Vibration analysis and experiment for a scale-down model of APR+ reactor barrel

Vibration characteristics of cylindrical shells either containing fluid or confined by fluid have been of concern in the development and design of nuclear power plants. Theoretical solutions were proposed for the free vibrations of the shells having a simple geometry, such as a cylindrical shell in confined fluid and two cylindrical shells concentrically or eccentrically submerged in fluid. It is known from researches that vibration characteristics for a cylindrical shell confined by fluid are different from the shell in air. In particular, when the shell is tightly confined by a high density fluid, the natural frequency of the shell significantly decreases. The decrement of the natural frequency is very dependent on the confinement; the lower the natural frequency, the tighter the confinement. The damping coefficient, as well as the natural frequency of the shell, shows the same characteristic. The APR+ design has several new features. As a new concept to enhance the safety of a nuclear power plant, the ECB duct as shown in Fig. 1 has been developed, so that the vibration characteristics of the barrel with and without the duct are necessarily identified. For this reason, experimental and numerical studies were carried out for the developing APR+ barrel considering the water between the barrel and the vessel