Numercial investigation of the thermal fatigue issue in the next generation nuclear power plants

Strong temperature fluctuations caused by turbulent mixing of cold and hot fluid streams may occur in the variety of places inside a nuclear power plant. The structural materials subjecting to the strong temperature fluctuations may cause thermal fatigue failure. Since the supercritical fluids are supposed to be used widely in the next generation nuclear power plants, this paper aims at investigating the temperature fluctuation characteristics in a Tee junction using supercritical water as coolant. A three dimensional computational fluid dynamics (CFD) numerical model is developed using commercial software FLUENT. The measures to reduce the temperature fluctuations such as applying porous media and changing the inclined angles are investigated. It is concluded that the porous media can smooth away the fluctuations in the mixing zone region, and the thermal fatigue issue can be improved by changing the inclined angles.