Research On The Characteristics Of The Different Media Effect On Flow Instability

With the fast development of the nuclear power,the long life nuclear waste disposal has been a tough problem.Refer to the international research in this flied, a lot of basic research on transmutation have been done. Accelerator driven subcritical reactor is one of the most promotion transmutation technology,as the candidate spallation target and coolant materials for ADS, lead bismuth eutectic is received widespread attention. It is a key issue to study the flow and heat transfer, and there was little about the stability of the lead-bismuth at natural circulation. So the paper one of the major points is the stability problem. The other point is comparitively study the stability of lead-bismuth, experimentally sudy the instability of the water, and theoretically study the instability of suduim.The paper using the FLUENT code to modeling and analyzes the2D loop of the lead-bismuth eutectic.Detailed research of the lead-bismuth fluid about the flow rate and heat transfer with the numercial method had done.Firstly. Using the CFD code FLUENT studied the velocity field and tempertature field in heating section. Compared with the experimental results of Karsten Litfin.etc. which verified the applicability of the selected turbulent model which lay the foundation for the natural circulation simulation.Then building the2D geometrical model for the natural circulation, finishing the gird divison. It was assumed two models that were2m and4m with different hight difference. There were four situations of the2m model and4m model were calculated. Compared with the influence of the hight difference of the two models:the more of the hight difference, the circulation flow rate is bigger, and the time settle to the new stable state is longer after introduction of a certain disturbance. Vibration period and amplitude of the higher hight difference were bigger than the small one’s. Added power to the models can obtain that:the heating power is increased to a certain extent, and the circulation flow rate can increase.So we can think of that the lead-bismuth will be a short instability in some situations.Experimentally sudy the instability of the water, and theoretically study the instability of suduim. It shows that the water has density wave and flow excurion, and the sodium has density wave. Based on the above research and literature summary, I do research of the instability about the lead-bismuth, water, sodium liquid and discuss the same or difference of the occurred conditions, generating process and the types. It shows that changeable intensity of the itself characters of media is very important to the instability; the structure of the geometry also plays a important role in the instability. Lastly, conbined with the actual conditions, the experimental facility and the components of the natural circulation system of the lead-bismuth were designed. An experiment plan were proposed combine with actual conditions. This research work for subsequent lead bismuth test bench construction and lead bismuth natural circulation flow heat transfer experiment laid the foundation.