Background & Methodology : The specific activity concentration of naturally occurring radionuclides 226Ra, 232Th, 40K and their health related effects were determined in different environmental samples(gemstones) collected from Delanta-Dawunt. Which is one of the mining place in Ethiopia to extract mainly opals (gemstones). Sample collection and the gamma spectroscopic analysis followed the recommended international procedures for such type of research. Gamma-ray spectrometry was applied using HPGe gamma-ray detector and PC-based MCA.
The Purpose of this research: to determine the activity concentrations of the radionuclides U/Th series and K of gemstones(opals), to determine life time cancer risk of radionuclide in the environment , to assess the hazard and risk to the public associated with these dose values , to conduct the geochemical studies by quantifying the levels of trace gemstones as well as the physical parameters in soil samples within and around it, and To determine the radiation doses from these activity concentrations and compare with international recommended dose limits.
Results: The results of the activity concentration on our research work showed significant variations from 11.97 ± 2.46 to 62.44 ± 14.99 Bq kg-1 for 226Ra, 25.69 ± 3.69 to 137.84 ± 13.23 Bq kg-1 for 232Th and 184.84 ± 3.59 to 969.56 ±18.16 Bq kg-1 for 40K. The mean radioactivity concentration of 226Ra, 232Th, and 40K was found to be around 29.84 ± 6.53, 68.44 ± 18.94, 390.87 ± 6.09 Bk kg-1 respectively.
Conculsion: The mean values of Radium equivalent activity (Raeq), absorbed dose, annual effective dose equivalent, external and internal radiation hazard (Hex and Hin) index ,and activity utilization index is 151.68±19.46 Bq kg-1, 72.19 ± 8.48 nGy h-1, 0.07 ± 0.01mSv y-1,0.43, 0.51, 0.57 ± 0.08 and 0.29 ± 0.03 respectively. The specific activity of 232Th is higher than the world mean value and 40K is the same as the world mean value. The radiation hazard indices, ELCR values found in this study are lower than the world mean values. However, the absorbed dose is higher than the world means value. This is due to the reason of high thorium concentration existence and opal mining is highly explored on such study areas.