Estimation of Dose Enhancement for Inhomogeneous Distribution of Nanoparticles: A Monte Carlo Study

: High atomic number nanoparticles are of increasing interest in radiotherapy due to their significant positive impact on the local dose applied to the treatment site. In this work, three types of metal nanoparticles were utilized to investigate their dose enhancement based on the GATE Monte Carlo simulation tool. Gold, gadolinium, and silver were implanted at three different concentrations to a 1 cm radius sphere to mimic a cancerous tumor inside a 10 × 10 × 30 cm3 water phantom. The innermost layer of the tumor represents a necrotic region, where the metal nanoparticles uptake is assumed to be zero, arising from hypoxic conditions. The nanoparticles were defined using the mixture technique, where nanoparticles are added to the chemical composition of the tumor. A directional 2 × 2 cm2 monoenergetic photon beam was used with several energies ranging from 50 keV to 4000 keV. The dose enhancement factor (DEF) was measured for all three metal nanoparticles under all beam energies. The maximum DEF was ~7 for silver nanoparticles with the 50 keV beam energy at the highest nanoparticle concentration of 30 mg/g of water. Gold followed the same trend as it registered the highest DEF at the 50 keV beam energy with the highest concentration of nanoparticles at 30 mg/g, while gadolinium registered the highest at 100 keV

Estimation of Thermal & Epithermal Neutron Flux and Gamma Dose Distribution in a Medical Cyclotron Facility for Radiation Protection Purposes Using Gold Foils and Gate 9

The aim of this study is to characterise the neutron flux generated directly behind targets used in medical cyclotrons. The characterisation process aims at determining the feasibility of using the generated neutrons for research purposes in neutron activation analysis. The study was performed by activating gold foils placed directly behind the cyclotron targets. The thermal and epithermal neutron flux were found to be 4.5E+05 ± 8.78E+04 neutrons cm-2 s-1 and 2.13E+06 ± 8.59E+04 neutrons cm-2 s-1, respectively. The flux value is the same order of magnitude listed in the manual produced by the cyclotron manufacturer. The results are encouraging and show high potential for using the cyclotron facility as a thermal neutron source for research purposes. However, it is important radiation protection procedures be followed to ensure the safety of researchers due to the high gamma dose rate measured directly behind the target at 2.46 Sv/h using an OSL chip during the beam on time

Hybridizing solar dish Stirling power system with single-effect desalination for sustainable electricity and freshwater co-generation: Mathematical modeling and performance evaluation

At present, poly-generation sustainable systems are highly promising pathways that could produce several beneficial energy outputs, such as electricity, heat, and freshwater, that have the potential to fulfill financial competitiveness and higher efficiencies. Considering the great advantages of the solar dish/Stirling cycle, this study introduces comprehensive theoretical modeling and performance analysis of a solar dish/Stirling-powered single effect distillation system (SDSPSEDS) for combined electricity, heat, and freshwater tri-production. A detailed mathematical model executed in MATLAB software based on energy balance and opt-geometric approaches was established to simulate the SDSPSEDS operation dynamically. In order to analyze its performance under real weather conditions of Tabuk, KSA, for four seasonal scenarios. The energetic performance of the hybrid SDSPSEDS is comprehensively evaluated in terms of net electric power, solar-to-electricity conversion efficiency, Stirling engine rejected heat, distilled freshwater productivity, and overall co-generation efficiency of the hybrid system. The simulation results show that the daily electrical energy produced by the SDSPSEDS is 234.7, 194.6, 159.8, and 190.0 kWh/day. In contrast, the daily freshwater production is obtained as 787.4, 657.3, 545.0, and 650.0 kg/day in June, September, January, and March, respectively. Moreover, it is also found that the overall daily co-generation efficiency of the hybrid SDSPSEDS is increased to 62.60%, 53.50%, 47.40%, and 52.96% compared to only daily average electrical efficiencies of 20.92%, 17.82%, 15.50%, and 17.60% attained; in the same examined seasonal days, respectively when utilizing only standalone solar dish/Stirling power system. Thus, the findings of this study proved that the hybrid SDSPSEDS is an efficient system to produce power and water in rural areas with no water piping network or electrical grid

Radiological characterization of the phosphate deposit in Al-Jalamid phosphate mining area, Saudi Arabia

It is a known fact that phosphate rocks have high levels of natural radioactivity due to the presence of large concentrations of radionuclides. This work aims to estimate radiation exposure and dose levels at Al-Jalamid site in northern Saudi Arabia. Al-Jalamid area is one of the largest reserves of phosphate worldwide. Ma’aden, a Saudi Government public company, owns the mine and is responsible for all mining activities. Phosphate and soil samples collected from Al-Jalamid phosphate mining area have been analysed for their uranium and thorium content by an α-spectrometer using radiochemical techniques. The quantity of radon gas was measured both in groundwater and in the atmosphere (indoor and outdoor) at the site using a portable radiation survey instrument. Groundwater samples collected from wells surrounding the mining area were analysed using a liquid scintillation counter in addition to an α-spectrometer. Finally, it is found that phosphate rock concentrate products cannot be utilized economically based on the standards set by the International Atomic Energy Agency (IAEA), since the average activity concentration does not reach the limit set by IAEA and hence are not commercially feasible

Radiological characterization of the phosphate deposit in Al-Jalamid phosphate mining area, Saudi Arabia

It is a known fact that phosphate rocks have high levels of natural radioactivity due to the presence of large concentrations of radionuclides. This work aims to estimate radiation exposure and dose levels at Al-Jalamid site in northern Saudi Arabia. Al-Jalamid area is one of the largest reserves of phosphate worldwide. Ma’aden, a Saudi Government public company, owns the mine and is responsible for all mining activities. Phosphate and soil samples collected from Al-Jalamid phosphate mining area have been analysed for their uranium and thorium content by an α-spectrometer using radiochemical techniques. The quantity of radon gas was measured both in groundwater and in the atmosphere (indoor and outdoor) at the site using a portable radiation survey instrument. Groundwater samples collected from wells surrounding the mining area were analysed using a liquid scintillation counter in addition to an α-spectrometer. Finally, it is found that phosphate rock concentrate products cannot be utilized economically based on the standards set by the International Atomic Energy Agency (IAEA), since the average activity concentration does not reach the limit set by IAEA and hence are not commercially feasible