The activity concentrations of the natural radionuclides 226Ra, 232Th and 40K in soil samples were measured by a gamma spectrometer with a HPGe detector. The average activity concentrations of the natural radionuclides 226Ra, 232Th and 40K are ± , ± and ± , respectively. The average activity concentrations of 226Ra and 232Th in this work are higher than those of the world average values. | VNU Journal of Science: Mathematics – Physics, Vol. 33, No. 4 (2017) 10-16 Natural Radioactivity and External Dose Assessment of Surface Soils in Bolikhamxay Province, Laos Somsavath Leuangtakoun1,2,*, Bui Van Loat1, Vu Thi Kim Duyen3, Khong Nam Khang4 1 Department of Nuclear Physics, Faculty of Physics,VNU University of Science, 334 Nguyen Trai, Hanoi,Vietnam 2 National University of Laos, : 7322, Dongdok Vientiane, Laos 3 Centre for . Tech., Ministry of Defence, 282 Lac Long Quan, Hanoi, Vietnam 4 Military Institute of Medical Radiology and Oncology Received 15 August 2017 Revised 23 October 2017; Accepted 25 October 2017 Abstract: We have determined activity concentrations in 33 soil samples collected from Bolikhamxay Province, Laos. The activity concentrations of the natural radionuclides 226Ra,232Th and 40K in soil samples were measured by a gamma spectrometer with a HPGe detector. The average activity concentrations of the natural radionuclides 226Ra, 232Th and 40K are ± , ± and ± , respectively. The average activity concentrations of 226Ra and 232Th in this work are higher than those of the world average values. Meanwhile, the activity concentration of 40 K is almost the same of the world average value. The estimated average outdoor annual effective dose (E) and radium equivalent actitvity (Raeq) are ± and ± , respectively. Keywords: Gamma spectrometry, Activity concentration, Radium Equivalent Activity, Absorbed gamma dose rate, Annual effective dose rate, Minimum Detection Limit. 1. Introduction Natural radioactivity is widespread in the earth’s environment, it exists in the soil, plants, water, and airs. The gamma radiation from natural radionuclides and cosmic rays constitute the external exposure. Natural radionuclides in the soil generate a significant component of the background radiation exposure to the population [1, 2]. Radionuclides in soils, belonging to .
