Investigation of low-frequency guided waves in a fluid-filled pipe submerged in LBE

This paper investigates the propagation characteristics of acoustic waves in liquid-filled pipes submerged in lead–bismuth eutectic(LBE). Expressions for the phase velocities of the fluid-dominated (s = 1) and shell-compressed (s = 2) waves in a fluid-filled pipe submerged in LBE are derived based on the Kennard equation, then, the effects of pipe radius, wall thickness, and temperature on the wave speed and attenuation of low-frequency such waves are analyzed via numerical simulations. The results show that LBE has less impact on the s = 1 phase velocity and a pronounced influence on the s = 2 phase velocity and the attenuation of the two waves. The s = 1 phase velocity is correlated positively with the thickness-to-radius ratio, and the s = 2 phase velocity is correlated negatively with the thickness-to-radius ratio. As the thickness-to-radius ratio increases, the acoustic attenuation in the fluid-filled pipe decreases. Increasing the temperature decreases the phase velocity of both the s = 1 and s = 2 waves. Comparing the pipe-wall radial vibration displacements induced by the two waves shows that the pipe-wall displacement caused by the fluid-dominated wave is greater, and it serves as the primary carrier of the acoustic signal during leakage. The present results contribute to the application and development of acoustic inspection techniques for the health monitoring of heat-exchange pipes in the steam generators of lead–bismuth fast reactors.