Natural radioactivity survey on soils originated from southern part of Thailand as potential sites for nuclear power plants from radiological viewpoint and risk assessment Rawiwan Kritsananuwat • Hideki Arae • Masahiro Fukushi • Sarata Kumar Sahoo • Supitcha Chanyotha Received: 11 November 2014 Ó Akade ´miai Kiado ´, Budapest, Hungary 2015 Abstract Natural radioactivity in surface soil samples collected at potential sites from southern part of Thailand to set up nuclear power plants has been investigated. 238 U and 232 Th were determined by inductively coupled plasma mass spectrometry whereas gamma-ray spectroscopy was used for 40 K determination. The activity concentrations for 238 U, 232 Th and 40 K varied in range from 4 to 122, 6 to 170 and 5 to 1,422 Bq kg -1 , respectively. The large variation of radionuclide concentrations showed heterogeneous dis- tribution that could be attributed to geological origin. The radiation hazard parameters were estimated from activity concentration of 238 U, 232 Th and 40 K in accordance with the UNSCEAR 2000. Data obtained indicated that soils in the study areas did not pose any significant radiological health hazard to the local population. Keywords Natural radionuclides  Soil  c-Spectroscopy  ICP-MS  Radiological risk Introduction Environmental radiation arising from natural and artificial sources to human are inevitable and is a continuous process [1]. The exposure of general public to ionizing radiation is mainly due to natural radiation including cosmic and ter- restrial radiation [2]. In case of terrestrial background ra- diation, the main contributor of external exposure is emitted from primordial radionuclides e.g. 238 U, 232 Th and their decay products as well as 40 K[3]. Since 238 U and 232 Th have very long half-lives and comparable to age of the earth; consequently, they exist in sufficient quantity to contribute significant radiation dose in human [4]. Their original sources in the natural environment are the Earth’s crust and mantle [5]. During weathering processes of lithosphere, rocks and minerals are transformed into parent material of soils; consequently, the radionuclides are derived from their parent rocks and deposited in soil. The concentration of primordial radionuclides in soil vary greatly depending on the nature of their parent rocks [6] (i.e. type of rocks and minerals and their abundances) as well as physical and geochemical processes (i.e. weather- ing, transportation, sorting and deposition) [7]. Igneous rocks, such as granite, contain higher radionuclide contents than sedimentary rocks. Sedimentary processes sorting weathered materials result in variations of radionuclide concentrations in different types of sedimentary rocks [8]. Furthermore, human activity, such as mining and milling [9], coal burning [10], oil and natural gas production [11], agricultural fertilizer application [12] and power generation [13] lead to elevated concentrations of natural radionu- clides in soils. Since, soil is one of the most important source of external exposure to natural radiation in humans [14, 15], evaluation of external dose and assessment of radiological risk have been estimated by various R. Kritsananuwat  H. Arae  S. K. Sahoo (&) Research Centre for Radiation Protection, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage, Chiba, Japan e-mail: sahoo@nirs.go.jp R. Kritsananuwat  M. Fukushi Department of Radiological Science, Tokyo Metropolitan University, 7-2-10 Higashiogu, Arakawa, Tokyo, Japan R. Kritsananuwat  S. Chanyotha Department of Nuclear Engineering, Chulalongkorn University, 254 Phayathai Road, Pathumwan, Bangkok, Thailand 123 J Radioanal Nucl Chem DOI 10.1007/s10967-015-3994-8