Radiation Physics and Engineering
Volume:5 Issue: 2, Spring 2024

In this research work, commercial beta-tricalcium phosphate powder is converted into tablets by pressure-less sintering method. Thermoluminescence responses of tablet and powder samples in the dose range of 20 to 1500 Gy have been compared and effective factors in tablet conversion such as mass in the range of 30 to 60 mg, force between 1 to 3 N, concentration of granulating solution and tablet diameter in the range of 0.4 to 15 mm are investigated based on the results of dosimetric response and tablet hardness. The results show that by turning into tablets, the grain size increases, and the possibility of the first-order kinetics increases by the conversion of powders into tablets. It is possible to achieve a better dosimetric response than the it’s powder by applying suitable conditions for turning into tablets; also, the diameter of the sample can affect hardness, and it is better to make the tablets with a smaller size. Based on the results obtained from fading, reproducibility, sensitivity, peak shaping of the glow curve, and microhardness measurement, it can be seen that the samples that have been subjected to less pressure perform better and in order to achieve the desired results of converting to TLD dosimetry tablets, it is better to use more mass for tablets if more pressure is needed.

In this analysis, nanofluid properties are evaluated by interaction correlations between particles using molecular dynamics (MD) method, and thermal-hydraulics characteristics of nanofluids in a WWER-1000 reactor is investigated by Computational Fluid Dynamics (CFD). This study conceptualizes power increase by changing the cooling from pure water to nanofluid without changing the safety parameters. The Copper nanoparticles are used in primary loop cooling system, to evaluate the heat removal from the core. Thermophysical properties such as thermal conductivity and shear viscosity of Cu-Water nanofluids are obtained by MD in operating pressure and temperature of the Bushehr reactor core. These properties have been used in thermal-hydraulics analysis and nanofluids are considered as a homogeneous fluid. Thermal hydraulic properties of coolant have been calculated for different volume fractions of nanofluids. Thermal hydraulic simulation illustrated enhancement of the thermal characteristics of the core, due to the increment in heat transfer coefficient and thermal diffusivity. The thermal-hydraulic analysis of the reactor core has been performed in steady state at different powers. The requirements for changing the reactor power are not to change the fuel center temperature and Outer Cladding Surface temperature compared to the current state.

Metal surface cleaning or etching techniques using reactive plasma are emerging as one of the dry processing techniques for surface contaminants with high bond energy, especially for cleaning and decontamination of nuclear components and equipment. In this study, the plasma reaction due to the discharge of a dielectric barrier of a mixture of 95% helium and 5% fluorine with cobalt oxide film (Co3O4) grown on the surface of stainless steel 304 was studied experimentally. Experimental results show that cobalt oxide becomes a powder after plasma irradiation and is easily separated from the surface of the base metal. The optimal plasma generating conditions of the dielectric barrier discharge used in this experimental study were obtained at atmospheric pressure, voltage 4.5 kV, and frequency 25 kHz with an etching rate of 10.875 μmol.min-1. The samples were analyzed before and after plasma irradiation, using Scanning Electron Microscopy with Energy Dispersive X-ray spectroscopy and the purification rate was performed using a sequential weighting of the samples with scales 10-4 g accurately obtained. The results show the ability of this method to effectively remove the surface contamination of cobalt from the surface of stainless steel 304.

Radiation therapy aims to maximize doses to cancer cells while minimizing damage to normal tissues. Today, nanoparticles containing high-atomic-number elements, such as gold, gadolinium, and silver, have proven effective as radiosensitizers in radiotherapy to enhance dose delivery for cancer treatment. In this study, we used the Geant4-DNA toolkit to investigate the effects of multiple nanoparticles (NPs) with varying sizes (radius= 3.15 to 5 nm) on DNA damage when exposed to monoenergetic photons with energies of 15, 40, 50, and 68 keV. Direct and indirect single-strand breaks (SSBs), double-strand breaks (DSBs), and hybrid double-strand breaks (Hybrid DSBs) were calculated in the presence and absence of 1 to 4 nanoparticles (NPs) of the same total volume of gold, gadolinium, and silver nanoparticles for the 1ZBB model (selected from the Protein Data Bank (PDB) library). The results show that increasing the number of gold, gadolinium, and silver NPs and decreasing the photon beam energy increases the total number of strand breaks. Furthermore, gold nanoparticles (GNPs) are more effective options than gadolinium nanoparticles (GdNPs), and silver nanoparticles (SNPs) for inhibiting and controlling cancer cells.

