Zohreh Gholamzadeh; Rohollah Adeli; Mahdi Keivani
Abstract
Routine gamma dosimetry of spent fuels in nuclear power stations is mandatory to manage their storage in dry or wet spent fuel storages. Mostly the spent fuel gamma dose rate measurements out of the spent fuel pool is impossible because of the high exposures of the operators. Therefore, ...
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Routine gamma dosimetry of spent fuels in nuclear power stations is mandatory to manage their storage in dry or wet spent fuel storages. Mostly the spent fuel gamma dose rate measurements out of the spent fuel pool is impossible because of the high exposures of the operators. Therefore, determination of a conversion factor as precise as possible is important that could be applied to convert the measured gamma dose rate inside the water shield to the air values. Simulation methods are powerfully applied to investigate the conversion factor variation trends due to different burnup, cooling time and irradiation history of the spent fuels. The present work uses MCNPX Monte Carlo-based code to determine the trend. The obtained results of this computational study showed that the conversion factor would not have any dependency to the cooling times, burnup values and irradiation history if the detector is placed at special positions in air or water environments. Comparison of the simulation and experimental data showed an acceptable conformity, so that the experimental verified the simulation data trend
Faezeh Rahmani; Ali Taaghibi Khotbesara; Farshad Ghasemi
Abstract
This work presents an alternative method for Mo-99 production as a parent nuclide of Tc-99m which is the most used radioisotope in diagnostic imaging processes. Regarding to some benefits of accelerator-based methods over reactor-based methods for Mo-99 production, the electron ...
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This work presents an alternative method for Mo-99 production as a parent nuclide of Tc-99m which is the most used radioisotope in diagnostic imaging processes. Regarding to some benefits of accelerator-based methods over reactor-based methods for Mo-99 production, the electron Linac-based method has been selected. In this way of production, two approaches (one-stage and two-stage) are available using photoneutron reaction in Mo-100 target using bremsstrahlung photons. The superiority of one-stage approach and optimal dimension of target has been demonstrated by nuclear simulation using MCNPX2.6 code. Thermal analysis of the optimized target has been performed by COMSOL software, which has been led to select the indirect cooling system. The final suggested conceptual design of the target includes nine Mo-100 stripe plates with 0.2, 3, and 30 cm in thickness, width and length, respectively which being surrounded by two copper clamps as the cooling ducts. The velocity of 2.5 m/s of inlet coolant (water) is sufficient for the suggested cooling system to satisfy the conditions of the turbulent regime as the desired cooling regime.
Mahdi Eshghi
Abstract
The buildup factor is becoming a required parameter for exposure and energy absorption in the area of radiation physics for shielding, dosimetry, health physics and medical physics. In this research, photon buildup for dysprosium doped lithium magnesium borate glasses system has been investigated. Photon ...
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The buildup factor is becoming a required parameter for exposure and energy absorption in the area of radiation physics for shielding, dosimetry, health physics and medical physics. In this research, photon buildup for dysprosium doped lithium magnesium borate glasses system has been investigated. Photon energy absorption buildup factors and photon exposure buildup factors were computed for the chosen glasses using the five-parameter geometric progression fitting method in energy range of 0.015 MeV to 15 MeV. Also, effective and equivalent atomic numbers were calculated for these compositions and discussed for possible implementation in radiation dosimetry.
Payman Rafiepour; Shahab Sheibani; Daryiush Rezaey Uchbelagh; Hossein Poorbaygi
Abstract
Radioactive stents loaded with I-125 seeds have been widely used for the treatment of advanced esophageal cancer. Understanding the dose distribution of such stents before the clinical use is essential. This study provides a dosimetric investigation of I-125 seed-loaded stents based on the seed's arrangement ...
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Radioactive stents loaded with I-125 seeds have been widely used for the treatment of advanced esophageal cancer. Understanding the dose distribution of such stents before the clinical use is essential. This study provides a dosimetric investigation of I-125 seed-loaded stents based on the seed's arrangement and activity. A cylindrical water equivalent phantom with an esophageal stent loaded with I-125 seeds, were employed. The seeds arrangements were determined based on the distance between the centers of two adjacent seeds (z) along the stent length. EBT3 films as well as Geant4 Monte Carlo toolkit were used to obtain the dose distribution around the stent. By modeling the MIRD phantom, the dose delivered to the related organs at risk was calculated. The appropriate dose distribution is achieved for z=15 mm, in which the absorbed dose at a depth of 5 mm reaches about 45% of the absorbed dose near the stent surface, thereby the therapeutic dose is delivered to the reference points. Both arrangements (z=15 and 20 mm) seemed to be clinically eligible and their utilization depends on the patient and the hospital facilities. Using esophageal stents with z>20 mm is not recommended due to the presence of cold spots in the dose distribution.
Zohreh Gholamzadeh; Atieh JozVaziri
Abstract
Thorium is more abundant in nature than uranium. The fertile thorium fuel can breed to fissile U-233 by absorbing a neutron. The produced fissile has good neutronic performance in both thermal and fast neutron spectra. Many types of thorium-based fuels were applied ...
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Thorium is more abundant in nature than uranium. The fertile thorium fuel can breed to fissile U-233 by absorbing a neutron. The produced fissile has good neutronic performance in both thermal and fast neutron spectra. Many types of thorium-based fuels were applied in different nuclear reactors. Also natural thorium oxide is used as seed/blanket configuration that the ThO2 rods are used in the outer sections of any fuel assembly. The present study aims to investigate the ThO2 fuel rod loading in 3000 MW VVER-1000 power reactor. MCNPX and ORIGEN codes were used to evaluate its effects on the core neutronic. In addition, the gamma emission rates of ThO2 spent fuel than the UO2 routine fuel of VVER-1000 was investigated. The obtained results of the computational study showed the ThO2 fuel rod loading in some VVER-1000 fuel assemblies would not end to a breeding behavior of the reactor core even after one-year burnup at 3000 MW power. However, the enriched uranium fuel loading reduction may make a motivation for thorium fuel application in the power reactor.
Berat Can Karatas; Ho Namgoong; Hoseung Song; Donghyup Ha; Jong-Seo Chai; Mitra Ghergherehchi
Abstract
A four-sector 14 MeV azimuthally varying field H-type cyclotron magnet has been designed for positron emission tomography (PET) at Sungkyunkwan University. Compactness, feasibility, and high performance are among the main factors that were considered in the design, which is ultimately intended made for ...
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A four-sector 14 MeV azimuthally varying field H-type cyclotron magnet has been designed for positron emission tomography (PET) at Sungkyunkwan University. Compactness, feasibility, and high performance are among the main factors that were considered in the design, which is ultimately intended made for use in hospitals and research institutes. After optimizing the initial parameters using the shimming method, an isochronous magnetic field along the cyclotron radius through Opera-3d was investigated. The particle trajectories were also illustrated. The Cyclone equilibrium orbit code program was used to examine the radial and axial betatron oscillations in relation to the cyclotron operating points. In addition, the integrated phase shift was explained and compared to the Korea Institute of Radiological Medical Sciences 13 MeV cyclotron (KIRAMS-13). In conclusion, the final shape magnet satisfied the orbital stability requirements. The RF cavity, vacuum pump, and injection system could be employed efficiently, and a reliable agreement was reached between KIRAMS-13 and our design characterization.
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