The presence of radioactive heavy minerals in prospecting trenches and concomitant occupational exposure

Abstract

Uranium, perhaps the most strategically important component of heavy minerals, finds particular significance in the nuclear industry. In prospecting trenches, the radioactivity of 238U and 232Th provides a good signature of the presence of heavy minerals. In the work herein, the activity concentrations of several key primordial radionuclides (238U, 232Th, and 40K) were measured in prospecting trenches (each of the latter being of approximately the same geometry and physical situation). All of these are located in the Seila area of the South Eastern desert of Egypt. A recently introduced industry standard, the portable hand-held RS-230 BGO gamma-ray spectrometer (1024 channels) was employed in the study. Based on the measured data, the trenches were classified as either non-regulated (U activity less than 1000 Bq kg-1) or regulated (with 238U activity more than 1000 Bq kg-1). Several radiological hazard parameters were calculated, statistical analysis also being performed to examine correlations between the origins of the radionuclides and their influence on the calculated values. While the radioactivity and hazard parameters exceed United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) guided limits, the mean annual effective doses of 0.49 and 1.4 mSv y-1 in non-regulated and regulated trenches respectively remain well below the International Commission on Radiological Protection (ICRP) recommended 20 mSv/y maximum occupational limit. This investigation reveals that the studied area contains high uranium content, suitable for extraction of U-minerals for use in the nuclear fuel cycle.

Radiological Hazard Evaluation of Some Egyptian Magmatic Rocks Used as Ornamental Stone: Petrography and Natural Radioactivity

“…Assuming equilibrium between uranium and radium, the mean of the 232 Th/ 226 Ra ratio in the examined samples of magmatic rocks was less than the mean worldwide value of crustal rocks, 3.94 [ 15 ]. The lowest results contributed to the high Ra content relative to Th in the studied samples, reflecting Ra mobility relative to Th, especially in the secondary environment.…”

“…Furthermore, the leaching of uranium minerals (uranophane, uraninite, and betauranophane) through rainwater aids in their migration and precipitation along joints and faults [30]. Assuming equilibrium between uranium and radium, the mean of the 232 Th/ 226 Ra ratio in the examined samples of magmatic rocks was less than the mean worldwide value of crustal rocks, 3.94 [15]. The lowest results contributed to the high Ra content relative to Th in the studied samples, reflecting Ra mobility relative to Th, especially in the secondary environment.…”

“…Natural sources of gamma radiation (background radiation) are predominantly attributable to primordial radionuclides, primarily the 232 Th and 238 U series and their decay products, as well as 40 K, all of which exist at trace amounts in the earth's crust. The natural radiation of soil and rocks depends on their mineralogical composition [15,16]. Measuring the concentration of radionuclides helps in monitoring environmental radioactivity.…”

Assessment of Radioactive Materials in Albite Granites from Abu Rusheid and Um Naggat, Central Eastern Desert, Egypt

“…Table 3 shows that the activity concentration of the 238 U series included 234m Pa that varied from 217.9 to 1135 Bq/kg and 234 As demonstrated in Table 5, the concentrations of all the samples were very high compared to the worldwide average, except 235 U, which is lower than the worldwide average. The average worldwide radioelement values are 32 Bq/kg for 226 Ra, 45 Bq/kg for 232 Th, and 412 Bq/kg for 40 K [2]. The 226 Ra/ 238 U for the samples were around the unity, which suggested that Abu Rusheid granites are characterized by secular uranium equilibrium.…”

“…Natural radioactivity in the environment is due to the presence of natural radionuclides, namely 238 U, 232 Th and 40 K, in various geological formations [1,2]. Terrestrial radiation comprises radiation emitted from these radionuclides and their progeny.…”