Radiation Physics and Engineering
Volume:6 Issue: 2, Spring 2025

In this research, an empirical correlation is derived to determine the Nusselt number for nanofluid forced convection flow in a vertical annulus with non-uniform heat flux. The experiments investigate the heat transfer of a homogeneous combined nanofluid composed of TiO2 and Al2O3 dispersed in water. Compared to other conventional fluids, nanofluids exhibit better heat transfer performance due to higher conductivity and reducing the thermal boundary layer. Nanofluids have the potential to function in an emergency core cooling system. A 25-bar test loop with a vertical test section generating non-uniform heat flux is used for the experiment. The tests are conducted at multiple Reynolds numbers and volumetric concentrations of the nanofluid. A new correlation for nanofluid heat performance is developed based on dimensional analysis and multiple linear regression analysis. The Nusselt number derived from the developed correlation shows high accuracy, with R2 = 0.92, indicating better performance compared to existing correlations.

Lithium is the lightest alkali metal with unique chemical properties, such as high electrochemical activity, high reduction potential, and high specific heat capacity. This element has a wide range of applications in various industries, including the nuclear industry. For instance, lithium-6 is a source of tritium for nuclear fusion fuel by absorbing neutrons. Therefore, the separation of lithium from relevant sources is highly important. Since the separation of lithium from these resources is not possible without knowledge of its inventory, in this report, the characterization of the coal gangue is done using XRF and ICP-OES analysis for geochemical studies and measurement of major and minor oxides, as well as XRD analysis for determining the crystalline phases present in the samples. Due to the ICP-OES analysis, the amount of Li in B1 and B2 samples are 279 and 214 ppm, respectively, which makes the B1 sample a suitable source for the extraction of this element. Moreover,as XRD analysis shows, both samples have similar structural minerals, with montmorillonite and quartz being the primary minerals.

For radiotherapy in patients with left-sided breast cancer, the deep inspiration breath-hold (DIBH) technique has been introduced to reduce cardiac toxicity and lower the risk of mortality due to cardiovascular complications. This technique was studied in 25 patients who had two sets of image data for DIBH and free-breathing (FB) treatments. The dose data from the FB and DIBH plans were then analyzed and compared. Additionally, the mean dose and dose-volume parameters for the heart, left ventricle (LV), and left anterior descending (LAD) artery were calculated and analyzed. Stricter criteria have been applied to these values, and the current treatment plans have been reviewed. Our results show that radiation doses to cardiac substructures, such as the LV and LAD artery, do not meet the stricter criteria in nearly all cases. Since radiation dose to these substructures is crucial in preventing late cardiac complications, relying solely on the DIBH technique is not enough for protecting the heart. It is essential to consider these substructures during the treatment planning phase for patients with left-sided breast cancer. Additionally, there should be an exploration of newer techniques that can help achieve the stricter criteria for protecting heart substructures.

This research simulated the natural circulation in a mini-loop using numerical calculations performed with a FORTRAN code and CFD simulations via Ansys Fluent. A stability map of the loop was derived, and the impact of the loop’s inclination angle on this stability map was examined. The findings indicate that at low power levels, particularly functional powers, the loop’s inclination angle does not significantly affect the stability map. The results of the numerical calculations were compared with Vijayan's experimental corrections for this mini-loop, showing good agreement within its functional power range. Additionally, a comparison was made between the numerical calculations and the Ansys Fluent simulation results, which also demonstrated a good agreement, thereby confirming the accuracy of the calculations. Two significant thermo-hydraulic parameters -the mass flow rate and temperature difference at the two heater heads- were calculated and compared for different loop inclinations. It was observed that increasing the inclination angle results in a decrease in the fluid’s mass flow rate and an increase in the temperature difference at the ends of the heat source. Notably, it was determined that achieving a specific temperature difference across the heat source does not necessarily require adjusting the power levels; simply changing the inclination angle is sufficient. Another important result of this research is that by making a series of straightforward assumptions, one-dimensional computations can be solved very precisely, thereby saving computation time.

