Determination of Natural Radioactivity Concentration and Radiogenic Heat Production in Selected Quarry Sites in Ondo State, Nigeria

Abstract

Gamma-ray spectrometer was used to measure radiation from
radio-nuclides inside and outside five different quarry sites in Ondo
State (Sutol, Batista, Aslos, Johnson and Stoneworks) in order to
determine the pattern of natural radioactivity, radiogenic heat
production effect and radiological health risk to the population
within the site vicinity. The average activity concentration of 238U,
232Th and 40K inside the quarries are 47.09±7.49, 95.02±14.11 and
1118.68±126.94 Bqkg-1 and outside the quarries are 35.76±7.83,
83.17±11.85 and 959.71±96.43 Bqkg-1
consecutively. The total
heat production and heat flow values estimated for all the quarries
varied from 0.97 to 5.37µWm-3 and 7.63 to 42.12 mWm-2
respectively. The radiogenic heat production variations with the
radionuclide from the quarries were presented as plots. Thorium
concentration is highest (43.5 ppm) followed by uranium (10.4
ppm). The mean values of all the hazard indices calculated were
lower than the internationally acceptable limits. This implies that,
the people working in the quarries, granite end-users and general
public living around the quarries area are safe from radiological
health risk. Considering radiogenic and thermal modeling point of
view, the Johnson quarry has the highest concentration of uranium,
total heat production and heat flow values. It is a manifestation of
the geological rock types and presence of highly weathered
minerals. So, it is of most promising Uranium mineralization and
further probe for potential geothermal exploration.