Assessment Of Radiological Doses Associated With Natural Radioactivity From Soil In The Communities Close To Uranium Mines In Namibia

ABSTRACT

Primordial radionuclides are ubiquitous in the environment and they exist in different ranges of concentration levels in minerals. Some human activities such as uranium mining can result in a rise of concentration of naturally occurring radioactive materials (NORM) and lead to exposure conditions. This necessitates a need to radiologically map and determine the extent of exposure of people who work in the mines and communities that live nearby as they can be the primary exposed population. The aim of this project was to assess the radiological doses of the members of the public who live in towns (Arandis, Walvis Bay, Swakopmund and Henties Bay) that are close to the uranium mines in the Erongo region of Namibia. A total of 28 soil samples were collected from the four towns and analysed for the activity concentration of 226Ra, 232Th and 40K using non-destructive Gamma spectrometry system with a high purity Germanium (HPGe) detector. Genie 2000 software was used to accumulate and analyse spectra. The average activity concentration for Arandis for 226Ra was 58.28± 9.88 Bq/kg, for 228Ra (232Th), the average concentration was 195±83.0Bq/kg, 40K is the radionuclide with the highest activity concentration of 617±85.4Bq/kg, Arandis has the highest activity concentrations than all other towns. In Swakopmund; 40K was the radionuclide with the highest average concentration from the radionuclides that were measured and the value was 379.15 ± 97.5 Bq/kg. Swakopmund had an estimated average activity concentration of 232Th to be 56.29±18.2 Bq/kg, whereas the average activity concentration of 226Ra was estimated to be 28.70 ± 11.2 Bq/kg which makes it the lowest activity concentration from the radionuclides that were measured. For Walvis Bay the radionuclide with the highest average activity concentration was 40K and its value was 285.9±116.9 Bq/, 232Th was found to have an average concentration of 14.44±6.51 Bq/kg, 226Ra activity concentration for Walvis Bay had the lowest xix activity concentration average value of 12.3±5.19 Bq/kg than the rest of the radionuclides, making it have the lowest activity concentrations than all the other towns. Henties Bay had a high average activity concentration for 40K of 648.28±31.1 Bq. The average concentration for 232Th was 140.30 ± 76.2 Bq/kg, the activity concentration for 226Ra was found to have an average concentration of 58.80±10.1Bq/kg. The mean annual effective dose values were below the recommended reference value in all the towns. The radium equivalent activity for all the towns except Arandis was below the limit of 370 Bq/kg. The mean external hazard indices, and internal hazard indices values for soil in the towns of; Walvis Bay, Swakopmund, and Henties Bay were below the limit except for Arandis. The results obtained indicate radiation from NORMs at the mining towns show insignificant public exposure.