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With the wide use of radioactive materials, it is important to look for locally available and inexpensive materials to serve as efficient absorbers, suitable for shielding against radiation hazards. Due to its widespread availability and affordability, natural bentonitic shale is a viable option for use as a nuclear shielding material. In this study, natural bentonitic samples were cut into cylindrical pellets of varying thicknesses. The chemical composition of the natural bentonitic shale samples was determined through the use of X-Ray Fluorescence (XRF) spectroscopy. The linear and mass attenuation coefficients of bentonitic samples were evaluated using a NaI(Tl) scintillation detector at 662 keV energy of 137Cs, as well as at 1,173 keV and 1,332 keV energies of 60Co, gamma-ray sources. The experimental results indicated that bentonitic samples B3 and M2 exhibited superior shielding parameters compared to other bentonitic samples, attributable to their elevated densities. These two samples are distinguished by a high CaO content and a low AL2O3 content. Furthermore, the Half Value Layer (HVL), Tenth Value Layer (TVL), and mean free path thicknesses were calculated at these energies using linear attenuation coefficients. The theoretical mass attenuation coefficient, calculated with the assistance of the XCOM program and experimental estimates, was found to be in good agreement with the theoretical value. [ABSTRACT FROM AUTHOR]

Humans benefit from nuclear technology, but it also generates nuclear radiation that is bad for both the environment and human health. The serious issue of radiation leakage affects many technological applications. Shielding is required to protect both users and the environment from negative side effects. This work describes the radioactive attenuation properties of some natural rocks, such as claystone, bentonitic claystone, bentonitic shale, sandstone, and basalt using a NaI(Tl) detector. The mass attenuation coefficients μ m of these rocks at various photon energies, half-value layer (HVL), tenth-value layer (TVL), and mean free path (MFP) were determined. The validation of obtained values of μ m was carried out against the theoretical calculations from the XCOM program, and the correlation factor and relative deviation between the two methods were evaluated. It was noted that basalt samples exhibit superior shielding parameters when compared to other rock samples. Also, the concentrations of naturally occurring radioactive elements (238U, 226Ra, 232Th, and 40K) were measured, allowing for the calculation of environmental hazard indices and assessment of attenuation (%) efficiency for certain natural rocks, such as bentonite, sandstone, and basalt. The results revealed that increasing the thickness of Basalt-AZ from 1.5 cm to 2 cm results in an approximate 11% rise in attenuation percentage, with values reaching 77.12%, 67.2%, 67.65%, and 59.8% for NMA-U, IAEA-Th, IAEA-Ra, and IAEA-K, respectively. [ABSTRACT FROM AUTHOR]

The main concern of this study is to test the ability of some fungi isolated from Sinai Peninsula carbonaceous shales to perform microbial leaching of rare earth elements (REEs) from these rocks. Two methods of REEs bioleaching were tested using both direct (active) and indirect (passive) processes. Direct bioleaching process of carbonaceous shale samples was found to be more effective than indirect process for all tested microorganisms. Bioleaching efficiency of REEs using different fungal strains increases with decreasing REEs concentrations when their growth rate decreases. Strains of Aspergillus (A. niger and A. flavus) were found to be the most efficient organisms. The maximum extraction yield of total REEs was 86% at 7days incubation time, 1% pulp density, and 30 °C incubation temperature. A. niger and A. flavus exhibit good potential in generating a variety of organic acids (citric and oxalic) effective for REEs solubilization. Citric and oxalic acids contents produced by A. niger was higher than by A. flavus interpreting higher REEs bioleaching efficiency of A. niger than A. flavus. From properly prepared pregnant bio-leach liquor, the leached REEs were recovered in the form of REEs oxalate product using classical chemical technique. [ABSTRACT FROM AUTHOR]