Distribution of natural radioactivity in surface soil from the vicinity of Lynas Rare-Earth Plant at Gebeng, Kuantan and its potential radiation hazard to humans

The concentrations of natural gamma ray emitting radionuclides in the surface soil from the vicinity of Lynas Rare earth plant in Kuantan, Pahang were studied with the aim of evaluating the environmental radioactivity of that area. The concentration of ²²⁶Ra ranged between 8.7 - 95.4 Bq/ kg with a mean value of 34.6 Bq/ kg; ²²⁸Ra activity between 6.6 - 134 Bq / kg with a mean of 61.9 Bq/ kg; the activity of ²³⁸U varied from 8.7 to 106 Bq/ kg with a mean value of 38.0 Bq/ kg; for ²³²Th, it ranged from 6.2 to 130 Bq/ kg with a mean value of 60.3 Bq/ kg, while for ⁴⁰K, the values were from 10.6 to 1160 Bq/ kg with a mean of 244.8 Bq/ kg. The activity standard deviation for ²²⁶Ra, ²²⁸Ra, ²³⁸U, ²³²Th and ⁴⁰K was 15.8 Bq/ kg, 27.3 Bq/ kg, 16.9 Bq/ kg, 26.6 Bq/ kg and 218.7 Bq/ kg, respectively. To estimate the potential radiation hazard to human, the radium equivalent activity, external hazard index and dose rate in air from the terrestrial natural gamma radiation were calculated. The maximum value found for these three parameters was 335.9 Bq/ kg, 0.94 and 161.8 nGy/ h, respectively. The data was discussed and compared with those reported in the literatures. The study found that the dose equivalent could be received by an individual at the vicinity area (outdoor) of Lynas plant was estimated in between 10.9 - 204.3 μSv/ yr with mean value of 84.3 μSv/ yr. This value is well below the annual dose limit 1,000 μSv/ yr for general public. (author)