Study on Damage of Joint for Overhead Traveling Crane of Nuclear Power Plant Under Earthquake

This paper deals with research on the intensity analysis of universal joint of overhead traveling crane and the damage experiments of miniature universal joint. The Kashiwazaki Kariwa nuclear power plant suffered damage from the Niigata Chuetsu offing earthquake which occurred on July 16, 2007. The earthquake motion damaged a driving shaft coupling of an overhead traveling crane of the No. 6 nuclear reactor building. The damaged portion was the universal joint. The purpose of this research is to examine the cause of breakage and proposed measures of a universal joint. First, the cause of breakage is examined. Next, the breakage experiment of miniature universal joints (it hereafter calls a test piece) is conducted. Moreover, the analytical models of test piece are created, stress analysis is conducted, and the validity of analytical models is shown by comparing with the experimental result. Seismic response analysis of the building of nuclear power station is conducted, and the response acceleration of overhead traveling crane floor is calculated. The torque working to the universal joint of crane is calculated from the floor response acceleration. Furthermore, the analytical model of the universal joint of overhead traveling crane is created, stress is calculated by the torque and the cause of breakage is checked. One effective method which avoids breakage of the overhead traveling crane under earthquake is proposed.