level (111 mBq/l).