Radiological Hazard Indices of Hollow Aggregate Filled Stone-Dust Blocks and Sandcrete Blocks Produced in Jos, Plateau State, Nigeria

Abstract

Measurement of gamma radiation emanating from hollow sandcrete and aggregate filled stone-dust blocks across major block industries in Jos North Central Nigeria was carried out using RS-230 Gamma Spectrometer. The purpose of the investigation is to determine the uranium (²³⁸U), thorium (²³²Th) and potassium (⁴⁰K) contents in them for assessment of radiological hazard indices. Results obtained show that concentrations of ²³⁸U, ²³²Th and ⁴⁰K in the two major types of blocks vary from 3.95-9.67 ppm, 14.93-30.20 ppm, and 0.62-4.16% respectively. Higher values were recorded in the aggregate filled stone-dust blocks compared with the sandcrete blocks. Activity concentration of the sandcrete blocks comprises 62.79 Bq/Kg for ²³⁸U, 71.83 Bq/Kg for ²³²Th, and 447.02 Bq/Kg for ⁴⁰K, while it is 110.16 Bq/Kg, 114.15 Bq/Kg, and 1194.88 Bq/Kg for ²³⁸U, ²³²Th and ⁴⁰K respectively for the aggregate filled stone-dust blocks. Consequently, the values of indoor absorbed dose rate, annual effective dose equivalents (indoor and outdoor), radium equivalent activity, internal hazard index (indoor and outdoor) as well as excess lifetime cancer risk (ELCR) are higher among the aggregate filled stone-dust blocks compared to the values recorded for the sandcrete blocks. Radiological hazard indices are not only higher in the aggregate filled stone-dust blocks but are much higher than the recommended limits in most cases. With excess lifetime cancer risk (ELCR) of up to 2.99 x10^-3, it is recommended that radiological safety be given priority over and above strength and durability in the choice of blocks for residential building.

Keywords: Aggregate filled stone-dust block; Sandcrete block; Uranium; Thorium; Potassium; Activity Concentration; Radiological Hazard indices; Jos Metropolis.