Hamman Tukur Gabdo

Isodose mapping of terrestrial gamma radiation dose rate of Selangor state, Kuala Lumpur and Putrajaya, Malaysia.

A terrestrial gamma radiation survey for the state of Selangor, Kuala Lumpur and Putrajaya was conducted to obtain baseline data for environmental radiological health practices. Based on soil type, geological background and information from airborne survey maps, 95 survey points statistically representing the study area were determined. The measured doses varied according to geological background and soil types. They ranged from 17 nGy h(-1) to 500 nGy h(-1). The mean terrestrial gamma dose rate in air above the ground was 182 ± 81 nGy h(-1). This is two times higher than the average dose rate of terrestrial gamma radiation in Malaysia which is 92 nGy h(-1) (UNSCEAR 2000). An isodose map was produced to represent exposure rate from natural sources of terrestrial gamma radiation.

Natural radioactivity measurements in Pahang State, Malaysia.

This study was aimed at providing the baseline data of terrestrial gamma dose rates and natural radioactivity to assess the corresponding health risk in the ambient environment of the Pahang State. Terrestrial gamma radiation (TGR) from 640 locations was measured with the mean value found to be 176 ± 5 nGy h−1. Ninety-eight soil samples were analysed using a high-purity germanium detector (HPGe), and the mean concentrations of the radionuclides 226Ra, 232Th and 40K are 110 ± 3, 151 ± 5 and 542 ± 51 Bq kg−1, respectively.226Ra and 232Th concentrations were found to be three times the world average, while that of 40K is quite higher than the world average value. The acid-intrusive geological formation has the highest mean concentrations for 226Ra (215 ± 6 Bq kg−1), 232Th (384 ± 12 Bq kg−1) and 40K (1564 ± 153 Bq kg−1). The radium equivalent activities (Req) and the external hazard index (Hex) for the various soil types were also calculated. Some of the soil types were found to have values exceeding the internationally recommended levels of 370 Bq kg−1 and the unity value, respectively.

Natural radioactivity and associated radiation hazards in soil of Kelantan, Malaysia

ABSTRACT Radiological effects due to external and internal exposure to natural radiation associated with the natural radionuclides 226Ra, 232Th, and 40K in soil of Kelantan, Malaysia was carried out. Terrestrial gamma radiation dose rates (TGRD) measurement was carried out using a portable [NaI(TI)] micro roentgen (µR) survey meter and hyper purity germanium (HPGe) detector for the activity concentrations of 226Ra, 232Th, and 40K in soil samples. The mean TGRD was found to be 209 nGy h−1 and from soil samples analyzed, the mean activity concentrations of 226Ra, 232Th, and 40K were found to be 82 Bq kg−1, 123 Bq kg−1, and 643 Bq kg−1 respectively, which were both about 3 times higher than the Malaysian average as reported by UNSCEAR 2000. The mean radium equivalent (Raeq), absorbed dose rates (D), annual effective dose (H), annual gonadal dose equivalent (AGDE) as well as external and internal radiation hazard index (Hex), which were the indicators of radiological health hazards, were found to be 307 Bq kg−1, 139 nGy h−1, 0.22 mSv y−1, 969.422 µSv y−1, 0.653 and 1.05, respectively.

Radiological mapping of Kelantan, Malaysia, using terrestrial radiation dose rate

Measurements of the environmental terrestrial gamma radiation dose rate (TGRD) in each district of Kelantan state, Malaysia, were carried out using a portable hand-held radiation survey meter and global positioning system. The measurements were done based on geology and soil types of the area. The mean TGRD was found to be 209 nGy h–1. Few areas of relatively enhanced activity were observed in Pasir Mas, Tanah Merah and Jeli districts, which have a mean TGRD between 300 and 500 nGy h–1. An isodose map of the area was produced using ArcGIS software version 9.3.