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- 저자 : GHOLAM REZA ANSARIFAR (검색결과 5 건)
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GHOLAM REZA ANSARIFAR,SAEED SAADATZI 한국원자력학회 2015 Nuclear Engineering and Technology Vol.47 No.7
One of the most important operations in nuclear power plants is load following, in which animbalance of axial power distribution induces xenon oscillations. These oscillations must bemaintained within acceptable limits otherwise the nuclear power plant could become unstable. Therefore, bounded xenon oscillation is considered to be a constraint for the loadfollowing operation. In this paper, the design of a sliding mode control (SMC), which is arobust nonlinear controller, is presented.SMCis ameansto control pressurized water nuclearreactor (PWR) power for the load following operation problem in a way that ensures xenonoscillations are kept bounded within acceptable limits. The proposed controller uses constantaxial offset (AO) strategy to ensure xenon oscillations remain bounded. The constant AO is arobust state constraint for the load following problem. The reactor core is simulated based onthe two-point nuclear reactor model with a three delayed neutron groups. The stabilityanalysis is given by means of the Lyapunov approach, thus the control system is guaranteedto be stable within a large range. The employed method is easy to implement in practicalapplications and moreover, the SMC exhibits the desired dynamic properties during theentire output-tracking process independent of perturbations. Simulation results are presentedto demonstrate the effectiveness of the proposed controller in terms of performance,robustness, and stability. Results show that the proposed controller for the load followingoperation is so effective that the xenon oscillations are kept bounded in the given region.
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GHOLAM REZA ANSARIFAR,MAESAM RAFIEI 한국원자력학회 2015 Nuclear Engineering and Technology Vol.47 No.1
This paper presents findings on the second-order sliding-mode controller for a nuclear research reactor. Sliding-mode controllers for nuclear reactors have been used for some time, but higher-order sliding-mode controllers have the added advantage of reduced chattering. The nonlinear model of Pakistan Research Reactor-1 has been used for higherorder sliding-mode controller design and performance evaluation. The reactor core is simulated based on point kinetics equations and one delayed neutron groups. The model assumes feedback from lumped fuel and coolant temperatures. The effect of xenon concentration is also considered. The employed method is easy to implement in practical applications, and the second-order sliding-mode control exhibits the desired dynamic properties during the entire output-tracking process. Simulation results are presented to demonstrate the effectiveness of the proposed controller in terms of performance, robustness, and stability
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SEYED MOHAMMAD MOUSAVIZADEH,GHOLAM REZA ANSARIFAR,MANSOUR TALEBI 한국원자력학회 2015 Nuclear Engineering and Technology Vol.47 No.7
The most important advantage of nanoparticles is the increased thermal conductivitycoefficient and convection heat transfer coefficient so that, as a result of using a 1.5%volume concentration of nanoparticles, the thermal conductivity coefficient would increaseby about twice. In this paper, the effects of a nanofluid (TiO2/water) on heat transfercharacteristics such as the thermal conductivity coefficient, heat transfer coefficient, fuelclad, and fuel center temperatures in a VVER-1000 nuclear reactor are investigated. To thisend, the cell equivalent of a fuel rod and its surrounding coolant fluid were obtained in thehexagonal fuel assembly of a VVER-1000 reactor. Then, a fuel rod was simulated in the hotchannel using Computational Fluid Dynamics (CFD) simulation codes and thermohydrauliccalculations (maximum fuel temperature, fluid outlet, Minimum Departure from NucleateBoiling Ratio (MDNBR), etc.) were performed and compared with a VVER-1000 reactorwithout nanoparticles. One of the most important results of the analysis was that heattransfer and the thermal conductivity coefficient increased, and usage of the nanofluidreduced MDNBR.
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Seyed Mohammad Hossein Mousakazemi,Navid Ayoobian,GHOLAM REZA ANSARIFAR 한국원자력학회 2018 Nuclear Engineering and Technology Vol.50 No.6
Various controllers such as proportionaleintegralederivative (PID) controllers have been designed andoptimized for load-following issues in nuclear reactors. To achieve high performance, gain tuning is ofgreat importance in PID controllers. In this work, gains of a PID controller are optimized for power-levelcontrol of a typical pressurized water reactor using particle swarm optimization (PSO) algorithm. Thepoint kinetic is used as a reactor power model. In PSO, the objective (cost) function defined by decisionvariables including overshoot, settling time, and stabilization time (stability condition) must be minimized(optimized). Stability condition is guaranteed by Lyapunov synthesis. The simulation resultsdemonstrated good stability and high performance of the closed-loop PSOePID controller to responsepower demand
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Ali Farsoon Pilehvar,Mohammad Hossein Esteki,Afshin Hedayat,GHOLAM REZA ANSARIFAR 한국원자력학회 2018 Nuclear Engineering and Technology Vol.50 No.5
Self-pressurization analysis of the natural circulation integral nuclear reactor through a new dynamicmodel is studied. Unlike conventional pressurized water reactors, this reactor type controls the systempressure using saturated coolant water in the steam dome at the top of the pressure vessel. Selfpressurizationmodel is developed based on conservation of mass, volume, and energy by predictingthe condensation that occurs in the steam dome and the flashing inside the chimney using the partialdifferential equation. A simple but functional model is adopted for the steam generator. The obtainedresults indicate that the variable measurement is consistent with design data and that this new model isable to predict the dynamics of the reactor in different situations. It is revealed that flashing andcondensation power are in direct relation with the stability of the system pressure, without whichpressure convergence cannot be established.
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