This article presents the design and implementation of a control system for a 1 MeV, 25 kW electrostatic accelerator, highlighting its architecture, instrumentation, and operational capabilities. The machine is designed for laboratory-scale irradiation experiments. A monolithic control system architecture was selected for its advantages in centralized data management, ease of maintenance, and simplified user access. The system integrates various subsystems, including a high-voltage rectifier, Hartley-type oscillator, voltage multiplier, electron gun, acceleration section, cooling, and gas handling system. Each of the subsystems are equipped with local and/or central interlocks for enhanced safety. The control software, developed using IEC 61131-3 LADDER language and the graphical programming language "G", provides a user-friendly interface for real-time monitoring and adjustment of operational parameters. Currently operational at 500 kV and 10 mA, the system demonstrates effective electron beam irradiation control, ensuring compliance with radiation safety regulations. Future enhancements are planned to optimize performance and expand functionality for diverse experimental needs.

Bisphosphonates have a very high affinity for bone minerals because they bind to hydroxyapatite crystals. Based on this fact, it was hypothesized to evaluate bone uptake for 99mTc/188Re radiolabeled bisphosphonates to determine the order of uptake in the bone as agents for imaging or treatment of skeletal disorders. Radiolabeling of bisphosphonate samples were performed by adding 185 MBq of 99mTc/188Re in saline, and SnCl2, 2H2O and ascorbic acid as reducing agents. Radioactive thin layer chromatography (RTLC) was used to determine the radiochemical purity. The stability of radiocomplexes was investigated in saline and human serum. Bone uptake was evaluated through biodistribution experiments in normal mice. A radiochemical purity of >90% was obtained for evaluated radiotracers. Bone accumulation and rapid renal excretion were observed in the biological assessment of all evaluated bisphosphonates at 2 hours post injection. Although bone uptake was desirable for investigated bisphosphonates, it appears that third-generation bisphosphonates can be used as novel bone imaging or therapeutic agents.

Single-crystal graphite grown in highly preferred orientation of (002)-planes known as pyrolytic graphite is used in many research centers to make monochromatic neutron beam the exited neutrons from the radial beam channels of the research reactors. Simulation methods could be effectively used to predict the crystal behavior before time-consuming and high-cost experimental tests. The present work aims to investigate the effect of the PG(002) crystal fine tuning on the reflected neutron spectra quality in Tehran Research Reactor (TRR) D channel neutron beam line. Hence, Vitess3.4 and McStas neutron optic-based computational codes were used in the present work to study the mentioned parameter. To evaluate the obtained code data accuracy a benchmark study was carried out in the present work. The obtained simulations showed that fine adjustment of the crystal angle than the parallel incident neutron beam is very important. In addition, the crystal mosaic spread has noticeably effect on the reflected neutron intensity so that its change from 1.0° to 0.5° decreases the monochromatic neutron peak intensity about 12%. In addition, the simulations showed the crystal reflectivity change from 1 to 0.7 could decrease the monochromatic neutron peak intensity about 43%. Comparison of the experimental monochromatic reflected beam from PG(002) crystal with the carried out simulations showed there is good agreement between the two obtained spectra.

Am-241 is one of the transuranic elements that is used in measuring and controlling the thickness of various industrial materials, diagnosing thyroid disorders, smoke detectors production, designing neutron sources for well logging, etc. Therefore, due to the wide applications of this isotope, research and development for its production, separation, and purification are of great importance. Nowadays, the commercial production of this isotope is done in the United States and Russia. Since the production of Am-241is carried out from irradiated fuel of power reactors or irradiation targets in research reactors, in this work, the possibility of production and activity of this radionuclide from the irradiated fuel of a typical 1000 MWe and 360 MWe reactors has been investigated using the ORIGEN code. Results indicate the highest production of Am-241 in a 1000 MWe reactor. Therefore, the irradiated fuel of the 1000 MWe reactor can be a suitable source for the extraction of this isotope.