Trường ĐH Nguyễn Tất Thành

Environmental radioactivity in building materials can pose radiol. risks to residents by exposure to the emitted gamma radiation and radon.In this study, we evaluated the radioactivity concentration of 53 raw building material samples (fly ash, cement, sand, and gravel) and estimated the dosimetric quantities in outdoor exposure scenarios for residents.The concentrations ranged from 40.1 to 77.4 Bq kg^-1 for ²²⁶Ra, 27.4 to 91.7 Bq kg^-1 for ²³²Th, and 253.5 to 956.2 Bq kg^-1 for ⁴⁰K.Annual ED and organ annual ED, were estimated for outdoor exposure scenarios for residents.Fly ash showed the highest values for these dosimetric quantities, while cement had the lowest.The annual organs ED rate was found to be min. for ovaries and maximum for testes.However, all measured values were reported to be lower than the recommended values set by radiation safety organizations worldwide.External radiation doses were noted to be influenced by factors such as air exchange rate, room dimensions, wall thickness, and the type of concrete mixture used.Considering all the dosimetric quantities, the study concludes that the studied building materials might pose low radiol. risks to public health.

Abstract: In the work, we studied the influences of dead layer thickness on the whole gamma spectrum response for HPGe detector by using Monte Carlo simulation.From the simulated relation of the FEPEs and the dead layer thicknesses, the dead layer thickness of 0.567 mm was derived which increased compared with the nominal value of 0.46 mm from manufacturer after 4 years of operation.The multiple scattering region and peak decreased with different rates and the valley region of the forward-scattering photon increased quickly when the dead layer thickness increased.The energy dependence of the P/T and the general range was also carried out.The results showed that the effect of the increase in dead layer thickness on regions in the spectrum was not the same.Through this study, among several scintillators, it was possible to find a HPGe detector suitable for the purpose of the study.

Water contamination caused by textile dyes can affect human health, calling for effective treatment method.Here, we report the preparation of MgFe₂O₄/C composite through hydrothermal method to adsorb three dyes including rhodamine B, methyl orange (MO) and acid yellow 17 (AY) in water.MgFe₂O₄/C obtained a surface area of 692.32 m²/g and MgFe₂O₄ particles were well-dispersed on porous carbon matrix.Taguchi exptl. design (L₁₆) was conducted to test the effect of four factors, including initial concentration, adsorbent dosage, contact time and pH at different four levels. pH was a first-ranked factor for adsorption of all three dyes with the highest contribution between 33.20 and 55.61%.The highest capacity (158.12 mg/g) was determined for MO dye adsorption under a concentration of 40 mg/L, pH 3, a dose of 0.05 g/L, and a duration of 240 min.The experiments of MgFe₂O₄/C reusability were performed, reaching at least fourth cycles offering potential for reuse.It is recommended that Taguchi orthogonal array design can be well adopted to reach the best condition of organic dyes adsorption by MgFe₂O₄/C composite.