Research On The Occurrence And Development Law Of Backflow In U-tube Of Steam Generator Based On RELAP5 Program

On the road of building a maritime power in my country,nuclear energy has received widespread attention due to its advantages such as high energy density and no oxygen required for fission reactions.Nuclear-powered ships have also been vigorously developed because nuclear energy can provide strong endurance and propulsion power.As one of the important equipment of nuclear reactor system,steam generator has always attracted attention.However,studies have found that under certain conditions,a small portion of the coolant in the U-tube in the steam generator will flow backwards,which will reduce the effective heat transfer area of the steam generator and reduce the flow through the reactor core.Ships operate under ocean conditions,and ocean conditions will further affect the flow of coolant.Therefore,the research on the reverse flow of steam generators under ocean conditions is of great significance.This paper first analyzes the various factors that affect the U-tube backflow,and then calculates the U-tube steam generator under three ocean conditions(inclination,undulation,sway),and compares the results with the land-based conditions to obtain a land-based The development law of the reverse flow of the U-tube of the steam generator under the ocean conditions and the law of the influence of the ocean conditions on the reverse flow of the U-tube of the steam generator.Under natural circulation conditions,the greater the swing amplitude or the shorter the swing period,the greater the impact on the flow rate in the pipe;the swing or tilt around different axes has different effects on the reverse flow.If it swings or tilts around the y axis,it will cause the relative height of the inlet and outlet.If there is a change,the impact on the reverse flow will be greater,while around the x-axis or z-axis is relatively small.The larger the fluctuation range or the smaller the fluctuation period,the greater the impact on the flow in the tube.The impact of different fluctuation directions on the flow in the tube is opposite.of.When the main pump is switched from high-speed operation to low-speed operation,the timing of introduction of ocean conditions also affects the reverse flow.The earlier the introduction of ocean conditions after switching to low-speed operation,the easier it is to cause reverse flow;the length of time for introducing undulation and sway conditions will also cause reverse flow.Impact,the longer the time,the more obvious the impact.Through the research on the backflow of the U-tube of the steam generator under land-based and ocean conditions,the main factors affecting the backflow are obtained,and the starting point of the backflow and the law of occurrence and development are obtained.Relevant research results can provide technical support for the safe operation of steam generators under ocean conditions.