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Abstract
Specific activity of natural (40K, 226 Ra and 232 Th) and anthropogenic radionuclides (137 Cs) in 103 soil
samples collected from Muang, Kathoo and Thalang districts in Phuket province, have been measured and
analyzed. Experimental results were obtained by using a high–purity germanium (HPGe) detector and gamma
spectrometry analysis system at Nuclear and Material Physics laboratory in Department of Physics, Faculty of
Science, Thaksin University Songkhla Campus. Gamma ray radioactive standard sources (Cesium-137(Cs-137)
Cobolt-60 (Co-60) and Barium-133(Ba-133)) were used to calibrate the measurement system. The KCl and two
well-known reference materials (RGU-1 and RGTh-1) obtained from the International Atomic Energy Agency
were also used to analyze and compute the K, U (or Ra) and Th specific activity in all of the soil samples,
respectively. The IAEA/SL-2 was also used to evaluate the specific activity of 137 Cs in all soil samples. The
measuring time of each sample is 10,800 seconds or 3 hours. It was found that specific activities range from
202.30 – 18803.28 Bq/kg for 40K, 0.00 – 830.82 Bq/kg for 226 Ra, 20.23 – 1014.21 Bq/kg for 232Th and 0.00
– 11.26 Bq/kg for 137 Cs with mean values of 4092.29 ± 267.05 Bq/kg, 212.55 ± 10.18 Bq/kg, 203.98 ± 9.58
Bq/kg and 1.15 ± 0.57 Bq/kg, respectively. Furthermore, absorbed dose rate in air (D), radium equivalent activity
(Raeq), external hazard index (Hex ), and annual effective dose rate of this area were also evaluated by using the
mean values of specific activities of the 40K, 226Ra and 232 Th. Moreover, the experimental results were also
compared with Office of Atoms for Peace (OAP) research data, Thailand and global radioactivity measurement
and evaluations.
Keywords : Specific activity, Absorbed dose rate in air, Radium equivalent activity, External hazard index,
Annual effective dose rate
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