Sultan J. Alsufyani

This study focused on identifying Th-, Nb-Ta-, Zr-, and REE-bearing minerals with a multivariate statistical approach in alkaline syenite to evaluate their radiological risks, at Nikeiba, Egypt. Through microchemical analyses, by utilizing electron probe microanalysis, horite, microlite, monazite, zircon, columbite, and fergusonite were shown to bear uranium and thorium. These minerals have played an important role in higher radioactive zones in the studied alkaline syenite. REE-minerals comprising bastnäsite, monazite, and fluorite and apatite are well recorded. The total rare earth elements (TREE₂O₃) reveal higher concentrations in bastnäsite than monazite, with averages 74.87 and 63.8 wt%. Ce is considered the most predominant LREE in the analyzed bastnäsite and monazite. The mean values of radionuclide activity concentrations of ²³⁸U, ²³²Th, and ⁴⁰K are 108 ± 20 Bq/kg, 107 ± 9 Bq/kg, and 1255 ± 166 Bq/kg, respectively. Radiological assessments revealed a radium equivalent activity of 357 Bq/kg, below global limits, but an air-absorbed dose rate (166 nGy/h) and annual effective doses (0.81 mSv/y indoors, 0.20 mSv/y outdoors) exceeding safe thresholds. Additionally, the excess lifetime cancer risk (ELCR) was calculated at 0.00071, surpassing the acceptable limit of 0.00029, making these rocks unsafe for construction use. Statistical analyses further underscored the relationships between radionuclide concentrations and associated risks, highlighting the necessity for continuous monitoring and mitigation.

The present study focuses on the calculation of selected shielding parameters of polycarbonate/poly(methyl methacrylate), polycarbonate/poly (methyl methacrylate)/cobalt tin sulphide, polycarbonate/poly(methyl methacrylate)/zinc molybdate, and polycarbonate/ poly(methyl methacrylate)/copper cobaltite oxide composites exposed to photon beams, with the aim of developing effective lead-free shielding materials. The mass and linear attenuation coefficients were calculated using the Phy-X/PSD program and subsequently used to determine the half-value layer and tenth-value layer. Furthermore, the effective atomic number, effective electron density, mean free path, equivalent atomic number, and exposure buildup factor of the analysed samples were calculated. The shielding properties were evaluated across a photon energy range of 0.01-15 MeV. The results demonstrated that the polycarbonate /poly(methyl methacrylate)/cobalt tin sulphide composite exhibited the most effective shielding performance compared to the studied composites.