Natural background radiation in the Kinta District, Perak Malaysia

Abstract

Measurement of natural background radiation levels in the Kinta District was carried out between 2003 and 2005. Gamma dose rates were measured from 1007 locations using a portable gamma-ray survey meter, Model 19 Micro R meter manufactured by Ludlum. The measured dose rates ranged from 39 to 1039 nGy h-1 and have a mean dose rate of 222 ± 191 nGy h-1 (1.36 mSv y-1). Two small areas of hot spots around Kampung Sungai Durian with dose rates of 1039 nGy h-1 were found. This is the highest dose rate recorded in Perak to date. A total of 128 soil samples collected were analyzed for the activities of the naturally occurring radionuclides, gross alpha and gross beta activities. The activity concentrations of 238U, 232Th and 40K were analyzed by using a HPGe detector. The ranges are 12 – 426 Bq kg-1 for 238U, 19 – 1377 Bq kg-1 for 232Th and from less than 19 – 2204 Bq kg-1 for 40K. Based on the radioactivity levels determined, the gamma absorbed dose rates in air at 1 meter above the ground were calculated using the procedure applied by UNSCEAR 2000. The total calculated dose rates and measured dose rates have shown good correlation coefficient of 0.94. The calculated Radium Equivalent Activity (Raeq) range from 0.14 to 6.01 mSv y-1. The gross alpha activity of the soil samples range from 15 to 9634 Bq kg-1 with a mean value of 1558 ± 121 Bq kg-1. The gross beta activity range from 142 to 6173 Bq kg-1 with a mean value of 1112 ± 32 Bq kg-1. The mean population weighted dose rate for the Kinta district is 1.2 mSv y-1. Gamma isodose map for the Kinta District was plotted. The isodose map is the most recent and can be used as a reference.