Vibrational characteristics of a coaxial double-pipe

A coaxial multi-pipe structure is to be used in both the main and auxiliary primary coolant systems of a very high-temperature gas-cooled reactor which has been developed at the Japan Atomic Energy Institute. By using a straight-type model of coaxial double-pipe, experiments on the folowing items have been carried out: the effects of both the pitch of spacers in the axial direction and the insulation inserted into the inner pipe on the vibrational characteristics. These experimental results are compared with the values calculated for a parallel-beam model using a structural analysis code, COSMOS-7. The followings are conclusions derived: (1) The vibrational characteristics of a coaxial double-pipe change considerably with the locations of spacers, (2) The natural frequencies and the vibration modes of a coaxial double-piece can be simulated by using a parallel-beam model. (orig.)