Research On The Acoustic Behavior Of The Leakage Of The Heat Transfer Tube Of The Steam Generator In Nuclear Power Plant

The steam generator is one of the most critical main equipment of a nuclear power plant,and it is also the weakest link in the safety barrier of the entire nuclear power plant.The heat transfer tube is an important part of the pressure boundary between the radioactive primary circuit and the non-radioactive secondary circuit of the PWR.In order to improve the heat transfer efficiency of the heat transfer tube,the wall of the heat transfer tube is very thin.Because the tube wall has a high working temperature for a long time,it will cause mechanical or chemical damage and cause leakage.The fission products released by the leakage or rupture of the heat transfer tube of the steam generator can directly enter the environment through the secondary side of the steam generator.In order to find the leakage in time and locate the leakage point,it is necessary to study the leakage acoustic behavior of the heat transfer tube.When the heat transfer tube of the steam generator leaks,the propagation medium of the leaking sound is divided into three parts:the fluid inside the pipe,the fluid outside the pipe,and the solid structure of the pipe.It can be seen that the sound mechanism involves multi-physics couplings such as fluid mechanics,thermals,and fluid-structure coupling.Because the mechanism is too complicated,the simplified discussion is the propagation characteristics of the small vibration sound source on the wall of the heat transfer tube.The study uses the method of calculating the interaction between sound and structure and uses the COMSOL Multiphysics software to simulate and calculate the vibration source of the pipe wall.The result found that the propagation of vibration sound sources of different frequencies on the pipe wall is very different,and under different frequencies A standing wave appears on the pipe wall.The higher the frequency,the more the number of standing waves;the pipe wall vibration caused by different sound source sizes is different.The larger the sound source size,the greater the displacement of the pipe wall vibration;the calculation of the pipe wall vibration under different pipe internal pressures For modal,the greater the pressure of the pipe,the greater the vibrational displacement of the pipe wall.The vibration modes of the pipe wall sound in the axial and circumferential directions are obtained.The sound field distribution of the tube wall vibration source in the tube is analyzed.When the frequency is lower than the cut-off frequency,the sound propagation in the pipe still follows the propagation law of the acoustic wave guide.When the frequency is higher than the cut-off frequency,the higher-order modes are dominant in the pipe.Due to the complexity of fluid-solid coupling,one-way fluid-solid coupling is considered,ignoring the influence of the pipe wall on the fluid,and only considering the effect of the fluid on the pipe wall.The flow field and pipeline structure are simulated,the natural frequency of the pipeline under the action of fluid-solid coupling is analyzed,and the influence of the different inlet flow velocity of the pipeline on the fluid-solid coupling is discussed.The small hole leakage model is used to simulate and analyze the flow field of the leakage port.And conduct experimental research on pipeline vibration under different flow velocity conditions.The propagation characteristics of vibration and sound on the tube wall with different inlet flow rates and the propagation of impulse vibration signals on the tube wall in the presence of the flow field in the tube are analyzed.The results show that considering the effect of fluid-solid coupling,the natural frequency of the pipeline increases,the inlet flow rate increases,and the natural frequency of the pipeline becomes larger.The pulse vibration of the tube wall causes the tube wall vibration to be mainly manifested in the low frequency.