Natural Circulation Research On Trough Instability Under Rolling Motion

This article uses a rolling experimental device in Harbin engineering university to simulate flow state of the primary loop in reactor under natural circulation condition. Make a simplification of the experimental device; calculate the change of flow rate and thermal parameters etc.This paper mainly studies the natural circulation trough instability under rolling motion.Through the analysis of experimental data, we find out that the steam production temperature is subcooled. According to the empirical relationships used to calculate subcooling, the results is different from this experiment, so this paper build the model to calculate trough instability based on the experimental data. The calculated results and the experimental values are compared and they fit well. After the construction of the trough instability model, analyze the causes of trough instability and affecting factors when trough instability occurred. We also analyzed the impact of the amplitude of the swing, the period of swing, the inlet subcooled temperature on trough instability.This paper analyzes the changes when considering nuclear thermal coupling effects and the condition not considering nuclear feedback, also analyzes the changes when feedback coefficients are different, at last analyses the impact of different feedback system on system parameters.Use C # program to calculate, according to the calculation results, the following conclusions can be made:When trough instability happens, the flow fluctuation amplitude increases, and present asymmetric form in wave trough; near the trough of flow rate, the frictional pressure drop and gravity pressure drop dominate flow alternately after the generation of steam.After the change of the swing parameters, the power corresponding to the trough instability starting point decreases along with the increase of swing intensity Change the inlet temperature in heating section entrance, the power corresponding to the trough instability starting point increases along with the increase of sub-cooled temperature; After changing the system pressure, the power corresponding to the trough instability starting point increases along with the increase of system pressure.After considering the feedback of nuclear feedback, power began to fluctuate. due to fluctuation of the fluid obtained power becomes small, the water temperature fluctuation becomes smaller; wall temperature fluctuations becomes smaller due to the wall heat storage fluctuation amplitude decreases. Due to the void negative feedback, steam production time becomes shorter,the asymmetric trend of flow rate becomes gentle,nuclear feedback has a slight suppress tendency on trough instability. When increasing the feedback coefficients, the reactivity fluctuation become larger, and fluctuation of the power becomes large; when considering only the coolant feedback, power decreases; when fuel feedback is only considered, power increases; when void feedback is only considered, power decreases. When three feedbacks are considered, the amplitude fluctuation of power is the biggest.