Distribution of radionuclides and assessment of risk exposure to the miners on a kaolin field

Mining of kaolin deposits are common in Nigeria without considering the background radiation in such environment and the health risks it might pose on the miners. In this study, in-situ measurements of the naturally occurring radionuclides were carried out with the aim of determining the distribution of these radionuclides on the mining field and estimation of the hazard indices exposure risks (γ- and α-radiation risks) to the miners. The study was achieved with the aid of gamma ray detector Super-Spec (RS-125) and global positioning system. The detector used has ability to measure activity concentrations of ²³⁸U, ²³²Th and ⁴⁰K and gamma doses. For the purpose of this study, only the concentrations of the three radionuclides were considered. For each location, measurements were taken four times, while its mean value was estimated for better accuracy. In all, nineteen locations were occupied in order to cover the study area. Basic kriging method was adopted for the production of spatial distribution of these radionuclides and their corresponding γ- and α-radiation hazard indices. The mean values of ²³⁸U, ²³²Th and ⁴⁰K are 46.7, 71.8 and 108.7 Bq kg⁻¹, respectively. When compared to the global standard, it was revealed that ²³⁸U and ²³²Th are greater than the global standard, while ⁴⁰K fall below the permissible limit. The γ- and α-radiation exposure risks estimated revealed that the mean values of I_γ and I_α are 0.6 and 0.2 respectively. Though the estimated γ- and α-radiation indices showed that the kaolin field is safe for the miners, periodic check is required in order to monitor the rate at which these natural primordial radionuclides (²³⁸U and ²³²Th and their progenies) are being enhanced. (paper)