Evaluation of NORM and Dose Assessment in an Aluminium Industry in Nigeria

Abstract

The activity concentrations of natural radionuclides 226 Ra, 232 Th and 40 K in bauxite ore, alumina, dross tailing, alumin ium scraps and soil samples collected from an aluminium industry in Nigeria were determined by gamma ray spectros copy method. The mean values of 226 Ra, 232 Th and 40 K content of the samples ranged from 16 ± 6 (alumina) to 31 ± 10 (scrap), 41 ± 0.12 (scrap) to 134 ± 21(bauxite) and 47 ± 14 (bauxite) to 354 ± 8 (scrap) Bq · kg -1 , respectively. The mean activity concentrations of 226 Ra and 40 K in all the samples are lower than the world average for soil while 232 Th is higher with the exception of alumina and scrap. As a measure of radiation hazard to the occupational workers and the members of the public, the radium equivalent activities and external gamma dose rates due to the radionuclides at 1 m above ground surface were calculated. The radium equivalent activities which varied between 88 ± 10 (alumina) and 222 ± 34 (bauxite) Bq · kg -1 are within the safety recommended limit of 370 Bq · kg -1 . The mean annual effective doses calculated from the absorbed dose rates in air were between 54 ± 6 (alumina) and 134 ± 20 (bauxite) μSv · y -1 , which is lower than the 1 mSv · y -1 recommended for the general public. The annual gonadal dose equivalent of all the samples with the ex ception of alumina was higher than the world average for soil.