Hamed Kargaran
Abstract
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. ...
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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.
Mostafa Heydari; Hamid Jafari; Zohreh Gholamzadeh
Abstract
The neutron transmutation doping method is widely used in various fields, such as solar cells, hybrid cars, etc. The Silicon doping process can provide direct commercial income for nuclear research reactors. In this study, we aim to find the optimal location for silicon doping in the thermal column ...
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The neutron transmutation doping method is widely used in various fields, such as solar cells, hybrid cars, etc. The Silicon doping process can provide direct commercial income for nuclear research reactors. In this study, we aim to find the optimal location for silicon doping in the thermal column nose of the Tehran research reactor. For this purpose, computational MCNPX and ORIGEN2 codes were used to calculate the neutronic and radioactivity parameters of the silicon ingot. The important parameters such as the thermal to fast neutron ratio, heat deposition by gamma and neutron, and the radioactivity level of the silicon ingot and the produced radioisotopes have been determined to obtain the optimal irradiation channel. The results showed that the irradiation channel placed in the thermal column at a distance of 90 cm from the center of the TRR core has optimal conditions for the implementation of silicon doping. The channel provides a thermal neutron flux in order of 1.721012 n.cm-2.s-1 which is the least acceptable value to achieve a proposed neutron fluence during the operation cycles of TRR reactor. Also, the channel has the least possible heat deposition inside the silicon ingot of about 191 W. In addition, the thermal to fast neutron flux ratio of about 311 is enough higher than the determined IAEA limit for NTD.
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.
