Radiation Physics and EngineeringRadiation Physics and Engineering
http://rpe.kntu.ac.ir/
Mon, 09 Dec 2019 06:43:39 +0100FeedCreatorRadiation Physics and Engineering
http://rpe.kntu.ac.ir/
Feed provided by Radiation Physics and Engineering. Click to visit.A fast Jacobian-Free Newton-Krylov iterative solver for eigenvalue search problems in the ...
http://rpe.kntu.ac.ir/article_89324_12055.html
‎The Jacobian-Free Newton-Krylov (JFNK) method has been widely used in solving nonlinear equations arising in many applications‎. ‎In this paper‎, ‎the JFNK solver is examined as an alternative to the traditional power iteration method for calculation of the fundamental eigenmode in reactor analysis based on even-parity neutron transport theory‎. ‎Since the Jacobian is not formed the only extra storage required is associated with the workspace of the Krylov solver used at every Newton step‎. ‎A new nonlinear function is developed for the even-parity neutron transport equation utilized to solve the eigenvalue problem using the JFNK‎. ‎This Newton-based method is compared with the standard iterative power method for a number of multi-groups‎, ‎one and two dimensional neutron transport benchmarks‎. ‎The results show that the proposed algorithm generally ends with fewer iterations and shorter run times than those of the traditional power method‎.Sat, 01 Jun 2019 19:30:00 +0100Optimization of beamline diameter in spot scanning proton therapy for minimization of secondary ...
http://rpe.kntu.ac.ir/article_89327_12055.html
‎Collision of protons with background gas and beamline wall in proton therapy causes the creation of secondary particles‎, ‎e.g. neutrons‎, ‎which results in more difficulties in curing the tumors‎. ‎In the present simulation-based study‎, ‎the optimum diameter of proton beamline was determined to minimize the production of secondary particles in the presence of electric field with the magnitude of 50 kV/m‎, ‎perpendicular equal magnetic fields of 0.7 T‎, ‎and background gas of argon under Bounce boundary conditions via finite element method‎. ‎The results showed that the optimum diameter of the beamline for minimization of the secondary particles in the spot scanning proton therapy in the aforementioned conditions was 7 mm‎. ‎Also‎, ‎the values of drift velocities of protons were plotted in different time steps of 10 ns to 50 ns for the optimized size of the beamline‎. ‎Due to few interactions of forwarding particles with background gas‎, ‎the results showed that the forwarding particles in the propagation direction have greater velocities than those of rear particles‎. ‎The results can be used in spot scanning proton therapy for curing the localized cancers‎.Fri, 31 May 2019 19:30:00 +0100Flow regimes classification and prediction of volume fractions of the gas-oil-water three-phase ...
http://rpe.kntu.ac.ir/article_89328_12055.html
‎The used metering technique in this study is based on the dual energy (Am-241 and Cs-137) gamma ray attenuation‎. ‎Two transmitted NaI detectors in the best orientation were used and four features were extracted and applied to the model‎. ‎This paper highlights the application of Adaptive Neuro-fuzzy Inference System (ANFIS) for identifying flow regimes and predicting volume fractions in gas-oil-water multiphase systems‎. ‎In fact‎, ‎the aim of the current study is to recognize the flow regimes based on dual energy broad-beam gamma-ray attenuation technique using ANFIS‎. ‎In this study‎, ‎ANFIS is used to classify the flow regimes (annular‎, ‎stratified‎, ‎and homogenous) and predict the value of volume fractions‎. ‎To start modeling‎, ‎sufficient data are gathered‎. ‎Here‎, ‎data are generated numerically using MCNPX code‎. ‎In the next step‎, ‎ANFIS must be trained‎. ‎According to the modeling results‎, ‎the proposed ANFIS can correctly recognize all the three different flow regimes‎, ‎and other ANFIS networks can determine volume fractions with MRE of less than 2% according to the recognized regime‎, ‎which shows that ANFIS can predict the results precisely‎.Fri, 31 May 2019 19:30:00 +0100A simulation study on neutronic behavior of non-fissionable and fissionable materials of ...
http://rpe.kntu.ac.ir/article_89329_12055.html
‎Spallation process is the most significant process for neutron generation in industry and medicine‎. ‎This process has been used in the subcritical reactor core‎. ‎In this research‎, ‎we study the neutronic behavior of non-fissionable and fissionable spallation targets consists of U-238‎, ‎Th-232‎, ‎Lead Bismuth Eutectic (LBE) and W-184 materials in cylindrical and conic shapes using MCNPX code‎. ‎Neutronic parameters consist of spallation neutron yield‎, ‎deposition energy‎, ‎and angular spectrum of the neutron output‎. ‎The gas production rate and residual mass spectrum were investigated‎. ‎The results of this research indicate that the shape of the target must be selected based on target material and operational purposes‎. ‎The number of neutrons per energy unit is stable at energies higher than 1 GeV‎, ‎and the rate of change in neutron generation has been reduced after that‎. ‎Furthermore‎, ‎hydrogen is the principal factor in swelling of spallation target and consists of about 88% of gas production‎. ‎It was found that a target of LBE provides the most favorite parameters for both neutronic and physical properties‎.Fri, 31 May 2019 19:30:00 +0100An analytical and Monte Carlo investigation of the sufficiency of the present shielding of ...
http://rpe.kntu.ac.ir/article_89330_12055.html
‎By the rapid development of imaging systems such as PET/CT for diagnosis of cancer‎, ‎the protection of staff and public has become a main health concern‎. ‎Due to serious and irreversible harms of ionization radiations‎, ‎protection of all those who are exposed is the main concern of health issues‎. ‎The main basis of the calculation of the shielding design in the medical imaging systems is that the absorbed dose should not exceed the allowed limit‎. ‎In this study‎, ‎the current shielding status of the PET/CT installations in Tehran's Shariati hospital was investigated using the MCNPX Monte Carlo code to ensure that the dose limits for both the controlled and uncontrolled area are not violated‎. ‎The proposed simulation method was benchmarked with a validated analytical method‎. ‎Shariati hospital provides services to four patients every day‎, ‎leading to a dose rate in the range of 2.6 × 10-6 to 9.35 × 10-3 mSv/week‎. ‎The minimum dose rate in this range represents the value behind the door of the waiting room (public uncontrolled area)‎, ‎while the maximum in this range corresponds to the value behind the glass of the scanner room (operator controlled area)‎. ‎The simulation results for 8 patients/day in this center showed that the dose rate behind the wall of the injection room will increase from 4.88 ×10-6 mSv/week to 2.81 × 10-2 mSv/week‎, ‎which is well below the recommended levels‎. ‎This indicates that the present shielding is adequate for up to four more patients per day‎.Fri, 31 May 2019 19:30:00 +0100