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

Janet Ayobami Ademola, Michael Adekunle Olatunji

Department of Physics, University of Ibadan, Ibadan, Nigeria.

DOI: 10.4236/wjnst.2013.34025                

Abstract

The activity concentrations of natural radionuclides ²²⁶Ra, ²³²Th and ⁴⁰K in bauxite ore, alumina, dross tailing, aluminium scraps and soil samples collected from an aluminium industry in Nigeria were determined by gamma ray spectroscopy method. The mean values of ²²⁶Ra, ²³²Th and ⁴⁰K 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 ²²⁶Ra and ⁴⁰K in all the samples are lower than the world average for soil while ²³²Th 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 exception of alumina was higher than the world average for soil.

Keywords

NORM; Gamma Radiation Dose; Radiation Hazards; Aluminium

Conflicts of Interest

The authors declare no conflicts of interest.

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