Articles
Ayoobian, N.,
Khodadadi h., H.,
Mokhtari j., ,
Abbassi y., Y. Publication Date: 2024
Nuclear Engineering and Design (00295493)427
This paper analyses the thermal–hydraulic performance of a proposed 50-kW aqueous homogeneous reactor (AHR) aimed at producing Mo-99. The reactor thermal–hydraulic characteristics are analyzed using ANSYS-FLUENT software and Relap code, and the results are validated through experiments conducted by a prototypic cylindrical sector of the reactor vessel. Boundary conditions in the CFD simulation are set up based on Relap modelling, while CFD outputs are validated by experimental results achieved using the laboratory model. Then, various parameters, including coolant mass flow rate, first cycle pipe diameter, coolant outlet temperature, average fuel solution temperature, and the elevation difference between the reactor and heat exchanger, are optimized using the least-squares optimization method. Results demonstrate that the heat removal system provides sufficient cooling capacity to ensure stable operation of the proposed AHR core by preventing fuel solution overheating and, consequently, boiling (void formation) in the active fuel solution. © 2024
Publication Date: 2022
Journal of Instrumentation (17480221)17(11)
Electron linear accelerator (LINAC) is a high-energy X-ray generator with extensive industrial, inspection, and medical applications. The studied LINAC uses a 2.6 MW magnetron as its RF generator derived with a Marx modulator. An electron gun of filament voltage 6 V and current 2.2 A connected to the accelerator tube is applied to establish electron current inside the drift tube. For this purpose, 9 kV and 25 kV voltages are applied to the cathode and anode of the electron gun pulse by pulse, generating dual-energy x-ray beams as outputs. An Automatic Frequency Control (AFC) system is designed for studied LINAC so that variation of output dose rate is lower than 2% and the required time to achieve the maximum output dose rate is lower than 1 s. Optimizing the Marx modulator's switching algorithm, the ripple in the output beam has been lower than 5%. The half-value layer (HVL) of steel has been measured for high and low energies equal to 6 MeV and 3 MeV, respectively. The output pulse of the electron beam and dose rate have been measured using a linear detector array (LDA) and dosimeter, respectively, with a pulse frequency of 35-400 Hz and pulse width of 2-4 μs. © 2022 IOP Publishing Ltd and Sissa Medialab.
Publication Date: 2021
Nuclear Engineering and Technology (2234358X)53(1)pp. 266-272
In the pulsed electron beam generators, such as plasma focus devices and linear induction accelerators whose electron pulse width is in the range of nanosecond and less, as well as in cases where there is no direct access to electron beam, like runaway electrons in Tokamaks, measurement of the electron energy spectrum is a technical challenge. In such cases, the indirect measurement of the electron spectrum by using the bremsstrahlung radiation spectrum associated with it, is an appropriate solution. The problem with this method is that the matrix equation between the two spectrums is an ill-conditioned equation, which results in errors of the measured X-ray spectrum to be propagated with a large coefficient in the estimated electron spectrum. In this study, a method based on the neural network and the MCNP code is presented and evaluated to recover the electron spectrum from the X-ray generated by collision of the electron beam with a target. Multilayer perceptron network showed good accuracy in electron spectrum recovery, so that for the X-ray spectrum with errors of 3% and 10%, the network estimated the electron spectrum with an average standard error of 8% and 11%, on all of the energy intervals. © 2020 Korean Nuclear Society
Publication Date: 2021
Thermal Engineering (00406015)68(12)pp. 922-929
Abstract: Computational Fluid Dynamics (CFD) is widely used in different industrial applications. In this research, the application of CFD in the thermo-hydraulic evaluation for a typical small modular Pressurized Water Reactor (PWR) was studied using ANSYS Fluent software. First, reactor core with different (pitch—fuel rod diameter) was simulated using MCNP code. Subsequently, axial neutron heat flux was calculated in the hottest rod. In the following, different fuel channels were simulated using ANSYS workbench and corresponding mass flow rate according to the fluid outlet temperature was computed using Fluent. Then, thermo-hydraulic parameters including pumping power, convective heat transfer coefficient and turbulent intensity were calculated. Artificial neural network (ANN) coupled with genetic algorithm (GA) was used for optimization; and pair pitch ‒ fuel rod diameter (0.012 m, 0.0072 m) was selected as the optimum value. Also, Critical Heat Flux (CHF) was computed with CFD-simulation, and compared with Tong CHF correlation and Groeneveld look-up table. A good agreement was observed between results, but CHF obtained from CFD simulation was more conservative. According to the results, Minimum Departure from Nucleate Boiling Ratio (MDNBR) was obtained as 2.12, which was compatible with its typical value. Accordingly, it could be concluded that the optimum reactor core was in the safe mode in the steady state conditions. © 2021, Pleiades Publishing, Inc.
