Numerical Simulation On Coolant Temperature Fluctuation From The Outlet Of The Core In China Experimental Fast Reactor

In the outlet of the core of the fast reactor, the coolant temperatures from different channels are different. The temperature fluctuation phenomenon will occur when the hot and cold fluids are mixed in the upper plenum of the core. It may cause thermal striping and even affect the safety of the reactor. In this article, the mixing process of the hot and cold fluids from the outlet of the core in China Experimental Fast Reactor was simulated using the large eddy simulation (LES) model. Considering the focus of this research we simplify the model. Based on China Experimental Fast Reactor actual operating parameters we designed four conditions and some measuring points on typical location to simulate the mixing process. We used dimensionless method to process each condition of transient temperature, and got transient temperature curves of the mixing area. The results show that the location of the large temperature fluctuations is on cold and hot fluid intersection, the amplitude of temperature fluctuations is increasing with the vertical height increases. When the fluid temperature remains constant, on the same height the fluctuation characteristics are similar where the cold and heat fluid intersection. For the same point, different fluid conditions only affect the amplitude, almost never affect the frequency. The lager temperature difference is, the greater amplitude is. In a word, temperature difference affects the amplitude, and the frequency of the fluctuation which has great amplitude is mainly of0-3Hz,5-10Hz,13-15Hz.