Natural Radioactivity in Soil and Radiological Risk Assessment in Lișava Uranium Mining Sector, Banat Mountains, Romania

Abstract

The specific activity and spatial distribution of 238U, 232Th and 40K were determined in the surface soil from the Lișava uranium mining sector. This sector belongs to the Banat district, an historically important uranium mining area in Romania (an area with closed uranium mines and a radioactive waste dump). Gamma-ray spectrometry using a high-purity germanium (HPGe) detector was used to measure the activity of naturally occurring radionuclides in the soil. The average specific activities of 238U, 232Th and 40K in the soil were 197.21 Bq/kg for 238U, 16.21 Bq/kg for 232Th and 543.21 Bq/kg for 40K. The mineral contents of selected waste rock samples (sandstones) were examined using a scanning electron microscope (SEM), which revealed that brannerite, pitchblende and coffinite were the most important uranium-bearing minerals. The means of the radiological hazard parameters were calculated to be 262.22 Bq/kg radium equivalent activity (Raeq), 123.72 nGy/h absorbed gamma dose rates (DR), 0.7 external hazard index (Hex) and 1.8 representative level index (RLI). The spatial distribution of the risk assessment indices associated with the investigated soils exceeded the median values provided by UNSCEAR and reflected the geological settings and influences of anthropic activities such as uranium mining practices and the tipping of radioactive mining waste.

Natural radioactivity level in graphite samples from the Cătălinul deposit, Parâng Mountains, Romania: sources identification and radiological risk assessment

“…The activity for 232 Th was calculated using the γ-lines of 338.4 and 911.2 keV for 228 Ac, 727 keV for 212 Bi, and 860 keV for 208 Tl. The activity of 40 K was computed using its emission at 1460 keV (Ion et al, 2022).…”

“…The radiological parameters were calculated based on the specific activities established for 238 U, 232 Th and 40 K in graphite samples using the following equations: Ra eq = A U + 1.43A Th + 0.077A K (Bq/kg) for radium equivalent activity (Raeq); D R = 0.462A U + 0.604A Th + 0.042A K (nGy/h) for absorbed gamma dose rate (DR), and H ex = (A U /370) + (A Th /259) + (A K /4810) for external hazard index (Hex). In all equations: A U , A Th and A K represent the specific activity of 238 U, 232 Th and 40 K (Bq/kg) (Ion et al, 2022).…”