Hakim Sabzevari University

Recently, some new composite shields have been introduced for radiation protection purposes.One of the useful parameters for dosimetry in radiation protection purposes is the Kerma factor which should be determined for each operational shield.The current study aims to evaluate and compare the Kerma factor relevant to these shields over a wide range of photon energies and compare them to those of the lead, as the reference shield for photon beam.Eleven composite materials including AT₄₀Fe₄₅Cu₁₅, Polypropylene/CdO, Red-Clay/CdO, Silicon-based WO₃, WO₃-TeO₂-B₂O₃, Ba₂P₂O₇-based polymer, BaZrO₃-based polymer, Epoxy Clay/PbO, Na₂Si₃O₇/Nano-Ag, B₂O₃-PbO-ZnO (PBBZ1), and PDMS-WO₃-Bi₂O₃ were regarded.The relevant Kerma factors over 0.001 MeV-20 MeV photon energy range were obtained by anal. and Monte Carlo-based approaches.The phys. reference data provided by NIST was used for the theor. approach, while MCNPX 2.6.0 Monte Carlo code was used for the second approach.The data were compared with those of the lead as the standard material for shielding against the photon beam.The obtained Kerma factors for studied composite shields can be used for radiation protection dosimetry using fluence to dose conversion technique.For all considered composite materials Kerma factors were lower than those of the lead.B₂O₃-PbO-ZnO (PBBZ1) showed the closest Kerma factors to the lead.On the other hand, the min. Kerma factors belonged to PDMS-WO₃-Bi₂O₃.There was a good agreement between the results of anal. approach and Monte Carlo technique in Kerma factor evaluation where the differences never exceeded 3 %.From the results, it can be concluded that none of the studied composite shields show inferior performance with respect to the lead in protection against photon beam.On the other hand, these shields have some advantages over the lead including light weight, low cost, easy production, nontoxic nature, etc.Among the considered composite materials B₂O₃-PbO-ZnO (PBBZ1) showed the maximum Kerma factors values which indicated the best performance in shielding against photon beam.The desirable accordance between the anal. and Monte Carlo results indicates the reliable applicability of the Monte Carlo technique in evaluating the photon shields Kerma factor.

The limited availability of natural gas (NG) and its associated emissions raise concerns about meeting residential energy demand.This work investigates the feasibility of hydrogen blending (HB) in a specified urban NG network from energy, economic, and environmental perspectives.First, the impact of 1-20 % volumetric hydrogen blending on gas composition and thermophys. properties is analyzed.The TOPSIS decision-making method then determines the optimal HB percentage for cold and hot months.Finally, dynamic network parameters-including volumetric flow, energy contribution, hydrogen production power requirements, efficiencies, CO₂ emissions, and costs-are evaluated based on the optimal HB percentages.Results illustrated that optimal HB levels of 12 % in winter and 13 % in summer (totaling 23024 m³ of hydrogen annually) could save 7044 m³ of NG.This integration required 93.4 MWh of PEM electrolyzer power to supply 70 MWh of hydrogen energy to end users annually (4.34 % of the total natural gas demand), while reducing CO₂ emissions by 13 tons.However, economic anal. showed that annual expenses were four times higher than revenues, with grid electricity purchasing costs being the most significant expense.Finally, to deliver the blended natural gas with hydrogen to end users with the same energy content as pure NG, an addnl. 27.2 % annual cost was incurred, resulting in a levelized cost of energy (LCOE) of 54.7 $/MWh.

Thermoluminescence dosimeters (TLDs) are widely used for radiation dose measurement in various applications, including radiation protection, radiotherapy, and diagnostic radiology. Therefore, efforts to improve TLD response and reduce uncertainty in measurements are highly valuable. This study aims to evaluate the effect of adding silver (Ag) nanoparticles to LiF:Mg,Ti TLD in terms of their structural characteristics, thermoluminescence (TL) properties, and dosimetric performance. The TLD samples were first synthesized, and Ag nanoparticles were subsequently incorporated as a third impurity. Both prepared samples (with and without Ag nanoparticles) were irradiated with predefined dose levels of 6 MV photons and corresponding glow curves and dose-response curves were compared. XRD, FESEM, and EDS analyses confirmed the proper formation of the LiF TLD structure. The presence of Ag nanoparticles was verified without any alteration in the overall crystalline structure of LiF. The obtained elemental correction coefficient (ECC) values were close to unity, indicating a nearly uniform distribution of impurities in the LiF structure. TLD glow curve at the same dose level enhanced when Ag nanoparticles were added to the TLD. Furthermore, the dose-response curve improved in the presence of Ag nanoparticles. Based on the results, it can be concluded that incorporating Ag nanoparticles into LiF:Mg,Ti enhances its thermoluminescence response and sensitivity.