Seismic Vibration Analysis of Fluid-Structure Interaction in LMFBR Piping Systems

This paper is a basic study on the vibrational characteristics of an LMFBR piping system containing liquid sodium under one-dimensional seismic excitation. Using Z-shaped piping, we formulate coupled equations for the pipe’s bending vibration and pressure wave, and transform them into two-degree-of-freedom vibration equations for the first modes of the piping vibration and pressure wave. A numerical study using the vibration model shows that: 1) the coupling effect appears between piping acceleration and liquid pressure for a piping configuration having a natural frequency ratio ν = about 0.5 to 2.0; 2) the magnitude of seismically induced pressure reaches 0.7 kPa to 1 kPa per gal; and 3) the dead-mass model of liquid gives a nonconservative response depending on the pipe’s geometrical configuration, compared to that from the pressure-wave-piping-interaction model.