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Numerical Simulation of Steam Explosion under the Condition of Severe Accidents of Nuclear Power Plants

Author: HuangXi
Tutor: YangYanHua
School: Shanghai Jiaotong University
Course: Nuclear Energy Science and Engineering
Keywords: Serious accident of the nuclear power plant Steam explosion Numerical Simulation Multiphase flow Melt water interaction
CLC: TL364.4
Type: Master's thesis
Year: 2011
Downloads: 153
Quote: 0
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Abstract

Severe accident in a nuclear power plant, the core melting and cooling water interaction may lead to the phenomenon of steam explosion, steam explosion process is accompanied by the generation of enormous energy and pressure wave may cause structural failure of containment, leading to the release of radioactive fission products to the environment in. Therefore, it is necessary to study under the serious accident of the nuclear power plant steam explosion phenomenon and its negative effects were evaluated. In addition, because China is still a lack of development of melt thermal-hydraulic program, therefore melt thermal-hydraulic numerical simulation program developed essential. The main means of numerical simulation, the first to use the the French IRSN developed three-dimensional multiphase melt the material thermal hydraulic program MC3D million-kilowatt nuclear power plant steam explosion negative effects were analyzed and evaluated. In addition, in the two-dimensional melt JASMINE-PRO source based on the thermal-hydraulic CFD program modification and optimization of the modified program applicability. Use than the new model, the stability program, and faster calculation advantage MC3D program in the study of steam explosions, so use MC3D million-kilowatt nuclear power plant steam explosion negative effects were analyzed and evaluated, first establish two dimensional model, the use of more sophisticated grid Analysis calculated for steam explosion phenomenon, studies show that the high temperature core melt into the cooling water to and interacting, first through a coarse mixing process, this process, in the interaction region, pressure changes does not affect the integrity of the reactor vessel and the containment negligible. Once the steam explosion process occurs, the molten material and the cooling water the mixing region will appear with a time duration is very short, the peak high pressure pulse, interested in the reactor cavity, the safety shell structure cause great damage. Furthermore, the payload size of the steam explosion process pressure decreases with distance explosive increase in the trigger position, the larger the sum of the volume of the contact with the cooling water in the reactor vessel the molten droplets, to produce pressure pulses greater the vapor explosion is triggered at that moment. Consider maintain melt heap the serious external cooling of coolant accident mitigation the measures (IVR-ERVC) case, to create a three-dimensional model for the million-kilowatt nuclear power plant, from the geometric structure sensitivity parameters to discuss different sensitive the impact of the negative effects of parameter changes in the steam explosion, and comprehensive parameter values ??lead to negative effects of the steam explosion, the worst accident conditions. In this condition, the peak steam explosion process pressure is high, long duration produce punch large, may result in structural failure of the reactor vessel, very dangerous. In addition, for the three-dimensional model of the nuclear power plant steam explosion sampling, and ultimately to obtain the probability distribution of the steam explosion load. Currently is not yet developed a special calculation of the steam explosion process, including melt thermal-hydraulic program, it is therefore necessary for the study of such problems in program development. This article from the conservation equations and numerical methods amount JASMINE-PRO program source code, program optimization and modify. First of all, because the program is used in the pressure correction equation not using the continuity equation of an order upwind discrete derived, and therefore a certain degree is not consistent with the volume share of the calculated flow field continuity equation, therefore, the pressure correction The equation to be modified so that the conservation of the program greatly improved; On the other hand, numerical methods of the program is optimized to improve the PISO method modified twice the pressure correction, enhance the convergence rate of the program. Melt droplet fragmentation accordance with MC3D use the melt groats model, modified fragmentation model used in the modified program. Completion of the optimization program and modify the program applicability. Applicability analysis shows that the applicability of the program to modify optimized expansion has been a certain degree of convergence speed, stability has also greatly improved.

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CLC: > Industrial Technology > Nuclear technology > Engineering of Nuclear Reactors > Reactor safety and control > Reactor safety > Reactor accidents and their analysis
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