Measurements of radiometric concentrations for 226Ra, 238U, 232Th and 40K in soil samples from two uranium mines’ stockpiles, Erongo region, Namibia

Abstract

The continuous exposures from radiations to human population has led to research studies on evaluating the radioactivity concentrations in most parts of the world. Naturally occurring radioactive materials (NORM) have been greatly regarded as the chief sources of both terrestrial and cosmological radiations. In this study a high-purity germanium well detector was used to measure the activity concentrations of samples from mines 1 and 2 considered in the study. The measured average activity concentration for ²²⁶Ra, ²³⁸U, ²³²Th and ⁴⁰K in mine 1 were estimated at 2546±10, 557±13, 215±2 and 1079±26 Bq.kg^-1, respectively. For mine 2, the estimated average values of the radionuclides of ²²⁶Ra, ²³⁸U, ²³²Th and ⁴⁰K were calculated as 4414±27, 842±29, 436±5 and 2225±52 Bq.kg^-1, respectively. The high concentration of radium in samples contributed to high rate of radon emanation into the atmosphere, ground and surface water as well and, if no remedial measures are put in place, this may contribute to plants, animals and eventually human exposures in the region. The study concludes that mine tailings contribute to an increase in background radiation in the environment due to the fact that they are uncovered and deposited in the open environment, resulting in wind-blown ²²⁶Ra carrying dust entering nearby residential dwellings. The exposures rates could also be increased by other possible transfer pathways, such as ingestions, inhalations and external gamma radiations. Mining companies are urged to decrease windblown atmospheric exposure by using water tanks mounted on mining equipment to sprinkle on top of the soil or covering the tailings with canvas sheet.