Radiological monitoring: terrestrial natural radionuclides in Kinta District, Perak, Malaysia

Natural background gamma radiation and radioactivity concentrations were investigated from 2003 to 2005 in Kinta District, Perak, Malaysia. Sample locations were distant from any 'amang' processing plants. The external gamma dose rates ranged from 39 to 1039 nGy h-1. The mean external gamma dose rate was 222 ± 191 nGy h-1. Small areas of relatively enhanced activity were located having external gamma dose rates of up to 1039 ± 104 nGy h-1. The activity concentrations of 238U, 232Th and 40K were analyzed by using a high-resolution co-axial HPGe detector system. The activity concentration ranges were 12-426 Bq kg-1 for 238U, 19-1377 Bq kg-1 for 232Th and <19-2204 Bq kg-1 for 40 K. Based on the radioactivity levels determined, the gamma-absorbed dose rates in air at 1 m above the ground were calculated. The calculated dose rates and measured dose rates had a good correlation coefficient, R of 0.94. To evaluate the radiological hazard of the natural radioactivity, the radium equivalent activity, the gamma-absorbed dose rate and the mean population weighted dose rate were calculated. An isodose map for the Kinta District was also produced.