Abstract
A total of 223 sand samples collected from seven provinces in Northeastern Thailand were analyzed for their gamma radioactivity from naturally occurring radioactive materials (NORMs), and the data were used to calculate the concentrations of Ra-226, Th-232, and K-40. Radiological safety indicators such as the indoor external dose rates (Din), the annual indoor effective dose (Ein), the activity concentration index (I), the radium equivalent activity (Raeq), the external hazard index (Hex), the internal haphazard index (Hin), and the excess lifetime cancer risk (ELCR) were calculated. The activity concentrations were found to be 36 ± 10 Bq/kg for Ra-226, 2.64 ± 0.58 Bq/kg for Th-232, and 323 ± 168 Bq/kg for K-40. Din is 62 ± 23 nGy/h. The Ein is 0.30 ± 0.11 mSv/y. The activity concentrations and other indicators were reported by each province and compared with the safety standards and are found to be within the safe limits in this study. The results can be used to develop the standard guideline levels for choosing building materials in Thailand.
Highlights
Building materials such as rock, soil and sand are formed from the earth’s crust, enriched with naturally occurring radioactive materials (NORMs)
The average indoor annual effective dose (Ein) is 0.30 ± 0.11 mSv/y which is lower than the dose limit of 1 mSv/y recommended by the International Commission on Radiological Protection (ICRP) (ICRP, 2007) [5]
Sand samples collected from Loei, Nong Bua Lam Phu, Khon Kaen, Nakhon Ratchasima, Nong Khai, Bueng Kan, and Sakon Nakhon provinces of Northeastern Thailand were measured using an HPGe gamma-ray detector to determine the activity concentrations, dose and hazard index values
Summary
Building materials such as rock, soil and sand are formed from the earth’s crust, enriched with naturally occurring radioactive materials (NORMs). This study found that normally human beings spend nearly 90% of their time indoors [2] Their exposure to radiation in the residence is strongly related to the radioactivity from building materials [3]. Several reported activity concentrations are relatively low compared with NORMs from the mineral industry; even though the ICRP 1990 reported that the chronic exposure of low doses from ionizing radiation can increase the risk of health damage to individuals, which may occur decades after exposure [4]. The index value of one can be used as a conservative screening tool for identifying materials that during their use would cause doses exceeding the reference level (1 mSv/y excess in addition to outdoor exposure) in the case of a bulk amount inbuilt [7]. The limit values of the index (I) depend on the dose criterion adopted and the use of the material (Table 1)
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