New nitrile butadiene rubber (NBR) materials are being considered to use for neutron shielding especially for the positions which needs a flexible neutron shield. Such light, low-cost, and suitable material could be used for sealing of the gaps or even for shielding of low radiation environments. In the present work, experimental investigation of NBR shielding performance of neutrons and gamma rays was proposed using the beam line of the Isfahan Miniature Neutron Source Reactor . MCNPX code was used to simulate the 30 kW research reactor beam line. Six NBR sheet with 2 cm thickness were used at the outlet of the beam line respectively to measure its neutron shielding as well as gamma shielding power on thickness. The experiment situations were modeled using the computational code. The obtained results showed the flexible and cheap material could be used as a good neutron shield while it acts as a very weak shield for gamma rays too. Also there is good conformity between simulation and experimental data with maximum 37% relative discrepancy.

Plasma technology has undeniably revolutionized industrial processes in recent decades. Atmospheric pressure plasma (APP) has emerged as a prominent and widely applicable tool in various scientific disciplines. Notably, plasma-assisted flow control has become a subject of intense interest, particularly applying surface dielectric barrier discharge (SDBD) plasma actuators for aerodynamic flow control. In this study, a two-dimensional model of the SDBD plasma actuator is developed using the COMSOL Multiphysics program, incorporating air gas discharge reactions with N2/O2/Ar gases in specific ratios (0.78, 0.21, 0.01). The investigation focuses on the impact of dielectric materials (mica, silica glass, quartz, and polytetrafluoroethylene (PTFE)) on plasma characteristics and body force within the plasma actuator under constant input parameters. Moreover, the study explores how variable pressure (760, 660, and 560 torr) in different applications influences plasma properties, ultimately affecting the magnitude of the body force in the plasma actuator. These findings contribute to optimizing plasma technology for flow control applications and enhance industrial efficiency and performance.

The estimation of flux in radiation transport Monte Carlo problems needs to calculate the volumes and surface areas of the geometric regions. The particle flux is often estimated as the track length per unit volume or the number of particles crossing a surface per unit area in Monte Carlo transport problems. Various representations such as constructive solid geometry (CSG), boundary representation (B-Rep), and combinatorial geometry (CG) are proposed in the literature for geometry modeling and calculation of surface area and volume. MCNP series and OpenMC as Monte Carlo particle transport codes utilize CG modeling and are not able to calculate surface area as well as volume for non-rotationally symmetric or non-polyhedral cells. In this work, a comprehensive approach based on the Cauchy-Crofton formula using the Monte Carlo method has been implemented to the radiation transport codes as an extra module for computing surface area and volume of complex geometries. We used a random sampling procedure to create the required probe lines and points in the computational approach. The results show that this method can accurately compute surface areas and volumes of complex geometries with a relative error of less than 0.1% and a short computation time of a few seconds, which is not achievable with the cuurent MCNP and OpenMC modules.

The International Atomic Energy Agency (IAEA), sends dosimeters annually to Secondary Standard Dosimetry Laboratories (SSDL) around the world, to calibrate their radiation field. Therefore, they mainly send thermo-luminescent dosimeters as transfer dosimeters to the SSDL laboratories, to be irradiated under the requested conditions and sent back to the IAEA laboratories for reading. In this way, by reading the dosimeters, the uncertainty of the dosimetry carried out by SSDL and, consequently, the calibration of its radiation fields is determined. In this research, with the aim of feasibility of comparative dosimetry program by SSDL laboratory for radiation therapy centers, this program was carried out for a number of centers. In this way, TLD-700 thermoluminescence dosimeters were irradiated in the same conditions in the SSDL laboratory and also in the selected centers to a certain amount. After reading and applying the correction coefficients and calibration factors, the obtained results were compared with the measurement results using ion chamber reference dosimeter. In this work the uncertainty of the dosimetry using TLD tablet was less than 1.12% in comparison to the reference ionization chamber dosimeter and was within the acceptable range of less than 3%.