A Study on Rocking Phenomena of Two-Degree-of-Freedom Coupled Systems Subjected to Base Excitation

Abstract

In nuclear power stations, the storage of a lot of spent fuels is becoming impossible because of the shortage of the residual space of the spent fuel pool. It is planned to construct an another plant where the spent fuels are temporarily stored. In that plant, the spent fuels are installed in a container which is called canister, and the canister is stored in a free-standing cylindrycal container which is called cask. The cask is freely standing on a horizontal floor in general. In this sense, the cask-canister system is considered as a two-degree-of-freedom coupled system which is freely standing on the floor. Thus, it is very important to evaluate the rocking motion of a cask-canister system due to seismic excitation. In an analytical model, the canister and the cask are treated as rigid bodies which are connected by spring. The equations of motion are derived for rocking motion when the floor is subjected to the horizontal earthquake excitation. The rocking angle of the cask and the relative displacement of the canister against the cask are evaluated by numerical simulation, and the effects of the canister vibration on the cask motion are discussed.